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  Pharmaceutical Patents  

 

Title:  Mycobacterial antigens expressed during latency
United States Patent: 
8,003,776
Issued: 
August 23, 2011

Inventors:
 James; Brian W. (Salisbury Wiltshire, GB), Marsh; Philip (Salisbury Wiltshire, GB), Hampshire; Tobias (Salisbury Wiltshire, GB)
Assignee:
  Health Protection Agency (Salisbury, GB)
Appl. No.:
 12/140,163
Filed:
 June 16, 2008


 

Outsourcing Guide


Abstract

A method is provided for identifying mycobacterial genes that are induced or up-regulated under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of a mycobacterium for at least 20 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium. Said induced or up-regulated genes form the basis of nucleic acid vaccines, or provide targets to allow preparation of attenuated mycobacteria for vaccines against mycobacterial infections. Similarly, peptides encoded by said induced or up-regulated genes are employed in vaccines. In a further embodiment, the identified genes/peptides provide the means for identifying the presence of a mycobacterial infection in a clinical sample by nucleic acid probe or antibody detection.

Description of the Invention

The present invention relates to a method of identifying a gene in mycobacteria the expression of which is induced or up-regulated during mycobacterial latency, to the isolated peptide products, variants, derivatives or fragments thereof, to antibodies that bind to said peptides, variants, derivatives or fragments, to DNA and RNA vectors that express said peptides, variants, derivatives or fragments, to attenuated mycobacteria in which the activity of at least one of said induced or up-regulated genes has been modified, to vaccines against mycobacterial infections, and to methods of detecting the presence of a mycobacterial infection.

Many microorganisms are capable of forming intracellular infections. These include: infections caused by species of Salmonella, Yersinia, Shigella, Campylobacter, Chlamydia and Mycobacteria. Some of these infections are exclusively intracellular, others contain both intracellular and extracellular components. However, it is the intracellular survival cycle of bacterial infection which is suspected as a main supportive factor for disease progression.

Generally, these microorganisms do not circulate freely in the body, for example, in the bloodstream, and are often not amenable to drug treatment regimes. Where drugs are available, this problem has been exacerbated by the development of multiple drug resistant microorganisms.

A number of factors have contributed to the problem of microbial resistance. One is the accumulation of mutations over time and the subsequent horizontal and vertical transfer of the mutated genes to other organisms. Thus, for a given pathogen, entire classes of antibiotics have been rendered inactive. A further factor has been the absence of a new class of antibiotics in recent years. The emergence of multiple drug-resistant pathogenic bacteria represents a serious threat to public health and new forms of therapy are urgently required.

For similar reasons, vaccine therapies have not proved effective against such intracellular microorganisms. Also, increased systemic concentration of antibiotics to improve bioavailability within cells may result in severe side effects.

Mycobacterium tuberculosis (TB) and closely related species make up a small group of mycobacteria known as the Mycobacterium tuberculosis complex (MTC). This group comprises four species M. tuberculosis, M. microti, M. bovis and M. africanum which are the causative agent in the majority of tuberculosis (TB) cases throughout the world.

M. tuberculosis is responsible for more than three million deaths a year world-wide. Other mycobacteria are also pathogenic in man and animals, for example M. avium subsp. paratuberculosis which causes Johne's disease in ruminants, M. bovis which causes tuberculosis in cattle, M. avium and M. intracellulare which cause tuberculosis in immunocompromised patients (eg. AIDS patients, and bone marrow transplant patients) and M. leprae which causes leprosy in humans. Another important mycobacterial species is M. vaccae.

M. tuberculosis infects macrophage cells within the body. Soon after macrophage infection, most M. tuberculosis bacteria enter and replicate within cellular phagosome vesicles, where the bacteria are sequestered from host defenses and extracellular factors.

It is the intracellular survival and multiplication or replication of bacterial infection which is suspected as a main supportive factor for mycobacterial disease progression.

A number of drug therapy regimens have been proposed for combating M. tuberculosis infections, and currently combination therapy including the drug isoniazid has proved most effective. However, one problem with such treatment regimes is that they are long-term, and failure to complete such treatment can promote the development of multiple drug resistant microorganisms.

A further problem is that of providing an adequate bioavailability of the drug within the cells to be treated. Whilst it is possible to increase the systemic concentration of a drug (eg. by administering a higher dosage) this may result in severe side effects caused by the increased drug concentration.

The effectiveness of vaccine prevention against M. tuberculosis has varied widely. The current M. tuberculosis vaccine, BCG, is an attenuated strain of M. bovis. It is effective against severe complications of TB in children, but it varies greatly in its effectiveness in adults particularly across ethnic groups. BCG vaccination has been used to prevent tuberculous meningitis and helps prevent the spread of M. tuberculosis to extra-pulmonary sites, but does not prevent infection.

The limited efficacy of BCG and the global prevalence of TB has led to an international effort to generate new, more effective vaccines. The current paradigm is that protection will be mediated by the stimulation of a Th1 immune response.

BCG vaccination in man was given orally when originally introduced, but that route was discontinued because of loss of viable BCG during gastric passage and of frequent cervical adenopathy. In experimental animal species, aerosol or intra-tracheal delivery of BCG has been achieved without adverse effects, but has varied in efficacy from superior protection than parenteral inoculation in primates, mice and guinea pigs to no apparent advantage over the subcutaneous route in other studies.

There is therefore a need for an improved and/or alternative vaccine or therapeutic agent for combating mycobacterial infections.

An additional major problem associated with the control of mycobacterial infections, especially M. tuberculosis infections, is the presence of a large reservoir of asymptomatic individuals infected with mycobacteria. Dormant mycobacteria are even more resistant to front-line drugs.

Infection with mycobacteria (eg. M. tuberculosis) rarely leads to active disease, and most individuals develop a latent infection which may persist for many years before reactivating to cause disease (Wayne, 1994). The current strategy for controlling such infection is early detection and treatment of patients with active disease. Whilst this is essential to avoid deaths and control transmission, it has no effect on eliminating the existing reservoir of infection or on preventing new cases of disease through reactivation.

Conventional mycobacterial vaccines, including BCG, protect against disease and not against infection. Ideally a new mycobacterial vaccine will impart sterile immunity, and a post-exposure vaccine capable of boosting the immune system to kill latent mycobacteria or prevent reactivation to active disease-causing microorganisms would also be valuable against latent infection.

Conventional detection of latent mycobacterial infection by skin testing may be compromised. For example, current TB detection methods based on tuberculin skin testing are compromised by BCG vaccination and by exposure to environmental mycobacteria.

New strategies are therefore required for more effective diagnosis, treatment and prevention of mycobacterial latent infection.

To develop specific strategies for addressing latent mycobacterial infection it is necessary to elucidate the physiological, biochemical and molecular properties of these microorganisms.

At present, there is no suitable in vivo model for studying mycobacterial latent infection and such a model is unlikely to provide sufficient microbial material to enable detailed analysis of the physiological and molecular changes that occur.

Studies to date have used either static cultures which allow tubercle bacilli to generate oxygen-depletion gradients and enter a non-replicating persistent state in the sediment layer, or agitated sealed liquid cultures (Wayne and Lin, 1982; Cunningham and Spreadbury, 1998; Wayne and Hayes, 1996). Transition to a non-replicating persistent state in these models coincides with a shift-down to glyoxylate metabolism, resistance to isoniazid and rifampicin and susceptibility to the anaerobic bactericidal action of metronidazole (Wayne and Hayes, 1996).

For example, a number of publications have described the analysis of mycobacterial gene and protein expression profiles following exposure of the mycobacteria to various environmental stimuli. These include Sherman, D. R. et al (2001) PNAS, vol. 98, no. 13, pp. 7534-7539; Hutter, B. (2000) FEMS Microbiol. Letts. 188, pp. 141-146; Michele, T. M. et al. (1999) Antimicrobial Agents and Chemotherapy, vol. 43, no. 2, pp. 216-225; Yuan, Y. et al. (1998) PNAS, vol. 95, pp. 9578-9583; Boon, C. et al (2001) J. Bacteriol., vol. 183, no. 8, pp. 2672-2676; Cunningham, A. F. et al (1998) J. Bacteriol., vol. 180, no. 4, pp. 801-808; Murugasu-Oei, B. et al (1999) Mol. Gen. Genet., vol. 262, pp. 677-682; and a number of patent publications such as WO99/24067, WO99/04005, WO97/35611, and WO92/08484. The mycobacteria employed in these analyses have been grown in crude, batch systems, with the result that there is little or no control of the environmental stimuli to which the mycobacteria have been exposed. Accordingly, the bacteria experience a large number of complex, interactive environmental stimuli, some of which may have rapid and transient effects in terms of gene and protein expression.

Such studies are poorly defined and controlled, and experiments relying on self-generated oxygen-depletion gradients have yielded inconsistent results. In addition, the described studies have been conducted over a relatively short duration in terms of post-inoculation growth, in many cases up to approximately 2 weeks post-inoculation, with the result that the cultured bacteria are exposed to environmental stimuli associated with the mid to late exponential phase, and/or the early stationary phase.

In view of the above, there is a need for a defined and controlled model for studying mycobacterial (eg. TB) persistence which simulates key features of the in vivo environment.

According to a first aspect of the present invention there is provided an isolated mycobacterial peptide, or a fragment or derivative or variant of said peptide, wherein the peptide is encoded by a mycobacterial gene the expression of which is induced or up-regulated under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of a mycobacterium for at least 20 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium.

Latency is synonymous with persistence. These terms describe a reversible state of low metabolic activity in which mycobacterial cells can survive for extended periods without cell division.

In contrast to the various prior art analyses, the present invention is concerned with the induction or up-regulation of mycobacterial genes (and the corresponding gene products) during long term latency conditions rather than during the onset of latency (ie. late exponential phase, or early stationary phase).

The preferred culture method of the present invention is that of batch fermenter culture. This method permits careful monitoring and control of growth culture parameters such as pH, temperature, available nutrients, and dissolved oxygen tension (DOT). In particular, temperature and DOT may be strictly controlled. In contrast, careful monitoring and control is not possible with convention, crude batch culture systems, with the result that mycobacteria cultured by such systems are exposed to a multiplicity of complex, interactive environmental stimuli, some of which may have rapid and transient effects in terms of gene and protein expression. Thus, the batch fermenter system of the present invention allows relatively careful control of environmental stimuli so that a mycobacterial response to a particular stimulus (eg. nutrient starvation) can be analysed in relative isolation from other environmental stimuli that may otherwise obscure or modify the particular mycobacterial response of interest.

In use of the present method it is possible to ensure that the principal latency induction parameter employed is starvation of carbon, and preferably the starvation of carbon and energy. This means that the accidental induction or up-regulation of genes that are solely responsive to other environmental switches may be substantially prevented. Accordingly, false-positive identification of genes that are induced or up-regulated under conditions unrelated to carbon starvation and/or energy limitation may be substantially avoided.

The term "nutrient-starving" in the context of the present invention means that the concentration of the primary carbon, and preferably the primary energy source, is insufficient to support growth of the mycobacteria. "Nutrient-starving" is a term associated with an established mid to late stationary phase of a batch culture growth curve. Under such conditions the mycobacteria are metabolically stressed, rather than simply reduced in growth rate.

In more detail, exponential growth is that period of growth which is associated with a logarithmic increase in mycobacterial cell mass (also known as the "log" phase) in which the bacteria are multiplying at a maximum specific growth rate for the prevailing culture conditions. During this period of growth the concentrations of essential nutrients diminish and those of end products increase. However, once the primary carbon and/or primary energy source falls to below a critical level, it is no longer possible for all of the mycobacterial cells within the culture to obtain sufficient carbon and/or energy needed to support optimal cellular function and cell division. Once this occurs, exponential growth slows and the mycobacteria enter stationary phase. Thereafter, the mycobacteria become nutrient starved, and enter latency. It is this latent state in the growth phase, rather than the late exponential phase or early stationary phase, with which the present invention is concerned.

Carbon starvation refers to a growth state in which the concentration of exogenous carbon is insufficient to enable the bacteria to grow and or replicate. However, when in this state, there may be other energy sources (eg. endogenous reserves, secondary metabolites) that are available to maintain essential cellular functions and viability without supporting growth. Thus, carbon starvation is associated with a mid or late stationary phase condition in which the exogenous carbon source has become depleted and bacterial growth has substantially ceased. In terms of a batch fermenter culture of mycobacteria, this typically occurs at 20 days (or later) post inoculation.

The onset of stationary phase vis-a-vis the time of inoculation will depend on a number of factors such as the particular mycobacterial species/strain, the composition of the culture media (eg. the particular primary carbon and energy source), and the physical culture parameters employed.

However, as a guide, the end of exponential phase and the onset of stationary phase generally corresponds to that point in the growth phase associated with the maximum number of viable counts of mycobacteria.

In use of the present invention, the exponential phase mycobacterial cells are harvested from the culture vessel at a point in the growth phase before the maximum number of total viable counts has been achieved. This point in the growth phase may be mimicked under continuous culture conditions employing a steady state growth rate approximating .mu..sub.max and providing a generation time of approximately 18-24 hours. In a preferred embodiment, the exponential phase mycobacterial cells are harvested when a value of between 2 and 0.5 (more preferably between 1 and 0.5) log units of viable counts per ml of culture medium less than the maximum number of viable counts per ml of culture medium has been achieved. Thus, the "exponential" phase cells are generally harvested during mid-log phase.

For example, if the maximum viable count value is 1.times.10.sup.10 per ml, then the "exponential" phase cells would be preferably harvested once a value of between 1.times.10.sup.8 and 1.times.10.sup.9.5 (more preferably between 1.times.10.sup.9 and 1.times.10.sup.9.5) viable counts per ml has been achieved. In the case of M. tuberculosis, this would be approximately 3-10, preferably 4-7 days post-inoculation.

In use of the present invention, the nutrient-starved, batch fermenter cultured mycobacterial cells are harvested from the culture vessel at a point in the growth phase after the maximum number of total viable counts has been achieved. This point in the growth phase may be mimicked under continuous culture conditions supporting a generation time of at least 3 days. In a preferred embodiment, the stationary phase mycobacterial cells are harvested when the viable counts per ml of culture medium has fallen by at least 0.5, preferably at least 1, more preferably at least 2 log units less than the maximum number of viable counts per ml of culture medium. Thus, the nutrient-starved cells are generally harvested during mid- to late-stationary phase.

For example, if the maximum viable count value is 1.times.10.sup.10 per ml, then the stationary phase cells would be preferably harvested once the viable count number had fallen to a value of at least 1.times.10.sup.9.5, preferably at least 1.times.10.sup.9, more preferably at least 1.times.10.sup.8 viable counts per ml. In the case of M. tuberculosis, this would be approximately at least day 20, preferably at least day 30, typically day 40-50 post-inoculation. Longer post-inoculation harvesting times of at least 100 days, even at least 150 days may be employed. For mycobacteria generally, the mid to late stationary phase cells are preferably harvested at least 20 days, preferably at least 30 days, more preferably at least 40 days post-inoculation.

Suitable media for culturing mycobacteria are described in Wayne, L. G. (1994) [in Tuberculosis: Pathogenesis, Protection, and Control published by the American Society for Microbiology, pp. 73-83]. These include Middlebrook 7H9 Medium [see Barker, L. P., et al. (1998) Molec. Microbiol., vol. 29 (5), pp. 1167-1177], and WO00/52139 in the name of the present Applicant.

In use of the batch fermenter culture method, the starting concentration of the primary carbon source (and preferably the primary energy source) is at least 0.5, preferably at least 1 gl.sup.-1 of culture medium. Such concentrations are considered to be not nutrient-starving. Conversely, "nutrient-starving" conditions are associated with a primary carbon and energy source concentration of less than 0.5, preferably less than 0.2, and more preferably less than 0.1 gl.sup.-1 of culture medium. The preferred carbon and energy source is glycerol.

In a preferred embodiment, the starting concentration of glycerol is at least 1, preferably 1-3, more preferably approximately 2 gl.sup.-1 of culture medium. The onset of "nutrient-starving" conditions is associated with a concentration of less than 0.2, preferably less than 0.1 gl.sup.-1 of culture medium.

Other primary carbon and energy sources may be employed such as glucose, pyruvate, and fatty acids (eg. palmitate, and butyrate). These sources may be employed at substantially the same concentrations as for glycerol.

The pH of the culture medium is preferably maintained between pH 6 and 8, more preferably between pH 6.5 and 7.5, most preferably at about pH 6.9.

In one embodiment, the dissolved oxygen tension (DOT) is maintained throughout the culture process at least 40% air saturation, more preferably between 50 and 70% air saturation, most preferably at 50% air saturation.

The dissolved oxygen tension parameter is calculated by means of an oxygen electrode and conventional laboratory techniques. Thus, 100% air saturation corresponds to a solution that is saturated with air, whereas 0% corresponds to a solution that has been thoroughly purged with an inert gas such as nitrogen. Calibration is performed under standard atmospheric pressure conditions and measured at 37.degree. C., and with conventional air comprising approximately 21% oxygen.

In another embodiment of the present invention, latency may be induced by a combination of carbon and/or energy source starvation, and a low DOT.

In a preferred embodiment, the DOT is maintained at least 40% air saturation, more preferably between 50 and 70% air saturation, until the mycobacterial culture has entered early-mid log phase. The DOT may be then lowered so as to become limiting, for example in increments over a 5 or 6 day period, and the culture maintained at a DOT of 0-10, preferably at a DOT of approximately 5% until the stationary phase cells are harvested.

The carbon and energy starvation, and optional low oxygen tension latency induction conditions of the present invention are culture conditions that are conducive for a mycobacterium to express at least one gene which would be normally expressed in vivo during latency of the mycobacterium's natural target environment which is believed to involve a low carbon and energy, and low oxygen environment.

The mycobacterium is selected from the species M. phlei, M. smegmatis, M. africanum, M. caneti, M. fortuitum, M. marinum, M. ulcerans, M. tuberculosis, M. bovis, M. microti, M. avium, M. paratuberculosis, M. leprae, M. lepraemurium, M. intracellulare, M. scrofulaceum, M. xenopi, M. genavense, M. kansasii, M. simiae, M. szulgai, M. haemophilum, M. asiaticum, M. malmoense, M. vaccae and M. shimoidei. Of particular interest are members of the MTC, preferably M. tuberculosis.

In use, it is preferred that those genes (ie. as represented by cDNAs in the detection assay) which are up-regulated by at least 1.5-fold under stationary phase conditions vis-a-vis exponential phase conditions are selected. In more preferred embodiments, the corresponding up-regulation selection criterium is at least 2-fold, more preferably 3-fold, most preferably 4-fold. In further embodiments up-regulation levels of at least 10-fold, preferably 50-fold may be employed.

The term peptide throughout this specification is synonymous with protein.

Use of mycobacterial peptide compositions, which peptides are associated with mycobacterial latency, provide excellent vaccine candidates for targeting latent mycobacteria in asymptomatic patients infected with mycobacteria.

The terms "isolated," "substantially pure," and "substantially homogenous" are used interchangeably to describe a peptide which has been separated from components which naturally accompany it. A peptide is substantially pure when at least about 60 to 75% of a sample exhibits a single peptide sequence. A substantially pure peptide will typically comprise about 60 to 90% w/w of a protein sample, more usually about 95%, and preferably will be over about 99% pure. Peptide purity or homogeneity may be indicated by, for example, polyacrylamide gel electrophoresis of a protein sample, followed by visualizing a single polypeptide band upon staining the gel. Alternatively, higher resolution may be provided by using, for example, HPLC. A peptide is considered to be isolated when it is separated from the contaminants which accompany it in its natural state. Thus, a peptide which is chemically synthesized or synthesized in a cellular system different from the cell from which it naturally originates will be substantially free from its naturally associated components. The present invention provides peptides which may be purified from mycobacteria as well as from other types of cells transformed with recombinant nucleic acids encoding these peptides. If desirable, the amino acid sequence of the proteins of the present invention may be determined by protein sequencing methods.

The terms "peptide", "oligopeptide", "polypeptide", and "protein" are used interchangeably and do not refer to a specific length of the product. These terms embrace post-translational modifications such as glycosylation, acetylation, and phosphorylation.

The term "fragment" means a peptide having at least five, preferably at least ten, more preferably at least twenty, and most preferably at least thirty-five amino acid residues of the peptide which is the gene product of the induced or up-regulated gene in question. The fragment preferably includes an epitope of the gene product in question.

The term "variant" means a peptide or peptide "fragment" having at least seventy, preferably at least eighty, more preferably at least ninety percent amino acid sequence homology with the peptide that is the gene product of the induced or up-regulated gene in question. An example of a "variant" is a peptide or peptide fragment of an induced/up-regulated gene which contains one or more analogues of an amino acid (eg. an unnatural amino acid), or a substituted linkage. The terms "homology" and "identity" are considered synonymous in this specification. In a further embodiment, a "variant" may be a mimic of the peptide or peptide fragment, which mimic reproduces at least one epitope of the peptide or peptide fragment. The mimic may be, for example, a nucleic acid mimic, preferably a DNA mimic.

For sequence comparison, typically one sequence acts as a reference sequence, to which test sequences may be compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequent coordinates are designated, if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percentage sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters.

Optimal alignment of sequences for comparison may be conducted, for example, by the local homology alignment algorithm of Smith and Waterman [Adv. Appl. Math. 2: 484 (1981)], by the algorithm of Needleman & Wunsch [J. Mol. Biol. 48: 443 (1970)] by the search for similarity method of Pearson & Lipman [Proc. Nat'l. Acad. Sci. USA 85: 2444 (1988)], by computer implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA--Sequence Analysis Software Package of the Genetics Computer Group, University of Wisconsin Biotechnology Center, 1710 University Avenue, Madison, Wis. 53705), or by visual inspection [see Current Protocols in Molecular Biology, F. M. Ausbel et al, eds, Current Protocols, a joint venture between Greene Publishing Associates, Inc. and John Wiley & Sons, Inc. (1995 Supplement) Ausbubel].

Examples of algorithms suitable for determining percent sequence similarity are the BLAST and BLAST 2.0 algorithms [see Altschul (1990) J. Mol. Biol. 215: pp. 403-410].

In a preferred homology comparison, the identity exists over a region of the sequences that is at least 10 amino acid residues in length.

The term "derivative" means a peptide comprising the peptide (or fragment, or variant thereof) which is the gene product of the induced or up-regulated gene in question. Thus, a derivative may include the peptide in question, and a further peptide sequence which may introduce one or more additional epitopes. The further peptide sequence should preferably not interfere with the basic folding and thus conformational structure of the peptide in question. Examples of a "derivative" are a fusion protein, a conjugate, and a graft. Thus, two or more peptides (or fragments, or variants) may be joined together to form a derivative. Alternatively, a peptide (or fragment, or variant) may be joined to an unrelated molecule (eg. a peptide). Derivatives may be chemically synthesized, but will be typically prepared by recombinant nucleic acid methods. Additional components such as lipid, and/or polysaccharide, and/or polyketide components may be included.

All of the molecules "fragment", "variant" and "derivative" have a common antigenic cross-reactivity and/or substantially the same in vivo biological activity as the gene product of the induced or up-regulated gene in question from which they are derived. For example, an antibody capable of binding to a fragment, variant or derivative would be also capable of binding to the gene product of the induced or up-regulated gene in question. It is a preferred feature that the fragment, variant and derivative each possess the active site of the peptide which is the induced or up-regulated peptide in question. Alternatively, all of the above embodiments of a peptide of the present invention share a common ability to induce a "recall response" of a T-lymphocyte which has been previously exposed to an antigenic component of a mycobacterial infection.

In a preferred embodiment, the peptide is selected from the group consisting of SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179, 181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239, 241, 243, 245, 247, 249, 251, 253, 255, 257, 259, 261, 263, 265, 267, 269, 271, 273, 275, 277, 279 and 281.

According to a second aspect of the invention there is provided a method of identifying a mycobacterial gene the expression of which is induced or up-regulated during mycobacterial latency, said method comprising:-- culturing a first mycobacterium under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of the first mycobacterium for at least 20 days post-inoculation; culturing a second mycobacterium under culture conditions that are not nutrient-starving and which support exponential growth of the second mycobacterium; obtaining first and second mRNA populations from said first and second mycobacteria respectively, wherein said first mRNA population is obtained from the first mycobacterium which has been cultured under nutrient-starving conditions obtainable by batch fermentation of the first mycobacterium for at least 20 days post-inoculation, and wherein said second mRNA is obtained from the second mycobacterium which has been cultured under conditions that are not nutrient-starving and which support exponential growth of said second mycobacterium; preparing first and second cDNA populations from said first and second mRNA populations respectively, during which cDNA preparation a detectable label is introduced into the cDNA molecules of the first and second cDNA populations; isolating corresponding first and second cDNA molecules from the first and second cDNA populations, respectively; comparing relative amounts of label or corresponding signal emitted from the label present in the isolated first and second cDNA molecules; identifying a greater amount of label or signal provided by the isolated first cDNA molecule than that provided by the isolated second cDNA molecule; and identifying the first cDNA and the corresponding mycobacterial gene which is induced or up-regulated during mycobacterial latency.

Reference to gene throughout this specification embraces open reading frames (ORFs).

The various embodiments described for the first aspect of the present invention apply equally to the second and subsequent aspects of the present invention.

The term "corresponding first and second cDNA molecules from the first and second cDNA populations" refers to cDNAs having substantially the same nucleotide sequence. Thus, by isolating the cDNA copies relating to a given gene under each culture condition (ie. exponential phase, and stationary phase), it is possible to quantify the relative copy number of cDNA for that gene for each culture condition. Since each cDNA copy has been produced from an mRNA molecule, the cDNA copy number reflects the corresponding mRNA copy number for each culture condition, and thus it is possible to identify induced or up-regulated genes.

In one embodiment, the first and second cDNA molecules are isolated from the corresponding first and second cDNA populations by hybridisation to an array containing immobilised DNA sequences that are representative of each known gene (or ORF) within a particular mycobacterial species genome. Thus, a first cDNA may be considered "corresponding" to a second cDNA if both cDNAs hybridise to the same immobilised DNA sequence.

In another embodiment, the first and second cDNAs are prepared by incorporation of a fluorescent label. The first and second cDNAs may incorporate labels which fluoresce at different wavelengths, thereby permitting dual fluorescence and simultaneous detection of two cDNA samples.

The type of label employed naturally determines how the output of the detection method is read. When using fluorescent labels, a confocal laser scanner is preferably employed.

According to one embodiment, fluorescently labelled cDNA sequences from stationary and exponential phase cultured systems were allowed to hybridise with a whole mycobacterial genome array. The first cDNA population was labelled with fluorescent label A, and the second cDNA population was labelled with fluorescent label B. The array was scanned at two different wavelengths corresponding to the excitable maxima of each dye and the intensity of the emitted light was recorded. Multiple arrays were preferably prepared for each cDNA and a mean intensity value was calculated across the two cDNA populations for each spot with each dye, against which relative induction or up-regulation was quantified.

In addition to the above mRNA isolation and cDNA preparation and labelling, genomic DNA may be isolated from the first and second mycobacteria. Thus, in a preferred embodiment, labelled DNA is also prepared from the isolated DNA. The labelled DNA may be then included on each array as a control.

According to a third aspect of the present invention, there is provided an inhibitor of a mycobacterial peptide, wherein the peptide is encoded by a gene the expression of which is induced or up-regulated under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of a mycobacterium for at least 20 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium, wherein the inhibitor is capable of preventing or inhibiting the mycobacterial peptide, from exerting its native biological effect.

Such inhibitors may be employed to prevent the onset of, or to cause a break in the period of mycobacterial latency (ie. induce re-activation). In this respect, mycobacteria are more susceptible to treatment regimens when in a non-latent state, and the combined use of drugs to kill latent mycobacteria (eg. TB) would significantly reduce the incidence of mycobacteria by targeting the reservoir for new disease and would thereby help reduce the problem of emerging drug-resistant strains.

The inhibitor may be a peptide, carbohydrate, synthetic molecule, or an analogue thereof. Inhibition of the mycobacterial peptide may be effected at the nucleic acid level (ie. DNA, or RNA), or at the peptide level. Thus, the inhibitor may act directly on the peptide. Alternatively, the inhibitor may act indirectly on the peptide by, for example, causing inactivation of the induced or up-regulated mycobacterial gene.

In preferred embodiments, the inhibitor is capable of inhibiting one or more of the following:-- 2-nitropropane dioxygenase, acetyltransferase, oxidoreductase, transcriptional regulator, acyl transferase, UDP-glucose dehydrogenase, phosphoribosylglycinamide formyltransferase, 1,4-dihydroxy-2-naphthoate octaprenyl, gmc-type oxidoreductase, 3-hydroxyisobutyrate dehydrogenase, methylmalonate semialdehyde dehydrogenase, dehydrogenase, mercuric reductase, glutathione reductase, dihydrolipoamide, transposase, proline iminopeptidase, prolyl aminopeptidase, quinolone efflux pump, glycine betaine transporter, phosphatidylethanolamine N-methyltransferase, chalcone synthase 2, sulfotransferase, glycosyl transferase, fumarate reductase flavoprotein, 8-amino-7-oxononanoate synthase, aminotransferase class-II pyridoxal-phosphate, bacteriophage HK97 prohead protease, penicillin-binding protein, fatty acyl-CoA racemase, nitrilotriacetate monooxygenase, histidine kinase response regulator, peptidase, LysR transcription regulator, excisionase, ornithine aminotransferase, malate oxidoreductase, thiosulphate binding protein, enoyl-CoA hydratase, acyl-CoA synthetase, methyltransferase, siroheme synthase, permease, glutaryl 7-aca acylase, sn-glycerol-3-phosphate transport system permease, enoyl-CoA hydratase/isomerase, acyl-CoA dehydrogenase, esterase, lipase, cytidine deaminase, crotonase, lipid-transfer protein, acetyl-CoA C-acetyltransferase, aminotransferase, hydrolase, and 2-amino-4-hydroxy-6-hydroxymethyldihydropterine pyrophosphokinase.

In a further embodiment, the inhibitor may be an antibiotic capable of targeting the induced or up-regulated mycobacterial gene identifiable by the present invention, or the gene product thereof. The antibiotic is preferably specific for the gene and/or gene product.

In a further embodiment, the inhibitor may act on a gene or gene product the latter of which interacts with the induced or up-regulated gene. Alternatively, the inhibitor may act on a gene or gene product thereof upon which the gene product of the induced or up-regulated gene acts.

Inhibitors of the present invention may be prepared utilizing the sequence information of provided herein. For example, this may be performed by overexpressing the peptide, purifying the peptide, and then performing X-ray crystallography on the purified peptide to obtain its molecular structure. Next, compounds are created which have similar molecular structures to all or portions of the polypeptide or its substrate. The compounds may be then combined with the peptide and attached thereto so as to block one or more of its biological activities.

Also included within the invention are isolated or recombinant polynucleotides that bind to the regions of the mycobacterial chromosome containing sequences that are associated with induction/up-regulation under low oxygen tension (ie. virulence), including antisense and triplex-forming polynucleotides. As used herein, the term "binding" refers to an interaction or complexation between an oligonucleotide and a target nucleotide sequence, mediated through hydrogen bonding or other molecular forces. The term "binding" more specifically refers to two types of internucleotide binding mediated through base-base hydrogen bonding. The first type of binding is "Watson-Crick-type" binding interactions in which adenine-thymine (or adenine-uracil) and guanine-cytosine base-pairs are formed through hydrogen bonding between the bases. An example of this type of binding is the binding traditionally associated with the DNA double helix and in RNA-DNA hybrids; this type of binding is normally detected by hybridization procedures. The second type of binding is "triplex binding". In general, triplex binding refers to any type of base-base hydrogen bonding of a third polynucleotide strand with a duplex DNA (or DNA-RNA hybrid) that is already paired in a Watson-Crick manner.

In a preferred embodiment, the inhibitor may be an antisense nucleic acid sequence which is complementary to at least part of the inducible or up-regulatable gene.

The inhibitor, when in the form of a nucleic acid sequence, in use, comprises at least 15 nucleotides, preferably at least 20 nucleotides, more preferably at least 30 nucleotides, and most preferably at least 50 nucleotides.

According to a fourth aspect of the invention, there is provided an antibody that binds to a peptide encoded by a gene, or to a fragment or variant or derivative of said peptide, the expression of which gene is induced or up-regulated during culture of a mycobacterium under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of a mycobacterium for at least 20 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium.

The antibody preferably has specificity for the peptide in question, and following binding thereto may initiate coating of the mycobacterium. Coating of the bacterium preferably leads to opsonization thereof. This, in turn, leads to the bacterium being destroyed. It is preferred that the antibody is specific for the mycobacterium (eg. species and/or strain) which is to be targeted.

In use, the antibody is preferably embodied in an isolated form.

Opsonization by antibodies may influence cellular entry and spread of mycobacteria in phagocytic and non-phagocytic cells by preventing or modulating receptor-mediated entry and replication in macrophages.

The peptides, fragments, variants or derivatives of the present invention may be used to produce antibodies, including polyclonal and monoclonal antibodies. If polyclonal antibodies are desired, a selected mammal (eg. mouse, rabbit, goat, horse, etc.) is immunized with an immunogenic polypeptide. Serum from the immunized animal is collected and treated according to known procedures. If serum containing polyclonal antibodies to a desired mycobacterial epitope contains antibodies to other antigens, the polyclonal antibodies may be purified by immunoaffinity chromatography. Alternatively, general methodology for making monoclonal antibodies by hybridomas involving, for example, preparation of immortal antibody-producing cell lines by cell fusion, or other techniques such as direct transformation of B lymphocytes with oncogenic DNA, or transfection with Epstein-Barr virus may be employed.

The antibody employed in this aspect of the invention may belong to any antibody isotype family, or may be a derivative or mimic thereof. Reference to antibody throughout this specification embraces recombinantly produced antibody, and any part of an antibody which is capable of binding to a mycobacterial antigen.

In one embodiment the antibody belongs to the IgG, IgM or IgA isotype families.

In a preferred embodiment, the antibody belongs to the IgA isotype family. Reference to the IgA isotype throughout this specification includes the secretory form of this antibody (ie. sIgA). The secretory component (SC) of sigA may be added in vitro or in vivo. In the latter case, the use of a patient's natural SC labelling machinery may be employed.

In one embodiment, the antibody may be raised against a peptide from a member of the MTC, preferably against M. tuberculosis.

In a preferred embodiment, the antibody is capable of binding to a peptide selected from the group consisting of SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179, 181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239, 241, 243, 245, 247, 249, 251, 253, 255, 257, 259, 261, 263, 265, 267, 269, 271, 273, 275, 277, 279, 281 and a fragment, variant, and derivative of said SEQ IDs.

In a further embodiment, the antigen is an exposed component of a mycobacterial bacillus. In another embodiment, the antigen is a cell surface component of a mycobacterial bacillus.

The antibody of the present invention may be polyclonal, but is preferably monoclonal.

Without being bound by any theory, it is possible that following mycobacterial infection of a macrophage, the macrophage is killed and the bacilli are released. It is at this stage that the mycobacteria are considered to be most vulnerable to antibody attack. Thus, it is possible that the antibodies of the present invention act on released bacilli following macrophage death, and thereby exert a post-infection effect.

It is possible that the passive protection aspect (ie. delivery of antibodies) of the present invention is facilitated by enhanced accessibility of the antibodies of the present invention to antigens on mycobacterial bacilli harboured by the infected macrophages. Indeed, acr expression is low during logarithmic growth, but increases at the stationary or oxygen limiting stage, and particularly in organisms which replicate within macrophages. As acr expression appears to be necessary for mycobacterial infectivity, it is possible that antibody binding may block macrophage infection by steric hindrance or disruption of its oligomeric structure. Thus, antibodies acting on mycobacterial bacilli released from killed, infected macrophages may interfere with the spread of re-infection to fresh macrophages. This hypothesis involves a synergistic action between antibodies and cytotoxic T cells, acting early after infection, eg. .quadrature..quadrature. and NK T cells, but could later involve also CD8 and CD4 cytotoxic T cells.

According to a fifth aspect of the invention, there is provided an attenuated mycobacterium in which a gene has been modified thereby rendering the mycobacterium substantially non-pathogenic, wherein said gene is a gene the expression of which is induced or up-regulated during culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of a mycobacterium for at least 20 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium.

The modification preferably inactivates the gene in question, and preferably renders the mycobacterium substantially non-pathogenic.

The term "modified" refers to any genetic manipulation such as a nucleic acid or nucleic acid sequence replacement, a deletion, or an insertion which renders the mycobacterium substantially reduced in ability to persist in a latent state. In one embodiment the entire inducible or up-regulatable gene may be deleted.

In a preferred embodiment, gene to be modified has a wild-type coding sequence selected from the group consisting of SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 166, 168, 170, 172, 174, 176, 178, 180, 182, 184, 186, 188, 190, 192, 194, 196, 198, 200, 202, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244, 246, 248, 250, 252, 254, 256, 258, 260, 262, 264, 266, 268, 270, 272, 274, 276, 278, 280 and 282.

It will be appreciated that the above wild-type sequences may include minor variations depending on the Database employed. The term "wild-type" indicates that the sequence in question exists as a coding sequence in nature.

According to a sixth aspect of the invention, there is provided an attenuated microbial carrier, comprising a peptide encoded by a gene, or a fragment orvariant or derivative of said peptide, the expression of which gene is induced or up-regulated under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of a mycobacterium for at least 20 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium.

In use, the peptide (or fragment, variant or derivative) is either at least partially exposed at the surface of the carrier, or the carrier becomes degraded in vivo so that at least part of the peptide (or fragment, variant or derivative) is otherwise exposed to a host's immune system.

In a preferred embodiment, the attenuated microbial carrier is attenuated salmonella, attenuated vaccinia virus, attenuated fowlpox virus, or attenuated M. bovis (eg. BCG strain).

In a preferred embodiment, the peptide is selected from the group consisting of SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179, 181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201, 203, 205, 207, 209, 211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239, 241, 243, 245, 247, 249, 251, 253, 255, 257, 259, 261, 263, 265, 267, 269, 271, 273, 275, 277, 279 and 281.

According to a seventh aspect of the invention, there is provided a DNA plasmid comprising a promoter, a polyadenylation signal, and a DNA sequence that is the coding sequence of a mycobacterial gene or a fragment or variant of derivative of said coding sequence, the expression of which gene is induced or up-regulated under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of a mycobacterium for at least 20 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium, wherein the promoter and polyadenylation signal are operably linked to the DNA sequence.

The term DNA "fragment" used in this invention will usually comprise at least about 5 codons (15 nucleotides), more usually at least about 7 to 15 codons, and most preferably at least about 35 codons. This number of nucleotides is usually about the minimal length required for a successful probe that would hybridize specifically with such a sequence.

In preferred embodiments, the DNA "fragment" has a nucleotide length which is at least 50%, preferably at least 70%, and more preferably at least 80% that of the coding sequence of the corresponding induced/up-regulated gene.

The term DNA "variant" means a DNA sequence that has substantial homology or substantial similarity to the coding sequence (or a fragment thereof of an induced/up-regulated gene. A nucleic acid or fragment thereof is "substantially homologous" (or "substantially similar") to another if, when optimally aligned (with appropriate nucleotide insertions or deletions) with the other nucleic acid (or its complementary strand), there is nucleotide sequence identity in at least about 60% of the nucleotide bases, usually at least about 70%, more usually at least about 80%, preferably at least about 90%, and more preferably at least about 95 to 98% of the nucleotide bases. Homology determination is performed as described supra for peptides.

Alternatively, a DNA "variant" is substantially homologous (or substantially similar) with the coding sequence (or a fragment thereof) of an induced/up-regulated gene when they are capable of hybridizing under selective hybridization conditions. Selectivity of hybridization exists when hybridization occurs which is substantially more selective than total lack of specificity. Typically, selective hybridization will occur when there is at least about 65% homology over a stretch of at least about 14 nucleotides, preferably at least about 70%, more preferably at least about 75%, and most preferably at least about 90%. See, Kanehisa (1984) Nuc. Acids Res. 12:203-213. The length of homology comparison, as described, may be over longer stretches, and in certain embodiments will often be over a stretch of at least about 17 nucleotides, usually at least about 20 nucleotides, more usually at least about 24 nucleotides, typically at least about 28 nucleotides, more typically at least about 32 nucleotides, and preferably at least about 36 or more nucleotides.

Nucleic acid hybridization will be affected by such conditions as salt concentration (eg. NaCl), temperature, or organic solvents, in addition to the base composition, length of the complementary strands, and the number of nucleotide base mismatches between the hybridizing nucleic acids, as will be readily appreciated by those skilled in the art. Stringent temperature conditions are preferably employed, and generally include temperatures in excess of 30.degree. C., typically in excess of 37.degree. C. and preferably in excess of 45.degree. C. Stringent salt conditions will ordinarily be less than 1000 mM, typically less than 500 mM, and preferably less than 200 mM. The pH is typically between 7.0 and 8.3. However, the combination of parameters is much more important than the measure of any single parameter. See, eg., Wetmur and Davidson (1968) J. Mol. Biol. 31:349-370.

The term DNA "derivative" means a DNA polynucleotide which comprises a DNA sequence (or a fragment, or variant thereof) corresponding to the coding sequence of the induced/up-regulated gene and an additional DNA sequence which is not naturally associated with the DNA sequence corresponding to the coding sequence. The comments on peptide derivative supra also apply to DNA "derivative". A "derivative" may, for example, include two or more coding sequences of a mycobacterial operon that is induced during nutrient-starvation. Thus, depending on the presence or absence of a non-coding region between the coding sequences, the expression product/s of such a "derivative" may be a fusion protein, or separate peptide products encoded by the individual coding regions.

The above terms DNA "fragment", "variant", and "derivative" have in common with each other that the resulting peptide products have cross-reactive antigenic properties which are substantially the same as those of the corresponding wild-type peptide. Preferably all of the peptide products of the above DNA molecule embodiments of the present invention bind to an antibody which also binds to the wild-type peptide. Alternatively, all of the above peptide products are capable of inducing a "recall response" of a T lymphocyte which has been previously exposed to an antigenic component of a mycobacterial infection.

The promoter and polyadenylation signal are preferably selected so as to ensure that the gene is expressed in a eukaryotic cell. Strong promoters and polyadenylation signals are preferred.

In a related aspect, the present invention provides an isolated RNA molecule which is encoded by a DNA sequence of the present invention, or a fragment or variant or derivative of said DNA sequence.

An "isolated" RNA is an RNA which is substantially separated from other mycobacterial components that naturally accompany the sequences of interest, eg., ribosomes, polymerases, and other mycobacterial polynucleotides such as DNA and other chromosomal sequences.

The above RNA molecule may be introduced directly into a host cell as, for example, a component of a vaccine.

Alternatively the RNA molecule may be incorporated into an RNA vector prior to administration.

The polynucleotide sequences (DNA and RNA) of the present invention include a nucleic acid sequence which has been removed from its naturally occurring environment, and recombinant or cloned DNA isolates and chemically synthesized analogues or analogues biologically synthesized by heterologous systems.

The term "recombinant" as used herein intends a polynucleotide of genomic, cDNA, semisynthetic, or synthetic origin which, by virtue of its origin or manipulation: (1) is not associated with all or a portion of a polynucleotide with which it is associated in nature; or (2) is linked to a polynucleotide other than that to which it is linked in nature; and (3) does not occur in nature. This artificial combination is often accomplished by either chemical synthesis means, or by the artificial manipulation of isolated segments of nucleic acids, eg., by genetic engineering techniques. Such is usually done to replace a codon with a redundant codon encoding the same or a conservative amino acid, while typically introducing or removing a sequence recognition site. Alternatively, it is performed to join together nucleic acid segments of desired functions to generate a desired combination of functions.

In embodiments of the invention the polynucleotides may encode a peptide (or fragment, variant, or derivative) which is induced or up-regulated under nutrient-starving conditions. A nucleic acid is said to "encode" a peptide if, in its native state or when manipulated, it can be transcribed and/or translated to produce the peptide (or fragment, variant or derivative thereof). The anti-sense strand of such a nucleic acid is also said to encode the peptide (or fragment, variant, or derivative).

Also contemplated within the invention are expression vectors comprising the polynucleotide of interest. Expression vectors generally are replicable polynucleotide constructs that encode a peptide operably linked to suitable transcriptional and translational regulatory elements. Examples of regulatory elements usually included in expression vectors are promoters, enhancers, ribosomal binding sites, and transcription and translation initiation and termination sequences. These regulatory elements are operably linked to the sequence to be translated. A nucleic acid sequence is operably linked when it is placed into a functional relationship with another nucleic acid sequence. For instance, a promoter is operably linked to a coding sequence if the promoter affects its transcription or expression. Generally, operably linked means that the DNA sequences being linked are contiguous and, where necessary to join two protein coding regions, contiguous and in reading frame. The regulatory elements employed in the expression vectors containing a polynucleotide encoding a virulence factor are functional in the host cell used for expression.

The polynucleotides of the present invention may be prepared by any means known in the art. For example, large amounts of the polynucleotides may be produced by replication in a suitable host cell. The natural or synthetic DNA fragments coding for a desired fragment will be incorporated into recombinant nucleic acid constructs, typically DNA constructs, capable of introduction into and replication in a prokaryotic or eukaryotic cell. Usually the DNA constructs will be suitable for autonomous replication in a unicellular host, such as yeast or bacteria, but may also be intended for introduction to and integration within the genome of a cultured insect, mammalian, plant or other eukaryotic cell lines. The polynucleotides of the present invention may also be produced by chemical synthesis, e.g., by the phosphoramidite method or the triester method, and may be performed on commercial automated oligonucleotide synthesizers. A double-stranded fragment may be obtained from the single stranded product of chemical synthesis either by synthesizing the complementary strand and annealing the strand together under appropriate conditions or by adding the complementary strand using DNA polymerase with an appropriate primer sequence. DNA constructs prepared for introduction into a prokaryotic or eukaryotic host will typically comprise a replication system recognized by the host, including the intended DNA fragment encoding the desired peptide, and will preferably also include transcription and translational initiation regulatory sequences operably linked to the polypeptide encoding segment. Expression vectors may include, for example, an origin of replication or autonomously replicating sequence (ARS) and expression control sequences, a promoter, an enhancer and necessary processing information sites, such as ribosome-binding sites, RNA splice sites, polyadenylation sites, transcriptional terminator sequences, and mRNA stabilizing sequences. Secretion signals from polypeptides secreted from the host cell of choice may also be included where appropriate, thus allowing the protein to cross and/or lodge in cell membranes, and thus attain its functional topology or be secreted from the cell. Appropriate promoter and other necessary vector sequences will be selected so as to be functional in the host, and may, when appropriate, include those naturally associated with mycobacterial genes. Promoters such as the trp, lac and phage promoters, tRNA promoters and glycolytic enzyme promoters may be used in prokaryotic hosts. Useful yeast promoters include the promoter regions for metallothionein, 3-phosphoglycerate kinase or other glycolytic enzymes such as enolase or glyceraldehyde-3-phosphate dehydrogenase, enzymes responsible for maltose and galactose utilization, and others.

Appropriate non-native mammalian promoters may include the early and late promoters from SV40 or promoters derived from murine moloney leukemia virus, mouse mammary tumour virus, avian sarcoma viruses, adenovirus II, bovine papilloma virus or polyoma. In addition, the construct may be joined to an amplifiable gene (e.g., DHFR) so that multiple copies of the gene may be made. While such expression vectors may replicate autonomously, they may less preferably replicate by being inserted into the genome of the host cell. Expression and cloning vectors will likely contain a selectable marker, a gene encoding a protein necessary for the survival or growth of a host cell transformed with the vector. The presence of this gene ensures the growth of only those host cells which express the inserts. Typical selection genes encode proteins that (a) confer resistance to antibiotics or other toxic substances, e.g. ampicillin, neomycin, methotrexate, etc.; (b) complement auxotrophic deficiencies; or (c) supply critical nutrients not available from complex media, e.g. the gene encoding D-alanine racemase for Bacilli. The choice of appropriate selectable marker will depend on the host cell. The vectors containing the nucleic acids of interest can be transcribed in vitro and the resulting RNA introduced into the host cell (e.g., by injection), or the vectors can be introduced directly into host cells by methods which vary depending on the type of cellular host, including electroporation; transfection employing calcium chloride, rubidium chloride, calcium phosphate, DEAE-dextran, or other substances; microprojectile bombardment; lipofection; infection (where the vector is an infectious agent, such as a retroviral genome). The cells into which have been introduced nucleic acids described above are meant to also include the progeny of such cells. Large quantities of the nucleic acids and peptides of the present invention may be prepared by expressing the nucleic acids or portions thereof in vectors or other expression vehicles in compatible prokaryotic or eukaryotic host cells. The most commonly used prokaryotic hosts are strains of Escherichia coli, although other prokaryotes, such as Bacillus subtilis or Pseudomonas may also be used. Mammalian or other eukaryotic host cells, such as those of yeast, filamentous fungi, plant, insect, amphibian or avian species, may also be useful for production of the proteins of the present invention. Propagation of mammalian cells in culture is perse well known. Examples of commonly used mammalian host cell lines are VERO and HeLa cells, Chinese hamster ovary (CHO) cells, and WI38, BHK, and COS cell lines, although other cell lines may be appropriate, e.g., to provide higher expression, desirable glycosylation patterns. Clones are selected by using markers depending on the mode of the vector construction. The marker may be on the same or a different DNA molecule, preferably the same DNA molecule. The transformant may be screened or, preferably, selected by any of the means well known in the art, e.g., by resistance to such antibiotics as ampicillin, tetracycline.

The polynucleotides of the invention may be inserted into the host cell by any means known in the art, including for example, transformation, transduction, and electroporation. As used herein, "recombinant host cells", "host cells", "cells", "cell lines", "cell cultures", and other such terms denoting microorganisms or higher eukaryotic cell lines cultured as unicellular entities refer to cells which can be, or have been, used as recipients for recombinant vector or other transfer DNA, and include the progeny of the original cell which has been transformed. It is understood that the progeny of a single parental cell may not necessarily be completely identical in morphology or in genomic or total DNA complement as the original parent, due to natural, accidental, or deliberate mutation. "Transformation", as used herein, refers to the insertion of an exogenous polynucleotide into a host cell, irrespective of the method used for the insertion, for example, direct uptake, transduction, f-mating or electroporation. The exogenous polynucleotide may be maintained as a non-integrated vector, for example, a plasmid, or alternatively, may be integrated into the host cell genome.

In one embodiment, a DNA plasmid or RNA vector may encode a component of the immune system which is specific to an immune response following challenge with a peptide, wherein said peptide is encoded by a mycobacterial gene that is induced or up-regulated during nutrient-starvation, and optionally oxygen starvation.

An example of such a component is an antibody to the peptide product of the induced or up-regulated gene. Thus, in one embodiment, the nucleic acid sequence (eg. DNA plasmid, or RNA vector) encodes the antibody in question.

An eighth aspect provides use of the aforementioned aspects of the present invention, namely a peptide or fragment or variant or derivative thereof, an inhibitor, an antibody, an attenuated mycobacterium, an attenuated microbial carrier, a DNA sequence that is the coding sequence of an induced or up-regulated mycobacterial gene or a fragment or variant or derivative of said coding sequence, a DNA plasmid comprising said DNA sequence, an RNA sequence encoded by said DNA sequence (including DNA fragment, variant, derivative), and/or an RNA vector comprising said RNA sequence, in the manufacture of a medicament for treating or preventing a mycobacterial infection.

The term "preventing" includes reducing the severity/intensity of, or initiation of, a mycobacterial infection.

The term "treating" includes post-infection therapy and amelioration of a mycobacterial infection.

In a related aspect, there is provided a method of treating or preventing a mycobacterial infection, comprising administration of a medicament (namely the aforementioned aspects of the present invention) selected from the group consisting of a peptide or fragment or variant or derivative thereof, an inhibitor, an antibody, an attenuated mycobacterium, an attenuated microbial carrier, a DNA sequence that is the coding sequence of an induced or up-regulated mycobacterial gene or a fragment or variant or derivative of said coding sequence, a DNA plasmid comprising said DNA sequence, an RNA sequence encoded by said DNA sequence, and/or an RNA vector comprising said RNA sequence, to a patient.

The immunogenicity of the epitopes of the peptides of the invention may be enhanced by preparing them in mammalian or yeast systems fused with or assembled with particle-forming proteins such as, for example, that associated with hepatitis B surface antigen. Vaccines may be prepared from one or more immunogenic peptides of the present invention. Typically, such vaccines are prepared as injectables, either as liquid solutions or suspensions; solid forms suitable for solution in, or suspension in, liquid prior to injection may also be prepared. The preparation may also be emulsified, or the peptide encapsulated in liposomes. The active immunogenic ingredients are often mixed with excipients which are pharmaceutically acceptable and compatible with the active ingredient. Suitable excipients are, for example, water, saline, dextrose, glycerol, ethanol, or the like and combinations thereof. In addition, if desired, the vaccine may contain minor amounts of auxiliary substances such as wetting or emulsifying agents, pH buffering agents, and/or adjuvants which enhance the effectiveness of the vaccine. Examples of adjuvants which may be effective include but are not limited to: aluminum hydroxide, N-acetyl-muramyl-L-threonyl-D-isoglutamine (thr-MDP), N-acetyl-nor-muramyl-L-alanyl-D-isoglutamine (CGP 11637, referred to as nor-MDP), N-acetylmuramyl-L-alanyl-D-isoglutaminyl-L-alanine-2-(1'-2'-dip- almitoyl-s n-glycero-3-hydroxyphosphoryloxy)-ethylamine (CGP 19835A, referred to as MTP-PE), and RIBI, which contains three components extracted from bacteria, monophosphoryl lipid A, trehalose dimycolate and cell wall skeleton (MPL+TDM+CWS) in a 2% squalene/Tween 80 emulsion. The vaccines are conventionally administered parenterally, by injection, for example, either subcutaneously or intramuscularly. Additional formulations which are suitable for other modes of administration include suppositories and, in some cases, oral formulations or formulations suitable for distribution as aerosols. For suppositories, traditional binders and carriers may include, for example, polyalkylene glycols or triglycerides; such suppositories may be formed from mixtures containing the active ingredient in the range of 0.5% to 10%, preferably 1%-2%. Oral formulations include such normally employed excipients as, for example, pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium carbonate, and the like. These compositions take the form of solutions, suspensions, tablets, pills, capsules, sustained release formulations or powders and contain 10%-95% of active ingredient, preferably 25%-70%. The peptides may be formulated into the vaccine as neutral or salt forms. Pharmaceutically acceptable salts include the acid addition salts (formed with free amino groups of the peptide) and which are formed with inorganic acids such as, for example, hydrochloric or phosphoric acids, or with organic acids such as acetic, oxalic, tartaric, maleic, and the like. Salts formed with the free carboxyl groups may also be derived from inorganic bases such as, for example, sodium, potassium, ammonium, calcium, or ferric hydroxides, and such organic bases as isopropylamine, trimethylamine, 2-ethylamino ethanol, histidine, procaine, and the like. The vaccines are administered in a manner compatible with the dosage formulation, and in such amount as will be prophylactically and/or therapeutically effective. The quantity to be administered, which is generally in the range of 5 micrograms to 250 micrograms of antigen per dose, depends on the subject to be treated, capacity of the subject's immune system to synthesize antibodies, and the degree of protection desired. Precise amounts of active ingredient required to be administered may depend on the judgment of the practitioner and may be peculiar to each subject. The vaccine may be given in a single dose schedule, or preferably in a multiple dose schedule. A multiple dose schedule is one in which a primary course of vaccination may be with 1-10 separate doses, followed by other doses given at subsequent time intervals required to maintain and or re-enforce the immune response, for example, at 1-4 months for a second dose, and if needed, a subsequent dose(s) after several months. The dosage regimen will also, at least in part, be determined by the need of the individual and be dependent upon the judgment of the practitioner. In addition, the vaccine containing the immunogenic mycobacterial antigen(s) may be administered in conjunction with other immunoregulatory agents, for example, immunoglobulins, as well as antibiotics.

The medicament may be administered by conventional routes, eg. intravenous, intraperitoneal, intranasal routes.

The outcome of administering antibody-containing compositions may depend on the efficiency of transmission of antibodies to the site of infection. In the case of a mycobacterial respiratory infection (eg. a M. tuberculosis infection), this may be facilitated by efficient transmission of antibodies to the lungs.

In one embodiment the medicament may be administered intranasally (i.n.). This mode of delivery corresponds to the route of delivery of a M. tuberculosis infection and, in the case of antibody delivery, ensures that antibodies are present at the site of infection to combat the bacterium before it becomes intracellular and also during the period when it spreads between cells.

An intranasal composition may be administered in droplet form having approximate diameters in the range of 100-5000 .mu.m, preferably 500-4000 .mu.m, more preferably 1000-3000 .mu.m. Alternatively, in terms of volume, the droplets would be in the approximate range of 0.001-100 .mu.l, preferably 0.1-50 .mu.l, more preferably 1.0-25 .mu.l.

Intranasal administration may be achieved by way of applying nasal droplets or via a nasal spray.

In the case of nasal droplets, the droplets may typically have a diameter of approximately 1000-3000 .mu.m and/or a volume of 1-25 .mu.l.

In the case of a nasal spray, the droplets may typically have a diameter of approximately 100-1000 .mu.m and/or a volume of 0.001-1 .mu.l.

It is possible that, following i.n. delivery of antibodies, their passage to the lungs is facilitated by a reverse flow of mucosal secretions, although mucociliary action in the respiratory tract is thought to take particles within the mucus out of the lungs. The relatively long persistence in the lungs' lavage, fast clearance from the bile and lack of transport to the saliva of some antibodies suggest the role of mucosal site specific mechanisms.

In a different embodiment, the medicament may be delivered in an aerosol formulation. The aerosol formulation may take the form of a powder, suspension or solution.

The size of aerosol particles is one factor relevant to the delivery capability of an aerosol. Thus, smaller particles may travel further down the respiratory airway towards the alveoli than would larger particles. In one embodiment, the aerosol particles have a diameter distribution to facilitate delivery along the entire length of the bronchi, bronchioles, and alveoli. Alternatively, the particle size distribution may be selected to target a particular section of the respiratory airway, for example the alveoli.

The aerosol particles may be delivered by way of a nebulizer or nasal spray.

In the case of aerosol delivery of the medicament, the particles may have diameters in the approximate range of 0.1-50 .mu.m, preferably 1-25 .mu.m, more preferably 1-5 .mu.m.

The aerosol formulation of the medicament of the present invention may optionally contain a propellant and/or surfactant.

By controlling the size of the droplets which are to be administered to a patient to within the defined range of the present invention, it is possible to avoid/minimise inadvertent antigen delivery to the alveoli and thus avoid alveoli-associated pathological problems such as inflammation and fibrotic scarring of the lungs.

I.n. vaccination engages both T and B cell mediated effector mechanisms in nasal and bronchus associated mucosal tissues, which differ from other mucosae-associated lymphoid tissues.

The protective mechanisms invoked by the intranasal route of administration may include: the activation of T lymphocytes with preferential lung homing; upregulation of co-stimulatory molecules, eg. B7.2; and/or activation of macrophages or secretory IgA antibodies.

Intranasal delivery of antigens may facilitate a mucosal antibody response is invoked which is favoured by a shift in the T cell response toward the Th2 phenotype which helps antibody production. A mucosal response is characterised by enhanced IgA production, and a Th2 response is characterised by enhanced IL-4 production.

Intranasal delivery of mycobacterial antigens allows targeting of the antigens to submucosal B cells of the respiratory system. These B cells are the major local IgA-producing cells in mammals and intranasal delivery facilitates a rapid increase in IgA production by these cells against the mycobacterial antigens.

In one embodiment administration of the medicament comprising a mycobacterial antigen stimulates IgA antibody production, and the IgA antibody binds to the mycobacterial antigen. In another embodiment, a mucosal and/or Th2 immune response is stimulated.

In another embodiment monoclonal antibodies, in particular, may be used to raise anti-idiotype antibodies. Anti-idiotype antibodies are immunoglobulins which carry an "internal image" of the antigen of the infectious agent against which protection is desired. These anti-idiotype antibodies may also be useful for treatment, vaccination and/or diagnosis of mycobacterial infections.

According to a ninth aspect of the present invention, the peptides (including fragments, variants, and derivatives thereof) of the present invention and antibodies which bind thereto are useful in immunoassays to detect the presence of antibodies to mycobacteria, or the presence of the virulence associated antigens in biological samples. Design of the immunoassays is subject to a great deal of variation, and many formats are known in the art. The immunoassay may utilize at least one epitope derived from a peptide of the present invention. In one embodiment, the immunoassay uses a combination of such epitopes. These epitopes may be derived from the same or from different bacterial peptides, and may be in separate recombinant or natural peptides, or together in the same recombinant peptides.

An immunoassay may use, for example, a monoclonal antibody directed towards a virulence associated peptide epitope(s), a combination of monoclonal antibodies directed towards epitopes of one mycobacterial antigen, monoclonal antibodies directed towards epitopes of different mycobacterial antigens, polyclonal antibodies directed towards the same antigen, or polyclonal antibodies directed towards different antigens. Protocols may be based, for example, upon competition, or direct reaction, or sandwich type assays. Protocols may also, for example, use solid supports, or may be by immunoprecipitation. Most assays involve the use of labelled antibody or polypeptide; the labels may be, for example, enzymatic, fluorescent, chemiluminescent, radioactive, or dye molecules. Assays which amplify the signals from the probe are also known; examples of which are assays which utilize biotin and avidin, and enzyme-labelled and mediated immunoassays, such as ELISA assays. Typically, an immunoassay for an antibody(s) to a peptide, will involve selecting and preparing the test sample suspected of containing the antibodies, such as a biological sample, then incubating it with an antigenic (i.e., epitope-containing) peptide(s) under conditions that allow antigen-antibody complexes to form, and then detecting the formation of such complexes. The immunoassay may be of a standard or competitive type. The peptide is typically bound to a solid support to facilitate separation of the sample from the peptide after incubation. Examples of solid supports that can be used are nitrocellulose (e.g., in membrane or microtiter well form), polyvinyl chloride (e.g., in sheets or microtiter wells), polystyrene latex (e.g., in beads or microtiter plates, polyvinylidine fluoride (known as Immulon), diazotized paper, nylon membranes, activated beads, and Protein A beads. For example, Dynatech Immulon microtiter plates or 60 mm diameter polystyrene beads (Precision Plastic Ball) may be used. The solid support containing the antigenic peptide is typically washed after separating it from the test sample, and prior to detection of bound antibodies. Complexes formed comprising antibody (or, in the case of competitive assays, the amount of competing antibody) are detected by any of a number of known techniques, depending on the format. For example, unlabelled antibodies in the complex may be detected using a conjugate of antixenogeneic Ig complexed with a label, (e.g., an enzyme label). In immunoassays where the peptides are the analyte, the test sample, typically a biological sample, is incubated with antibodies directed against the peptide under conditions that allow the formation of antigen-antibody complexes. It may be desirable to treat the biological sample to release putative bacterial components prior to testing. Various formats can be employed. For example, a "sandwich assay" may be employed, where antibody bound to a solid support is incubated with the test sample; washed; incubated with a second, labelled antibody to the analyte, and the support is washed again. Analyte is detected by determining if the second antibody is bound to the support. In a competitive format, a test sample is usually incubated with antibody and a labelled, competing antigen is also incubated, either sequentially or simultaneously.

Also included as an embodiment of the invention is an immunoassay kit comprised of one or more peptides of the invention, or one or more antibodies to said peptides, and a buffer, packaged in suitable containers.

As used herein, a "biological sample" refers to a sample of tissue or fluid isolated from an individual, including but not limited to, for example, plasma, serum, spinal fluid, lymph fluid, the external sections of the skin, respiratory, intestinal, and genitourinary tracts, tears, saliva, milk, blood cells, tumours, organs, and also samples of in vitro cell culture constituents (including but not limited to conditioned medium resulting from the growth of cells in cell culture medium, putatively virally infected cells, recombinant cells, and cell components).

In a related diagnostic assay, the present invention provides nucleic acid probes for detecting a mycobacterial infection.

Using the polynucleotides of the present invention as a basis, oligomers of approximately 8 nucleotides or more can be prepared, either by excision from recombinant polynucleotides or synthetically, which hybridize with the mycobacterial sequences, and are useful in identification of mycobacteria. The probes are a length which allows the detection of the induced or up-regulated sequences by hybridization. While 6-8 nucleotides may be a workable length, sequences of 10-12 nucleotides are preferred, and at least about 20 nucleotides appears optimal. These probes can be prepared using routine methods, including automated oligonucleotide synthetic methods. For use as probes, complete complementarity is desirable, though it may be unnecessary as the length of the fragment is increased. For use of such probes as diagnostics, the biological sample to be analyzed, such as blood or serum, may be treated, if desired, to extract the nucleic acids contained therein. The resulting nucleic acid from the sample may be subjected to gel electrophoresis or other size separation techniques; alternatively, the nucleic acid sample may be dot blotted without size separation. The probes are usually labeled. Suitable labels, and methods for labeling probes are known in the art, and include, for example, radioactive labels incorporated by nick translation or kinasing, biotin, fluorescent probes, and chemiluminescent probes. The nucleic acids extracted from the sample are then treated with the labeled probe under hybridization conditions of suitable stringencies. The probes may be made completely complementary to the virulence encoding polynucleotide. Therefore, usually high stringency conditions are desirable in order to prevent false positives. The stringency of hybridization is determined by a number of factors during hybridization and during the washing procedure, including temperature, ionic strength, length of time, and concentration of formamide. It may be desirable to use amplification techniques in hybridization assays. Such techniques are known in the art and include, for example, the polymerase chain reaction (PCR) technique. The probes may be packaged into diagnostic kits. Diagnostic kits include the probe DNA, which may be labelled; alternatively, the probe DNA may be unlabeled and the ingredients for labelling may be included in the kit in separate containers. The kit may also contain other suitably packaged reagents and materials needed for the particular hybridization protocol, for example, standards, as well as instructions for conducting the test.

In a preferred embodiment, a peptide (or fragment or variant or derivative) of the present invention is used in a diagnostic assay to detect the presence of a T-lymphocyte which T lymphocyte has been previously exposed to an antigenic component of a mycobacterial infection in a patient.

In more detail, a T-lymphocyte which has been previously exposed to a particular antigen will be activated on subsequent challenge by the same antigen. This activation provides a means for identifying a positive diagnosis of mycobacterial infection. In contrast, the same activation is not achieved by a T-lymphocyte which has not been previously exposed to the particular antigen.

The above "activation" of a T-lymphocyte is sometimes referred to as a "recall response" and may be measured, for example, by determining the release of interferon (eg. IFN-Y) from the activated T-lymphocyte. Thus, the presence of a mycobacterial infection in a patient may be determined by the release of a minimum concentration of interferon from a T-lymphocyte after a defined time period following in vitro challenge of the T-lymphocyte with a peptide (or fragment or variant or derivative) of the present invention.

In use, a biological sample containing T-lymphocytes is taken from a patient, and then challenged with a peptide (or fragment, variant, or derivative thereof) of the present invention.

The above T-lymphocyte diagnostic assay may include an antigen presenting cell (APC) expressing at least one major histocompatibility complex (MHC) class II molecule expressed by the patient in question. The APC may be inherently provided in the biological sample, or may be added exogenously. In one embodiment, the T-lymphocyte is a CD4 T-lymphocyte.
 

Claim 1 of 23 Claims

1. An isolated M. tuberculosis DNA sequence selected from the group consisting of SEQ ID NOs: 8, 56, 126 and 130, or a variant thereof having at least 70% nucleotide sequence identity therewith, or a derivative thereof, wherein the peptide encoded by said variant or derivative has a common antigenic cross-reactivity to the peptide encoded by said DNA sequence; wherein said M. tuberculosis DNA sequence is the coding sequence of an M. tuberculosis gene, the expression of which is induced or up-regulated under culture conditions that are nutrient-starving and which maintain mycobacterial latency, said conditions being obtainable by batch fermentation of an M. tuberculosis bacterium for at least 40 days post-inoculation, when compared with culture conditions that are not nutrient-starving and which support exponential growth of said mycobacterium.
 

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