Patent 6,890,538

The invention relates to a vaccine against herpes simplex virus (HSV) comprising an invasive but attenuated or non-pathogenic bacterium, which bacterium comprises a coding sequence encoding a HSV antigen in a form that enables said coding sequence to be transferred to a host cell of a human or animal host which the bacterium is capable of invading and to be expressed in said cell to form said antigen without the introduction of an antimicrobial agent to lyse the bacterium. The invention also provides similar vaccines against other viruses.

Description of the Invention

FIELD OF THE INVENTION

The invention relates to vaccines, especially prophylactic vaccines, against Herpes Simplex Virus (HSV)-mediated disease and other viral diseases.

BACKGROUND OF THE INVENTION

As noted in Bernstein and Stanberry (1999) in a recent review and discussed more extensively there and in the references cited therein, herpes simplex viruses type 1 and 2 (HSV-1 and HSV-2) are common throughout the world. They produce not only a primary infection but also latent and recurrent infections. HSV can cause a variety of clinical illnesses including genital herpes, oral-facial infections (e.g. gingivosto-matitis, labialis, pharyngitis), cutaneous infections (e.g. whitlow, herpes gladatorium), ocular infections, neonatal herpes, herpes encephalitis, disseminated infection and erythema multiforme.

The severity and duration of most symptomatic primary infections can be reduced by antiviral therapy but this does not generally affect the establishment of latency or reduce recurrence.

Similarly, treatment of recurrent infections can decrease the severity of the disease and daily suppressive therapy can decrease both symptomatic and asymptomatic recurrences, but treatment does not affect latency and the effect is lost when therapy is discontinued. The life-long nature of this infection, the increasing prevalence of genital herpes despite the availability of effective antiviral therapies and the severity of the disease in neonates and the immunocompromised make HSV an important target for vaccine development. However, no effective vaccine is yet available (Bernstein et al, 1999).

A distinction needs to be drawn between prophylactic and therapeutic vaccines. As discussed by Bernstein et al (1999) the aims for a prophylactic, preventative, vaccine are to prevent acute clinical disease, viral infection and viral replication in the genital tract, and to prevent or reduce the establishment of latency and subsequent recurrences of the disease, either symptomatic or asymptomatic. Ideally, such a vaccine would provide a broad and durable "sterilising immunity" at the points of entry of the virus into the body, e.g. the genital tract, nasal and oro-pharingeal mucosa and the eye. This would eliminate the virus at the entry point before .3replication or entry into the peripheral nervous system. Naturally, such a prophylactic vaccine is highly desirable as it would prevent infection rather than merely treating an established infection. That is generally true for any vaccine but a prophylactic vaccine is all the more desirable in case of HSV-mediated disease because of HSV's ability to establish latency and give rise to recurrent infections.

By contrast, therapeutic vaccines are aimed at treating patients who have an established latent infection. Thus, they are intended to reduce clinical recurrences of the disease and to reduce viral shedding. (Shedding is the phenomenon by which viruses are released from the genital tract, possibly in the absence of disease symptoms, leading to transmission of HSV disease to previously unaffected individual. Thus, in addition to treating the individual in question, therapeutic vaccines are intended to prevent further spread of HSV-mediated disease.)

Bernstein et al (1999) identify six possible types of HSV vaccine. These are: (i) inactivated virion vaccines, (ii) recombinantly produced virion components or subunits (i.e. proteins), (iii) live genetically attenuated HSV mutants, (iv) replication-deficient HSV mutants, (v) live vected vaccines expressing HSV antigens, and (vi) DNA vaccines.

Virion-based vaccines (i) have not proved effective against HSV and have several drawbacks, e.g. problems with providing consistent concentrations of immunogens, ensuring that all virus is inactivated, eliminating potentially oncogenic viral contaminant DNA and high production costs.

Subunit vaccines (ii) are considered safer but less effective at inducing cell mediated responses. Subunit vaccines have had some success in the treatment of experimental recurrent genital herpes and in the reduction of viral shedding but this strategy has not yet been successfully applied to prophylactic, as opposed to therapeutic, vaccines.

Attenuated live virus vaccines (iii) have similarly been unsuccessful. Generally, live viral vaccines are developed by repeatedly passaging virus in cell culture until the virus becomes less virulent. This has not worked for HSV, where passaging in cell culture does not result in stable attenuation, such that passaged HSV strains have the potential to regain full virulence. Defining and eliminating specific genes involved in viral latency or reactivation has also been attempted. One candidate gene was the thymidase kinase (Tk) gene. An HSV-2 vaccine was developed which was protective in experimental challenge systems but proved to be poorly immunogenic in phase 1 trials and thus not effective. Deletion of the gamma 34.5 gene (ICP 34.5), believed to be central to neurovirulence, appears to diminish virulence and to increase but maybe not eliminate latency and reactivation.

Replication deficient HSV mutants (iv) have been used in the treatment of experimental recurrent genital herpes in guinea pigs but no effective prophylactic vaccine has been designed using this strategy.

Live vectored vaccines (v) have also been investigated. In a live vectored vaccine, one or more HSV genes are inserted into a replication-competent viral or bacterial vector, such as an adenovirus. Following immunisation, the vector replicates and expresses immunogenic proteins. Possible vectors include vaccinia viruses, varicella-zoster viruses, adeno-associated viruses and the bacterium Salmonella typhimurium. This approach is exemplified by Chabalgoity et al (1996) and Karem et al (1997).

DNA vaccines (vi) have also had only limited success. There are some reports indicating that intramuscular immunisation with a plasmid carrying a gene encoding HSV antigen (glycoprotein D or B) under the control of a eukaryotic promoter is effective to induce protection in mice and guinea pigs against an intravaginal challenge with the virus. However, these studies also make it clear that these vaccines are ineffective in actually preventing infection. Attempts to induce protective mucosal immunity by administering DNA intranasally have similarly shown poor results in preventing infection despite eliciting production of high titers of specific IgA antibodies.

Accordingly, it can be seen that no truly prophylactic vaccine is yet available, in the sense that no vaccine is yet available that prevents viral invasion. If viral invasion cannot be prevented, latency can be established and recurrent disease may result. This is particularly serious for infants born to infected mothers suffering recurrent disease.

Clearly, there is therefore a need to develop prophylactic HSV vaccines. Currently, there is no effective prophylactic HSV vaccine and the prevalent idea is that immunity to HSV is seldom if ever adequate to prevent viral invasion. For example, Bernstein et al (1999) indicate that they do not consider the induction of a durable sterilising immunity, especially in the genital tract, to be feasible at this time. As a result, their view is that prophylactic HSV vaccines in humans should not be expected to prevent infection completely but only to provide protection against clinical signs and symptoms of HSV infection.

SUMMARY OF THE INVENTION

Against this background, we have, surprisingly, identified a strategy for the development of an effective prophylactic HSV vaccine.

Recently, it has been reported the use of attenuated strains of Shigella and Salmonella as vehicles to deliver plasmid DNA in vivo into eukaryotic cells (Sizemore et al, 1995; Darji et al, 1997; Paglia et al, 1998; Fennelly et al, 1999). U.S. Pat. No. 5,877,159 (Powell/University of Maryland at Baltimore, 2 Mar. 1999) also provides similar findings. However, U.S. Pat. No. 5,877,159 does not provide any data showing protection against HSV. In particular, it provides no means by which a specific mucosal immune response against HSV can be obtained. Here, we show that the use of such an attenuated strain of Salmonella to transfer the HSV glycoprotein gene is effective to induce protection against an intravaginal challenge. This forms the basis of a strategy to develop a prophylactic vaccine against HSV.

Furthermore, we have definitively demonstrated that the immunity obtained is due to the transcription of the protein by a eukaryotic nuclear process, probably in macrophages and dendritic cells, and not by the expression of the protein by the invading bacteria This is a point of fundamental importance when an intracellular bacterium is used to deliver DNA to eukaryotic cells. The other possibility is that the protein is produced by the invading bacteria themselves by an unspecific initiation of the transcription under the control of a cryptic promoter. In other reports using this technique in non-HSV systems, reporter genes (beta galactosidase or GFP) were put under the control of prokaryotic or eukaryotic promoters (Darji et al, 1997; Paglia et al, 1998). In these reports, the absence of activity when a prokaryotic promoter was used was taken as an indication that the synthesis of the protein was due to eukaryotic events. Furthermore, by means of RT-PCRT, the removal of an intron placed in a non-coding region was demonstrated in a small fraction of RNA (Darji et al, 1997).

To demonstrate rigorously that the totality of the protein produced was derived from a eukaryotic nuclear process we introduced an intron in the GFP. We found similar levels of expression of the GFP in peritoneal macrophages after the intraperitoneal inoculation of salmonellae harboring the GFP plasmid with or without the intron. Furthermore, after the oral administration we found transfected macrophages in the Peyer patches, lamina propria of the small intestine and in the spleen. This is the first time that expression has been conclusively demonstrated to occur only in the cells of the eukaryotic host.

In addition, the distinction between the techniques of the present invention and those of Chabalgoity et al (1996) and Karem et al (1997) should be noted. In those studies, S. typhimurium was used as a vector to deliver HSV-1 antigens to an organism. However, crucially, expression took place in the bacterium, rather than by transfer to the eukaryotic cells of the host.

Further, WO 98/44131 (Walter Reed Army Institute of Research) describes a method whereby attenuated Shigella are transformed with DNA encoding antigens and allowed to enter baby hamster kidney (BHK) cells. Antimicrobial agents are then introduced to lyse the attenuated bacteria such that the antigen-encoding DNA is released into the cells. The present invention does not require the use of such lytic antimicrobial agents. Rather, the antigen-encoding DNA is transferred without any need for external lytic agents to be introduced.

We have shown that Salmonella-based DNA immunisation with expression of antigens taking place in the cells of the mammalian host is an effective method to induce a protective mucosal and systemic cellular immune response against HSV infection. In other reports where DNA from plasmids carrying the gD gene was administered by the intramuscular route, the humoral immune response was mainly tested, and even though protection after an intravaginal challenge was obtained, the infection was not prevented (Bourne et al, 1996 (a) and (b)). However, in the present study we obtained 100% protection in the presence of very low levels of antibodies (none detectable in the vaginal washing). Furthermore, in contrast to what was observed after intramuscular immunisation, no virus was recovered in vaginal washes after challenge.

Recently, the question of which type of immunity is involved in protection after a mucosal challenge was readdressed (Kuklin et al, 1997). It is now believed that protection against HSV infection is mediated by T cells and that IFN-γ-producing cells may play a major role.

In previous studies it was shown that high levels of specific secretory IgA were not enough to protect mice against an intravaginal infection with high or even low doses of HSV (Kuklin et al, 1997). The conclusion that antibodies at the site of mucosal infection was usually inadequate to prevent invasion came from experiments in which mice immunised intranasally with recombinant vaccinia expressing HSV glycoproteins were challenged vaginally with HSV. Despite high titers of both IgA and IgG vaginal antibodies against the immunising glycoprotein, following viral challenge infection occurred and virus was recovered from vaginal washes. Furthermore, the infection was confirmed because Ab response against other glycoproteins were induced, and in addition challenged animals developed secondary Ab responses to the immunising glycoprotein.

This pattern of events was evident even in some immune animals challenged with a minimal dose of virus (Kuklin et al, 1998).

Herein, we present data that strongly support the idea that cellular immunity is responsible for the clearance of the virus. Our results show that, after intravaginal challenge, mice immunised with salmonellae carrying a plasmid comprising the glycoprotein D gene (pCIgD) did not develop a secondary antibody response against the immunising glycoprotein. Furthermore, in contrast to what we observed after intra-muscular immunisation with naked plasmid-DNA, immunisation with salmonellae harboring the pCIgD vector results in the absence of virus in the vaginal tract after the challenge, i.e. complete viral clearance. Cellular immunity can additionally be stimulated using cytokines such as Granulocyte Macrophage Colony Stimulating Factor (GMCSF), Interleukin-12 or other molecules that enhance the cellular immune response. According to the invention, therefore, coadministration of such molecules may assist in securing viral clearance.

Currently, there is no effective prophylactic HSV vaccine and the prevalent idea is that immunity to HSV is seldom if ever adequate to prevent viral invasion. Herein, we provide results indicating that immunisation with salmonealla harboring the glycoprotein D gene induce a strong activation of IFN-γ-secreting cells at mucosal and systemic level, similar to those observed after a primary infection.

Our results open up the possibility of preparing a prophylactic vaccine against HSV. The success of this strategy of immunisation to prevent the infection could be due to the fact that the right immune response is induced in the right places, that is a strong activation of IFN-γ-secreting cells in systemic and mucosal compartments including the genital tract.

Accordingly, the invention provides:

A vaccine against herpes simplex virus (HSV) comprising an invasive but attenuated or non-pathogenic bacterium, which bacterium comprises a coding sequence encoding a HSV antigen in a form that enables said coding sequence to be transferred to a host cell of a human or animal host which the bacterium is capable of invading and to be expressed in said cell to form said antigen without the introduction of an antimicrobial agent to lyse the bacterium.

The invention also provides:

A bacterium as just defined (a bacterium of the invention).

The invention also provides:

A bacterium of the invention for use in a method of treatment of the human or animal body.

The invention also provides:

Use of a bacterium of the invention in the manufacture of a medicament for the treatment or prevention of an HSV-mediated human or animal disease.

The invention also provides:

A method of treating or preventing HSV-mediated disease in a human or animal host comprising administering to said subject an HSV vaccine comprising an invasive but attenuated or non-pathogenic bacterium comprising a coding sequence encoding a herpes simplex virus (HSV) antigen in a form that enables said coding sequence to be transferred to a host cell of a mammalian host animal which the bacterium is capable of invading and to be expressed in said cell to form said antigen, in an amount effective to secure vaccination by means of transfer of said coding sequence to said host cell and expression in said host cell without the introduction of an antimicrobial agent to lyse the bacterium.

The invention also provides:

A pharmaceutical composition for vaccination against HSV-mediated disease comprising a bacterium of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Bacteria

The bacteria of the invention are either attenuated or non-pathogenic. This is to prevent the bacteria causing disease in the subject being treated. One alternative is to use bacteria which do not naturally have pathogenic characteristics. Another alternative is to use attenuated bacteria, i.e. bacteria whose pathogenic characteristics have been eliminated or reduced to a clinically acceptable level. Herein, the term "attenuated" covers any bacterium whose undesirable characteristics have been reduced to an acceptable level by any means. Bacteria may thus be attenuated by any suitable means known in the art.

Attenuated Bacteria

Typically, attenuation is effected by introducing one or more attenuating mutations. Known attenuating techniques and mutations may be used, or new ones may be devised by those of skill in the art in the context of the invention.

Attenuating mutations can be introduced into bacterial pathogens using non-specific mutagenesis either chemically, using agents such as N-methyl-N′-nitro-N-nitrosoguanidine, or using recombinant DNA techniques; classical genetic techniques, such as Tn10 mutagenesis, P22-mediated transduction, λ phage mediated crossover, and conjugational transfer, or site-directed mutagenesis using recombinant DNA techniques. Recombinant DNA techniques are preferred. Examples of such attenuating mutations include:

	(i) auxotrophic mutations, such as aro (Hoiseth et al, Nature, 291: 238-239 (1981), gua (McFarland et al, Microbiol. Path., 3:129-141 (1987), nad (Park et al, J. Bact., 170:3725-3730 (1988), thy (Nnalue et al, Infect. Immun. 55:955-962 (1987), and asd (Curtiss, supra) mutations;
	(ii) mutations that inactivate global regulatory functions, such as cya (Curtiss et al, Infect. Immun., 55:3035-3043 (1987), crp (Curtiss et al (1987), supra), phoP/phoQ (Groisman et al, Proc. Natl. Acad. Sci., USA, 86:7077-7081 (1989); and Miller et al, Proc. Natl. Acad. Sci., USA, 86:5054-5058 (1989), phoP^c(Miller et al, J. Bact., 172: 2485-2490 (1990)) or ompR (Dorman et al, Infect. Immun., 57: 2136-2140 (1989)) mutations;
	(iii) mutations that modify the stress response, such as recA (Buchmeier et al, Mol. Micro., 7:933-936 (1993)), btrA (Johnson et al, Mol. Micro., 5:401-407 (191)), htpR (Neidhardt et al, Biochem. Biophys. Res. Com., 100:894-900 (1981)), hsp (Neidhardt et al, Ann. Rev. Genet., 18:295-329 (1984)) and groEL (Buchmeier et al, Sci., 248:730-732 (1990)) mutations;
	(iv) mutations in specific virulence factors, such as lsyA (Libby et al, Proc. Natl. Acad. Sci., USA, 91:489-493 (1994)), pag or prg (Miller et al (1990), supra; and Miller et al (1989), supra), iscΛ or virG (d'Hauteville et al, Mol. Micro., 6:833-841 (1992)), plcA (Mengaud et al, Mol. Microbiol., 5:367-72 (1991); Camilli et al, J. Exp. Med., 173:751-754 (1991)), and act (Brundage et al, Proc. Natl. Acad. Sci., USA, 90:11890-11894 (1993)) mutations;
	(v) mutations that affect DNA topology, such as topA (Galan et al, Infect. Immun., 58:1879-1885 (1990)) mutation;
	(vi) mutations that block biogenesis of surface polysaccharides, such as rfb, galE (Hone et al, J. Infect. Dis., 156:164-167 (1987)) or via (Popoff et al, J. Gen. Microbiol., 138:297-304 (1992)) mutations;
	(vii) mutations that modify suicide systems, such as sacB (Recorbet et al, App. Environ. Micro., 59:1361-1366 (1993); Quandt et al, Gene, 127:15-21 (1993)), nuc (Ahrenholtz et al, App. Environ. Micro., 60:3746-3751 (1994)), hok, gef, kil, or phlA (Molin et al, Ann. Rev. Microbiol., 47:139-166 (1993)) mutations;
	(viii) mutations that introduce suicide systems, such as lysogens encoded by P22 (Rennell et al, Virol., 143:280-289 (1985)), λ murein transglycosylase (Bienkowska-Szewczyk et al, Mol. Gen. Genet., 184:111-114 (1981)) or S-gene (Reader et al, Virol., 43:623-628 (1971); and
	(ix) mutations that disrupt or modify the correct cell cycle, such as minB (de Boer et al, Cell, 56:641-649 (1989)) mutation.

The attenuating mutations can be either constitutively expressed or under the control of inducible promoters, such as the temperature sensitive heat shock family of promoters (Neidhardt et al, supra), or the anaerobically induced nirB promoter (Harborne et al, Mol. Micro., 6:2805-2813 (1992)), or repressible promoters, such as uapA (Gorfinkiel et al, J. Biol. Chem., 268:23376-23381 (1993)) or gev (Stauffer et al, J. Bact., 176:6159-6164 (1994)).

Invasive Bacteria

In addition to being attenuated or non-pathogenic, the bacteria of the invention are invasive. An invasive bacterium is one which is capable of entering the subject's body in such a way that it is able to deliver the coding sequence encoding the HSV antigen of the invention in a manner which allows expression of that sequence by cells of the host. Invasive bacteria include bacteria that are naturally capable of entering the cytoplasm or nucleus of animal cells and also bacteria that are not naturally capable of this but that have been altered to become so capable. Thus, any invasive bacterium can be used. The bacterium which is used may be chosen to complement the host to be treated. For example, where treatment of humans is concerned, a bacterium which naturally infects humans may be used.

Preferred naturally occurring invasive bacteria include Samonella spp., Shigella spp., Listeria spp., Rickettsia spp. and enteroinvasive Escherichia coli. Salmonella is preferred.

Amongst these species, any suitable strain of bacterium may be used.

One example of a suitable Salmonella strain (see the examples) is the auxotrophic S. typhimurium AroA⁺ strain SL7207. Other examples of Salmonella include Salmonella typhi (ATCC No. 7251) and S. typhimurium (ATCC No. 13311). Attenuated Salmonella strains are preferably used in the present invention and include S. typhi aroAaroD (Hone et al, Vacc., 9:810-816 (1991) and S. typhimurium aroA mutant (Mastroeni et al, Micro. Pathol., 13:477-491 (1992)).

Alternatively, new attenuated strains can be constructed by introducing an attenuating mutation either singularly or in conjunction with one or more additional attenuating mutations. The same applies to the construction of new attenuated strains of other bacteria.

Examples of Shigella strains include Shigella flexneri 2a (ATCC No. 29903), Shigella sonnei (ATCC No. 29930), and Shigella disenteriae (ATCC No. 13313). An attenuated Shigella strain, such as Shigella flexneri 2a 2457T ΔaroAΔvirG mutant CVD 1203 (Noriega et al, supra), Shigella flexneri M90T ΔicsA mutant (Goldberg et al, Infect. Immun., 62:5664-5668 (1994)), Shigella flexneri Y SFL114 aroD mutant (Karnell et al, Vacc., 10:167-174 (1992)), and Shigella flexneri ΔaroAΔaroD mutant (Verma et al, Vacc., 9:6-9 (1991)) is preferably employed.

Examples of Listeria strains which can be employed in the present invention include Listeria monocytogenes (ATCC No. 15313). Attenuated Listeria strains include monocytogenes ΔactA mutant (Brundage et al, supra) or L. monocytogenes ΔplcA (Camilli et al, J. Exp. Med., 173:751-754 (1991).

Examples of Rickettsia strains include Ricketsia rickettsiae (ATCC Nos. VR149 and VR891), Ricketsia prowaseckii (ATCC No. VR233), Ricketsia tsutsugamuchi (ATCC Nos. VR312, VR150 and VR609), Ricketsia mooseri (ATCC No. VR144), Ricketsia sibirica (ATCC No. VR151), and Rochalimaea quitana (ATCC No. VR358).

Examples of enteroinvasive Escherichia strains include Escherichia coli strains 4608-58, 1184-68, 53638-C-17, 13-80, and 6-81 (Sansonetti et al, Ann. Microbiol. (Inst. Pasteur). 132A:351-355 (1982)).

Examples of bacteria which can be genetically engineered to be invasive include Yersinia spp., Escherichia spp., Klebsiella spp., Bordetella spp., Neisseria spp., Aeromonas spp, Franciesella spp., Corynebacterium spp., Citrobacter spp., Chlamydia spp., Hemophilus spp., Brucella spp., Mycobacterium spp., Legionella spp., Rhodococcus spp., Pseudomonas spp., Helicobacter spp., Salmonella spp., Vibrio spp., Bacillus spp. and Erysipelothrix spp. These organisms can be engineered to mimic the invasive properties of bacteria such as Shigella spp., Listeria spp., Rickettsia spp., or enteroinvasive E. coli spp. by inserting genes that enable them to access the cytoplasm of an animal cell. This may be done by any suitable technique known in the art.

Examples of such genes include the genes incoding the invasive proteins of Salmonella Shigella, other invasive bacteria, e.g. as mentioned herein, hemolysin or the invasion plasmid of Escherichia, or listeriolysin O of Listeria, as such techniques are known to result in strains that are capable of entering the cytoplasm of infected animal cells (Formal et al, Infect. Immun., 46:465 (1984); Bielecke et al, Nature, 345:175-176 (1990); Small et al, In: Microbiology—1986, pages 121-124, Levine et al, Eds., American Society for Microbiology, Washington, D.C. (1986); and Zychlinksy et al, Molec. Micro., 11:619-627 (1994)). Any gene or combination of genes, from one or more sources, that mediates entry into the cytoplasm of animal cells will suffice. Thus, such genes are not limited to bacterial genes, and include viral genes, such as influenza virus hemagglutinin HA-2 which promotes endosmolysis (Plank et al, J. Biol. Chem., 269:12918-12924(1994)).

Invasive genes can be introduced into the target strain using chromosome or plasmid mobilisation (Miller, A Short Course in Bacterial Genetics, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1992); Bothwell et al, supra; and Ausubel et al, supra), bacteriophage-mediated transduction (de Boer, supra; Miller, supra; and Ausubel et al, supra), or chemical (Bothwell et al, supra; Ausubel et al, supra, Felgner et al, supra; and Farhood, supra), electroporation (Bothwell et al, supra; Ausubel et al, supra; and Sambrook, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Habor, N.Y.) and physical transformation techniques (Johnston et al, supra; and Bothwell, supra). The genes can be incorporated on bacteriophage (de Boer et al, Cell, 56:641-649 (1989)), plasmids vectors (Curtiss et al, supra) or spliced into the chromosome (Hone et al, supra) of the target strain.

Examples of Yersinia strains include Y. enterocolitica (ATCC No. 9610) or Y. pestis (ATCC No. 19428). Attenuated Yersinia strains include Y. enterocolitica Ye03-R2 (al-Hendy et al, Infect. Immun., 60:870-875 (1992) or Y. enterocolitica aroA (O'Gaora et al, Micro. Path., 9:105-116 (1990)).

Examples of Escherichia strains include E. coli H10407 (Elinghorst et al, Infect. Immum., 60:2409-2417 (1992), and E. coli EFC4, CFT325 and CPZ005 (Donnenberg et al, J. Infect. Dis., 169:831-838 (1994)). Attenuated Escherichia strains include the attenuated turkey pathogen E. coli 02 carAB mutant (Kwaga et al, Infect. Immun., 62:3766-3772 (1994)).

Examples of Klebsiella strains include K. pneumoniae (ATCC No. 13884).

Examples of Bordetella strains include B. bronchiseptica (ATCC No. 19395).

Examples of Neisseria strains include N. meningitidis (ATCC No. 13077) and N. gonorrhoeae (ATCC No. 19424). Attenuated Neisseria strains include N. gonorrhoeae MS11 aro mutant (Chamberlain et al, Micro. Path., 15:51-63 (1993)).

Examples of Aeromonas strains include A. eucrenophila (ATCC No. 23309).

Examples of Franiesella strains include F. tularensis (ATCC No. 15482).

Examples of Corynebacterium strains include C. pseudotuberculosis (ATCC No. 19410).

Examples of Citrobacter stains include C. freundii (ATCC No. 8090).

Examples of Chlamydia strains include C. pneumoniae (ATCC No. VR1310).

Examples of Hemophilus strains include H. sornnus (ATCC No. 43625).

Examples of Brucella strains include B. abortus (ATCC No. 23448).

Examples of Mycobacterium strains include M. intracellulare (ATCC No. 13950) and M. tuberculosis (ATCC No. 27294).

Examples of Legionella strains include L. pneumophila (ATCC No. 33156). Attenuated Legionella strains include L. pneumophila mip mutant (Ott, FEMS Micro. Rev., 14:161-176(1994).

Examples of Rhodococcus strains include R. equi.

Examples of Pseudomonas strains include P. aeruginosa (ATCC No. 23267).

Examples of Helicobacter strains include H. mustelae (ATCC No. 43772).

Examples of Vibrio strains include Vibrio cholerae (ATCC No. 14035) and Vibrio cincinnatiensis (ATCC No. 35912). Attenuated strains include V. cholerae RSI virulence mutant (Taylor et al, J. Infect. Dis., 170:1518-1523 (1994)) and V. cholerae ctxA, ace, zot, cep mutant (Waldor et al, J. Infect. Dis., 170:278-283 (1994)).

Examples of Bacillus strains include Bacillus subtilis (ATCC No. 6051). Attenuated strains include B. anthracis mutant pX01 (Welkos et al, Micro. Pathol., 14:381-388 (1993)) and attenuated BCG strains (Stover et al, Nat., 351:456-460 (1991)).

Examples of Erysipelothrix strains include Erysipelothrix rhusiopathiae (ATCC No. 19414) and Erysipelothrix tonsillarum (ATCC No. 43339). Attenuated strains include E. rhusiopathiae Kg-1a and Kg-2 (Watarai et al, J. Vet. Med. Sci., 55:595-600 (1993) and E. rhusiopathiae ORVAC mutant (Markowska-Daniel et al, Int. J. Med. Microb. Virol. Parisit. Infect. Dis., 277:547-553 (1992)).

Antigens

Any HSV antigen may be delivered. Antigens may be derived from any strain of either serotype (HSV-1 or HSV-2) of HSV. Preferred HSV antigens include glycoprotein D, glycoprotein H, glycoprotein B and ICP27. Any suitable antigenic protein may be used, and such antigenic proteins may be structural or non-structural in nature.

According to the invention, vaccination may thus be achieved against any HSV strain. Generally, vaccination against HSV strains that are medically problematical to humans will be most desirable. However, veterinary aspects are also of interest. Thus, vaccination of animals against HSV strains that infect them is also an aspect of the invention. Vaccination of mammals is preferred in this context. Livestock animals, including bovine, ovine, suine and equine livestock such as cows, sheep, goats, pigs and horses is desirable, as is vaccination of companion animals such as cats and dogs. Vaccination of avian hosts, i.e. birds, is also preferred. Poultry species of birds, e.g. chickens, turkeys, ducks, geese and pheasants are especially preferred for vaccination in this context.

Typically, a full-length HSV antigen having the sequence of the naturally occurring antigen will be used. However, modified antigens can also be used. For example, fragments of naturally occurring antigens can be used, as can mutants having a slightly different amino acid sequence. Such modified antigens can be prepared by any means known in the art, typically recombinant means, for example site-directed mutagenesis. Modified, e.g. mutated and truncated antigens, are considered to be HSV antigens in the context of the invention. Such modified antigens can be used if they retain a sufficient degree of antigenicity, e.g. if they have a degree of antigenicity equivalent to the full-length antigen. Preferably, if a modified antigen has a lower degree of antigenicity than the naturally occurring antigen, it will still have a high enough degree to ensure that a prophylactic effect sufficient to ensure complete viral clearance from the subject's mucosae is conferred. However, the invention also encompasses the use of modified antigens that achieve lesser degrees of clearance.

In this context, a vaccine of the invention may secure any statistically significant degree of viral clearance, e.g. from the genital tract, for example up to 99%, up to 95%, up to 90%, up to 80%, up to 70%, up to 50%, up to 20% or up to 10%. As discussed in more detail below, this may be measured by reference to viral titers in vaccinated and non-vaccinated subjects or titers before and after vaccination in a single subject in some cases. Where a lesser degree of clearance is achieved, it may be desirable to use an alternative anti-HSV treatment in combination with the treatment of the invention.

Expression of Antigens

According to the invenion, HSV antigens are expressed, by any suitable mechanism, in eukaryotic cells of the host, which is the first step in the route to vaccination against HSV-mediated disease. Coding sequences encoding HSV antigens are delivered to the cells by means of an attenuated or non-pathogenic but invasive bacterium as discussed herein. Within the bacterium, the coding sequence is typically operably linked to regulatory sequences capable of securing the expression in the target host cell. In principle, however, the coding sequence can be integrated into the host cell genome such that expression is driven by host regulatory sequences.

Thus, the coding sequence is typically operably linked to a promoter capable of driving expression in the host cell. Typically, this would be a eukaryotic promoter, though it could be any promoter capable of securing expression. For example, instead of a promoter derived from a eukaryotic organism, it could be a promoter derived from a virus which infects eukaryotic cells.

Any promoter capable of securing expression in the host cell may be used. Suitable promoters include the SV40, CMV and retroviral LTR promoters, as well as HEF 1α and PDGF promoters.

In general, the coding sequence will be comprised within an expression construct. Such constructs typically comprise: a promoter (see above) capable of directing the expression of the coding sequence of the invention, and optionally a regulator of the promoter, a translational start codon, and, operably linked to the promoter, a coding sequence according to the invention. Preferably, these components are arranged in a 5′-3′ orientaion.

The construct may also comprise any other suitable components. For example, the construct may comprise a nucleic acid encoding a signal sequence, so positioned in such a position relative to the coding sequence such that, when it is translated, it is capable of directing the expressed protein to a given cell type or cell compartment. Any such signal sequence will typically be positioned immediately 3′ or immediately 5′ to the coding sequence, such that the signal sequence and coding sequence are translated as a single fusion protein, with the signal sequence at the C- or N-terminus.

The construct may also comprise an enhancer which enhances the degree of expression provided by the promoter. Any enhancer which enhances the expression provided by the selected promoter may be used.

Optionally, the construct may comprise a transcriptional terminator 3′ to the coding sequence. Any suitable terminator may be used.

Optionally, the construct may comprise a polyadenylation signal operably linked 3′ to the coding sequence.

Optionally, the construct may comprise one or more selectable marker genes, e.g. antibiotic resistance genes, to allow selection of transformed cells in culture. For example, cells may selected for antibiotic resistance.

Optionally, the construct may comprise one or more introns, or other non-coding sequences, for example 3′ or 5′ to the coding sequence. In the context of the invention, these may be useful in checking that expression takes place in the eukaryotic cells of the host, not the bacterial ones of the delivery system.

Additional genetic elements may be included. Such elements include mammalian artificial chromosome elements or elements from the autonomous replicating circular minichromosomes, such as found in DiFi colorectal cancer cells, to allow stable non-integrated retention of the expression cassette (Huxley et al, Bio/Technology, 12:586-590 (1994); and Untawale et al, Canc. Res., 53:1630-1636 (1993)), integrase to direct integration of the expression cassette into the recipient cell's chromosome (Bushman, Proc. Natl. Acad. Sci., USA, 91:9233-9237 (1994), the inverted repeats from adeno-associated virus to promote non-homologous integration into the recipient cells chromosome (Goodman et al, Blood, 84:1492-1500 (1994), recA or a restriction enzyme to promote homologous recombination (WO9322443 (1993); and WO9323534-A (1993)) or elements that direct nuclear targeting of the eukaryotic expression cassette (Hodgson, supra; and Lewin, supra).

Typically, the expression construct will be comprised within a vector, preferably for example a plasmid vector.

According to the invention, it is not necessary to introduce an antimicrobial agent to lyse the bacterium. This is a distinction between the methods of the present invention and those of WO 98/44131 (Walter Reed, supra) where the antigen-encoding DNA cannot be released except by lysing the bacteria with an antimicrobial agent introduced for that purpose.

HSV-mediated Disease

Any HSV-mediated disease can be treated according to the invention. HSV-1-mediated diseases may be treated, as may HSV-2-mediated diseases. In particular, dental herpes, oral/facial infections (e.g. gingivostomatitis, labialis, pharyngitis), cutaneous infections, (e.g. whitlow, herpes gladatorium), ocular infections, neonatal herpes, herpes encephalitis, disseminated infection and erythema multiforme. Treatment of genital herpes is particularly preferred. As discussed herein, both human and animal HSV-mediated disease can be treated and prevented according to the invention.

As discussed above, the present invention is principally concerned with prophylactic vaccines, which is to say vaccines that prevent infection from taking place. Preferably, complete prevention is achieved, as measured by complete clearance of HSV from a subject, typically measured at a mucosal surface of the subject, e.g. the vaginal tract, after challenge with HSV. As a specific test, clearance from the vaginal tract after intravaginal challenge with 5×10⁶PFU of HSV may be measured by determining viral titers before and after challenge or in vaccinated and non-vaccinated subjects. Preferably, complete clearance is achieved. However, vaccines that achieve a lesser degree of clearance are also within the scope of the invention. A vaccine of the invention may achieve any statistically significant degree of clearance, for example up to 99%, 95%, 90%, 80%, 70%, 50% and 20% clearance. Where lesser degrees of clearance are achieved, it may be desirable to combine vaccination according to the present invention with another type of vaccination or treatment.

In the context of prophylactic vaccines, clearance will typically be measured by comparing the degree of viral clearance in vaccinated and non-vaccinated subjects. This can be measured by comparing viral titers in the two types of subject Viral titers can be measured by any suitable means, e.g. as described in the Examples or by any other known method.

Although the present invention is principally concerned with prophylactic vaccines, the invention can also be applied to the design of therapeutic vaccines as appropriate. Thus, both prophylactic and therapeutic vaccines are provided.

In the context of therapeutic vaccines, efficacy will typically be measured in a similar manner to that described above for prophylactic vaccines, i.e. by measuring the degree of viral clearance achieved by measuring viral titers in subjects. However, the comparison will typically be between the viral titers in a single subject at different times, i.e. before and after administration of the vaccine.

As discussed above, the vaccines of the invention will typically act by eliciting cellular immunity, specifically cellular mucosal immunity. Such immunity may arise at any or all the body's mucosal surfaces, most preferably the genital mucosae.

Pharmaceutical Formulations, Routes of Delivery and Dosages

Typically, a vaccine of the invention will contain bacteria of the invention in combination with a pharmaceutically acceptable carrier or diluent.

Examples of diluents include a phosphate buffered saline, buffer for buffering against gastric acid in the stomach, such as citrate buffer containing sucrose, bicarbonate buffer alone (Levine et al, J. Clin. Invest., 79:888-902 (1987); and Black et al, J. Infect. Dis., 155:1260-1265 (1987), or bicarbonate buffer containing ascorbic acid, lactose, and optionally aspartame (Levine et al, Lancet, II:467-470 (1988)). Examples of carriers include proteins, e.g., as found in skim milk, sugars, e.g. sucrose, or polyvinylpyrrolidone. Typically these carriers would be used at a concentration of about 0.1-90% (w/v) but preferably at a range of 1-10% (w/v).

Vaccines of the invention may be administered by any suitable route and will be formulated accordingly. Preferably, delivery will be to a mucosal surface, most preferably a genital mucosal (e.g. vaginal) surface. Another preferred route of delivery is oral delivery. Alternatively, intrarectal or intranasal delivery may be used as may delivery to the respiratory tract, in which case the vaccine may be formulated as respiratory spray.

The amount of the live invasive bacteria of the present invention to be administered will vary depending on the species of the subject, as well as the disease or condition that is being treated. Generally, the dosage employed will be about 10³to 10¹¹viable organisms, preferably about 10⁵to 10⁹viable organisms, e.g. about 10⁶, 10⁷or 10⁸. For Samonella, doses will typically be in the range of 10⁵to 10¹¹viable organisms. Lower doses may be possible with other microorganisms that are naturally invasive or are engineered to be invasive.

Combination Treatments

This efficacy of a vaccine of the invention may be enhanced by the use of stimulatory agents capable of stimulating cellular immunity, preferably cellular mucosal immunity. These may be co-administered with the vaccine, for example, as part of the vaccine (by the same means of delivery), or at the same time as the vaccine but by a different means of delivery. Alternatively, the stimulatory agent may be administered at a different time, but close enough in time to the administration of the vaccine to have a combined prophylactic or therapeutic effect. Thus, the vaccine and the stimulatory agent may be administered simultaneously, sequentially or separately.

Any agent capable of stimulatory cellular immunity may be used. Cytokines having this property are one option. GMCSF (granulocyte macrophage colony stimulating factor) is preferred, as is Interleukin-12 (IL-12).

Interleukin-14 (IL-14) can also be used, to stimulate other types of immune response, in combination with the treatments of the invention.

Additionally, treatments of the invention may be combined with any other type of treatment for HSV infection, e.g. other prophylactic or therapeutic treatments.

Vaccination Against Viral Diseases in General

Although the principal object of this invention is to combat HSV-mediated disease, the teachings of the invention can also be applied to combat infection by other viruses that infect the mucosae of human and/or animal hosts. All of the foregoing discussion relating to HSV vaccines applies equally to vaccines according to this aspect of the invention.

According to this aspect of the invention, any viral infection that may be treated or prevented by stimulating cellular mucosal immunity by the methods described herein may be combatted by therapeutic or prophylactic vaccination. In this context, some preferred viral infections that may be combatted are, in addition to HSV as described above, infections by Human Immunodeficiency virus (HIV). Hepatitis C virus (HCV), Hepatitis B virus (HBV), Hepatitis A virus (HAV) and Human Papilloma virus (HPV).

Accordingly, this aspect of the invention provides:

A vaccine against a virus which infects the mucosae of a human or animal host, which vaccine stimulates cellular mucosal immunity and comprises a bacterium which is invasive but attenuated or non-pathogenic in respect of said human or animal host and comprises a coding sequence encoding an antigen from said virus in a form that enables said coding sequence to be transferred to a host cell of said human or animal host and to be expressed in said cell to form said antigen.

This aspect of the invenion also provides:

Use of a bacterium of this aspect of the invention, in the manufacture of a vaccine for the treatment or prevention of a viral infection of the mucosae of a human or animal host by stimulating cellular mucosal immunity against the virus.

This aspect of the invenion also provides:

A method of treating or preventing a viral infection of the mucosae a human or animal host by stimulating cellular mucosal immunity against said virus, said method comprising administering to said host an effective amount of a vaccine comprising an invasive but attenuated or non-pathogenic bacterium comprising a coding sequence encoding an antigen from said virus in a form that enables said coding sequence to be transferred to a host cell of a human or animal host which the bacterium is capable of invading and to be expressed in said cell to form said antigen.

This aspect of the invenion also provides:

A pharmaceutical composition for vaccination against a viral infection of the mucosae a human or animal host by stimulating cellular mucosal immunity against said virus which composition comprises a vaccine of this aspect of the invention.

Claim 1 of 24 Claims

1. A method of generating an immune response to a herpes simplex virus (HSV) in a human or animal host, said method comprising:

(a) providing an immunogenic compositions; wherein said composition is comprised of an invasive but attenuated or non-pathogenic bacterium selected from the group consisting of Salmonella, Shigella, Listeria and E. coli bacteria; said bacterium is comprised of a coding sequence encoding a herpes simplex virus (HSV) antigen selected from the group consisting of glycoprotein D, glycoprotein H, glycoprotein B and ICP27; and said coding sequence is comprised within an expression construct and operably linked to one or more regulatory sequences and

(b) administering said composition to said host such that said bacterium invades a host cell of said host selected from the group consisting of macrophages and dendritic cells and said expression construct is transferred to said host cell where said regulatory sequences direct expression of said coding sequence, and said HSV antigen is transcribed and translated in said host cell without introduction of an antimicrobial agent to lyse the bacterium to generate said immune response against HSV.

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