Title:  Molecular clones with mutated HIV gag/pol, SIV gag and SIV env genes

United States Patent:  6,656,706

Issued:  December 2, 2003

Inventors:  Pavlakis; George N. (Rockville, MD)

Assignee:  The United States of America as represented by the Department of Health and (Washington, DC)

Appl. No.:  872733

Filed:  June 1, 2001

Abstract

Nucleic acid constructs containing HIV-1 gag/pol and SIV gag or SIV env genes which have been mutated to remove or reduce inhibitory/instability sequences are disclosed. Viral particles and host cells containing these constructs and/or viral particles are also disclosed. The exemplified constructs and viral particles of the invention may be useful in gene therapy for numerous disorders, including HIV infection, or as a vaccine for HIV-1 immunotherapy and immunoprophylaxis.

MODES FOR CARRYING OUT THE INVENTION

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention, as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention.

One aspect of the invention comprises vectors that encode the Gag and/or Pol of HIV-1 in a Rev-independent manner. An example of such a vector which is described herein is the plasmid pCMVgagpolBNkan, which encodes the complete Gag and Pol of HIV-1 in a Rev-independent manner, and also contains a gene conferring kanamycin resistance. This plasmid is Tat and Rev-independent and was generated by eliminating the inhibitory/instability sequences present in the gag/pol mRNA without altering the amino acid sequence of the proteins coded by the genes.

The gag/pol clone of the invention is a DNA construct of the gag/pol region of HIV which has had the inhibitory/instability regions removed. The construct is expected to be useful as a component a new type of lentivirus vector for use in gene therapy or as a vaccine.

The gag, pol or gag/pol sequences of the invention can be highly expressed in human and other mammalian cells in the absence of any other regulatory and structural protein of HIV, including Rev. When the gag/pol sequences are combined with a sequence encoding an envelope protein, such as the VSV G protein or the HIV envelope protein (e.g., in the same vector or in another expression vector), infectious virus is produced after transfection into human cells. When a gene encoding a non-HIV envelope protein is used, for example, in the presence of the HIV gag/pol gene, the virus particles produced would contains only the HIV proteins Gag and Pol.

Lentiviral vectors or vector systems based on the gag, pol or gag/pol sequences of this invention, as exemplified by the Rev-independent pCMVgagpol BNkan construct described herein, may be used for gene therapy in vivo (e.g., parenteral inoculation of high titer vector) or ex vivo (e.g., in vitro transduction of patient's cells followed by reinfusion into the patient of the transduced cells). These procedures are been already used in different approved gene therapy protocols.

The HIV gag/pol clone and SIV gag clone of the invention were made using the method for eliminating inhibitory/instability regions from a gene as described in U.S. Pat. No. 6,174,666, and also in related U.S. Pat. Nos. 5,972,596 and 5,965,726, which are incorporated by reference herein. This method does not require the identification of the exact location or knowledge of the mechanism of function of the INS. Generally, the mutations are such that the amino acid sequence encoded by the mRNA is unchanged, although conservative and non-conservative amino acid substitutions are also envisioned where the protein encoded by the mutated gene is substantially similar to the protein encoded by the non-mutated gene. The mutated genes can be synthetic (e.g., synthesized by chemical synthesis), semi-synthetic (e.g., a combination of genomic DNA, cDNA, or PCR amplified DNA and synthetic DNA), or recombinantly produced. The genes also may optionally not contain introns. The nucleic acids of the invention may also contain Rev-independent fragments of these genes which retain the desired function (e.g., for antigenicity of Gag or Pol, particle formation (Gag) or enzymatic activity (Pol)), or they may also contain Rev-independent variants which have been mutated so that the encoded protein loses a function that is unwanted in certain circumstances. In the latter case, for example, the gene may be modified to encode mutations (at the amino acid level) in the active site of reverse transcriptase or integrase proteins to prevent reverse transcription or integration. Rev-independent fragments of the gag gene are described in U.S. patent application Ser. No. 07/858,747, filed Mar. 27, 1992, and also in related U.S. Pat. Nos. 5,972,596 and 5,965,726, which are incorporated by reference herein.

In addition to being capable of producing HIV Gag and Pol proteins in the absence of Rev regulatory protein in a cell in vivo, the HIV gag/pol clone and SIV gag clone of the invention are also capable of producing HIV Gag and Pol proteins in the absence of any added cis acting transport element, such as CTE or CTE-like elements (collectively referred herein as RNA Transport Elements (RTE)). Experiments indicate that the mutated vectors of the invention for SIV gag are far superior to those adding CTE (see Qiu et al., J. Virol. 73:9145-52 (1999)).

The expression of the proteins encoded by these vectors after transfection into human cells may be monitored at both the level of RNA and protein production. RNA levels are quantitated by methods known in the art, e.g., Northern blots, S1 mapping or PCR methods. Protein levels may also be quantitated by methods known in the art, e.g., western blot or ELISA or fluorescent detection methods. A fast non-radioactive ELISA protocol can be used to detect gag protein (DUPONT or COULTER gag antigen capture assay).

At least three types of lentiviral vectors based on the gag/pol genes of the invention for use in gene therapy and/or as a vaccine are envisioned, i.e., lentiviral vectors having

a) no round of replication (i.e., a zero replication system)

b) one round of replication

c) a fully replicating system

For a system with no round of replication, a gag/pol gene, or separate gag and pol genes, or fragments of these genes, expressed using appropriate transcription units, e.g., a CMV promoter and a BGH poly (A) site. This will allow expression of the gag/pol unit (or gag or pol or fragment(s) thereof) for vaccine purposes. This expression can be accomplished without the production of any functional retroviral enzymes, provided that the appropriate mutation(s), e.g., a missense mutation, are introduced. In a zero replication system, a virus stock will be administered to the cells or animals of interest. For example, if one creates and uses a virus stock with the exemplified system using the packaging vector PCMVgagpolBNkan, the transfer construct pmBCwCNluci or pmBCmCNluci, and the envelope containing vector pHCMV-G, one obtains a zero replication system. The virus particles produced by such system can infect cells, and the reverse transcribed transfer construct DNA will go into the nucleus but, because the coding regions for viral structural proteins are not present, there will be no virus expression and replication (0 rounds). If one transfects cells in vivo with the same 3 DNAs, they will go to the nucleus, express viral proteins, make infectious virus particles and go out and infect another cell or cells (1 round). Since in vivo delivery of three plasmids may result in lower expression, at least two different embodiments are envisioned. In the first, two plasmids may be used, e.g., MV1 and an envelope expression plasmid such as pHCMV-G. Other plasmids encoding functional envelopes from HIV, SIV, or other retroviruses can also be used. Transfection by the two plasmids results in infectious virus that can infect and integrate into new cells (1 round). The infected cells produce gagpol but virus propagation is not possible in the absence of env.

For a system with one round of replication, at least two additional embodiments are envisioned. In the first method, a combination of the genes, e.g., a gag/pol gene, an env encoding gene and, preferably, a gene encoding a reporter protein or other polynucleotide or protein of interest, are delivered into the cells of interest in vivo. As discussed above for the exemplified system, if one transfects cells in vivo with the same 3 DNAs, they will go to the nucleus, express viral proteins, make infectious virus particles, be released and infect another cell or cells (1 round).

In another embodiment, the same result (i.e., only one round of replication) can be obtained by using transfer vectors that have deletions in the 3' LTR and in which a heterologous-promoter (e.g., the CMV-promoter, or inducible promoter, or tissue-specific promoter), is used in place of the `3` LTR promoter. The mutations in the 3' LTR making it inactive upon reverse transcription and integration. This is because the integrated provirus derives both its 5' LTR and its 3' LTR from the 3' LTR of the starting (transfer) construct. (This is a well-known property of all retroviruses and has been used to make self-inactivating vectors (SIN)). There are several reasons one may want to inactivate the incoming LTR promoter, one of which is to use a different tissue specific or regulated promoter for expression of a gene of interest in the integrated provirus. Note that, with SIN vectors, if one uses a viral stock made in vitro after transfection into cells and collection of infectious virus, there will be no round of replication. If one transfects cells with the DNAs in vivo, there will be one round of replication. If functional gag, pol, or env are not included in the DNA mix, there will not be any infection at all (i.e., infectious viruses will not be made).

A fully replicating Rev-independent system has not been constructed yet, although it is expected that a functional system can be constructed using Rev-independent gag/pol and env sequences. If desired, extra posttranscriptional control elements such as the CTE element, which can replace Rev and give infectious virus (see e.g., Zolotukhin et al., J. Virol.68:944-7952 (1994)) are included. The fully replicating system should be in one piece, containing the LTR, packaging signal, gag/pol, splice site, env, tat, one or more CTE or CTE-like elements (if desired for optimal results), and LTR. Tat is thought to be required in this construct, at least in non-permissive cells. Such a system is depicted in FIG. 5, (construct MV2). In this system, a cell or animal of interest (preferably human) would be infected with virus stock that then propagates. CTE or CTE-like elements (depicted in construct MV2 as RTE (RNA Transport Elements)) are desirable since they have been shown to improve expression, and since many retroviruses require the presence of posttranscriptional control elements. There are several types of CTE and CTE-like elements, and these elements appear to work via a different pathway from the Rev-RRE pathway. See, e.g., Tabernero et al., J. Virol. 71:95-101 (1997). See also, Pavlakis and Nappi, PCT/US99/11082, filed May 22, 1999, published as WO 99/61596 on Dec. 2, 1999 (and incorporated herein by reference), which describes a new type of post-transcriptional control element that is able to replace CTE and HIV RRE/Rev. The Pavlakis-Nappi element does not work in the same way as CTE and does not have any sequence or structure homology.

In a preferred embodiment, a lentiviral system of the invention comprises the following three components:

1. a packaging vector containing nucleic acid sequences encoding the elements necessary for vector packaging such as structural proteins (except for HIV env) and the enzymes required to generate vector particles, the packaging vector comprising at least a mutated HIV or SIV gag/pol gene of the invention;

2. a transfer vector containing genetic cis-acting sequences necessary for the vector to infect the target cell and for transfer of the therapeutic or reporter or other gene(s) of interest, the transfer vector comprising the encapsidation signal and the gene(s) of interest or a cloning site for inserting the gene(s) of interest; and

3. a vector containing sequences encoding an element necessary for targeting the viral particle to the intended recipient cell, preferably the gene encoding the G glycoprotein of the vesicular stomatis virus (VSV-G) or amphotrophic MuLV or lentiviral envs.

Using the CMV promoter or other strong, high efficiency, promoter instead of the HIV-1 LTR promoter in the packaging vector, high expression of gag, pol or gag/pol can be achieved in the total absence of any other viral protein. The exchange of the HIV-1 LTR promoter with other promoters is beneficial in the packaging vector or other vectors if constitutive expression is desirable and also for expression in other mammalian cells, such as mouse cells, in which the HIV-1 promoter is weak. Vectors containing the sequences of the invention can be used for the Rev independent production of HIV-1 Gag/Pol, HIV-1 Gag, HIV-1 Pol, and SIV Gag proteins. In certain embodiments, the presence of heterologous promoters will also be desired in the transfer vector and the envelope encoding vector, when such vectors are used.

The gene(s) of interest are chosen according to the effect sought to be achieved. For gene therapy purposes there will be at least one therapeutic gene encoding a gene product which is active against the condition it is desired to treat or prevent. Alternatively or additionally, there may be a gene which acts as a marker by encoding a detectable product. Therapeutic genes may encode, for example, an anti-sense RNA, a ribozyme, a transdominant negative mutant of a target protein, a toxin, a conditional toxin, an antigen that induces antibodies or helper T-cells or cytotoxic T-cells, a single chain antibody or a tumor suppresser protein. See, e.g., WO 98/17816.

An even more extensive list of genes of interest for use in lentiviral vectors is described, e.g., in WO 99/04026 on page 10, line 20 to page 12, line 7. Table 2 of Klimatcheva et al. (1999) also provides a list of disorders and target cells for gene therapy, as well as a number of lentiviral vectors used by others. This list includes genetic/metabolic deficiencies, viral infection and cancer. Inherited genetic defects such as adenosine deaminase deficiency, familial hypercholesterolemia, cystic fibrosis, mucopolysaccharidosis type VII, types I and II diabetes, classical phenylketonuria and Gaucher disease are diseases which are listed as being possible to overcome by lentiviral vector-mediated gene therapy because they constitute single-gene deficiencies for which the involved genes are known. Viral diseases are also listed as constituting appropriate targets for lentiviral gene delivery. In particular, a number of gene therapy approaches have been proposed for the treatment of HIV infection and, for some of these strategies, phase I studies have recently begun in humans. The article states that preliminary studies have dealt with defective murine oncoviruses for delivery of anti-sense RNAs, ribozymes and trans-dominant proteins against HIV replication.

In any of the vectors, but preferably in the transfer vector, an inserted gene could have an internal ribosomal entry site (IRES), e.g., from picornaviral RNA. An IRES will be used in circumstances that one wants to express two proteins from the same promoter. For example one protein of interest and a marker gene, e.g., green fluorescent protein (GFP) or a marker gene and a drug resistance gene (e.g. the firefly luciferase gene and neomycin phosphotransferase gene) as described on p. 58 of WO 99/04026, for example. Using an IRES the expression of the two proteins is coordinated. A further gene or genes may also be present under the control of a separate promoter. Such a gene may encode for example a selectable marker, or a further therapeutic agent which may be among the therapeutic agents listed above. Expression of this gene may be constitutive; in the case of a selectable marker this may be useful for selecting successfully transfected packaging cells, or packaging cells which are producing particularly high titers of the retroviral vector particles. Alternatively or additionally, the selectable marker may be useful for selecting cells which have been successfully infected with the lentiviral vector and have the provirus integrated into their own genome.

One way of performing gene therapy is to extract cells from a patient, infect the extracted cells with a lentiviral vector and reintroduce the cells back into the patient. A selectable marker may be used to provide a means for enriching for infected or transduced cells or positively selecting for only those cells which have been infected or transduced, before reintroducing the cells into the patient. This procedure may increase the chances of success of the therapy. Selectable markers may be for instance drug resistance genes, metabolic enzyme genes, or any other selectable markers known in the art. Typical selection genes encode proteins that confer resistance to antibiotics and other toxic substances, e.g., histidinol, puromycin, hygromycin, neomycin, methotrexate etc. and cell surface markers.

However, it will be evident that for many gene therapy applications of lentiviral vectors, selection for expression of a marker gene may not be possible or necessary. Indeed expression of a selection marker, while convenient for in vitro studies, could be deleterious in vivo because of the inappropriate induction of cytotoxic T lymphocytes (CTLs) directed against the foreign marker protein. Also, it is possible that for in vivo applications, vectors without any internal promoters will be preferable. The presence of internal promoters can affect for example the transduction titres obtainable from a packaging cell line and the stability of the integrated vector. Thus, single transcription unit vectors, which may be bi-cistronic or poly-cistronic, coding for one or two or more therapeutic genes, may be the preferred vector designed for use in vivo. See, e.g., WO 98/17816.

Suitable host or producer cells for use in the invention are well known in the art. May lentiviruses have already been split into replication defective genomes and packaging components. For those which have not the technology is available for doing so. The producer cell encodes the viral components not encoded by the vector genome such as the Gag, Pol and Env proteins. The gag, pol and env genes may be introduced into the producer cell transiently, or may be stably integrated into the cell genome to give a packaging cell line. The lentiviral vector genome is then introduced into the packaging cell line by transfection or transduction to create a stable cell line that has all of the DNA sequences required to produce a lentiviral vector particle. Another approach is to introduce the different DNA sequences that are required to produce lentiviral vector particle, e.g., the env coding constrict, the gag-pol coding construct and the transfer construct into the cell simultaneously by transient triple transfection.

Target cells identified by Klimatcheva et al. (1999), and the references cited therein, include airway epithelial cells for cystic fibrosis; retinal photoreceptor cells for retinitis pigmentosa; progenitors for red blood cells, macrophages, and lymphocytes for hematopoietic disorders, sickle cell anemia, .beta.-thalassemia, lysosomal storage disorders, mucopolysaccharidoses, and severe combined immunodeficiency syndrome; bone marrow cells and macrophages for Gaucher's disease; liver cells for familial hypercholesterolaemia; T-lymphocytes and macrophages for HIV infection; brain tissue, neurons, and glial cells for neurodegenerative diseases such as Parkinson's and Alzheimer's diseases; endothelial cells and cardiac myocytes for cardiovascular diseases; and cancer cells in various tissues (e.g. liver or brain) for cancer. Target cells for other diseases would be apparent to one of skill in the art.

Vaccines and pharmaceutical compositions comprising at least one of the nucleic acid sequences, vectors, vector systems, or transduced or transfected host cells of the invention and a physiologically acceptable carrier are also part of the invention.

As used herein, the term "transduction" generally refers to the transfer of genetic material into the host via infection, e.g., in this case by the lentiviral vector. The term "transfection" generally refers to the transfer of isolated genetic material into cells via the use of specific transfection agents (e.g., calcium phosphate, DEAE Dextran, lipid formulations, gold particles, and other microparticles) that cross the cytoplasmic membrane and deliver some of the genetic material into the cell nucleus.

Systems similar to those described herein can be produced using elements of lentiviruses in addition to the HIV and/or SIV genes described herein.

Pharmaceutical Compositions

The pharmaceutical compositions of the invention contain a pharmaceutically and/or therapeutically effective amount of at least one nucleic acid construct, vector, vector system, viral particle/virus stock, or host cell (i.e., agents) of the invention. In one embodiment of the invention, the effective amount of an agent of the invention per unit dose is an amount sufficient to cause the detectable expression of the gene of interest. In another embodiment of the invention, the effective amount of agent per unit dose is an amount sufficient to prevent, treat or protect against deleterious effects (including severity, duration, or extent of symptoms) of the condition being treated. The effective amount of agent per unit dose depends, among other things, on the species of mammal inoculated, the body weight of the mammal and the chosen inoculation regimen, as is well known in the art. The dosage of the therapeutic agents which will be most suitable for prophylaxis or treatment will also vary with the form of administration, the particular agent chosen and the physiological characteristics of the particular patient under treatment. The dose is administered at least once. Subsequent doses may be administered as indicated.

To monitor the response of individuals administered the compositions of the invention, mRNA or protein expression levels may be determined. In many instances it will be sufficient to assess the expression level in serum or plasma obtained from such an individual. Decisions as to whether to administer another dose or to change the amount of the composition administered to the individual may be at least partially based on the expression levels.

The term "unit dose" as it pertains to the inocula refers to physically discrete units suitable as unitary dosages for mammals, each unit containing a predetermined quantity of active material (e.g., nucleic acid, virus stock or host cell) calculated to produce the desired effect in association with the required diluent. The titers of the virus stocks to be administered to a cell or animal will depend on the application and on type of delivery (e.g., in vivo or ex vivo). The virus stocks can be concentrated using methods such as centrifugation. The titers to be administered ex vivo are preferably in the range of 0.001 to 1 infectious unit/cell. Another method of generating viral stocks is to cocultivate stable cell lines expressing the virus with the target cells. This method has been used to achieve better results when using traditional retroviral vectors because the cells can be infected over a longer period of time and they have the chance to be infected with multiple copies of the vector.

For in vivo administration of nucleic acid constructs, vectors, vector systems, virus stocks, or cells which have been transduced or transfected ex vivo, the dose is to be determined by dose escalation, with the upper dose being limited by the onset of unacceptable adverse effects. Preliminary starting doses may be extrapolated from experiments using lentiviral vectors in animal models, by methods known in the art, or may be extrapolated from comparisons with known retroviral (e.g., adenoviral) doses. Generally, small dosages will be used initially and, if necessary, will be increased by small increments until the optimum effect under the circumstances is reached. Exemplary dosages are within the range of 10⁸ up to approximately 5x10¹⁵ particles.

Inocula are typically prepared as a solution in a physiologically acceptable carrier such as saline, phosphate-buffered saline and the like to form an aqueous pharmaceutical composition.

The agents of the invention are generally administered with a physiologically acceptable carrier or vehicle therefor. A physiologically acceptable carrier is one that does not cause an adverse physical reaction upon administration and one in which the nucleic acids are sufficiently soluble to retain their activity to deliver a pharmaceutically or therapeutically effective amount of the compound. The pharmaceutically or therapeutically effective amount and method of administration of an agent of the invention may vary based on the individual patient, the indication being treated and other criteria evident to one of ordinary skill in the art. A therapeutically effective amount of a nucleic acid of the invention is one sufficient to prevent, or attenuate the severity, extent or duration of the deleterious effects of the condition being treated without causing significant adverse side effects. The route(s) of administration useful in a particular application are apparent to one or ordinary skill in the art.

Routes of administration of the agents of the invention include, but are not limited to, parenteral, and direct injection into an affected site. Parenteral routes of administration include but are not limited to intravenous, intramuscular, intraperitoneal and subcutaneous. The route of administration of the agents of the invention is typically parenteral and is preferably into the bone marrow, into the CSF intramuscular, subcutaneous, intradermal, intraocular, intracranial, intranasal, and the like. See, e.g., WO 99/04026 for examples of formulations and routes of administration.

The present invention includes compositions of the agents described above, suitable for parenteral administration including, but not limited to, pharmaceutically acceptable sterile isotonic solutions. Such solutions include, but are not limited to, saline and phosphate buffered saline for nasal, intravenous, intramuscular, intraperitoneal, subcutaneous or direct injection into a joint or other area.

In providing the agents of the present invention to a recipient mammal, preferably a human, the dosage administered will vary depending upon such factors as the mammal's age, weight, height, sex, general medical condition, previous medical history and the like.

The administration of the pharmaceutical compositions of the invention may be for either "prophylactic" or "therapeutic" purpose. When provided prophylactically, the compositions are provided in advance of any symptom. The prophylactic administration of the composition serves to prevent or ameliorate any subsequent deleterious effects (including severity, duration, or extent of symptoms) of the condition being treated. When provided therapeutically, the composition is provided at (or shortly after) the onset of a symptom of the condition being treated.

For all therapeutic, prophylactic and diagnostic uses, one or more of the agents of the invention, as well as antibodies and other necessary reagents and appropriate devices and accessories, may be provided in kit form so as to be readily available and easily used.

Where immunoassays are involved, such kits may contain a solid support, such as a membrane (e.g., nitrocellulose), a bead, sphere, test tube, rod, and so forth, to which a receptor such as an antibody specific for the target molecule will bind. Such kits can also include a second receptor, such as a labeled antibody. Such kits can be used for sandwich assays to detect toxins. Kits for competitive assays are also envisioned.

INDUSTRIAL APPLICABILITY

Mutated genes of this invention can be expressed in the native host cell or organism or in a different cell or organism. The mutated genes can be introduced into a vector such as a plasmid, cosmid, phage, virus or mini-chromosome and inserted into a host cell or organism by methods well known in the art. In general, the mutated genes or constructs containing these mutated genes can be utilized in any cell, either eukaryotic or prokaryotic, including mammalian cells (e.g., human (e.g., HeLa), monkey (e.g., Cos), rabbit (e.g., rabbit reticulocytes), rat, hamster (e.g., CHO and baby hamster kidney cells) or mouse cells (e.g., L cells), plant cells, yeast cells, insect cells or bacterial cells (e.g., E. coli. The vectors which can be utilized to clone and/or express these mutated genes are the vectors which are capable of replicating and/or expressing the mutated genes in the host cell in which the mutated genes are desired to be replicated and/or expressed. See, e.g., F. Ausubel et al., Current Protocols in Molecular Biology, Greene Publishing Associates and Wiley-Interscience (1992) and Sambrook et al. (1989) for examples of appropriate vectors for various types of host cells. The native promoters for such genes can be replaced with strong promoters compatible with the host into which the gene is inserted. These promoters may be inducible. The host cells containing these mutated genes can be used to express large amounts of the protein useful in enzyme preparations, pharmaceuticals, diagnostic reagents, vaccines and therapeutics.

Mutated genes or constructs containing the mutated genes may also be used for in-vivo or in-vitro gene therapy. For example, a mutated gene of the invention will produce an mRNA in situ to ultimately increase the amount of protein expressed. Such gene include viral genes and/or cellular genes. Such a mutated gene is expected to be useful, for example, in the development of a vaccine and/or genetic therapy.

The constructs and/or proteins made by using constructs encoding the mutated gag, env, and pol genes could be used, for example, in the production of diagnostic reagents, vaccines and therapies for AIDS and AIDS related diseases. The inhibitory/instability elements in the HIV-1 gag gene may be involved in the establishment of a state of low virus production in the host. HIV-1 and the other lentiviruses cause chronic active infections that are not cleared by the immune system. It is possible that complete removal of the inhibitory/instability sequence elements from the lentiviral genome would result in constitutive expression. This could prevent the virus from establishing a latent infection and escaping immune system surveillance. The success in increasing expression of the entire gag/pol gene by eliminating the inhibitory sequence element suggests that one could produce lentiviruses without any negative elements. Such lentiviruses could provide a novel approach towards attenuated vaccines.

For example, vectors expressing high levels of Gag can be used in immunotherapy and immunoprophylaxis, after expression in humans. Such vectors include retroviral vectors and also include direct injection of DNA into muscle cells or other receptive cells, resulting in the efficient expression of gag, using the technology described, for example, in Wolff et al., Science 247:1465-1468 (1990), Wolff et al., Human Molecular Genetics 1(6):363-369 (1992) and Ulmer et al., Science 259:1745-1749 (1993). Further, the gag constructs could be used in transdominant inhibition of HIV expression after the introduction into humans. For this application, for example, appropriate vectors or DNA molecules expressing high levels of p55^gag or p37^gag would be modified to generate transdominant gag mutants, as described, for example, in Trono et al., Cell 59:113-120 (1989). The vectors would be introduced into humans, resulting in the inhibition of HIV production due to the combined mechanisms of gag transdominant inhibition and of immunostimulation by the produced gag protein. In addition, the gag constructs of the invention could be used in the generation of new retroviral vectors based on the expression of lentiviral gag proteins. Lentiviruses have unique characteristics that may allow the targeting and efficient infection of non-dividing cells. Similar applications are expected for vectors expressing high levels of env.

Identification of similar inhibitory/instability elements in SIV indicates that this virus is a convenient model to test these hypotheses. SIV similarly modified could be used in place of HIV in an effort to further minimize the possibility of rearrangement events that would lead to the generation of infectious HIV.

Claim 1 of 22 Claims

What is claimed is:

1. A nucleic acid construct comprising a HIV-1 gag/pol gene having the coding sequence of the gag/pol gene set forth in FIG. 1 (SEQUENCE ID NO: 1).

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