Compositions and methods for protecting animals from...

Drug – bio-affecting and body treating compositions – Whole live micro-organism – cell – or virus containing – Genetically modified micro-organism – cell – or virus

Reexamination Certificate

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C536S023100, C435S235100

Reexamination Certificate

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06764676

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed to a novel strain of feline immunodeficiency virus (FIV) and to a variety of mutated forms of this virus. Compositions and methods are disclosed that can be used in the protection of animals from lentiviral associated disease.
BACKGROUND OF THE INVENTION
Feline immunodeficiency virus (FIV) infection in cats results in a disease syndrome that is similar to that caused by human immunodeficiency virus-1 (HIV-1) infection in humans. Disease progression begins with a transient acute phase (8-10 weeks), followed by a prolonged asymptomatic phase (lasting from weeks to years) and a terminal symptomatic phase (Ishida et al., 1990, Jpn. J. Vet. Sci. 52:645-648). Viral load in plasma has been demonstrated to correlate with disease stage in infected cats and can be used to predict disease progression in accelerated FIV infection (Diehl et al., 1996, J. Virol. 70:2503-2507).
Structurally, the FIV provirus contains two long terminal repeats (LTRs), one at either end of the genome (Talbott et al., 1989, Proc. Nat'l Acad. Sci. USA 86:5743-5747). There are three large open reading frames (Gag (group antigens); Pol (polymerase); and ENV (envelope)) and three small open reading frames encoding regulatory proteins (Rev (regulator of expression of virion, a protein that binds to “RRE” elements present in all viral transcripts and promotes their translocation from the nucleus to the cytoplasm of infected host cells); Vif (virion infectivity factor); and ORF(2) (open reading frame 2)). The Gag precursor polypeptide of FIV is processed into three mature structural proteins: a matrix protein (MA), a capsid protein (CA), and a nucleocapsid protein (NC). The Pol gene encodes four enzymatic proteins: a protease (PR), a reverse transcriptase (RT), a deoxyuridine triphosphatase (DU), and an integrase (IN). Finally, the ENV precursor polypeptide is processed into two envelope proteins: a surface protein (SU) and a transmembrane (TM) protein.
There have been several attempts to develop a safe and effective vaccine to FIV. Matteucci found that cats inoculated with a conventional fixed cell vaccine were protected from challenge with homologous virus despite an apparent absence of neutralizing antibodies after vaccination. Protection was found to be short-lived and difficult to boost (Matteucci et al., 1996, J. Virol. 70:617-622; Matteucci et al., 1997, J. Virol. 71:8368-8376). These results may be contrasted with those of Verschoor, who observed no protection after the administration of a fixed cell vaccine (Verschoor et al., 1995, Vet. Immunol. Immunopathol. 46:139-149).
Another type of conventional vaccine that has been tested is comprised of whole, inactivated FIV virus. Yamamoto reported that greater than 90% of cats administered a vaccine of this type exhibited essentially complete protection against homologous challenge and slight protection against heterologous virus (Yamamoto et al., 1993, J. Virol. 67:601-605). Both humoral and cellular immunity against FIV were induced and a high level of anti-ENV, anti-core and virus neutralizing (VN) antibodies were observed in the vaccinated cats. In contrast, vaccination of cats with inactivated whole FIV incorporated into immune stimulating complexes (ISCOMs) failed to protect animals from homologous challenge (Hosie et al., 1992, Vet. Immunol. Immunopathol. 35:191-197).
Another approach to vaccine development has involved the use of subunit vaccines containing recombinant core protein, synthetic V3 peptides, and recombinant ENV protein (Elyar et al., 1997, Vaccine 15:1437-1444). Although significant levels of antibodies were induced by such vaccines, none were identified that could protect cats against homologous FIV challenge (Huisman et al., 1998, Vaccine 16:181-187; Flynn et al., 1997, J. Virol. 71:7586-7592; Tijhaar et al., 1997, Vaccine 15:587-596). The results suggest that it is likely to be difficult to obtain protective immunity against FIV using subunit type vaccines.
Recently, Cuisinier reported on tests conducted on a DNA vaccine for FIV (Cuisinier et al., 1997, Vaccine 15:1085-1094). Cats were vaccinated with a plasmid carrying FIV structural genes, including ENV and p10. Although strong humoral immune responses were observed, all cats eventually succumbed to homologous challenge.
SUMMARY OF THE INVENTION
The present invention is based, in part, upon the isolation and characterization of a new strain of feline immunodeficiency virus, designated herein as FIV-141 and deposited as ATCC No. VR-2619. The complete genomic sequence of the virus has been determined and is distinct from all other known FIV sequences. A plasmid encoding FIV-141 has been deposited as ATCC No. 203001.
A. Compositions and Methods Based Upon the FIV-141 Virus
In its first aspect, the present invention is directed to a substantially purified FIV-141 virus having a genomic sequence corresponding to that of SEQ ID NO:1, to host cells infected with the virus and to progeny virus produced in the host cells. The term “substantially purified” means that FIV-141 has been separated from all other strains of virus and, particularly, from all other strains of FIV. Host cells are typically cells grown in in vitro culture. Host cells that may be used for growing virus include peripheral blood mononuclear cells (PBMCs). Progeny virus may be isolated using standard procedures as discussed below. The present invention further provides a substantially purified virus having a nucleotide sequence which is a degenerate variant of a nucleotide sequence corresponding to SEQ ID NO:1, as based on the degeneracy of the genetic code, host cells infected with such a virus, and progeny virus produced in the host cells, which are useful for all of the purposes disclosed herein for the substantially purified FIV-141 virus having a genomic sequence corresponding to that of SEQ ID NO:1, and for which all of the disclosure provided herein below is equally applicable.
The FIV-141 virus and host cells infected with the virus can be used to infect animals for the purpose of inducing the production of antibodies that react preferentially with one or more strains of FIV. “Preferential binding” of antibodies, as used herein, refers to an antibody having at least a 100-fold greater affinity for FIV than for any other virus or non-FIV protein. Antibodies may be generated in any of the animals commonly used for this purpose (such as, e.g., mice, rabbits, goats, or sheep) but, preferably, antibodies will be made in domestic cats. When virus is used to induce antibody production, it may, if desired, be inactivated prior to infection. Inactivation procedures may involve treating the virus with formalin, paraformaldehyde, phenol, lactopropionate, ultraviolet light, heat, psorlens, platinum complexes, ozone or other viricidal agents. When host cells expressing FIV-141 are used to induce antibody production, the cells may be fixed prior to infection. Typically, this will involve treating the cells with paraformaldehyde as described herein, but other methods may also be employed. Antibodies made to FIV-141 are themselves included within the scope of the invention and may be purified using techniques well known in the art (see, e.g., Harlow et al., 1988
, Antibodies: A Laboratory Manual
, Cold Spring Harbor Laboratory, N.Y.).
In another aspect, the invention is directed to a whole virus vaccine comprising inactivated FIV-141 virus, or an inactivated virus encoded by a degenerate variant of a nucleic acid molecule having a nucleotide sequence corresponding to SEQ ID NO:1. An immune response may be induced in a cat by administering this vaccine at a dosage and for a duration sufficient to induce protective immunity against subsequent infection with FIV-141. Typically, the vaccine will be administered parenterally with two or more inoculations being given at intervals of, e.g., two to eight weeks. The invention also includes a fixed cell vaccine, which is comprised of a host cell infected with the FIV-141 virus or a degenerate variant thereof. Administration of this v

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