title: Recombinant FeLV vaccine: long-term protection and effect on course and outcome of FIV infection.
abstract: The efficacy and the long-term protection of a recombinant feline leukemia virus (FeLV) vaccine were determined in 30 specified pathogen free cats for over 3 years. At the same time, in order to specify the effects of feline immunodeficiency virus (FIV) on the immune system, one half of the cats (n = 15) were previously infected with the Swiss isolate FIV Zurich 2. The second half of the animals (n = 15) served as non-infected controls. Eighteen (nine FIV-negative, nine FIV-positive) vaccinated and 12 (six FIV-negative, six FIV-positive) non-vaccinated cats were intraperitoneally challenged with FeLV A. Seventeen of 18 vaccinated cats were protected against persistent viremia, while ten of 12 non-vaccinated controls became infected. An increase of antibodies against FeLV SU was found in all protected cats after the challenge exposure. No difference in vaccine efficacy was found between FIV-negative and FIV-positive animals. The whole group of cats was observed for over 3 years. There were no further vaccinations during this period. CD4+ and CD8+ cell subsets, clinical outcome and time of survival of the cats were recorded. FIV-negative and FIV-positive animals were kept in two different rooms. However, FeLV-negative and FeLV viremic cats were housed together in both rooms in order to imitate a natural FeLV exposure situation. Anti-recombinant FeLV SU antibodies were measured by enzyme-linked immunosorbent assay. Although a continuous decline of antibodies was found in FeLV vaccinated cats, they remained protected against constant FeLV challenge for over 3 years. FIV infection had a stronger effect on the depression of the CD4+:CD8+ ratio than FeLV infection. Within the group of FIV-positive cats, the FeLV-vaccinated animals had significantly better survival rates as well as better clinical and laboratory parameters. FIV- and FeLV-coinfected cats showed the lowest CD4+:CD8+ ratio, mainly caused by decreased CD4+ lymphocyte counts. CD8+ lymphocytes with strong fluorescence (CD8(high)) disappeared and cells with weak fluorescence (CD8(low)) appeared instead. Prevention of coinfection by immunizing FIV-positive cats against FeLV infection improved the clinical outcome and prolonged the cat's life expectancy.
authors.affiliation: Department of Internal Veterinary Medicine, University of Zurich, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Hofmann-Lehmann
authors.forename: E
authors.initials: E
authors.lastname: Holznagel
authors.forename: A
authors.initials: A
authors.lastname: Aubert
authors.forename: P
authors.initials: P
authors.lastname: Ossent
authors.forename: M
authors.initials: M
authors.lastname: Reinacher
authors.forename: H
authors.initials: H
authors.lastname: Lutz
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D016516:CD4-CD8 Ratio / Q000662:veterinary; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002415:Cats; D004797:Enzyme-Linked Immunosorbent Assay; D016181:Feline Acquired Immunodeficiency Syndrome / Q000276:immunology / Q000401:mortality / Q000517:prevention & control*; D005260:Female; D005434:Flow Cytometry / Q000662:veterinary; D016089:Immunodeficiency Virus, Feline / Q000276:immunology*; D005256:Leukemia Virus, Feline / Q000276:immunology*; D008297:Male; D013047:Specific Pathogen-Free Organisms; D016019:Survival Analysis; D014611:Vaccination / Q000662:veterinary*; D014614:Vaccines, Synthetic / Q000276:immunology; D014765:Viral Vaccines / Q000276:immunology*; D014766:Viremia / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D000914:Antibodies, Viral; D014614:Vaccines, Synthetic; D014765:Viral Vaccines