title: No benefit of therapeutic vaccination in clinically healthy cats persistently infected with feline leukemia virus.
abstract: Therapeutic vaccinations have a potential application in infections where no curative treatment is available. In contrast to HIV, efficacious vaccines for a cat retrovirus, feline leukemia virus (FeLV), are commercially available. However, the infection is still prevalent, and no effective treatment of the infection is known. By vaccinating persistently FeLV-infected cats and presenting FeLV antigens to the immune system of the host, e.g., in the form of recombinant and/or adjuvanted antigens, we intended to shift the balance toward an advantage of the host so that persistent infection could be overcome by the infected cat. Two commercially available FeLV vaccines efficacious in protecting naïve cats from FeLV infection were tested in six experimentally and persistently FeLV-infected cats: first, a canarypox-vectored vaccine, and second, an adjuvanted, recombinant envelope vaccine was repeatedly administered with the aim to stimulate the immune system. No beneficial effects on p27 antigen and plasma viral RNA loads, anti-FeLV antibodies, or life expectancy of the cats were detected. The cats were unable to overcome or decrease viremia. Some cats developed antibodies to FeLV antigens although not protective. Thus, we cannot recommend vaccinating persistently FeLV-infected cats as a means of improving their FeLV status, quality of life or life expectancy. We suggest testing of all cats for FeLV infection prior to FeLV vaccination.
authors.affiliation: Clinical Laboratory and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. Electronic address: khungerbuehler@vetclinics.uzh.ch.
authors.forename: A Katrin
authors.initials: AK
authors.lastname: Helfer-Hungerbuehler
authors.affiliation: Clinical Laboratory and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. Electronic address: aspiri@vetclinics.uzh.ch.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Spiri
authors.affiliation: Clinical Laboratory and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. Electronic address: briond@vetclinics.uzh.ch.
authors.forename: Barbara
authors.initials: B
authors.lastname: Riond
authors.affiliation: Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. Electronic address: grest@vetpath.uzh.ch.
authors.forename: Paula
authors.initials: P
authors.lastname: Grest
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. Electronic address: fboretti@vetclinics.uzh.ch.
authors.forename: Felicitas S
authors.initials: FS
authors.lastname: Boretti
authors.affiliation: Clinical Laboratory and Center for Clinical Studies, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland. Electronic address: rhofmann@vetclinics.uzh.ch.
authors.forename: Regina
authors.initials: R
authors.lastname: Hofmann-Lehmann
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D002371:Cat Diseases / Q000628:therapy* / Q000821:virology; D002415:Cats; D015683:Gene Products, gag / Q000097:blood; D005256:Leukemia Virus, Feline / Q000276:immunology* / Q000472:pathogenicity; D008017:Life Expectancy; D011788:Quality of Life; D012192:Retroviridae Infections / Q000628:therapy / Q000662:veterinary* / Q000821:virology; D015682:Retroviridae Proteins, Oncogenic / Q000008:administration & dosage / Q000627:therapeutic use*; D014412:Tumor Virus Infections / Q000628:therapy / Q000662:veterinary* / Q000821:virology; D014611:Vaccination / Q000662:veterinary; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000627:therapeutic use*; D019562:Viral Load; D014765:Viral Vaccines / Q000008:administration & dosage / Q000627:therapeutic use*; D014766:Viremia / Q000628:therapy / Q000662:veterinary
chemical_list: C078788:ALVAC vaccine; D000914:Antibodies, Viral; D015683:Gene Products, gag; D015682:Retroviridae Proteins, Oncogenic; D014614:Vaccines, Synthetic; D014765:Viral Vaccines; C117471:feline leukemia virus protein p27; C045569:feline leukemia virus vaccine
keywords: Cat; FeLV; Retrovirus; Therapeutic vaccination