FELINE IMMUNODEFICIENCY VIRUS-INFECTION OF CATS AS A MODEL TO TEST THE EFFECT OF CERTAIN IN-VITRO SELECTION PRESSURES ON THE INFECTIVITY AND VIRULENCE OF RESULTANT LENTIVIRUS VARIANTS

Three groups of specific pathogen-free (SPF) domestic cats, each conta ining 5 animals, were infected with one of three closely related FIV v ariants and monitored for 36 weeks. A fourth group of 5 cats was sham- infected and served as uninfected controls. FIV variants included: (1) a fully virulent animal passaged FIV-Petaluma; (2) a Crandell feline kidney (CrFK) cell-adapted FIV-Petaluma (FIV-CrFK); and (3) a variant of FIV-CrFK (FIV-CrFK(AZT)) that had been selected in vitro for resist ance to azidothymidine. Cats infected with fully virulent FIV-Petaluma strongly seroconverted, became persistently viremic, and exhibited ly mphadenopathy, neutropenia, and inversion of the CD4+:CD8+ T cell rati o. Cats infected with FIV-CrFK seroconverted but the antibody response s were much weaker and more variable; two of the cats became transient ly viremic and no hematologic abnormalities or clinical signs of illne ss other than a very mild lymphadenopathy were observed. None of the f ive cats inoculated with FIV-CrFK(AZT) seroconverted, became viremic, or exhibited any gross or hematologic signs of disease, even though pr oviral DNA was transiently detected in tissue following inoculation. T his study demonstrates that the FIV infection model can be used to ass ess differences in the virulence of FIV variants, including variants s elected for antiretroviral drug resistance.