FELINE IMMUNODEFICIENCY VIRUS IN EXOTIC FELIDS: A SEROEPIDEMIOLOGIC AND PHYLOGENETIC CHARACTERIZATION

Abstract

Feline immunodeficiency virus is a recently isolated T-lymphotropic lentivirus that is genetically homologous and functionally analagous to the human AIDS viruses, HIV-1 and HIV-2. FIV has been documented to cause immunosuppression by gradually destroying the CD4 bearing T-cell subsets in infected domestic cats. Recent studies have revealed the existence of cross-reactive antibodies to FIV in several species of nondomestic felids. This thesis reports on the results of a seroepidemiologic survey of nearly 2000 serum samples from 20 different feline species and a molecular characterization of the pol gene from African lion FIV isolates. Evidence of exposure to feline lentiviruses was found in ten species of felids including lions, pumas, cheetahs, and bobcats. FIV exposure rates were found to be endemic in several populations of East African lions with an incidence as high as 90% in some areas. This report also documents the natural seroconversion of two East African lions. The phylogenetic reconstruction of the conserved viral poi gene has revealed huge intra- and inter- individual genetic diversity at the sequence level. The analysis has shown that feline lentiviruses appear to assort monophyletically with respect to the host species suggesting that interspecies transfer is a rare event. Three major phylogenetic clades of lion lentivirus (LLV) have been described that may be ancestral in their origins. The physiological consequences of FIV infection in big cats remains unclear, but the results of these studies show large parallels to the natural history of SIV infection in African primates, notably of the genus, Cercopithecus.