Molecular epidemiology of feline immunodeficiency virus in the domestic cat (Felis catus)

Studying the evolutionary mechanisms of feline immunodeficiency virus in the domestic cat (Felis catus), FIVFca, provides a good comparison to other lentiviruses, such as HIV and FIVPco in the cougar (Puma concolor). We review the current epidemiological and evolutionary findings of FIVFca. In addition to the five accepted FIVFca, subtypes, several recent phylogenetic studies have found strains that form separate clades, indicative of novel subtypes. In New Zealand cats, these strains of unknown subtype have been found to be involved in complex patterns of intergenic recombination, and whole genome sequences are required to resolve these. Evidence of recombination events has been documented with the highest levels in the env gene, the region involved in host cell receptor recognition. Several cases of FIVFca multiple infections, both inter- and intra-subtype, have been reported. The findings of both unknown subtypes and relatively high levels of recombination suggest the need for further testing of the current vaccine. Limited studies on the evolutionary rate of FIVFca document a value twice to three times that of FIV in the cougar, a result suggesting the different levels of co-adaptation between the viruses and their respective hosts. We studied the tissue distribution of FIVFca in feral domestic cats, finding the first case of FIV compartmentalisation, a phenomenon well documented in HIV-1 patients.