Abstract:
Feline Immunodeficiency Virus (FIV) is a lentivirus analogous to Human Immunodeficiency Virus that infects domestic cats (Felis catus). A large-scale epidemiological and phylogenetic-based FIV study has been undertaken in naturally-infected populations Of domestic cats (Felis catus) in New Zealand. An FIV prevalence of 19 % (n=416) was established from lymph node samples from feral cats. Male1 adult cats were found to have the highest prevalence. Phylogenetic analysis showed that known FIV subtypes A and C circulate in New Zealand cat populations. Furthermore, groups of sequences of unknown subtype in all three amplified regions of the gag, pol and env genes were identified. Evidence of intragenic recombination has been found in all three gene fragments, with the highest levels in the env gene. Complex intergenic recombination has also been identified in several infected hosts. Endpoint dilution sequencing was used to confirm the putative recombinant consensus sequences, and also showed no evidence for dual infection in the cats from which these putative recombinants were isolated. However, several cases of dual infection were detected in feral cats across multiple tissue types. The rate of evolution of the viral env V3-V6 region was estimated using a Bayesian coalescent framework. The rate of approximately 3 - 6 % per decade from three serially-sampled companion cats was found, about two to three times higher than that previously documented for a similar region from the cougar (Puma concolor) FIV strain. In addition, evidence of positive selection was identified in FIV sequences from two companion cats, with the majority of these sites located in variable regions. Low intrahost genetic diversity was observed from env sequences amplified from different tissue types of naturally-infected feral cats, suggesting recent infection events in these animals. The first evidence of compartmentalisation in a domestic cat was also found. A correlation between lymph node proviral load and phylogenetic diversity was shown, with higher average lymph node proviral load values in cats with presence of amplifiable FIV from non-lymphoid tissues.