Discovery of a New Endogenous Type C Retrovirus (FcEV) in Cats: Evidence for RD-114 Being an FcEVGag-Pol/Baboon Endogenous Virus BaEVEnv Recombinant

ABSTRACT Analysis of a cat genomic DNA library showed that cats harbor a previously unrecognized endogenous type C retrovirus, whoseenv gene has homology to the murine Fv-4resistance gene. This unique retrovirus, designated FcEV (Felis catus endogenous retrovirus), has a type C pol gene, closely related to the primate Papio cynocephalusendogenous virus (PcEV) pol, not overlapping theenv gene, unlike in other type C retroviruses, and is presumably present in a higher copy number than RD-114. Phylogenetic analysis of FcEV and RD-114 fragments amplified from cat species and comparison with baboon endogenous virus (BaEV) fragments from monkeys suggested that RD-114 does not represent the cat strain of BaEV but is actually a new recombinant between FcEV type C genes and theenv gene of BaEV. Although BaEV did appear to have infected an ancestor of the domestic cat lineage, it was a de novo recombinant that made its way into the cat germ line.