Feline immunodeficiency virus infects both CD4+ and CD8+ T lymphocytes.

Monoclonal populations of feline T cells, derived from a specific-pathogen-free cat and expressing either the CD4 or CD8 surface antigen, were infected in vitro with two geographically distinct isolates of feline immunodeficiency virus (FIV). Both infected T-cell subsets exhibited decreased cell viability, expressed FIV-encoded proteins, and generated reverse transcriptase activity. All clones examined retained their original surface phenotype after infection. It appears, therefore, that both CD4+ and CD8+ T cells may be productively infected by FIV in vivo.