Study design to assess effects of immunosuppressive therapies on feline immunodeficiency virus (FIV) infection. Phase I: Twelve cats were divided into two groups (n = 6) and treated with either ATOPICA® for Cats (cyclosporine A, CsA)(5 mg/kg per os (PO) once a day (SID)) or prednisolone (2 mg/kg PO SID) for 28 days. Following a 6-week wash-out period, groups were alternated so that each cat received the opposite treatment for 28 days. Phase II: Following a 6-week wash-out period from Phase I, eleven cats received CsA for 5 days, after which, six cats received antiretroviral therapy (ART + CsA) for 28 days (zidovudine 10 mg/kg + lamivudine 50 mg/kg, PO BID), while the remaining five cats received no further treatment (CsA Only). See Materials and Methods for additional details. ART, antiretroviral therapy.