INFECTION OF CATS WITH MOLECULARLY CLONED AND BIOLOGICAL ISOLATES OF THE FELINE IMMUNODEFICIENCY VIRUS

Molecularly cloned viruses are considered essential reagents for chara cterizing viral domains responsible for infectivity and disease pathog enesis in the host. The infectivity and hematological alterations asso ciated with two molecularly cloned isolates of feline immunodeficiency virus (FIV-pPPR and FIV-pF34) and an uncloned isolate (FIV-PPR) were assessed by inoculation of cats. Inoculated cats were tested for viral antibody, viremia, and clinical pathological disease. Peripheral bloo d mononuclear cells isolated from inoculated cats were assayed for vir us infection by virus isolation, amplification of proviral DNA (by pol ymerase chain reaction), and in situ hybridizatioo for viral RNA. Over 50% of the cats inoculated with cloned Virus FIV-pF34 failed to seroc onvert even when coinfected with feline leukemia virus; these cats wer e consistently virus positive only by amplification of proviral DNA. A ll cats inoculated with cloned virus FIV-pPPR seroconverted and were f ound virus positive by at least two of three virus detection assays. B oth cloned viruses were less capable of suppressing CD4:CD8 ratios whe n compared to the biological isolates from which they were cloned. Iso lates which replicate efficiently in feline peripheral blood mononucle ar cells (PBMC), i.e., FIV-pPPR or biological FIV-PPR, caused greater virus toad and lower CD4:CD8 ratios when compared to cloned FIV-pF34, which replicates efficiently in feline adherent cell lines and macroph ages but poorly in primary feline PBMC. Molecular clones FIV-pF34 and FIV-pPPR will be useful reagents for characterization of viral determi nants of virus load and possibly, cell tropism in vivo. (C) 1994 Acade mic Press, Inc.