Summary: Lion lentivirus (LLV) and puma lentivirus (PLV) exist as highly divergent virus clades among populations of indigenously infected nondomestic felidae. The feline immunodeficiency virus (FIV) is highly divergent from LLV and PLV and is pathogenic for domestic cats. When domestic cats are infected with LLV or PLV, they have immunologically and clinically silent persistent infections. We examined whether LLV or PLV infection might impart resistance to FIV superinfection in vitro by infecting domestic cat lymphoid cells with PLV and assessing resistance of these cells to FIV. We found that infection with FIV was highly restricted by prior established PLV infection. To examine whether this resistance applied in vivo, domestic cats were asymptomatically infected with either LLV or PLV and then challenged with pathogenic FIV. Although all cats became infected with FIV, prior LLV or PLV exposure blunted CD4+ cell depletion and suppressed plasma and peripheral blood mononuclear cell FIV loads relative to FIV-challenged controls not infected with LLV or PLV, despite the lack of prechallenge neutralizing antibody activity against FIV. Thus, as compared with naive controls, cats previously infected with LLV or PLV were able to more effectively control FIV infection and resist its immunologic effects, despite the substantial genetic divergence between these lentiviruses-raising the possibility that superinfection may impart resistance to lentivirus infection by heightening innate immune mechanisms.
(C) 2002 Lippincott Williams & Wilkins, Inc.