The Cd8(+) Cell Phenotype Mediating Antiviral Activity In Feline Immunodeficiency Virus-Infected Cats Is Characterized By Reduced Surface Expression Of The Cd8 Beta Chain

The acute stage of feline immunodeficiency virus (FIV) infection is characterized by a CD8(+) anti-FIV response that parallels the appearance of a CDS' subpopulation with reduced expression of the beta chain (CD8 alpha(+)beta(lo)). The relationship between the CD8 alpha(+)beta(lo) phenotype and CD8(+) anti-FIV activity was examined. Flow cytometric analysis of peripheral blood mononuclear cells with anti-CD8 beta chain monoclonal antibody 117 revealed that the CD8 alpha(+)beta(lo) phenotype expanded throughout the asymptomatic infection, constituting 80%-90% of the CD8 beta(+) cells in long-term-infected cats. Purified CD8 alpha(+)beta(hi) and CD8 alpha(+)beta(lo) subpopulations were analyzed for anti-FIV activity in an acute infection assay. Anti-FIV activity resided principally in the CD8 alpha(+)beta(lo) population and was demonstrated in acute FIV infections, as well as in long-term asymptomatic infections. These data suggest that a unique CD8 alpha(+)beta(lo) anti-FIV phenotype arises early in infection and may play a major role in eliminating virus and maintaining the asymptomatic infection.