Depressed CD4+ T lymphocyte proliferative response and enhanced antibody response to viral antigen in chronic lentivirus-induced arthritis.

The proliferative response of peripheral blood mononuclear cells (PBMC) stimulated with caprine arthritis-encephalitis virus (CAEV) surface glycoprotein (SU) was depressed 4- to 20-fold in Saanen goats with chronic CAEV-induced arthritis compared with asymptomatic goats. Phytohemagglutinin-stimulated responses were not depressed. Complement depletion of PBMC with anti-CD4 or anti-CD8 monoclonal antibodies identified CD4+ T lymphocytes as the antigen-responsive cells in both high-responder asymptomatic goats and low-responder arthritic goats. Serum antibody titers to CAEV SU were 8- to 32-fold higher in goats with chronic arthritis. Increased anti-CAEV SU titers as early as 3 months after infection predicted the eventual development of clinical arthritis. Thus, CAEV-induced arthritis is associated with chronic B cell activation resulting from dominant type 2 immune responses to viral antigen. The clinical outcome of CAEV infection may be determined by differential activation of type 1 or 2 T lymphocyte phenotypes at or near the time of initial exposure to CAEV.