The relationship between antibody response to caprine arthritis-encephalitis virus surface protein and the development of viral-induced arthritis

The purpose of this study was to test the hypothesis that antibody response to caprine arthritis-encephalitis virus (CAEV) surface envelope (SU) promotes development of viral-induced arthritis. This hypothesis was tested by inducing antibody responses to CAEV SU by immunization and evaluating the incidence and severity of arthritis following CAEV challenge of immunized goats. Immunizations utilized recombinant vaccinia virus rWR-63env expressing the CAEV envelope (env) gene. In one experiment, Saanen goats were co-immunized with rWR-63env and vaccinia virus rWR-IL4 in an attempt to enhance antibody responses to SU prior to virus challenge. In this experiment, rWR-IL4 enhanced antibody responses to rWR-63env-encoded SU. In addition, co-immunized goats maintained enhanced anti-SU antibody responses following viral challenge. However, co-immunized goats did not have significantly increased incidence or severity of arthritis at 52 weeks post-challenge. A second experiment utilized goats primed with rWR-63env or vaccinia rWR-SC11 without the CAEV env gene and boosted with purified SU envelope protein in incomplete Freund's adjuvant (SU-IFA). CAEV challenge specifically activated immunoglobulin G1 memory induced by SU-FIA boost. Six of eight non-immunized control goats and all three goats with extant anti-SU IgG1 memory developed severe carpal joint inflammatory lesions following viral challenge. Antibody titers to SU were higher in all arthritic goats compared to the two non-arthritic control goats, and arthritis was associated with dominant SU specific IgG1 responses.