Neutralizing antibody response of rabbits and goats to caprine arthritis-encephalitis virus

Rabbits were immunized with purified caprine arthritis-encephalitis virus and examined for neutralizing activity. Analysis of virus-antiserum interaction at 37 degrees C demonstrated little loss of viral infectivity after incubation with heat-inactivated rabbit antiserum for 60 min. However, sensitization of virus (as assessed by the addition of complement) occurred almost immediately and was 95% complete after 10 min. The complement-dependent neutralizing activity was associated with the immunoglobulin G fraction of rabbit antiserum. Addition of goat anti-rabbit immunoglobulin G to the immune rabbit serum-caprine arthritis-encephalitis virus mixture also resulted in neutralization of infectivity when unbound antibody was removed before addition of the anti-immunoglobulin. Serum from most caprine arthritis-encephalitis virus-infected goats contains antibody activity to the core protein p28, as demonstrated by immunodiffusion and enzyme-linked immunosorbent assay. However, attempts to demonstrate neutralizing activity in the serum of goats up to 1.5 years post-inoculation or in serum of hyperimmunized goats were unsuccessful when the sera were examined alone or in combination with complement or rabbit anti-goat immunoglobulin or both.