Antibodies produced by rabbits immunized with visna virus

Immunization of New Zealand White rabbits with purified visna virus elicited antibody activity demonstrated by passive hemagglutination (PHA), complement fixation (CF), and indirect immunofluorescent tests. The antibody activities of hyperimmune sera and Sephadex G-200 fractions of the sera were studied. It was found that the PHA test was 10 to 100 times more sensitive than the CF test in detecting visna antibodies in rabbits. It was also found that the immunoglobulin M fractions from Sephadex G-200 filtration displayed greater PHA activity than did the immunoglobulin G fractions. Although neutralizing antibody was demonstrated in the serum of the natural host (sheep), our attempts to demonstrate neutralizing antibody in the sera from hyperimmunized rabbits (non-natural host) so far have failed.