ANTIIDIOTYPE ANTIBODIES THAT MIMIC A CONSERVED AQUATIC BIRNAVIRUS EPITOPE INDUCE NEUTRALIZING ANTIBODIES AND BIND TO FISH CELLS WITH INHIBITION OF VIRUS-REPLICATION

Polyclonal anti-idiotype (anti-Id) antibodies were prepared in rats ag ainst a monoclonal antibody (MAb AS-1) which defines a highly conserve d neutralization epitope on virion protein 2 (VP2) of Serogroup A aqua tic birnaviruses. Anti-mouse IgG cross-reactive antibodies were remove d from rat sera by adsorption to an affinity column of normal mouse Ig G and further purified by subsequent adsorption to and elution from an affinity column coupled with MAb AS-1. Confirmation that these anti-I d antibodies were directed against the paratope of MAb AS-1 and molecu larly mimicked the virus epitope was demonstrated in a variety of assa ys. Anti-Id antibodies reacted in enzyme-linked immunosorbent assay (E LISA) with both whole MAb AS-1 IBG and F(ab)(2) fragments, but did not react with 2 unrelated mouse IgGs or F(ab)(2) fragments. Anti-Id anti bodies blocked binding of virus to MAb AS-1 in a dose-dependent manner with 100% inhibition at the highest concentration. Similarly, virus i nhibited anti-Id/idiotype binding by 60%. Furthermore, anti-Id antibod ies inhibited the ability of MAb AS-1 to neutralize virus in plaque re duction assays. Anti-Id antibodies induced the production of virus neu tralizing antibodies in mice. Anti-Id antibodies also were used to sho w that the AS-1 epitope is a presumptive cell attachment site on the v irus which recognizes and binds to specific cell receptors. Anti-Id an tibodies were shown to bind to a variety of both salmonid and non-salm onid fish cell cultures. Pretreatment of fish cell cultures with virus inhibited (28 to 50%) binding of anti-Id antibodies. Treatment of fis h cell cultures with anti-Id antibodies also resulted in a decrease (9 8%) in the yield of progeny virus compared with replication of the vir us in untreated cells or cells treated with normal rat immunoglobulin.