Protective effects of monoclonal antibodies against lethal canine distemper virus infection in mice.

Monoclonal antibodies (MAbs) against the haemagglutinin (H), fusion protein (F) and nucleoprotein of canine distemper virus (CDV) were examined for their ability to protect mice against lethal CDV infection. One MAb against H and two of six MAbs against F protected mice, the protective effect of the anti-H MAb being stronger than that of the anti-F MAbs. The anti-H MAb showed virus neutralizing activity, but the two anti-F MAbs, which recognized the same epitope, did not. Protection by the anti-F MAbs correlated with cell fusion inhibition, but not with complement-dependent neutralization, complement-dependent cytolysis or antibody-dependent cell-mediated cytotoxicity. These results suggest that neutralization by antibody against H and cell fusion inhibition by antibody against F play important roles in the protective mechanism against CDV infection.