Monoclonal antibodies against the glycoproteins of mumps virus: fusion inhibition by anti-HN monoclonal antibody.

Six monoclonal antibodies (MAbs) against the haemagglutinin-neuraminidase (HN) protein and three against the fusion (F) protein of mumps virus were obtained. Anti-HN MAbs were classified into three antigen-specific groups in competitive binding assays. All of the anti-HN MAbs showed virus-neutralizing and haemolysis-inhibiting activities and inhibited fusion from without (FFWO). Three of them inhibited fusion from within (FFWI) and the cell-to-cell spread of infection. The most effective MAb in inhibiting FFWI possessed neuraminidase-inhibiting activity and little haemagglutination-inhibiting activity. All anti-F MAbs inhibited virus-induced haemolysis but none of them inhibited FFWO, FFWI or the cell-to-cell spread of infection.