Biological Activity of a Monoclonal Antibody to a Measles Virus Haemagglutinin Epitope Detected Late in Infection

Abstract

SUMMARYA hybrid cell line secreting monoclonal antibody 2H9c (mAb 2H9c) with measles virus haemagglutinin (HA) specificity was produced. The mAb 2H9c was non-reactive in haemagglutination inhibition and neutralization assays. A protein of apparent mol. wt. 79000 was immune-precipitated using a Triton X-100/SDS/sodium deoxycholate detergent buffer and two proteins with mol. wt. of 79000 and 69000 were immuneprecipitated using 1% Nonidet P40/sodium deoxycholate buffer in SDS-PAGE assays. Similar results were obtained with other anti-HA monoclonal antibodies, supporting the assumption that mAb 2H9c was directed against the HA polypeptide. The indirect immunofluorescence (IFA) staining pattern of acetone-fixed infected cells with mAb 2H9c differed substantially from that with other HA-specific monoclonal antibodies. Kinetic studies revealed that the reactivity of mAb 2H9c lagged behind other HAspecific monoclonal antibodies by 18 to 36 h post-infection in IFA assays. This suggests that mAb 2H9c may be directed against a binding site that arises late in infection, possibly as a result of a conformational alteration of the HA polypeptide.