Measurement of polypeptide- and antigenic site-specific antibodies to measles virus using a competitive enzyme immunoassay.

A competitive enzyme immunoassay (EIA) for measuring polypeptide- and antigenic site-specific antibodies against measles virus (MV) was developed. Three monoclonal antibodies (MAbs) against the fusion (F) and one MAb against the hemagglutinin (H) protein of MV were labelled with biotin and used in biotin-streptavidin EIA system. The inhibition of the binding of the labelled MAbs by the bound serum samples was measured in EIA and the titers were defined by reading at the level of 25% inhibition. The titers increased from acute to early convalescent measles sera in all the tests and antibody levels to the F protein increased earlier than antibodies to the H protein. The ratio of antibodies against 2 different antigenic sites on the F protein was significantly higher in subacute sclerosing panencephalitis patients than in normal blood donors. Similarly, SJL mice immunized with MV antigen had higher ratios of the corresponding antibodies than Balb/c mice. The results indicate that antibody response to different polypeptides and antigenic sites on the same polypeptide can be studied with the developed method and that the responses against different antigenic sites are independent.