Antibody response to different antigenic sites on measles virus surface polypeptides in patients with multiple sclerosis.

Antibodies to different antigenic sites on measles virus (MV) surface proteins were examined in sera from 34 HLA-typed age- and sex-matched pairs of multiple sclerosis (MS) patients and control subjects by a previously developed competitive enzyme immunoassay in which human sera and monoclonal MV-specific antibodies compete for binding to the same antigen. Antibodies specific to 4 partly overlapping sites on the haemagglutinin protein and two sites on the fusion protein of MV were measured in addition to previously determined total antibody titres and antibody levels were compared between groups. MS patients had significantly higher levels of antibodies in six out of seven comparisons. Both the MS and the control group were further divided to subgroups with HLA-Dw2, -Dw1, -A2, -A3 and -B7 histocompatibility antigens and MV antibody levels in these groups were compared. The presence of the HLA-A2 or -A3 antigen did not have a significant effect on the antibody levels but both the HLA-Dw2 and -B7 antigens were associated with elevated antibody levels to antigenic sites defined by monoclonal antibodies. This was also supported by higher frequencies of these alleles in subgroups with high antibody titre both in MS patients and controls. Moreover, presence of Dw1 antigen was associated with lower mean titres especially against the fusion protein in control patients. The findings indicate that HLA antigens can control immune response to separate sites on a protein antigen either directly as immune response genes or through linkage to other genes.