T cell responses to the paramyxovirus simian virus 5: studies in multiple sclerosis and normal populations

A recent study suggested that a significant portion of the oligoclonal IgG found in multiple sclerosis (MS) cerebrospinal fluid may be removed by absorption with simian virus 5 (SV5). We have now evaluated the proliferative responses to SV5 generated by peripheral blood mononuclear cells from normal adult subjects and from patients with MS. Positive responses were detected in 16 of 16 subjects in each group. The magnitude of the response was not significantly different in the two groups. There was no correlation between the level of response and the presence or absence of HLA-DR2. No cross-reactivity with SV5 was demonstrated by panels of human T cell clones directed against myelin basic protein or measles virus. More than 60% of normal individuals between 10 and 16 years of age also generated positive T cell proliferative responses to SV5, while fewer than 25% of subjects below the age of 6 generated positive responses. Intermediate percentages of positive responders were detected in subjects 6-9 years of age. We conclude that the adult human population has been widely exposed to this organism and that initial exposure generally occurs in the early to middle school-age years.