Role of the humoral immune response in resistance to Theiler's virus infection.

Theiler's virus, a murine picornavirus, persists in the central nervous system of susceptible strains of mice, causing chronic inflammation and demyelination in the white matter of the spinal cord. Resistant strains, however, clear the virus and do not develop late disease. In this study, we compared the characteristics of T and B lymphocytes in C57BL/6 (resistant) and SJL/J (susceptible) mice 1 week after intracerebral infection. We detected a marked increase of the number of immunoglobulin M (IgM)-secreting cells in the spleens of C57BL/6 detected a marked increase of the number of immunoglobulin M (IgM)-secreting cells in the spleens of C57BL/6 mice (but not in those of SJL/J mice), which correlated with higher levels of serum IgM antiviral antibodies. The role of the humoral response in virus clearance and resistance was demonstrated by a marked decrease in the number of infected spinal cord cells in SJL/J mice after passive transfer of serum from infected C57BL/6 donors. The B-cell response was found to be partly T cell independent. These results suggest an important role of the early humoral immune response in resistance to Theiler's virus-induced disease.