HTLV-1 infection in tropical spastic paraparesis: lymphocyte culture and serologic response.

All 17 patients with tropical spastic paraparesis (TSP) in a series seen in the United Kingdom have antibodies to the human T cell leukemia virus type 1 (HTLV-1). Cultured peripheral blood lymphocytes from these patients formed multinucleated giant cells and reacted with sera and monoclonal antibodies to HTLV-1 in a manner identical to adult T cell leukemia-lymphoma (ATLL) patient lymphocytes. Western blot analysis failed to reveal any marked difference in the antigens recognized by sera from TSP and ATLL patients. The sera from TSP patients, their asymptomatic relatives and ATLL patients were titrated using the following assays: enzyme-linked immunosorbent assays (ELISA), particle agglutination, antibody-dependent cell-mediated cytotoxicity, and pseudotype neutralization. There were significantly stronger serologic responses in the TSP patients than in their relatives or ATLL patients. High antibody titers in the presence of replicating virus often reflect the antigen load; however, these data are also consistent with the suggestion that neurologic damage in TSP may be immunologically mediated.