Experimental bystander encephalitis induced by immunization with HTLV-I-producing T cells in mice

ICR mice were immunized with HTLV-I carrier T lymphocytes (MT-2 cell line) and then inoculated intracerebrally with these cells. After non-specific traumatic hemorrhage, perivascular cell infiltration was noted diffusely throughout the brain on day 2 and lasted for over 2 weeks. HTLV-I antigens were detected in both sides of the cerebral hemisphere by Western blotting analysis. Tissue damage consisting of demyelination, axonal degeneration, and astrogliosis was observed most heavily on days 10 and 14. Non-immunized mice inoculated with the cells showed only transient hemorrhage. In cases using the HTLV-I free T-cell line (MOLT-4) inflammatory cell infiltration and tissue damage was much less conspicuous and disappeared after day 10. These experiments support the hypothesis that HAM/TSP is a bystander disease initiated and progresses via HTLV-I-infected T-cell invasion into the spinal cord of a patient who has been infected and sensitized to the virus.