HTLV‐1‐associated Myelopathy/Tropical Spastic Paraparesis‐like Rats by Intravenous Injection of HTLV‐1‐producing Rabbit or Human T‐Cell Line into Adult WKA Rats

We intravenously injected Ra‐1 cells or MT‐2 cells into female adult WKA rats. Spastic paraparesis mainly in the hind‐limbs was observed in 1 out of 2 Ra‐1 cell‐injected WKA rats and in 3 out of 8 MT‐2 cell‐injected WKA rats 20 27 months after injection. The main neuropathological finding was symmetrical white matter degeneration with mononuclear cell infiltration of the spinal cord, similar to that of HTLV‐1‐associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients, and degeneration of nerve roots and peripheral nerves. Antibodies against HTLV‐1 antigens were detected in plasma and cerebrospinal fluid from these HAM/TSP‐like rats. HTLV‐1 provirus was detected from the peripheral blood mononuclear cells of one of these rats 20 months after injection. Interestingly, spastic paraparesis was not observed in F344 rats.