There is no direct evidence that HTLV-1 infects neurons, astrocytes, or microglia, but infected CD4+ T cells have been observed within spinal cord lesions (Matsuoka et al., 1998), and CD8+ T cells directed against HTLV-1 antigens accumulate in the CSF of patients with HAM/TSP (Nagai et al., 2001; Kubota et al., 2002). This evidence concerns the gene CD8A and tropical spastic paraparesis.