Transmission of HTLV-I to rats via peripheral blood mononuclear cells and serum from a patient with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) with amyotrophic lateral sclerosis (ALS)-like features

We tested the possibility that lymphocytes and serum obtained directly from a patient with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) induce infection in rats. Inbred Fischer F344 immunosupressed rats were inoculated intravenously with 10 x 10(6) peripheral blood mononuclear cells (PBMC; 3 rats) and serum (3 rats) obtained from a HAM/TSP patient, who was seropositive and polymerase chain reaction (PCR)-positive for the HTLV-I proviral genome. Antibodies to HTLV-I appeared in the rat sera 2 months later; rat peripheral blood lymphocytes, spleen, salivary gland, and spinal cord were found to contain the proviral genome. Control rats inoculated with normal donor PBMC and serum tested negative for the HTLV-I antibodies and for the HTLV-I proviral genome by PCR. The positive control F344 rats inoculated with 5 x 10(6) cells of a SLB-1 HTLV-I cell line were found to be infected after 2 months. This study demonstrates for the first time that HTLV-I can be transmitted not only by human cellular components but also by human cell-free sera in a rat model.