Fig. 7

Hypothesized contribution of exosomes to HAM/TSP immunopathogenesis. HTLV-1 infected PBMCs, especially HTLV-1 infected CD4⁺CD25⁺ T cells, produce exosomes containing HTLV-1 Tax. These cells are present in the periphery and produce Tax⁺ exosomes in the periphery that can potentially cross the blood brain barrier (BBB). However, these infected T cells are also capable of crossing the BBB and producing exosomes in the CNS. Both scenarios may explain the presence of Tax⁺ exosomes in HAM/TSP patient CSF. These Tax⁺ exosomes can then be taken up by CNS resident cells, including microglia, oligodendrocytes, astrocytes, etc. and become targets for lysis by HTLV-1 Tax-specific CTLs which cross the BBB. The resulting destruction perpetuates the neuroinflammation observed in HAM/TSP