t H ro MB o SP on D in -1 e XP re SS ion in HUM an t - l YMPH otro P ic V ir US 1 a SYMP to M atic carrier S an D P atient S W it H H tl V- a SS ociate D MY elo P at HY/ tro P ical SP a S tic P ara P are S i S

Human T-lymphotropic Virus type 1 (HTLV-1) is associated with a myelopathy (named HTLV-associated myelopathy/Tropical Spastic Paraparesis–HAM/TSP). Thrombospondin-1 (TSP-1) is a matrix protein which interferes with cell adhesion, motility, and proliferation. The expression levels of the mRNA for this protein were evaluated in HTLV-1 infected individuals: 11 asymptomatic, 18 with myelopathy or oligosymptomatic, and 13 non-infected participants. RNA from peripheral blood mononuclear cells was submitted to TSP-1 RT-PCR analysis. The number of individuals expressing thrombospondin-1 was more frequent in the symptomatic group (14/18,