MMP9 and tropical spastic paraparesis: However, since HTLV primarily infects T cell populations, we chose to focus on the production of MMP-9 and its TIMP-3 inhibitor by peripheral blood mononuclear cells (PBMC) in asymptomatic HTLV-1 carriers, HTLV-1-infected individuals with OAB (HTLV-1-OAB), and HAM/TSP patients.