Exploitation of new therapies for HTLV-I-assotiated myelopathy

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In this research project, we have deeply improved our understanding for the pathogenesis of HTLV-I-associated myelopathy(HAM) and developed a hopeful therapy for the disease. It is an initial event that HTLV-I-infected cells infiltrate into the central nervous system for the development of HAM, where matrix metalloproteinase(MMP)-2 and -9 play an important role. We found that a selective MMP inhibitor specific for MMP-2 and -9, N-Biphenyl sulfonyl-phenylalanine hydroxamic acid(BPHA), significantly inhibited migration activity of CD4+ T lymphocytes (which are a main reservoir of HTLV-I) from HAM patients. This suggests that the compound is a candidate for a new therapy for HAM patients. We had identified many genetic factors which increase susceptibility for the disease, and we newly identified two genetic factors, polymorphism of interleukin-10 promoter, and the length of tandem repeat in MMP-9 promoter. Using these host genetic factors, we made a formula to predict the risk of the development of HAM. When we utilized it for HTLV-I asymptomatic carriers, the carriers with high risk values showed faint abnormalities on the neurological examination, suggesting that the formula is very useful for prediction of the prognosis. In a genetic analysis of HTLV-I, the ratio of non-synonymous change to synonymous change (dN/dS ratio) of HTLV-I gene was lower in HAM patients than in HTLV-I carriers, implying that viral replication is more effectively inhibited in HAM patients than in the carriers. Moreover, HAM patients with HLA-A^*02 had lower dN/dS ratio than those without HLA-A^*02, suggesting that HL-A^*02 has an inhibitory effect on viral replication. Additionally, an analysis of dN/dS ratio, cytotoxic T lymphocytes(CTL) epitopes and frequency of mutant virus demonstrated that CTL had antiviral pressure in vivo, however, a mutant virus did not predominate. Further studies are needed to establish a more effective therapy for HAM patients.