High circulating proviral load with oligoclonal expansion of HTLV-1 bearing T cells in HTLV-1 carriers with strongyloidiasis

Adult T cell leukemia (ATLL) develops in 3-5% of HTLV-1 carriers after a lo ng period of latency during which a persistent polyclonal expansion of HTLV -1 infected lymphocytes is observed in all individuals. This incubation per iod is significantly shortened in HTLV-1 carrier with Strongyloides stercor alis (Ss) infection, suggesting that Ss could be a cofactor of ATLL, As an increased T cell proliferation at the asymptomatic stage of HTLV-1 infectio n could increase the risk of malignant transformation, the effect of Ss inf ection on infected T lymphocytes was assessed in vivo in HTLV-1 asymptomati c carriers. After real-time quantitative PCR, the mean circulating HTLV-1 p roviral load was more than five times higher in HTLV-1 carriers with stongy loidiasis than in HTLV-1+ individuals without Ss infection (P < 0,009), Thi s increased proviral load was found to result from the extensive proliferat ion of a restricted number of infected clones, i,e, from oligoclonal expans ion, as evidenced by the semiquantitative amplification of HTLV-1 flanking sequences. The positive effect of Ss on clonal expansion was reversible und er effective treatment of strongyloidiasis in one patient with parasitologi cal cure whereas no significant modification of the HTLV-1 replication patt ern was observed in an additional case with strongyloidiasis treatment fail ure. Therefore, Ss stimulates the oligoclonal proliferation of HTLV-1 infec ted cells in HTLV-1 asymptomatic carriers in vivo, This is thought to accou nt for the shortened period of latency observed in ATLL patients with stron gyloidiasis.