Human T-cell leukemia virus type 1 (HTLV-1) can cause fatal diseases, including adult T-cell leukemia in humans after long-term asymptomatic infection. In asymptomatic HTLV-1 carriers, substantial proviruses are detectable in lymphocytes, and the association of a higher proviral load with a higher risk of disease progression has been observed. However, viral replication is controlled and HTLV-1 production is poor in asymptomatic carriers. Virus-host immune interaction during latent infection has not been fully determined. In the present study, virus-specific antibody and T-cell responses in asymptomatic HTLV-1 carriers were investigated. Neutralizing antibody responses were positively correlated with proviral loads. Tax-specific CD8+ T-cell frequencies were not associated with proviral loads but inversely correlated with the ratios of p19-expressing CD4+ T-cell frequencies to proviral loads, supporting the notion that Tax-specific CD8+ T-cell responses play an important role in the control of HTLV-1 replication. These results provide insights into the mechanism of virus-host immune interaction in latent HTLV-1 infection.
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