Evolution in a chronic RNA virus infection: selection on HTLV-I tax protein differs between healthy carriers and patients with tropical spastic paraparesis |
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Authors: | Stefan Niewiesk Charles R. M. Bangham |
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Affiliation: | (1) Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DU, United Kingdom, GB;(2) Public Health Laboratory, John Radcliffe Hospital, Headington, Oxford OX3 9DU, United Kingdom, GB |
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Abstract: | HTLV-I causes T-cell leukemia and tropical spastic paraparesis (TSP) in a minority of infected people, whereas the majority remain healthy. The virus differs little in sequence between isolates but has been shown to have a quasispecies structure. Using the Nei and Gojobori algorithm, we have shown that the proportion of nonsynonymous to synonymous changes in HTLV-I proviral tax gene sequences from healthy seropositive subjects (Dn/Ds= 0.9 to 1.3) is significantly higher than those from TSP patients (Dn/Ds= 0.3 to 0.6). Here we show that the distinction between healthy seropositives and TSP patients can only be seen with proviral tax sequences, but not with cDNA, the amino-terminal or carboxy-terminal half of tax, or the rex gene. The Dn/Ds ratio of proviral tax sequences was used to analyze two TSP patients with atypical features and to investigate the influence of cytotoxic T cells (CTL) on the viral quasispecies. Received: 18 January 1995 / Accepted: 7 November 1995 |
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Keywords: | : HTLV — Tax — Rex — CTL — Deletion — Selection forces |
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