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Abstract

Previous studies on patients who develop drug resistant HIV-1 variants have shown that contin- ued use of failing regimens might provide clinical benefit. However, the effect of long-term expo- sure to drug resistant variants may lead to emergence of compensatory mutations that may jeopardize this effect. In this study, we assess associations among type and number of drug resistant mutations, viral load and disease progression in patients with long-term follow up. Patients with genotypic testing performed at the time of treatment failure were enrolled. Compar- ison of viral load and CD4 cell count between different resistance groups was performed using analysis of variance. Multiple linear regression analysis was performed to assess the simulta- neous effects of the presence of particular muta- tions and their accumulation on viral load. Data from 475 patients who were followed for a median of 43 months from October 1999 to July 2005 were studied. A "V shape" relationship was observed between the number of mutations and viralload.Specifically, inpatientsharboring upto five mutations, viral load was reduced by 0.8 log/ copies when compared to wild-type variants. However, with more than six mutations viral load progressively increased. Certain reverse tran- scriptase mutations such as M184V/I, K70R, V108I, and protease mutations such as L33FIV, M84V, and M36I were associated with reduced viral load. Together, these findings suggest that long-term maintenance of a sub-optimal antire- troviral regimen may have deleterious conse- quences for the patient.

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