Evaluation of viral resistance to Reverse Transcriptase Inhibitors (RTI) in HIV-1-infected patients before and after 6 months of single or double antiretroviral therapy

Abstract

We evaluated samples of peripheral blood mononuclear (PBMC) cells from 46 AIDS patients, before starting therapy with HIV-1 reverse transcriptase inhibitors (RTI), and after 6 months of drug use. PBMC were stored and tested by a Line Probe Assay (LiPA), in order to assess the frequency of RT mutations in this population. Six patients were taking AZT before initial blood collection (1 to 16 weeks of drug use) and 40 patients had no prior therapy. After baseline evaluation, 19 patients received AZT, 23 AZT plus DDI, 3 started AZT only with DDI added after 3 months, and 3 received a combination of AZT plus 3TC. Detection of at least one mutation was found in 33% (15/46) of patients at baseline, and 83% (38/46) had at least 1 mutation after 6 months of therapy. In the majority of cases, samples presented with the wild type and variants of HIV, simultaneously. Patients receiving monotherapy had a higher frequency of mutations (L41 and F214, Y215) than did patients receiving double-drug therapy (19 vs. 10). No specific mutation associated with DDI was identified in 26 patients so treated. Despite the finding of a mean increase in CD4 count and a mild decrease in viral load, patients tended to have an inverse correlation between the CD4 variation and number of mutations detected after 6 months, suggesting potential loss of drug efficacy in the presence of these genotypic changes.