Prevalence of R5 and X4 HIV variants in antiretroviral treatmentexperienced patients with virologic failure

Abstract

Background: Antiretroviral therapy (ART) inhibits virus replication. Nevertheless, ART has the disad-vantage of generate selective resistance and adverse events. Coreceptor antagonists are a family ofantiretroviral drugs that are used with the prior knowledge of patients HIV tropism.Objectives: The purpose of this work was to estimate the prevalence of R5 and X4 variants among Chileanpatients under antiretroviral therapy and virological failure and investigate variables such as plasma viralload (pVL) and CD4 cell count in the population studied.Study design: HIV RNA or proviral DNA was extracted from 454 consecutives patients and tropism testingwas performed using a genotypic method performed with Geno2pheno setting a cutoff value for FPR5.75%.Results: Among 454 individuals analyzed, 299 (66%) harbouring exclusively R5 variants. They not dis-played a better clinical profile than individuals harbouring X4 strains (22%). For R5 patients the medianof pVL and CD4 cell count were 268,000 copies/mL, and 223 cells/uL respectively. For X4 samples thevalues were 368,000 copies/mL and 214 cells/uL [P > 0.05]). Only, 53 patients (12%) could not be analyzedand were categorized as non-reportable. Conclusions: The genotypic method confirmed that R5 strains were more prevalent despite the fact thatpatients were treatment-experienced for several years. The genotypic strategy proved to be a fasterand cost-effective option as compared to phenotypic assays. According to our results, two of every threepatients under antiretroviral therapy and with virologic failure harbour R5 strains, and may be candidatesfor use of a CCR5 antagonist.