ObjectiveThe aim of the study was to evaluate the use of proviral DNA as a source of viral genetic material for genotypic coreceptor tropism testing (GTT). MethodsGTT consisted of bulk V3 sequencing followed by geno2pheno interpretation with the interpretative cut-off [false positive rate (FPR)] set at 5 and 10%. GTT was performed for 165 patients with a viral load of 4500 HIV-1 RNA copies/mL on simultaneously collected plasma RNA and proviral DNA, and for 126 patients with a viral load of o500 copies/mL on current proviral DNA and pretreatment plasma RNA. Phenotypic tropism testing (PTT) results were available for 142 samples. ResultsIn the simultaneous RNA/DNA comparison, concordance in prediction was 95.2% (at FPR 10%) and 96.4% (at FPR 5%). Six RNA-R5/DNA-X4 and two RNA-X4/DNA-R5 discordances were observed at an FPR of 10%, and six RNA-R5/DNA-X4 discordances were observed at an FPR of 5%. In the longitudinal RNA/DNA comparison, concordance was 88.1% (at FPR 10%) and 90.5% (at FPR 5%). Eight RNA-X4/DNA-R5 and seven RNA-R5/DNA-X4 discordances were seen at an FPR of 10%, and 10 RNA-R5/DNA-X4 and two RNA-X4/DNA-R5 discordances at an FPR of 5%. The overall concordance of RNA GTT with PTT was 82% (at FPR 10%) and 83% (at FPR 5%). The overall concordance of DNA GTT with PTT was 85% (at both 10 and 5% FPRs). ConclusionsGTT produced highly concordant tropism predictions for proviral DNA and plasma RNA. GTT on proviral DNA offers a promising approach for tropism prediction in clinical practice, particularly for the assessment of treated patients with low or suppressed viraemia.Keywords: chemokine (C-C motif) receptor 5 (CCR5) inhibitors, genotypic tropism testing, HIV-1 coreceptor, HIV-1 proviral DNA Accepted 25 January 2011Introduction Chemokine (C-C motif) receptor 5 (CCR5) antagonists, members of the class of HIV-1 entry inhibitors, selectively inhibit the replication of CCR5-using (R5) viral strains. Before introducing a CCR5 antagonist as a component of antiretroviral therapy (ART), coreceptor usage, or viral tropism, must be determined to exclude the possibility of the presence of chemokine (C-X-C motif) receptor 4 (CXCR4)-using (X4) strains, as these are associated with poor virological response to the drug [1]. The output of the earliest HIV-1 phenotypic tropism testing (PTT) assay was the formation of syncytia in cultured MT2 cells after virus inoculation. This assay is less well suited for use in routine clinical practice because of inherent difficulties with Correspondence: Prof. Chris Verhofstede, AIDS Reference Laboratory, University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. Tel: 1 32 9 332 51 61; fax: 1 32 9 332 38 41; e-mail: Chris.verhofstede@ugent.be DOI: 10.1111/j.1468-1293.2011.00922.x HIV Medicine (2011 GTT is based on analysis of the V3-loop sequence of the HIV-1 envelope (env) gene using bioinformatic prediction models to deduce coreceptor usage. GTT has the advantage of being less technically demanding, more rapid and less expensive than PTT, thereby meeting today's need for a fast and...

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Access to antiretroviral therapy (ART) is increasing in resource-limited settings (RLS) and can successfully reduce HIV-related morbidity and mortality. However, virologic failure and development of viral drug resistance can result in reduced treatment options and disease progression. Additionally, transmission of resistant virus, and particularly multi-drug resistance, could become a public health concern. This study evaluated treatment success and development of ART drug resistance after short-term treatment among patients attending the Comprehensive HIV Care Centre (CCC) of Coast Province General Hospital, Mombasa, Kenya. One hundred and fifty HIV-infected individuals receiving ART were consecutively recruited to participate in the study. After determination of plasma viral load, patients with detectable viral load levels were subjected to genotypic drug resistance testing. At the time of sampling, 132 of the 150 participants were on ART for more than 6 months (median 21 months, IQR = 12-26). An efficient viral load reduction to below 50 copies/ml was observed in 113 (85.6%) of them. Of the 19 patients with a detectable viral load, sequencing of the protease (PR) and reverse transcriptase (RT) gene was successful in 16. Eleven (11) of these 16 patients were infected with a subtype A1 virus. Major PR mutations were absent, but mutations associated with drug resistance in RT were detected in 14 of the 16 patients (87.5%). High-level resistance against at least 2 drugs of the ART regimen was observed in 9/14 (64.3%). The 3TC mutation M184V and the NNRTI mutation K103N were most frequent but also the multi-drug resistance Q151M and the broad NRTI cross-resistance K65R were observed. The results of this study revealed a high rate of treatment success after short term ART in patients treated at a public provincial hospital in a RLS. Nevertheless, the observed high risk of accumulation of resistance mutations among patients failing treatment and the selection of multi-drug resistance mutations in some, remains of great concern for future treatment options and potential transmission to partners.

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