BACKGROUND: Genotypic tropism testing (GTT) has been developed largely on HIV-1 subtype B. Although a few reports have analysed the utility of GTT in other subtypes, more studies using HIV-1 subtype C (HIV-1C) are needed, considering the huge contribution of HIV-1C to the global epidemic. METHODS: Plasma was obtained from 420 treatment-naive HIV-1C infected Ethiopians recruited 2009-2011. The V3 region was sequenced and the coreceptor usage was predicted by five tools: Geno2Pheno clinical-and clonal-models, PhenoSeq-C, C-PSSM and Raymond's algorithm. The impact of baseline tropism on antiretroviral treatment (ART) outcome was evaluated. RESULTS: Of 352 patients with successful baseline V3 sequences, the proportion of predicted R5 virus varied between the methods by 12.5% (78.1%-90.6%). However, only 58.2% of the predictions were concordant and only 1.7% were predicted to be X4-tropic across the five methods. Compared pairwise, the highest concordance was between C-PSSM and Geno2Pheno clonal (86.4%). In bivariate intention to treat (ITT) analysis, R5 infected patients achieved treatment success more frequently than X4 infected at month six as predicted by Geno2Pheno clinical (77.8% vs 58.7%, P = 0.004) and at month 12 by C-PSSM (61.9% vs 46.6%, P = 0.038). However, in the multivariable analysis adjusted for age, gender, baseline CD4 and viral load, only tropism as predicted by C-PSSM showed an impact on month 12 (P = 0.04, OR 2.47, 95% CI 1.06-5.79). CONCLUSION: Each of the bioinformatics models predicted R5 tropism with comparable frequency but there was a large discordance between the methods. Baseline tropism had an impact on outcome of first line ART at month 12 in multivariable ITT analysis but only based on prediction by C-PSSM which thus possibly could be used for predicting outcome of ART in HIV-1C infected Ethiopians.
Kalu, A. W., Telele, N. F., Gebreselasie, S., Fekade, D., Abdurahman, S., Marrone, G., & Sönnerborg, A. (2017). Prediction of coreceptor usage by five bioinformatics tools in a large Ethiopian HIV-1 subtype C cohort. PLoS ONE, 12(8). https://doi.org/10.1371/journal.pone.0182384