Dynamics of HIV tropism under suppressive antiretroviral therapy: implications for tropism testing in subjects with undetectable viraemia.

OBJECTIVES: The use of maraviroc as part of a simplification of antiretroviral therapy (ART) is hampered by the difficulty of assessing viral tropism in patients with undetectable viraemia. In this context, information on tropism might be obtained from testing either older stored viraemic sera collected before initiation of ART or current proviral DNA in peripheral blood cells.
METHODS: HIV-1-infected individuals who had initiated ART and had undetectable viraemia for >2 years were identified. V3 genotyping was performed in parallel from plasma HIV-RNA and proviral DNA before starting ART and from proviral DNA while on suppressive ART. Viral tropism was interpreted using geno2pheno (false positive rate = 10%) and an optimized version of position specific scoring matrices (PSSM) with a greater sensitivity to detect X4 variants (PSSM(X4/R5-8)).
RESULTS: A total of 78 HIV-1 infected individuals were examined. Mean time under suppressive ART was 3.5 years (interquartile range: 2.3-4.4). The rate of X4 variants in plasma and proviral DNA samples at baseline was 32.8% and 34.0%, respectively. It was 33.9% after >2 years of suppressive ART in DNA samples. Paired RNA/DNA tropism results at baseline could be obtained for 38 patients, with an overall 82% concordance. After >2 years of suppressed plasma viraemia, HIV tropism was re-assessed in proviral DNA; tropism switches were uncommon, especially comparing baseline and most recent DNA longitudinal specimens (12%).
CONCLUSIONS: HIV tropism switches over time under suppressive ART are rare. There is a relatively good correlation between RNA and DNA tropism estimations using genotypic tests. Thus, HIV-1 tropism might confidently be examined either in older stored viraemic plasma specimens or in current proviral DNA samples.