Cellular levels of HIV unspliced

Cellular levels of HIV unsplicedRNA from patients on combination antiretroviral therapy with undetectable plasma viremia predict the therapy outcome.

Combination antiretroviral therapy, the standard of care for HIV-1 infection, is considered to be successful when plasma viremia remains below the detection limit of commercial assays. Yet, combination antiretroviral therapy fails in a substantial proportion of patients after the apparent success. No laboratory markers are known that are predictive of combination antiretroviral therapy outcome in initial responders during the period of undetectable plasma viremia. Here, the authors report the results of a retrospective longitudinal study of twenty-six HIV-infected individuals who initially responded to cART by having plasma viremia suppressed to <50>. Eleven of these patients remained virologically suppressed, whereas fifteen experienced subsequent combined antiretroviral therapy failure. Using sensitive methods based on seminested real-time PCR, they measured the levels of HIV-1 proviral (pr) DNA, unspliced (us) RNA, and multiply spliced RNA in the peripheral blood mononuclear cells (PBMC) of these patients at multiple time points during the period of undetectable plasma viremia on combination antiretroviral therapy. Median under-therapy level of usRNA was significantly higher (0.43 log(10) difference, P = 0.0015) in patients who experienced subsequent combination antiretroviral therapy failure than in successfully treated patients. In multivariate analysis, adjusted for baseline CD4(+) counts, prior antiretroviral therapy experience, and particular combination antiretroviral therapy regimens, the maximal usRNA level under therapy was the best independent predictor of subsequent therapy failure (adjusted odds ratio [95% CI], 24.4 [1.5-389.5], P = 0.024). The only other factor significantly associated with combination antiretroviral therapy failure was prior antiretroviral therapy experience (adjusted odds ratio [95% CI], 12.3 [1.1-138.4], P = 0.042). Levels of usRNA under combination antiretroviral therapy inversely correlated with baseline CD4(+) counts (P = 0.0003), but did not correlate with either baseline usRNA levels or levels of prDNA under therapy. The authors conclude that their data demonstrate that the level of HIV-1 usRNA in PBMC, measured in combination antiretroviral therapy-treated patients with undetectable plasma viraemia, is a strong predictive marker for the outcome of therapy.

Editors’ note: Ultrasensitive assays can detect low-level viraemia (virus in the blood) in people who have undetectable viral loads by standard commercial tests. It is unknown whether this reflects ongoing virus replication despite antiretroviral treatment or release of virus from stable reservoirs without new replication cycles. Likewise, whether the presence of intracellular virus reflects ongoing replication or viral production from stable reservoirs is unclear. This is the first study to find an association, and it was strong, between subsequent treatment failure and the level of unspliced RNA in peripheral blood mononuclear cells in people considered to be treatment successes with viral loads below 50 copies/ml. Furthermore, the unspliced RNA level was inversely associated with baseline CD4+ count, possibly explaining the link between baseline CD4+ count and risk of therapy failure. It is important that this study be replicated because it implies that testing the level of unspliced RNA may actually be a sensitive prognostic indicator, picking up drug-resistant escape mutants before treatment failure occurs.