Abstract
New methods of HIV-1 RNA quantification based on dual-target detection are increasingly used in HIV viral load monitoring, but clinical implications and impact of dual-target detection on HIV-1 infection management are not established. Aptima HIV-1 Quant Dx assay is a last generation HIV viral load method, that uses pol and LTR as simultaneous target, providing quantitative results based mainly on pol target, while LTR target is used to report the results when pol signal is absent. In our laboratory, about 6% of results of all HIV-1 viral load tests performed with this platform in one year period resulted from LTR signal. Interestingly, LTR-based viremia (sometimes exceeding 1,000 copies/mL) was observed in a small proportion (up to 1%) of patients under ART, considered for long time virologically suppressed on the basis of a single target (pol-based) assay. Male gender, >700 vs <200 CD4 cell/mL and dual therapy including NRTI plus either NNRTI, or PI/b or INSTI were independently associated with increased risk of LTR-based HIV-1 viral load detection by multivariable logistic regression. A significant linear correlation was observed between LTR-based HIV-1 RNA levels and PBMC-associated proviral DNA. Moreover, in a small group of patients with HIV-1 RNA levels >200 copies/mL, longitudinal assessments showed parallel kinetics between plasma viremia and proviral DNA. Sequencing of pol region for drug resistance assessment in patients with LTR-based viremia failed on plasma HIV-1 RNA, while it was successful on proviral DNA. The detection/quantification of HIV-1 viremia based only on LTR signal with a dual target assay in samples resulting undetectable with the more conventional target pol needs accurate evaluation; unravelling the biological basis of this phenomenon, here described for the first time, is mandatory to establish relevance and implication by both pathogenetic (i.e. infectivity of LTR-detected viruses, reservoir turnover, immune activation, etc.) and clinical standpoint.
Highlights
Aptima HIV-1 Quant Dx assay (Aptima) exploits dual-target approach to detect and quantify HIV-1 RNA, viral load (VL) results calculated by the platform software derive from one of the two amplified targets: on a total of 14,865 plasma clinical samples, 13,972 (93.99%) were quantified with pol signal, while 893 (6.01%) were based only on the signal provided by LTR
It is worth to note that a sample collected in 2015 and resulting at that time with HIV-1 RNA undetectable with RealTime, stored at -80 ̊C and never thawed before, was re-tested with Aptima and showed 1,031 copies/mL based on LTR signal, confirming persistent LTR-based VL dated at least 4 years back the introduction of the Aptima assay in the laboratory
This study is the first report addressing the detection/quantification of HIV-1 viremia based only on LTR signal with a dual target assay in samples resulting undetectable with the more conventional target pol
Summary
According to international guidelines for clinical management of HIV-1 disease, HIV-1 RNA viral load (VL) and CD4+ T lymphocyte (CD4) cell count are the two main laboratory. The design of several available HIV-1 RNA assays is based on the detection of a single target region of HIV-1 genome, such as pol, gag or LTR, while in the last generation assays the design tends to shift towards the simultaneous detection of two regions of viral genome. After the implementation of Aptima as routine VL test, we observed that some patients, historically considered fully suppressed with the previous method (RealTime), showed measurable HIV-1 RNA detected only with LTR target. For this reason we analyzed the frequency, among our patient population, of VL results based only on LTR detection, the reproducibility of LTR-based HIV-1 viremia results, and the characteristics of patients displaying LTR-based viremia. These data may have considerable implication in clinical management of HIV1 infection and could reveal unanticipated pathogenetic scenarios
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