Ultrasensitive assessment of residual HIV viraemia in HAART-treated patients with persistently undetectable plasma HIV-RNA: a cross-sectional evaluation

Improvements in HIV-RNA assays have made accurate detection of as few as 2 copies/ml possible. This study objective was the evaluation of ultrasensitive HIV-RNA quantitation (beneath current threshold: 50 copies/ml) in patients receiving different antiretroviral regimens. A cross-sectional, ultrasensitive measurement of HIV-RNA levels (detection limit: 2.5 HIV-RNA copies/ml) was performed in 154 HIV-1-infected patients receiving ARV therapy, all classed as full responders according to the 50 copies/ml cut-off. Patients were undergoing treatment with two nucleoside/nucleotide reverse transcriptase inhibitors (N/NtRTIs) plus nevirapine (NVP, n = 48), efavirenz (EFV, n = 57) or lopinavir/ritonavir (LPV/r, n = 49). Undetectable HIV-RNA (<2.5 copies/ml) occurred in 29/48 (60.4\%), 24/57 (42.1\%) and 14/49 (28.6\%) NVP, EFV and LPV/r recipients, respectively. Mean virological-suppression (<50 copies/ml) duration was 28.6 months (median = 22, SD = 17.8), and only in LPV/r recipients length of suppression was associated with significantly lower HIV-RNA levels (P = 0.015). Mean nadir CD4+ cell count of 270 cells/mm(3) (median = 240, SD = 194.5) was significantly lower in the LPV/r arm (P < 0.001). Nadir CD4+ level correlated with virological suppression but had opposite trends between NVP (positive) and LPV/r (negative; two tailed P = 0.01). Logistic regression analysis showed NVP was the only independent factor associated with virologic suppression. NVP has demonstrated a distinct virological advantage at sub-clinical viral loads, possibly due to its greater penetration in extra-vascular compartments, warranting further investigation in the context of persistent low-level viraemia in long-term HAART.