Efficiency of HIV-2 cultures from clinical isolates is enhanced after purification by anti-CD44 microbeads

In-depth study of HIV often requires large stock of patients-derived viruses obtained through viral cultures. HIV cultures are currently limited by low recovery rates, especially when viral load is below 100,000 copies per mL. This is problematic for HIV-2 as most patients have spontaneously low to undetectable viremia. New approaches have been developed to enhance viral recovery rates but they are complex or costly to implement. We tested the impact of μMACS^TM VitalVirus Isolation Kit (Miltenyi), a HIV virions capture method using paramagnetic microbeads directed against CD44, a human glycoprotein present in HIV envelope. This method separates viruses from interfering proteins in 45 min, using a reduced sample volume (200 μL versus 1000 μL for classic culture assays). The impact of this purification method on virus recovery rate was assessed with 23 HIV-1 and 29 HIV-2 plasma samples with a wide range of viral loads, in comparison to a classic culture assay used routinely in our laboratory. For both HIV-1 and HIV-2, the culture identification delay was decreased using viral purification (≤7days in most cases). The recovery rate of cultures was improved for HIV-2 isolates (17/29 versus 8/29; p = 0.03) but not for HIV-1 (7/23 versus 5/23; p = 0.74). Notably, HIV-2 isolates with viral loads over 10,000 copies per mL were frequently recovered in culture (68% versus 32% without purification; p = 0.03). This marked improvement on HIV-2, but not on HIV-1, cultures is puzzling. CD44-microbeads may enable a close and prolonged contact between cells and viruses, and may thus overcome HIV-2 difficulties to infect target cells.