Magnetic-silica based nucleic acid extraction for Human Immunodeficiency Virus Type-1 drug-resistance testing in low viremic patients

Human Immunodeficiency Virus Type-1 (HIV-1) drug-resistance testing is challenging for viral loads below 1,000 copies/mL, but, according to HIV-1 guidelines, it should be considered for improving patient management and treatment options. High-recovery and high-purity extraction methods can enhance standard performances of HIV-1 genotyping assays based on direct full-population sequencing. Aim of the present study was to evaluate performances of the NucliSENS easyMAG (NeM) (BioMerieux, Marcy l'Etoile, F) semi-automated nucleic acid extraction system combined with the direct full-population sequencing ViroSeq HIV-1 genotyping (Abbott, IL, US), for detecting drug resistance in samples with HIV-1 RNA< 1,000 copies/mL (n = 62). Data were compared with those from the ViroSeq manual extraction in 86 samples with HIV-1 RNA< 1,000 copies/mL and studied on HIV-1 reference standards. HIV-1 genotyping was successful in 98% of samples extracted with NeM (61/62) and in 84% of those extracted with ViroSeq (72/86) (X-2 = 8.508, p = 0.004). HIV-1 RNA levels in samples successfully processed with NeM were significantly lower than those in manually processed ones (mean + SD, respectively, 285 +/- 222 copies/mL vs. 403 +/- 269 copies/mL) (p = 0.004). For HIV-1 RNA levels <300 and 500 copies/mL, performances of HIV-1 genotyping with NeM were significantly high (97% and 98%, vs. 68% and 78% for manual extraction). As assessed on HIV-1 RNA reference standards, the detection rate at 200 copies/mL for HIV-1 genotyping with NeM extraction was 100%. In conclusion, these data support that HIV-1 direct full-population sequencing combined with NeM is associated with a significantly high success rate, thus improving the management of HIV-1 drug resistance in low viremic patients. (C) 2009 Elsevier B.V. All rights reserved.