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Session 81 Poster Presentations
Isolation and Quantification of HIV-1 in Biological Specimens
Session Day and Time: Tuesday 1:30 - 3:30 pm
Room: Hall A


667
Quantitation of Genetically Diverse HIV Group M and O Specimens: A Challenge for Viral Load Assays
P. Swanson1, A. Golden1, C. de Mendoza2, Y. Joshi3, P. Bodelle1, J. Yamaguchi1, C. Brennan1, V. Soriano2, R. L. Hodinka3, G. Schochetman1, S. Devare1, J. Hackett Jr.*1
1Abbott Labs, Abbott Park, IL; 2Inst de Salud Carlos III, Madrid, Spain; and 3Children's Hosp of Philadelphia and Univ of Pennsylvania Sch of Med, PA

Background: HIV-1 evolution and changing strain distribution presents a challenge to nucleic acid-based assays. Reliable patient monitoring of viral loads should ensure the detection and accurate quantification of genetically diverse HIV-1 strains. In this study, a well-characterized panel of genetically diverse group M, group O, and recombinant viruses was used to evaluate performance of four commercially available quantitative viral load tests.

Methods: A panel of 97 HIV seropositive plasma specimens was collected in Cameroon, South Africa and Brazil. The gag p24, pol integrase, and env gp41 region sequences of each sample were characterized to assign group/subtype and to assess genetic diversity at primer/probe binding sites. HIV RNA concentrations were compared using 4 ultrasensitive viral load assays: LCx HIV RNA Quantitative (LCx) (Abbott Laboratories), AMPLICOR HIV-1 MONITOR version 1.5 (Monitor v1.5) (Hoffman La Roche), Versant HIV-1 RNA version 3.0 (bDNA) (Bayer Diagnostics) and NucliSens HIV-1 QT (NucliSens) (bioMerieux).

Results: Based on phylogenetic analysis, the panel included group M subtypes A, B, C, D, F, G, and mosaics (CRF01_AE, CRF02_AG, G/A, F/B, and H/A) as well as group O. In this study, the LCx HIV assay quantified 97 (100%) of the samples. In comparison, bDNA, Monitor v1.5 and NucliSens quantified 94 (96.9%), 92 (94.8%), and 86 (88.6%) of the samples, respectively. Monitor v1.5, bDNA and NucliSens failed to detect 1 subtype C and 2 group O samples. Monitor v1.5 and NucliSens also failed to detect 2 CRF02_AG samples while NucliSens did not detect 6 additional samples: 1 A, 1 C, 1 G, and 3 mosaics. Relative to LCx, Monitor v1.5 underquantified 2 CRF02_AG and 1 subtype A by more than 1 log10 RNA copies/ml. These 2 AG mosaics were underquantified by Monitor v1.5 compared to NucliSens. Relative to Monitor v1.5 and bDNA, LCx underquantified 1 G/A mosaic sample by more than 1 log10 RNA copies/ml. For group M strains, mean total mismatches at primer/probe sites were 1.4 for LCx, 4.1 for Monitor v1.5 and 7.9 for NucliSens.

Conclusions: Overall, the highest correlation for group M-infected plasma specimens was observed between bDNA and LCx with progressively lower correlations for Monitor v1.5 and NucliSens. However, only the LCx assay quantified the group O samples. Of the tests evaluated, performance of the LCx was the most subtype- and group-independent.