Elite controllers or misquantification of virus load by Cobas TaqMan?
© Taylor et al; licensee BioMed Central Ltd. 2008
Published: 10 November 2008
Our outdoor patient clinic in Salzburg (Austria) comprises 170 HIV-infected patients. Since 2004 our laboratory has been using Cobas TaqMan 48 real time PCR analyser (Roche) for detection and quantification of HIV-1 RNA. To date we could identify four patients who remained undetectable (3/4) or who presented with very low viremia (<200 copies per ml) while receiving no antiretroviral therapy at all.
To evaluate this issue, further analyses of the HIV-1 RNA in plasma were undertaken using Cobas Amplicor version 1.5, and the Abbott m2000 system. For patients 1 and 2, virus was isolated by co-cultivation of patients' PBMCs with uninfected donor PBMCs and the nucleic acid sequences of the gag, pol, and env genes of both virus isolates were determined. For patients 3 and 4, gag and pol genes were sequenced directly from PCR amplicons. All sequences were subsequently subtyped using standard phylogenetic analysis tools. Finally, a positive control amplicon of Cobas TaqMan was compared to the sequences of our patients.
Summary of results
Cobas TaqMan Real Time PCR [cop/ml]
Abbott m2000 PCR [cop/ml]
Cobas Amplicor Version 1.5 PCR [cop/ml]
In the face of the severe consequences for therapeutic decisions and patient counseling, the observed rate of misquantifications in our patient cohort by Cobas TaqMan HIV-1 is unacceptable. Misquantifications can not be assigned to a rare subtype but occur with different virus strains. There is an urgent need for refinement of the Cobas TaqMan. In addition, these findings shed a different light concerning the definition of so-called elite controllers in clinical practice.
This article is published under license to BioMed Central Ltd.