A new quantitative HIV load assay based on plasma virion reverse transcriptase activity for the different types, groups and subtypes
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Amplifying and Quantifying HIV-1 RNA in HIV Infected Individuals with Viral Loads Below the Limit of Detection by Standard Clinical Assays
Published on: September 26, 2011
Joséphine Braun1, Jean-Christophe Plantier, Marie-France Hellot
1Laboratoire de Virologie, Biostatistique, Centre Hospitalier Charles Nicolle, 1 rue de Germont, 76031 Rouen cedex, France.
Background:
Plasma viral load monitoring is an integral part of the standard of care for HIV-infected patients in industrialized countries. In developing countries, viral load assay is either unaffordable or hindered by on-site maintenance and/or technical problems.
Objectives:
To evaluate a new and simple quantitative assay for plasma HIV reverse transcriptase (RT) activity; and to compare RT activity-based and RNA-based quantification in plasma samples from patients infected by different subtypes of HIV-1 group-M, HIV-1 group-O and HIV-2.
Methods:
The RT-based viral load assay involves separation of the virion-protected RT and quantification of its activity with an enzyme immunoassay. Plasma viraemia was quantified both by RT activity and by RNA copies in 322 samples from 236 HIV-1 group M-infected patients, including serial samples from 54 patients. Samples from 49 patients infected by HIV-1 group O or HIV-2 were also tested.
Results:
RT activity and RNA copies were detected in 70% of plasma samples; respectively 25% and 1% of samples contained detectable RNA copies or RT activity alone. Measured RT activity corresponded to 48%, 96% and 100% of samples with 1.7-4.0 log(10), 4.1-4.8 log(10) and 4.9-6.7 log(10) RNA copies/ml, respectively. The values of the two assays correlated independently of the HIV subtype (P < 0.0001) and group/type (P < 0.03). Patient follow-up showed a similar pattern of viraemia with the two assays.
Conclusion:
Plasma RT activity assay is a simple, cheap and reliable alternative for HIV viral load determination. As such, it could be particularly valuable for diagnosis and treatment monitoring in developing countries.
