HIV-1 viral diversity and its implications for viral load testing: review of current platforms

The 2008 Recommendations for care of the International AIDS Society reaffirmed the importance of both accurate and sensitive viral load assessment, and by necessity, access to viral load assays. HIV-1 viral load testing is considered essential when initiating antiretroviral therapy (ART), when monitoring ART response, and when considering switching ART regimens. The demand for accurate, reproducible, and cost-effective viral load assays is therefore a global issue. Although the North American and Western European experience has historically been with HIV-1 group M subtype B virus, this paradigm is changing rapidly as migrants and refugees from developing countries with non-B subtype infections often now present for care in the developed world, and travelers to developing countries acquire non-B subtype infection abroad and present for care at home. Awareness of any clinical or laboratory differences between the common HIV-1 group M subtype B and the newer HIV-1 strains being seen in practice is therefore increasingly important. This review of current HIV-1 viral load testing is focused on the potential value of a standardized genotype assignment for HIV-1 viral subtypes, regular monitoring of the performance of available commercial HIV viral load assays on emerging non-B HIV subtypes, circulating recombinant forms (CRFs) and unique recombinant forms (URFs), and a discussion of the implications for resource-limited settings.