Differences in proviral DNA load between HIV-1- and HIV-2-infected patients.

Introduction: The lesser pathogenicity of HIV-2 relative to HIV-1 is generally attributed to its slower replication. To compare the amounts of total HIV DNA during human HIV-1 and HIV-2 infection, we developed a quantitative real-time PCR method with a unique external quantification standard based on a single plasmid harboring both the HIV-1 and the HIV-2 LTR.

Methods: Viral DNA load was compared between 40 HIV-1-infected and 42 HIV-2-infected antiretroviral-naive patients.

Results: The difference between HIV-1 and HIV-2 proviral DNA load was highly significant in patients with CD4 cell counts > 500 cells/microl [HIV-1: n = 14; median, 2.5; interquartile range (IQR), 2.1-2.7; HIV-2: n = 22, median, 1.6; IQR, 1.0-2.0] and in patients with CD4 cell counts between 300 cells/microl and 500 cells/microl (HIV-1: n = 12; median, 2.7; IQR, 2.3-2.8; HIV-2: n = 11; median, 2.0; IQR, 1.0-2.4). Too few HIV-2-infected patients had CD4 cell counts < 300 cells/microl to detect a significant difference but DNA values were again lower in HIV-2-infected patients (HIV-1: n = 14; median, 2.9; IQR, 2.2-3.2; HIV-2: n = 9; median, 2.7; IQR, 2.2-3.3).

Conclusions: These differences are in line with the natural histories of the two infections and show that HIV-2 infection is a valid model for studying the pathophysiology of HIV infection in general.