HIV-1 outcompetes HIV-2 in dually infected Senegalese individuals with low CD4⁺ cell counts

Objective: Dual infection with HIV-1 and HIV-2, which is not uncommon in West Africa, has implications for transmission, progression, and antiretroviral therapy (ART). Few studies have examined viral dynamics in this setting. Our objective was to directly compare HIV-1 and HIV-2 viral loads and to examine whether this relationship is associated with CD4⁺ cell count.

Study design: This is a retrospective analysis of data from observational cohort studies.

Methods: We compared HIV-1 and HIV-2 viral loads from 65 dually infected, ART-naive Senegalese individuals. Participants provided blood, oral fluid, and cervicovaginal lavage (CVL) or semen samples for virologic and immunologic testing. We assessed relationships between HIV-1 and HIV-2 levels using linear regression with generalized estimating equations to account for multiple study visits.

Results: After adjusting for CD4⁺ cell count, age, sex, and commercial sex work, HIV-1 RNA levels were significantly higher than HIV-2 levels in semen, CVL, and oral fluids. Despite similar peripheral blood mononuclear cell DNA levels among individuals with CD4⁺ cell counts above 500 cells/μl, individuals with CD4⁺ cell counts below 500 cells/μl had higher HIV-1 and lower HIV-2 DNA levels. Individuals with high CD4⁺ cell counts had higher mean HIV-1 plasma RNA viral loads than HIV-2, with HIV-1 levels significantly higher and HIV-2 levels trending toward lower mean viral loads among individuals with low CD4⁺ cell counts.

Conclusion: Our data are consistent with the hypothesis that with disease progression, HIV-1 outcompetes HIV-2 in dually infected individuals. This finding helps explain differences in prevalence and outcomes between HIV-1, HIV-2, and HIV-dual infection.