The relationship of Plasmodium falciparum humeral immunity with HIV-1 immunosuppression and treatment efficacy in Zambia

Background
HIV-1 infection affects malaria humoral immunity during pregnancy, but data for non-pregnant adults are lacking. This study reports the impact of HIV-1 infection and other variables on the level of malaria humoral immunity in adults with clinical malaria and whether humoral immune suppression was a risk factor for treatment failure.
Methods
Sera of 224 HIV-1 infected and 115 uninfected adults were compared for IgG to merozoite antigens AMA-1 and MSP2 (3D7 and FC27 types) determined by ELISA, and for IgG to the Variant Surface Antigens (VSA) of three different parasite line E8B, A4 and HCD6 determined by flow cytometry.
Results
Compared to HIV-1 uninfected adults, AMA-1 IgG was lower in HIV-1 infected (P=0.02) and associated with low CD4 count AMA-1 IgG (P=0.003). Low IgG to all three merozoite antigens was associated with less anaemia (P=0.03). High parasite load was associated with low MSP2 IgG 3D7 and FC27 types (P=0.02 and P=0.08). Antibody levels to VSA did not differ between HIV-1 infected and uninfected adults. However, low VSA IgGs were associated with high parasite load (P[less than or equal to]0.002 for each parasite line) and with treatment failure (P[less than or equal to]0.04 for each parasite line).
Conclusion
HIV-1 affects humoral responses to AMA-1, but seems to marginally or not affect humoral responses to other merozoite antigens and VSAs. The latter were important for controlling parasite density and predict treatment outcome.