A sudden rise in viral load is infrequently associated with HIV-1 superinfection

Objective: To investigate the association between an unexpected increase in the blood plasma HIV-1 viral load in chronically untreated HIV-infected patients and the occurrence of an HIV superinfection, we analyzed the HIV-1 quasispecies in plasma samples before and at peak level in 14 patients. Results: Phylogenetic analysis of HIV-1 env-V3 fragments showed that in 2 patients a superinfection had occurred: their dominant V3 population at the peak level clustered separately from the V3 sequences in a sample predating the peak level. The rapid rise in viral load could be attributed to upper respiratory tract infections or a vaccination in 4 patients, suggesting that even minor health problems can result in significantly increased HIV-1 replication. In most other patients, no minor or major medical condition accompanied the rise in HIV-1 viral load, implying that in these patients the viral load increase was probably associated with disease progression. Conclusion: This study suggests that an unexpected rapid rise in the plasma HIV-1 viral load of untreated patients can infrequently be ascribed to an HIV-1 superinfection.