The Neutralizing Antibody Response in an Individual with Triple HIV-1 Infection Remains Directed at the First Infecting Subtype.

The effect of serial HIV-1 infection on the development of the broadly neutralizing antibody (bNAb) response was studied in an individual, H01-10366, with a serial HIV-1 superinfection (SI), hence triple infection, and compared with the bNAb response in three superinfected as well as 11 monoinfected men who have had sex with men (MSM) from Amsterdam, the Netherlands. Neutralization assays measuring heterologous neutralizing antibody (NAb) titers on a panel of six representative viruses from different HIV-1 subtypes were performed on blood serum samples obtained ∼3 years after primary HIV infection (PHI) and longitudinally for H01-10366. A bNAb response was defined as having a geometric mean neutralization titer (the reciprocal serum dilution giving 50% inhibition of virus infection, inhibitory dilution (ID50)) ≥100 and neutralizing >50% of viruses in the panel with an ID50 titer ≥100. H01-10366 quickly developed a potent NAb response against subtype B viruses before subtype B SI, but no broadening of the response occurred after the second subtype B infection or the third infection with CRF01_AE. When comparing H01-10366 with matched monoinfected (N = 11) and superinfected (N = 3) individuals analyzed 3 years after PHI, we found that 5 of the 15 individuals (4/11 monoinfected, 1/4 SI) developed a bNAb response. However, there was no statistically discernible difference between the bNAb response and HIV-1 SI. Thus, HIV-1 SI was not associated with the breadth and potency of the bNAb response in this small group of Dutch MSM with SI that included a triple HIV-1-infected individual.