Short Communication: Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy.

The effects of antiretroviral therapy (ART) on the performance of HIV incidence assays have been well documented. To improve upon current assay approaches or focus the development of future assays, studies are needed to characterize the effects of ART on all candidate HIV incidence assays. In this study, we compared the performance of three antibody avidity-based HIV incidence assays, the Limiting Antigen (LAg), Bio-Rad Avidity, and HIV-1 Multiplex assays, using a well-defined cohort of recent HIV-1 seroconverters composed of ART-naive HIV-1-infected individuals and those who received ART early or delayed in the course of infection. Differences in the performance of all three avidity-based incidence assays were noted with study subjects who received ART. The LAg assay and Multiplex total antibody measurements (nMFI) exhibited similar kinetics in reactivity, as these assays tended to fluctuate with changes in viral load. In the early ART group, all seven subjects remained recent by both assays at time points >1 year postseroconversion, and assay values declined dramatically postdelayed ART initiation. In contrast, the two-well, antibody-dissociation avidity assays, Bio-Rad Avidity and Multiplex avidity index (AI) measurements, continued to mature in the early ART group, although blunted relative to the ART-naive group, and assay values remained stable after delayed ART initiation. In summary, although the HIV incidence assays evaluated in this study are all designed to measure antibody avidity, each assay is affected differently by ART-induced virus suppression, presumably because of the distinct assay formats and procedures for measuring avidity.