Background
Nonsuppressible viremia (NSV) represent a subset of individuals with persistent low-level viremia due to a hyperactive HIV reservoir. Little is known about whether persistent antigenemia during NSV can induce a stronger immune response. Autologous neutralizing antibodies (aNAb) represent a key adaptive immune response for viral control and HIV rebound during treatment interruption has been linked to aNAb escape. We performed extended range plasma HIV RNA and near-full length (NFL) proviral sequencing at longitudinal timepoints from two participants with NSV. We evaluated the aNAb sensitivities of HIV env from both the plasma HIV (i.e., from producer proviruses) and intact proviruses that did not match any plasma sequences (i.e., non-producer proviruses).
Methods
We performed an in-house assay for the extended range single-genome amplification (pol-env) of low-level plasma viremia and NFL single-genome sequencing (SGS) to identify both producer and nonproducer proviruses from multiple timepoints. We then cloned the HIV-1 env using ABC cloning to create pseudoviruses. aNAb neutralization of plasma RNA and nonproducer proviral env were evaluated using purified IgG from plasma samples collected at longitudinal timepoints. Serial dilutions of IgG that neutralized 50% of viral infection (IC50) was determined.
Results
We compared the aNAb response for two NSV participants, LV8 and LV9, who demonstrated NSV with detectable viral loads of between 34-578 HIV-1 RNA copies/mL over 12 years for LV8 and 39-1270 copies/mL over 13 years for LV9. We evaluated aNAb activity in LV8 at 6 time points over 2 years and for LV9 at 5 timepoints over 3 years. Plasma env from both participants demonstrated relatively high levels of aNAb resistance over the entire period with IC50 of >101 ug/mL for LV8 and 57.5-94.9 ug/mL for LV9. This is despite no changes in LV8 plasma RNA env sequences over 2 years. HIV Env from non-producer proviruses demonstrated a range of resistance to aNAb activity.
Conclusions
During nonsuppressible viremia, plasma virus can show sustained resistance to aNAb activity over several years despite no changes in the plasma HIV env sequence. The underlying proviral reservoir demonstrated a wider range of aNAb sensitivity. Additional studies are needed to explore why detectable viremia may not stimulate a robust HIV-specific humoral response during ART.
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