Background
Understanding the sensitivity of viral envelopes to broadly neutralizing antibodies (bNAbs) encoded within the reservoir is of major importance in evaluating efficacy in analytical treatment interruption (ATI) trials using bNAbs as an intervention in people living with HIV (PLWH). BNAbs have been shown to impact viral load setpoint during interruption of antiretroviral therapy (ART) for viruses sensitive to bNAb neutralization. In this study, we assessed the sensitivity of viral envelopes (Envs) sequenced from RV254 participants who started ART during acute infection for sensitivity to the bNAbs VRC07-523LS and PGDM1400LS. VRC07-523LS and PGDM1400LS target two separate sites on the HIV Env, the CD4 binding site and the V2 apex, respectively, increasing the likelihood of sensitivity of these viral Envs when they are combined together.
Methods
Following sequencing and cloning of 119 representative Envs from 116 RV254 participants, pseudoviruses (pSVs) harboring functional Envs were produced via transfection. Env sensitivity was measured in neutralization assays in which several concentrations of VRC07-523LS alone, PGDM1400LS alone, and a combination of VRC07-523LS and PGDM1400LS were tested against uniform volumes of each candidate-derived pSV. IC80s and IC50s of each mAb were determined and compared between the single mAbs and the combination of PGDM1400LS and VRC07-523LS. IC50s or IC80 <1mg/mL were considered sensitive to bNAb neutralization.
Results
Of the 119 Envs, 59% were sensitive to PGDM1400LS (potency=0.116μg/mL), 77% were sensitive to VRC07-523LS (0.324 μg/mL), and 87% were sensitive to the combination using IC50 <1mg/mL (Fig. 1a). When assessing IC80, 47% were sensitive to PGDM1400 (potency=0.202 μg/mL), 49% were sensitive to VRC07-523LS (0.483 μg/mL), and 63% were sensitive to the combination (Fig. 1b). The majority of Envs (85%) tested were CFR01_AE.
Conclusions
A key component evaluating efficacy in ATI trials using bNAbs is the sensitivity of the glycoprotein envelope to antibody neutralization. Combining VRC07-523LS and PGDM1400LS bNAbs provided increased coverage across viral Envs. Furthermore, PGDM1400LS demonstrated more potent neutralization across the screened candidates and required lower concentrations to achieve a higher level of viral inhibition in comparison to VRC07-523LS. These data provide evidence that CRF01_AE Envs sequenced from viral Env are sensitive to VRC07-523LS and PGDM1400LS and antibodies may be used as candidate bNAbs in future ATI trials.
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