Combinations of Single Chain Variable Fragments From HIV Broadly Neutralizing Antibodies Demonstrate High Potency and Breadth.

Rebecca T. van Dorsten,Penny L. Moore,Kshitij Wagh,Lynn Morris

doi:10.3389/fimmu.2021.734110

Abstract

Broadly neutralizing antibodies (bNAbs) are currently being assessed in clinical trials for their ability to prevent HIV infection. Single chain variable fragments (scFv) of bNAbs have advantages over full antibodies as their smaller size permits improved diffusion into mucosal tissues and facilitates vector-driven gene expression. We have previously shown that scFv of bNAbs individually retain significant breadth and potency. Here we tested combinations of five scFv derived from bNAbs CAP256-VRC26.25 (V2-apex), PGT121 (N332-supersite), 3BNC117 (CD4bs), 8ANC195 (gp120-gp41 interface) and 10E8v4 (MPER). Either two or three scFv were combined in equimolar amounts and tested in the TZM-bl neutralization assay against a multiclade panel of 17 viruses. Experimental IC50 and IC80 data were compared to predicted neutralization titers based on single scFv titers using the Loewe additive and the Bliss-Hill model. Like full-sized antibodies, combinations of scFv showed significantly improved potency and breadth compared to single scFv. Combinations of two or three scFv generally followed an independent action model for breadth and potency with no significant synergy or antagonism observed overall although some exceptions were noted. The Loewe model underestimated potency for some dual and triple combinations while the Bliss-Hill model was better at predicting IC80 titers of triple combinations. Given this, we used the Bliss-Hill model to predict the coverage of scFv against a 45-virus panel at concentrations that correlated with protection in the AMP trials. Using IC80 titers and concentrations of 1μg/mL, there was 93% coverage for one dual scFv combination (3BNC117+10E8v4), and 96% coverage for two of the triple combinations (CAP256.25+3BNC117+10E8v4 and PGT121+3BNC117+10E8v4). Combinations of scFv, therefore, show significantly improved breadth and potency over individual scFv and given their size advantage, have potential for use in passive immunization.

Highlights

Neutralizing antibodies, isolated from a subset of HIV-1 positive individuals, are capable of neutralizing a wide range of HIV viruses
These two Antibody-Mediated Prevention (AMP www.ampstudy.org.za) trials showed that VRC01 had 75% prevention efficacy in high-risk men and women if the infecting virus was sensitive to the antibody at
Combinations of scFv antibodies were able to enhance the breadth and potency of HIV-1 neutralization compared to a single scFv

Summary

Introduction

Neutralizing antibodies (bNAbs), isolated from a subset of HIV-1 positive individuals, are capable of neutralizing a wide range of HIV viruses. Several studies have investigated the potential of antibody combinations and observed, as expected, an increase in breadth and potency [18, 19] These studies demonstrate that the complementary neutralization profiles of individual bNAbs can improve the overall breadth and provide higher coverage of multiclade panels of viruses at much lower antibody concentrations [18, 20]. By using those antibodies that target the HIV subtypes predominant in a specific area, a geographically relevant set of antibodies may be selected to provide optimal coverage and potency [20]. These trials test the aforementioned antibodies in addition to V3 (10–1074) and V2 (PGDM1400) antibodies and the broadly neutralizing MPER-targeting antibody 10E8v4 [23, 24]

Methods

Results

Conclusion