Synergistic Effect by Combining a gp120-Binding Protein and a gp41-Binding Antibody to Inactivate HIV-1 Virions and Inhibit HIV-1 Infection

Xinling Wang,Shibo Jiang,Miao Cao,Lu Lu,Qian Wang,Tianlei Ying,Yanling Wu,Wei Xu

doi:10.3390/molecules26071964

Abstract

Acquired immune deficiency syndrome (AIDS) has prevailed over the last 30 years. Although highly active antiretroviral therapy (HAART) has decreased mortality and efficiently controlled the progression of disease, no vaccine or curative drugs have been approved until now. A viral inactivator is expected to inactivate cell-free virions in the absence of target cells. Previously, we identified a gp120-binding protein, mD1.22, which can inactivate laboratory-adapted HIV-1. In this study, we have found that the gp41 N-terminal heptad repeat (NHR)-binding antibody D5 single-chain variable fragment (scFv) alone cannot inactivate HIV-1 at the high concentration tested. However, D5 scFv in the combination could enhance inactivation activity of mD1.22 against divergent HIV-1 strains, including HIV-1 laboratory-adapted strains, primary HIV-1 isolates, T20- and AZT-resistant strains, and LRA-reactivated virions. Combining mD1.22 and D5 scFv exhibited synergistic effect on inhibition of infection by divergent HIV-1 strains. These results suggest good potential to develop the strategy of combining a gp120-binding protein and a gp41-binding antibody for the treatment of HIV-1 infection.

Highlights

HIV-1 is a type I enveloped virus that infects CD4+T cells and destroys the human immune system, resulting in acquired immune deficiency syndrome (AIDS)
We proposed to use a gp41 N-terminal heptad repeat (NHR)-binding antibody D5 scFv in the combination because: (1) Antibodies have the advantage of specificity, good stability, and high affinity [23]; (2) gp41 NHR is covered by gp120 in the native conformation of HIV-1 and only transiently exposed to immune system at the fusion intermediate stage, being unsusceptible to mutations of resistance to the NHR-specific neutralizing antibodies
Without D5 scFv, mD1.22 could efficiently inactivate HIV-1 primary isolates (91US_4 (B, R5), 97TH_NP1525 (A/E, X4, and R5) and 92UG024 (D, X4)) with EC50 values of 4.28-13.43 nM and EC90 values of 8.51-41.49 nM, respectively. As expected, such activity was enhanced by 1.15- to 5.10-fold and 0.98- to 2.43-fold when combined with D5 scFv. These results suggested that combinatorial use of the antibody binding gp41 NHR and gp120-binding protein could enhance the total inactivation effect on HIV-1 cell-free virions, both in laboratory-adapted HIV-1 strains and primary HIV-1 isolates of different subtype and tropism

Summary

Introduction

HIV-1 is a type I enveloped virus that infects CD4+T cells and destroys the human immune system, resulting in acquired immune deficiency syndrome (AIDS). For AZT-resistant strains, mD1.22 and D5 scFv in combination exhibited strong synergism, e.g., for the strain 964, the CI value was 0.24, and enhancement of inhibitory activity was 6.99- and 7.65-fold, respectively These results suggest that the gp41-targeting antibody has a synergistic effect with gp120-binding protein. We identified the synergistic effect of combining gp120-binding protein mD1.22 and gp41-binding antibody D5 scFv on inhibition of infection by divergent HIV-1 Molecules 2021, 26, x FOR PEER REVIsEtWrains, including laboratory-adapted strains, primary HIV-1 isolates, T20-resistant HIV-1 7 of 1 strains, and AZT-resistant HIV-1 strains. The dual synergistic effect in inactivating cell-free HIV-1 virions and inhibiting HIV-1 infection of target cells make this combinational strategy a promising candidate for further therapeutic development

Materials and Methods

Inactivation of HIV-1 Virions

Inhibition of HIV-1 Infection

Conclusions