Monoclonal antibodies targeting two immunodominant epitopes on the Spike protein neutralize emerging SARS-CoV-2 variants of concern

Abstract

Background The emergence of new SARS-CoV-2 variants of concern B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta) that harbor mutations in the viral S protein raised concern about activity of current vaccines and therapeutic antibodies. Independent studies have shown that mutant variants are partially or completely resistant against some of the therapeutic antibodies authorized for emergency use. Methods We employed hybridoma technology, ELISA-based and cell-based S-ACE2 interaction assays combined with authentic virus neutralization assays to develop second-generation antibodies, which were specifically selected for their ability to neutralize the new variants of SARS-CoV-2. Findings AX290 and AX677, two monoclonal antibodies with non-overlapping epitopes, exhibit subnanomolar or nanomolar affinities to the receptor binding domain of the viral Spike protein carrying amino acid substitutions N501Y, N439K, E484K, K417N, and a combination N501Y/E484K/K417N found in the circulating virus variants. The antibodies showed excellent neutralization of an authentic SARS-CoV-2 virus representing strains circulating in Europe in spring 2020 and also the variants of concern B.1.1.7 (Alpha), B.1.351 (Beta) and B.1.617.2 (Delta). In addition, AX677 is able to bind Omicron Spike protein just like the wild type Spike. The combination of the two antibodies prevented the appearance of escape mutations of the authentic SARS-CoV-2 virus. Prophylactic administration of AX290 and AX677, either individually or in combination, effectively reduced viral burden and inflammation in the lungs, and prevented disease in a mouse model of SARS-CoV-2 infection. Interpretation The virus-neutralizing properties were fully reproduced in chimeric mouse-human versions of the antibodies, which may represent a promising tool for COVID-19 therapy. Funding The study was funded by AXON Neuroscience SE and AXON COVIDAX a.s.

Immune Escape Associated with RBD Omicron Mutations and SARS-CoV-2 Evolution Dynamics

“…The rapid emergence of new mutations in the Spike protein of the virus affects its virulence and its avoidance of the developed immune defense. Examining the mutation effect on the neutralizing properties of vaccines and antibodies is important for the disclosure of immunodominant regions [ 82 ] and for the development and improvement of therapies against SARS-CoV-2.…”

Potential for a Plant-Made SARS-CoV-2 Neutralizing Monoclonal Antibody as a Synergetic Cocktail Component

“…The development of antibody cocktails composed of nAbs that have non-redundant epitopes reduces the risk of viral escape due to mutations in the RBD, the dominant target for nAbs [ 21 ]. The ongoing need for developing new nAb cocktails is highlighted by the emergence of variants of concern that have mutations in previously identified neutralizing epitopes, thereby reducing the efficacy of previously potent nAbs [ 20 , 22 , 23 ]. Specifically, several nAbs that received emergency use authorization (EUA) by the Food and Drug Administration (FDA) for the treatment or prevention of COVID-19, have been revoked due to the emergence of the dominant omicron variant and the reduced activity these mAbs have against this variant [ 24 , 25 ].…”

Sensitivity to Vaccines, Therapeutic Antibodies, and Viral Entry Inhibitors and Advances To Counter the SARS-CoV-2 Omicron Variant

“…Regdanvimab from Celltrion lost its neutralization activities against the Omicron variant ( 49 ). AX290 and AX677, two MAbs with nonoverlapping epitopes, bind to the RBD of the viral S protein with subnanomolar or nanomolar affinities ( 97 ). These antibodies neutralize Omicron S protein with the same efficiency as wild-type S protein.…”

“…These antibodies neutralize Omicron S protein with the same efficiency as wild-type S protein. In a mouse model, the prophylactic administration of AX290 and AX677, either alone or in combination, successfully reduced viral load and inflammation in the lungs, as well as preventing illness after SARS-CoV-2 infection ( 97 ). The virus-neutralizing characteristics of chimeric mouse-human forms of the antibodies were fully replicated, indicating that they could be a promising approach for COVID-19 therapy ( 97 ).…”

“…In a mouse model, the prophylactic administration of AX290 and AX677, either alone or in combination, successfully reduced viral load and inflammation in the lungs, as well as preventing illness after SARS-CoV-2 infection ( 97 ). The virus-neutralizing characteristics of chimeric mouse-human forms of the antibodies were fully replicated, indicating that they could be a promising approach for COVID-19 therapy ( 97 ). Despite having a nearly 46-fold lower efficacy than wild-type SARS-CoV-2, hu33, a non-ACE2-blocking neutralizing antibody, can still neutralize Omicron at a median neutralization dose of 154.3 ng/mL ( 98 ).…”