Comparative Immunomodulatory Evaluation of the Receptor Binding Domain of the SARS-CoV-2 Spike Protein; a Potential Vaccine Candidate Which Imparts Potent Humoral and Th1 Type Immune Response in a Mouse Model.

Tripti Shrivastava,Milan Surjit,Sankar Bhattacharyya,Amit Awasthi,Sudipta Sonar,Sandeep Goswami,Rohit Verma,Preeti Vishwakarma,Shailendra Mani,Kamini Jakhar,Balwant Singh,Zaigham Abbas Rizvi

doi:10.3389/fimmu.2021.641447

Tripti Shrivastava, Milan Surjit + Show 10 more

Open Access

https://doi.org/10.3389/fimmu.2021.641447

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Abstract

The newly emerged novel coronavirus, SARS-CoV-2, the causative agent of COVID-19 has proven to be a threat to the human race globally, thus, vaccine development against SARS-CoV-2 is an unmet need driving mass vaccination efforts. The receptor binding domain of the spike protein of this coronavirus has multiple neutralizing epitopes and is associated with viral entry. Here we have designed and characterized the SARS-CoV-2 spike protein fragment 330-526 as receptor binding domain 330-526 (RBD330-526) with two native glycosylation sites (N331 and N343); as a potential subunit vaccine candidate. We initially characterized RBD330-526 biochemically and investigated its thermal stability, humoral and T cell immune response of various RBD protein formulations (with or without adjuvant) to evaluate the inherent immunogenicity and immunomodulatory effect. Our result showed that the purified RBD immunogen is stable up to 72 h, without any apparent loss in affinity or specificity of interaction with the ACE2 receptor. Upon immunization in mice, RBD generates a high titer humoral response, elevated IFN-γ producing CD4+ cells, cytotoxic T cells, and robust neutralizing antibodies against live SARS-CoV-2 virus. Our results collectively support the potential of RBD330-526 as a promising vaccine candidate against SARS-CoV-2.

Highlights

Emerging and reemerging pathogens are always a threat and a challenge for society and public health globally
In order to maintain proper folded conformation with paired cysteine residues (Figure 1B), angiotensin-converting enzyme 2 (ACE2) binding sites (Figure 1C), and natural N-linked glycosylation sites (Figure 1B), we selected 330PNITNLCPF to HAPATVCG526 amino acid sequences of the SARS-CoV-2 spike protein to express as the receptor binding domain (RBD) of SARS-CoV2 (Figure 1A)
The spike protein of SARSCoV-2 is a potential target for vaccine development because of its role in virus-host receptor binding and membrane fusion, and because of its ability to elicit a neutralizing antibody response

Summary

Introduction

Emerging and reemerging pathogens are always a threat and a challenge for society and public health globally. The outbreak of a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Wuhan, China, in December 2019 with an unidentified form of viral pneumonia, has stirred a global public health crisis affecting more than 235 countries and Cellular and Humoral Responses Evaluation of RBD territories worldwide. The other two previously known members of the beta coronavirus genus are severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) which were responsible for the outbreaks in 2002-2003 and 2012 respectively and have been linked to fatal illness [2]. The SARS-CoV-2 viral genome shares 79.5% nucleic acid sequence identity with SARS-CoV [3] and 96.2% with that of a bat coronavirus (RaTG13) [3, 4]. As per WHO, more than 180 vaccine candidates are currently in various stages of research and development across the world, utilizing different platforms such as inactive virus, mRNA, protein subunits, replicating viral vector, and virus-like particles (VLP)

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