A Comprehensive Review of Possible Immune Responses against Novel SARS-CoV-2 Coronavirus: Vaccines Strategies and Challenges

Review Article

Austin J Microbiol. 2021; 6(1): 1028.

A Comprehensive Review of Possible Immune Responses against Novel SARS-CoV-2 Coronavirus: Vaccines Strategies and Challenges

Shahriar A1*, Mahmud AR2, Ahmed H3, Rahman N4 and Khatun MC4

1Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka, Bangladesh

2Department of Biochemistry and Molecular Biology, Mawlana Bhashani Science and Technology University, Santosh, Tangail, Bangladesh

3Department of Biotechnology and Genetic Engineering, University of Development Alternative (UODA), Dhanmondi R/A, Dhaka, Bangladesh

4Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar, Dhaka, Bangladesh

*Corresponding author: Asif Shahriar, Research Assistant, Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka 1217, Bangladesh

Received: February 19, 2021; Accepted: March 13, 2021; Published: March 20, 2021

Abstract

The current deadly COVID-19 pandemic caused by the SARS-CoV-2 virus appeared in late December 2019 in Wuhan, China, and spread globally. The epidemic is still spreading, and there are no effective strategies to prevent the infection. Many companies and institutes are trying to figure out the solution by developing vaccines and antiviral drugs, but still, it requires advanced research and long times. However, scientists were able to decide that Immunological response induction is the ultimate target for any vaccine candidate. The immune response to SARS-CoV-2 involves all the immune system components that together appear responsible for viral elimination and recovery from the infection. Many immunological studies have been conducted based on T cell immunity because dependence on the antibody is not the only solution whether some studies showed that antibody wiped out very early. Some studies suggest that cytotoxic T cells and memory T cells give long term immunity. Nonetheless, the vaccines racing from the front provide promising results in various phases (preliminary to phase 2) to induce enough potent neutralizing antibodies. Besides, some vaccines showed T cell-based immune response, which may induce long-term immunity memory T cells. This review mainly illustrated potential vaccine development strategies and challenges by focusing on T-cellbased immune response against SARS-CoV-2 Coronavirus.

Keywords: SARS-CoV-2; T-cell based immunity; Cytotoxic T cells; Vaccines; Immunological paradox

Introduction

Severe Acute Respiratory Syndrome Coronavirus 2 (SARSCoV- 2) is one of the deadliest viruses among the other viruses. The virus has significantly impacted the world and has brought serious concern. The adaptive immune system is the vital player to fight against this pandemic. The adaptive immune system’s central players are mainly two types of T cells and plasma B cells. However, the mechanism of human T cells functions in opposition to the SARSCoV- 2 virus is still opaque. It is crucial to perceive how the T cells respond to this novel virus.

Understanding the response of our immune system against COVID-19 may play a pivotal role. This knowledge is also essential to develop a well-performed vaccine. Cytotoxic T cells attack viruscontaminated cells directly, and helper T cells vivify B cells to produce antibodies against that virus’s particular protein. It is unclear whether adaptive immune responses against SARS-CoV-2 are preventive or harmful [1]. As we know very little about SARS-CoV-2. There are many inquiries than answers for the recently recognized infection, including the etiology, the study of disease transmission, the basic premise, a system of pathogenesis, neurotic invulnerable reaction, and so on. Particularly, the host’s cellular and humoral immune response in response to the virus infection crucial for vaccine design remains unclear. All these important aspects need to be addressed by basic research shortly for successful vaccine development [2]. Recently, a team lead by Scripps Research has discovered antibodies from the convalescent person that yield robust protection against the virus SARS-CoV-2.

The team quickly screened over 1800 antibodies and analyzed animal models to experiment with shielding [3]. They separated strong Neutralizing Antibody (nAbs) against two epitopes of receptor-binding domains, which can distinguish non-RBD epitopes on the spike protein [3]. They used Syrian hamsters to show the protection of a nAb against SARS-CoV-2. This evaluation proposes nAbs in preventive treatment and the possible remedy of COVID-19 [3]. Neutralizing antibodies, CD4+, and CD8+ T cells are affiliated with the ferocity of COVID-19 [4]. We have to focus on B-cell and T-cell responses to help flourish a potent contemporary vaccine [4]. A recent study in the U.K. showed that persons recovered from severe conditions showed strong and varied T cells response than those recovering from mild conditions [5]. However, their T cells react to spike proteins and the virus’s internal components [5].

Humoral immunity and memory B cell response are not longlasting in SARS-CoV patients through robust neutralizing specific antibody induced against SARS-CoV spike glycoprotein [4]. In SARS-CoV, affected severe patients manifested an extreme reduction in T cell quantity in the blood [6,37,38,88]. Previous studies have demonstrated that full-length S protein can cause severe liver damage and may result in enhanced infection, defined as Antibody Dependent Enhancement (ADE). S protein-specific antibodies may probably cause this effect. Further, there is a report that the enhanced virulence mediated by the murine coronavirus, mouse hepatitis virus strain J.H.M, is associated with glycine at residue 310 of the spike glycoprotein, and this mutation may contribute to the spreading within the Central Nervous System (CNS) [2].

Although the rapid development of the SARS-CoV-2 vaccine, it still faces many challenges with unknown knowledge, including the antigenic characteristics of the SARS-CoV-2, the influence of antigenic variation, the protective immune response of the host, the protection of the elderly population, and the downstream manufacturing process of the new vaccine [7]. Nonetheless, to accelerate the production of emerging technology-based vaccines against SARS-CoV-2, it has to face challenges to implement, including revealing the relationship between virology and immunology, followed by production capability. A long-term study on several types of viruses like- Dengue virus, influenza virus, etc., helps accelerate vaccine discovery because we know in detail the antigenicity of viral structural proteins and protective immunity characteristics [8]. However, many vaccines with different approaches entered into human trials, though safety and efficacy data in details are not known yet. Researchers are taking advantage to make most of the vaccines against SARS-CoV-2 from either previous study on SARS-CoV, MERS-CoV, and other types of coronavirus or developmental strategies of other vaccines helping [9]. In this review, we discussed about a variety of immune responses, COVID-19 vaccine development strategies, the prospectus of COVID-19 vaccines, and upcoming challenges.

Strategies for Covid-19 Vaccine Development

Scientists worldwide are implementing various technologies; some of that vaccine’s strategy never implemented or licensed before [10]. The adaptive immune system is the key player in developing immunity against SARS-CoV-2. All vaccines target to induce the immune response against an antigen, whatever the strategies are targeted spike protein or not [10]. Various vaccination strategies for SARS-CoV-2 are implemented, such as D.N.A vaccines, R.N.A vaccines, killed or inactivated vaccines, live attenuated vaccines, and viral vector-based vaccines [11] (Figure 1).