Emerging COVID-19 variants and their impact on SARS-CoV-2 diagnosis, therapeutics and vaccines

Abstract

The emergence of novel and evolving variants of SARS-CoV-2 has fostered the need for change in the form of newer and more adaptive diagnostic methods for the detection of SARS-CoV-2 infections. On the other hand, developing rapid and sensitive diagnostic technologies is now more challenging due to emerging variants and varying symptoms exhibited among the infected individuals. In addition to this, vaccines remain the major mainstay of prevention and protection against infection. Novel vaccines and drugs are constantly being developed to unleash an immune response for the robust targeting of SARS-CoV-2 and its associated variants. In this review, we provide an updated perspective on the current challenges posed by the emergence of novel SARS-CoV-2 mutants/variants and the evolution of diagnostic techniques to enable their detection. In addition, we also discuss the development, formulation, working mechanisms, advantages, and drawbacks of some of the most used vaccines/therapeutic drugs and their subsequent immunological impact.Key messageThe emergence of novel variants of the SARS-CoV-2 in the past couple of months, highlights one of the primary challenges in the diagnostics, treatment, as well as vaccine development against the virus.Advancements in SARS-CoV-2 detection include nucleic acid based, antigen and immuno- assay-based and antibody-based detection methodologies for efficient, robust, and quick testing; while advancements in COVID-19 preventive and therapeutic strategies include novel antiviral and immunomodulatory drugs and SARS-CoV-2 targeted vaccines.The varied COVID-19 vaccine platforms and the immune responses induced by each one of them as well as their ability to battle post-vaccination infections have all been discussed in this review.

Keywords: COVID-19; Coronaviruses; Omicron; SARS-CoV-2; Viral epidemic; diagnostic testing; immunological responses; vaccine.

Figure 1.

The figure explains about the reported amino acid mutations in RBD region of different SARS- CoV-2 strains.

Figure 2.

The figure explains about the different COVID-19 vaccine platforms, the immune response to the vaccine and the protective immune response during the post-vaccination infection. (A) Different COVID-19 vaccine platforms. a. DNA vaccine in which SARS-CoV-2 spike open reading frame (ORF) is cloned into a plasmid DNA which will be injected intramuscularly; b. Viral vector platforms in which, the spike protein ORF is cloned into adenovirus genome to form an infectious recombinant virus which will be injected intramuscularly; c. mRNA vaccine, in which SARS-CoV-2 spike mRNA is chemically synthesized and enclosed with lipid nanoparticles then it is injected into human body; d. Protein vaccine in which total or subunit part of spike protein is mixed with specific adjuvant before being injected into human system; e. Inactivated virus vaccine whereby SARS-CoV-2 virus is chemically inactivated, mixed with specific adjuvant then injected intramuscularly. (B) Immune response to the SARS-CoV-2 vaccine: Once in the human body, the different vaccine platforms will synthesize or deliver SARS-CoV-2 total or subunit spike protein which will induce specific memory immune response against SARS-CoV-2 virus. (C) SARS-CoV-2 virus neutralization during post-vaccination infection. 1. If an infection occurs after vaccination, anti-SARS-COV-2 antibodies bind to the SARS-CoV-2 virus and inhibit its attachment to the host cell. 2. Antibody Dependent Cellular Cytotoxicity: The anti-spike antibodies recognize the spike antigen on the infected cells. Four major immune effector cells (neutrophils, eosinophils, macrophages, and NK cells) will recognize the cell bounded antibodies and infected cells and the killing is achieved by cytolytic processes. 3. The memory T cells are quickly converted into cytotoxic T cells and eliminate the infected cells.