COVID-19: A review of newly formed viral clades, pathophysiology, therapeutic strategies and current vaccination tasks

Abstract

Today, the world population is facing an existential threat by an invisible enemy known as severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) or COVID-19. It is highly contagious and has infected a larger fraction of human population across the globe on various routes of transmission. The detailed knowledge of the SARS-CoV-2 structure and clinical aspects offers an important insight into the evolution of infection, disease progression and helps in executing the different therapies effectively. Herein, we have discussed in detail about the genome structure of SARS-CoV-2 and its role in the proteomic rational spread of different muted species and pathogenesis in infecting the host cells. The mechanisms behind the viral outbreak and its immune response, the availability of existing diagnostics techniques, the treatment efficacy of repurposed drugs and the emerging vaccine trials for the SARS-CoV-2 outbreak also have been highlighted. Furthermore, the possible antiviral effects of various herbal products and their extracted molecules in inhibiting SARS-CoV-2 replication and cellular entry are also reported. Finally, we conclude our opinion on current challenges involved in the drug development, bulk production of drug/vaccines and their storage requirements, logistical procedures and limitations related to dosage trials for larger population.

Keywords: And drugs; Phytocomponent; SARS-CoV-2; Spike protein mutation; Vaccines; Variants.

Fig. 1

Diagrammatic depictions reveal the SARS-CoV-2 virion structure and morphology.

Fig. 2

Statistical reports of the SARS-CoV-2 pandemic. (A) Worldwide report of SARS-CoV-2 infection and (B) topmost leading countries with SARS-CoV-2 infection as on October 17, 2021.

Fig. 3

Key routes of human-human transmission of SARS-CoV-2.

Fig. 4

Genomic distribution profile of SARS-CoV and SARS-CoV-2. (Adapted and reprinted with permission from ref. [34]), copyrights © 2020 Cell press.

Fig. 5

The structure of E protein pentameric ion channel predicted by nuclear magnetic resonance (NMR) spectroscopy (Adapted, redrawn and reprinted with permission from ref. , copyrights © 2018 Elsevier).

Fig. 6

The Structure of N protein predicted by NMR (Adapted, redrawn and reprinted with permission from ref. , copyrights © 2020 Elsevier).

Fig. 7

(A-B) Structural representation of the smaller peptides in a spike protein RBD domain occurs as ‘open’ or ‘closed’ orientations (C) (Adapted and reprinted with permission from ref. , copyrights © 2020 Cell press).

Fig. 8

The cellular interaction between the host cell ACE2 and SARS-CoV-2 S protein.

Fig. 9

Scheme reveals the SARS-CoV-2 life cycle in host epithelial cells. The cellular interaction between ACE2 receptor and S-protein facilitates SARS-CoV-2 entry into host cells. After completing the endocytosis and uncoating process, the SARS-CoV-2 components can be reused to formulate new viruses by host cells. Lastly, the new progeny viruses are released from host cells by exocytosis process.

Fig. 10

Overview of innate immune response and interferon signaling between the recovery and severely affected patients by SARS-CoV-2.

Fig. 11

Host responses during the viral infection. SARS-CoV-2 infects ACE2 expressing target cells in (a) brain, (b) lung, (c) kidney and (d) heart.

Fig. 12

Various diagnostic methods for SARS-CoV-2 identification in the given biological samples.

Fig. 13

Disparate treatment options for treating SARS-CoV-2 infection.

Fig. 14

Schematic illustration showing the role of different repurposed drugs in targeting SARS-CoV-2.