SARS-CoV-2's Variants of Concern: A Brief Characterization

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disclose the variants of concern (VOC) including Alpha (B.1.1.7), Beta (B.1.351), Gamma (P1), Delta (B.1.617.2), and Omicron (B.1.1.529). Its spike protein (S) present on the surface of the virus is recognized by the host cell receptor, the angiotensin-2 converting enzyme (ACE2) which promotes their entry into the cell. The mutations presented by VOCs are found in RBD and the N-terminal region of S protein. Therefore, mutations occurring in RBD can modify the biological and immunogenic characteristics of the virus, such as modifying the spike affinity for ACE2, increasing the virus transmissibility, or conferring the ability to escape the immune responses. The raise of a potential new SARS-CoV-2 variant capable of evading the host defenses at the same time maintaining its fitness justifies the importance of continued genetic monitoring of the pandemic coronavirus.

Keywords: COVID-19; COVID-19 vaccination; SARS-COV-2 variants; SARS-CoV-2; viral immune escape.

Figure 1

Time line emergence of COVID-19 VOCs.

Figure 2

Main mutations present in SARS-CoV-2 Spike protein variants. In the center, structures from Spike proteins (colored in ivory) in their closed and open states (complexed with ACE2, in light brown). The RBD domain is highlighted in salmon. Closes from the ACE2 interaction interfaces of RBD domains are depicted for Beta, Gamma, and Omicron (top), Alpha (bottom left), and Delta (bottom right) variants. Mutated residues are colored in red with their respective name and positions. To improve the visualization of variants mutated regions, transparency was applied to ACE2 protein surfaces.