Omicron variant infection and the associated immunological scenario

Abstract

The million-dollar question that has been the talk of the day is how effective the COVID 19 vaccines are against the Omicron variant. Still, there is no clear-cut answer to this question but several studies have concluded that this Variant of Concern (VOC) successfully weakens the neutralizing capability of the antibodies acquired from the COVID 19 vaccines and prior infections, which indicates that Omicron can easily bypass an individual's humoral immune response. However, the most significant confusion revolves around cell-mediated immunity tackling the Omicron variant. This paper aims to provide a clear idea about the status of the body's immune surveillance concerning the infection caused by the Omicron variant by producing the effectivity of the humoral and cell-mediated immunity in handling the same. This work also provides complete detail of the various characteristics of the Omicron variant and how it may be a blessing in disguise. The effectiveness of the current vaccines, the transmissibility rate of the variant compared to the other variants, and the importance of administering a booster dose to prevent the spread of this variant are also discussed. Finally, this work aims to bridge the gap between the past and the current status of the Omicron infection and sheds light on the hypothetical idea that herd immunity developed from the SARS-COV2 infection may help tackle other dangerous variants.

Keywords: Booster; Delta; Immunity; Mutation; Omicron; Variants.

Fig. 1

This figure demonstrates the overall pathophysiology and the immune responses associated with the Omicron variant. It shows the mechanism adopted by the Omicron variant to enter the body binding to the ACE 2 receptor and undergoing endosomal fusion to enter the cells. Upon entering the cells, it leads to several mechanistic pathways leading to the trigger of humoral and cell-mediated immunity, which coordinate to tackle the virus.

Fig. 2

Comparison of the cell entry of the Omicron variant with the delta variant. Fig (a) shows the Delta variant, which requires a serine protease TMPRSS2 cleaves between the S1 and S2 part of the spike protein for cell entry. The S2 part of the spike protein then fuses with the cell membrane to release the viral mRNA into the cell. Fig (b) shows the entry of the Omicron variant by endocytosis. It requires only the ACE2 receptors, and the TMPRSS2 does not play a role in the entry of the Omicron variant. Once the virus undergoes endocytosis, the cathepsin present in the cell membrane liberates the viral mRNA from the phagosome.