Question

Considering the structure and composition of SARS-CoV-2, list possible antigens for antibody binding. Which one do you think would be the most effective for a diagnostic serological assay?

Answer 1

Following antigens can be used for developing the serological assay.

There are two categories of antigens

1) Which require the digestion process ( Virion particle rupture), so that antigens which are not exposed can be extracted and serologically detected by specefic antobodies. The antigens are as follows,

a) Viral RNA

b) Membrane envelope proteins

c) Membrane glycoproteins

d) Nucleocapsid proteins

2) Second category of antigens does not require cellular extraction/digestion process

a) Spike proteins

Based on the structural analysis,

SARS-CoV-2 (2019-nCoV) spike protein, that belongs to class I virus fusion protein, consists of two subunits, S1 and S2. S1 contains receptor binding domain (RBD), that mediates the recognition off cell receptors.

S2 consists of the basic architecture needed for the membrane fusion process. It has been indetified that SARS-CoV-2 (2019-nCoV) spike protein interacts with human ACE2 in order to infect human respiratory epithelial cells.

However, mutation in the spike proteins are indetified which are mainly responsible for variation in the transmissability and virulence. The prime identified mutant is D614G, the point mutation which replace the aspartic acid to glycine. This mutation may cause major shift in the 3D structure of the spike subunit.

Hence, 3D homology modelling should be perfomed to indetify the structurally invariant region which can be targetted for developing the serological assay for all the mutated forms of SARS-CoV-2 (2019-nCoV)