4. Possible vaccine candidates for COVID-19
Since the SARS-CoV-2 shares a considerable genetic sequence homology and
sequence identity of various essential enzymes with SARS-CoV (Hui et
al., 2020; Zhu et al., 2020; Perlman 2020; Zhou et al., 2020), the
vaccine strategies already built for SARS could potentially facilitate
the early design of COVID-19 vaccine (Morse et al., 2020; Chen et al.,
2020). Both SARS-CoV-2 and SARS-CoV bind to similar ACE2 receptors of
human lungs (Hoffmann et al., 2020; Zhou et al., 2020). Similar to other
CoVs, genome of SARS-CoV-2 translates four major structural proteinsviz . nucleocapsid protein (N), spike glycoprotein (S), membrane
glycoprotein (M), and envelop protein (E) (Saif, 2020). The S protein is
the major focus in vaccine development because it contains receptor
binding domain (RBD), functions in viral attachment via S1 subunit,
fuses with host cell via S2 subunit, and strongly induces VN antibodies
which blocks binding with the host receptor cells in lungs (Zhou et al.,
2020). However, M protein has the ability to induce VN antibodies and N
protein contains T-cell epitopes in SARS-CoV, which means they can also
act as an efficient vaccine targets (Rauch et al., 2018; Roper and Rehm
2009; Enjuanes et al., 2008).