4.3 Nucleocapsid protein (N)
The N protein is highly conserved and most abundant protein in
coronavirus which is actively involved in viral propagation (McBride et
al., 2014) and is a potential additional target for the development of
SARS and MERS vaccines. It is highly antigenic and induced specific
humoral and cellular immune responses in convalescent-phase SARS
patients (Leung et al., 2004) and C57BL/6 mice (Kim et al., 2004).
However, in contrast, it has been reported that it does not elicit VN
antibodies to block virus binding the ACE2 receptor and prevent viral
infection (Liu et al., 2006; Zheng et al., 2009). Also, in hamsters N
protein immunization did not induce VN antibodies and provided no
protection against SARS-CoV (Buchholz et al., 2004). These conflicting
results suggest that N protein is not a reliable candidate for vaccine
development for SARS-CoV but has a good diagnostic value because of its
high immunogenicity (Zhang et al., 2020).