Molecular advances in the cell biology of SARS-CoV and current disease prevention strategies

Stark, Caren J; Atreya, CD

The N protein of SARS-CoV appears to be more conserved than S and M proteins and it has been suggested that this protein may play a role in cell-mediated immunity in SARS-CoV infections and also is an important viral antigen for the early diagnosis. Vaccination of C57BL/6 mice with a SARS-CoV N protein expressed by an E1/partially E3-deleted, replication-defective human adenovirus 5 vector was shown to produce potent SARS-CoV-specific humoral and T cell-mediated immune responses, suggesting the potential of this construct to be used as SARS-CoV vaccine [63] . Along the same line, intra-muscular immunization of BALB/c mice with a plasmid DNA construct encoding the full-length N protein was shown to elicit serum anti-N antibodies and spenocyte proliferative responses against the N protein [64] . The immunized mice also produced strong delayed-type hypersensitivity (DTH) and CD8 (+) CTL responses to the N protein, suggesting that the N protein is not only an important B cell immunogen, but also can elicit broad-based cellular immune responses [64] . In another novel strategy, the N protein was expressed in the cytoplasm of Lactococcus lactis bacterium and the N-expressing bacteria were administered to mice by intranasal or oral route [65] . In this case, significant levels of N-specific IgG in the mice sera were detected, suggesting that the engineered bacteria may serve as a mucosal vaccine against SARS-CoV [65].