Post-translational modifications of coronavirus proteins: roles and function

Fung, To Sing; Liu, Ding Xiang

Caution should also be taken regarding the biological systems used to express the coronavirus S protein. For example, a recent study evaluated the antigenicity of recombinant IBV S1 protein expressed in mammalian cells. The result showed that the recombinant S1 protein was highly glycosylated and was able to induce the production of antibodies against S1 in immunized chickens. However, these antibodies had lower neutralizing activity compared with those generated by chickens immunized with inactivated IBV [66] . Therefore, the glycosylation pattern of IBV S protein synthesized in mammalian cells may differ from those produced in avian cells, thereby affecting its antigenicity in vivo. Similarly, the glycosylation pattern of other coronavirus proteins may also be differentially affected by the expression systems, thereby changing their behaviors in relevant functional assays.