Two consecutive proline substitutions in the fusion peptide of swine acute diarrhea syndrome coronavirus spike protein reduce cell-cell fusion

Two consecutive proline substitutions in the fusion peptide of swine acute diarrhea syndrome coronavirus spike protein reduce cell-cell fusion

Previous studies have shown that proline mutations in the heptad repeat region stabilize the coronavirus spike (S) protein in a pre-fusion state. To understand the impact of proline substitutions on the fusogenicity of the S protein, we engineered the swine acute diarrhea syndrome coronavirus (SADS-CoV) S protein with two proline substitutions (S-PP) and examined its fusogenicity using dual-split-protein based cell-cell fusion assay. Unlike the wild-type S (S-WT), S-PP rarely formed syncytia. Additionally, protein expression of S-PP was impaired compared to S-WT, as previously reported. Our results indicate that pre-fusion stabilized S protein is unable to induce membrane fusion and provide a better understanding of SADS-CoV S and vaccine antigen design.