Surface display of the HPV L1 capsid protein by the autotransporter Shigella IcsA

Autotransporters have become attractive tools for surface expression of foreign proteins in Gram-negative bacteria. In this study, the Shigella autotransporter IcsA, has been exploited to express the human papillomavirus (HPV) type 16 L1 capsid protein in Shigella sonnei and Escherichia coli. The L1 gene was fused in-frame to replace the coding sequence of the IcsA passenger domain that is responsible for actin-based motility. The resultant hybrid protein could be detected by an anti-L1 antibody on the surface of S. sonnei and E. coli. In E. coli, the protein was expressed on the entire surface of the bacterium. In contrast, the protein was detected mainly at one pole of the Shigella bacterium. However, the protein became evenly distributed on the surface of the Shigella bacterium when the icsP gene was removed. Our study demonstrated the possibility of exploiting autotransporters for surface expression of large, heterologous viral proteins, which may be a useful strategy for vaccine development.