Cell-surface display of heterologous epitopes on Staphylococcus xylosus as a potential delivery system for oral vaccination.

A system has been developed for the surface expression of heterologous receptors on the cell surface of Staphylococcus xylosus. Gene fragments encoding peptides to be displayed on the cell surface can be assembled by applying a polymerization strategy based on the class-IIS restriction enzyme BspMI and thereafter subcloned into an Escherichia coli-staphylococci shuttle vector designed for targeting of produced fusion proteins to the outer cell surface of the Gram-positive host cell. A heterologous receptor was genetically assembled and expressed on the surface of S. xylosus where the separate regions could be independently probed in immunogold assays, using antisera reacting with different regions of the recombinant receptor. In addition, a receptor-specific humoral immune response could be elicited in mice by oral immunization with recombinant S. xylosus cells, suggesting that these type of Gram-positive bacteria might offer potential vehicles for oral vaccination.