The OmpS maltoporin of Vibrio cholerae as carrier of foreign epitopes.

Insertion of additional epitopes to outer membrane proteins can lead to display of the hybrid protein on the bacterial outer surface. OmpS is the maltoporin of Vibrio cholerae and forms trimeric pores which function in uptake of maltose and maltodextrins through the membrane. OmpS is present in all V. cholerae 01 and 0139 strains. Each monomer traverses the membrane 18 times and has thus 9 loops facing the outside world. We have developed an ompS-expression-plasmid based system where foreign epitopes can be inserted in one of its surface accessible loops leading to production of a hybrid protein which still has the normal OmpS folding and function. The immunogenic peptides tested as OmpS hybrids include the CTP3 epitope of cholera toxin B-subunit and the C3 epitope of poliovirus. These hybrids can be detected with epitope-specific antisera on the bacterial cell surface. OmpS hybrid proteins carrying 38, 76 or 115 aa of the fibronectin binding D1-D3 repeats of FnBPA of Staphylococcus aureus have been tested for binding characteristics.