EXPRESSION OF SHIGELLA-SONNEI LIPOPOLYSACCHARIDE IN VIBRIO-CHOLERAE

Making use of a newly designed mobilizable suicide vector, the genetic determinants encoding Shigella sonnei lipopolysaccharide (LPS) were s tably integrated into the chromosome of the live attenuated Vibrio cho lerae vaccine strain CVD103-HgR. Expression studies showed that the pr oduction of complete S. sonnei O-polysaccharide (O-PS)-bearing LPS was limited in bivalent recombinant strains that were also proficient in the synthesis of the host-encoded Inaba O-PS. Conversely, high amounts of LPS carrying S. sonnei O-PS are produced in monovalent Inaba-defic ient derivatives, even in those strains which do not co-express the co mpatible R1 LPS core. Thus, the non-enterobacterial V. cholerae LPS co re efficiently acts as a receptor for covalent binding of S. sonneiO-P S provided that competition with the host O-PS is avoided. Expression of the R1 core interferes with cell division in recombinant V. cholera e without affecting other physiological properties of vaccine strain C VD103-HgR. Both monovalent and bivalent strains stimulated high serum- antibody titres specific for their respective O-serotype(s) when admin istered to rabbits. The potential of V. cholerae as an expression carr ier for heterologous O-serotypes is discussed.