CLONING AND CONSTITUTIVE EXPRESSION OF STRUCTURAL GENES ENCODING GONOCOCCAL PORIN PROTEIN IN ESCHERICHIA-COLI AND ATTENUATED SALMONELLA-TYPHIMURIUM VACCINE STRAINS

Previous reports [Gotschlich et al., Proc. Natl. Acad. Sci. USA 84 (19 87) 8135-8139; Carbonetti and Sparling, Proc. Natl. Acad. Sci. USA 84( 1987) 9084-9088; Carbonetti et al., Proc. Natl. Acad. Sci. USA 85 (198 8) 6841-6845] concluded that synthesis of the porin protein (For) from Neisseria gonorrhoeae in Escherichia coli was toxic to that organism, which limited studies of the biology of For in foreign hosts. We asse mbled intact por genes from the gonococcal strains, FA19 (serogroup PI A) and FA6434 (a hybrid For containing epitopes from serogroups PIA an d PIB), and observed stable expression in E. coli without evident toxi city. Expression of por from strain MS11 (serogroup PIB) in E. coli wa s difficult, but por from MS11 was expressed without toxicity when the -35 region of the por promoter was removed. Encouraged by this, we mo ved por from E. coli into attenuated Salmonella typhimurium strains an d expressed por either in single copy from the chromosome or in multip le copy from plasmids. Expression levels of por in S. typhimurium were higher from plasmids than from the chromosome, probably due to a gene dosage effect. This work will enable study of the immune response to Por in mice vaccinated orally with live S. typhimurium.