Scientific Publications by FDA Staff

Vaccine 2007 Aug 14;25(33):6167-75

Core-linked LPS expression of Shigella dysenteriae serotype 1 O-antigen in live Salmonella Typhi vaccine vector Ty21a: Preclinical evidence of immunogenicity and protection.

Xu de Q, Cisar JO, Osorio M, Wai TT, Kopecko DJ

Kopecko DJ (reprint author), FDA CBER, Lab Enter & STDs, Bldg 29,NIH Campus,HFM440 Rockville Pike, Bethesda, MD 20892 USA FDA CBER, Lab Enter & STDs, Bethesda, MD 20892 USA Natl Inst Dental & Carniofac Res, NIH, Oral Infect & Immun Branch, Bethesda, MD 20892 USA

Shigella dysenteriae serotype 1 (S. dysenteriae 1) causes severe shigellosis that is typically associated with high mortality. Antibodies against Shigella serotype-specific O-polysaccharide (O-Ps) have been shown to be host protective. In this study, the rfb locus and the rfp gene with their cognate promoter regions were PCR-amplified from S. dysenteriae 1, cloned, and sequenced. Deletion analysis showed that eight rfb ORFs plus rfp are necessary for biosynthesis of this O-Ps. A tandemly-linked rfb-rfp gene cassette was cloned into low copy plasmid pGB2 to create pSd1. Avirulent Salmonella enterica serovar Typhi (S. Typhi) Ty21a harboring pSd1 synthesized S. Typhi 9, 12 LPS as well as typical core-linked S. dysenteriae 1 LPS. Animal immunization studies showed that Ty21a (pSd1) induces protective immunity against high stringency challenge with virulent S. dysenteriae 1 strain 1617. These data further demonstrate the utility of S. Typhi Ty21a as a live, bacterial vaccine delivery system for heterologous O-antigens, supporting the promise of a bifunctional oral vaccine for prevention of shigellosis and typhoid fever.