We have been investigating the utilization of the live constricted Salmonella enterica serovar Typhi Ty21a immunization strain as an adaptable oral antibody vector for the articulation and conveyance of different unfamiliar antigens, including Shigella O-antigens. In this examination, we independently cloned qualities vital for the biosynthesis of the Shigella flexneri serotype 2a and 3a O-antigens, which have been appeared to give wide cross-security to numerous infection transcendent S. flexneri serotypes. The cloned S. flexneri 2a rfb operon, alongside bgt and gtrII, contained on the SfII bacteriophage, was adequate in Ty21a to communicate the heterologous S. flexneri 2a O-antigen containing the 3,4 antigenic determinants. Further, this rfb operon, alongside gtrA, gtrB, and gtrX contained on the Sfx bacteriophage and oac contained on the Sf6 bacteriophage, was adequate to communicate S. flexneri 3a O-antigen containing the 6, 7, and 8 antigenic determinants. Ty21a, with these plasmid-conveyed or chromosomally embedded qualities, exhibited synchronous and stable articulation of homologous S. Typhi O-antigen in addition to the heterologous S. flexneri O-antigen. Up-and-comer Ty21a antibody strains communicating heterologous S. flexneri 2a or 3a lipopolysaccharide (LPS) evoked huge serum neutralizer reactions against both homologous S. Typhi and heterologous Shigella LPS and secured mice against destructive S. flexneri 2a or 3a difficulties.

Reference link- https://cvi.asm.org/content/24/12/e00181-17