CVD 1208S

CVD 1208S is a live, attenuated oral vaccine candidate developed for the prevention of shigellosis, a diarrheal disease caused by *Shigella* bacteria. It is a genetically modified strain of *Shigella flexneri* 2a attenuated through deletions in the *guaBA* operon, *sen*, and *set* genes. This modification renders the bacteria non-pathogenic while retaining the ability to stimulate an immune response. The vaccine was initially developed by the University of Maryland and has been reconstructed using animal-free media to comply with regulatory guidelines. CVD 1208S has undergone Phase 2 clinical trials for bacillary dysentery (shigellosis). A previous Phase 1 trial evaluated single oral doses of 10^8 or 10^9 CFU, demonstrating a favorable safety and immunogenicity profile. The vaccine was generally well-tolerated, with reported side effects including mucoid or loose stools and fever in some subjects. Immunogenicity data from the 10^9 CFU dose in Phase 1 subjects showed: * 100% mounted an anti-lipopolysaccharide (LPS) IgA antibody-secreting cell response * 43% developed serum IgG responses * 29% showed fecal IgA responses * 57% exhibited Interferon gamma production in response to Shigella antigens A bivalent version of this vaccine, CVD 1208S-122, which includes protective antigens from enterotoxigenic *Escherichia coli* (ETEC), is also under development.