Live Attenuated Shigella dysenteriae Type 1 Vaccine Strains Overexpressing Shiga Toxin B Subunit

Abstract

Shigella dysenteriae serotype 1 (S. dysenteriae 1) is unique among the Shigella species and serotypes in the expression of Shiga toxin which contributes to more severe disease sequelae and the ability to cause explosive outbreaks and pandemics. S. dysenteriae 1 shares characteristics with other Shigella species, including the capability of causing clinical illness with a very low inoculum (10 to 100 CFU) and resistance to multiple antibiotics, underscoring the need for efficacious vaccines and therapeutics. Following the demonstration of the successful attenuating capacity of deletion mutations in the guaBA operon in S. flexneri 2a vaccine strains in clinical studies, we developed a series of S. dysenteriae 1 vaccine candidates containing the fundamental attenuating mutation in guaBA. All strains are devoid of Shiga toxin activity by specific deletion of the gene encoding the StxA subunit, which encodes enzymatic activity. The StxB subunit was overexpressed in several derivatives by either plasmid-based constructs or chromosomal manipulation to include a strong promoter. All strains are attenuated for growth in vitro in the HeLa cell assay and for plaque formation and were safe in the Serény test and immunogenic in the guinea pigs. Each strain induced robust serum and mucosal anti-S. dysenteriae 1 lipopolysaccharide (LPS) responses and protected against wild-type challenge. Two strains engineered to overexpress StxB induced high titers of Shiga toxin neutralizing antibodies. These candidates demonstrate the potential for a live attenuated vaccine to protect against disease caused by S. dysenteriae 1 and potentially to protect against the toxic effects of other Shiga toxin 1-expressing pathogens.Within the genus Shigella, four species, including S. dysenteriae, S. flexneri, S. sonnei, and S. boydii, cause diarrheal disease and dysentery in humans. It is estimated that more than 160 million cases of shigellosis and 1

Effect of Wild-Type Shigella Species and Attenuated Shigella Vaccine Candidates on Small Intestinal Barrier Function, Antigen Trafficking, and Cytokine Release

“…The two vaccine candidates showed a much smaller number of bacteria in the monolayer compared to their isogenic parents, in line with their attenuated properties [30].…”

Differential Response of the Cynomolgus Macaque Gut Microbiota to Shigella Infection

“…To assess the stability of the fecal microbiota in cynomolgus macaques, we compared the Shannon diversity index and community type variation over time, as well as the impact of immunization and wild-type challenge on community composition. In macaques from studies 1 and 2, we assessed the efficacy of two live-attenuated S. dysenteriae 1 vaccine candidates, CVD1255 and CVD1256 [18], to protect against subsequent challenge with wild-type S. dysenteriae 1 strain 1617 using macaques that received phosphate buffered saline (PBS) as controls. Macaques in study 3 were only challenged with wild-type S. dysenteriae 1 strain 1617.…”

“…Macaques from studies 1, 2 and 3 were involved in live-attenuated and/or wild-type S. dysenteriae 1 immunization studies to assess the efficacy of live attenuated S. dysenteriae 1 vaccine candidates [10], [18]. Two S. dysenteriae 1 strain 1617 vaccine candidates were used in immunization studies 1 and 2: CVD1255 (strain 1617 Δ guaBA Δ sen Δ stxAB ) and CVD1256 (strain 1617 Δ guaBA, Δ sen Δ stxA::mLpp-stxB ).…”

Novel Approach for Differentiating Shigella Species and Escherichia coli by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

“…Five of the 138 isolates were ATCC reference strains of E. coli (25922), S. sonnei (25931), S. flexneri (12022), S. boydii (8700), and S. boydii (BAA-1247). Two of four S. dysenteriae isolates were genetically related strains lacking Shiga toxin expression: CVD 1254 (⌬stxAB) and CVD 1255 (⌬guaBA ⌬sen ⌬stxAB; gifts from Eileen Barry, University of Maryland) (15). E. coli isolates were characterized as "inactive" if they displayed two or more of the following properties: lack of lactose fermentation, lack of motility, and lack of gas production (13).…”