A Colanic Acid Operon Deletion Mutation Enhances Induction of Early Antibody Responses by Live Attenuated Salmonella Vaccine Strains

Abstract

bColanic acid (CA) is a common exopolysaccharide produced by many genera in the Enterobacteriaceae. It is critical for biofilm formation on HEp-2 cells and on chicken intestinal tissue by Salmonella. In this study, we generated different CA synthesis gene mutants and evaluated the immune responses induced by these mutants. One of these mutations, ⌬(wza-wcaM)8, which deleted the whole operon for CA synthesis, was introduced into two Salmonella vaccine strains attenuated by auxotrophic traits or by the regulated delayed attenuation strategy (RDAS). The mice immunized with the auxotrophic Salmonella vaccine strain with the deletion mutation ⌬(wza-wcaM)8 developed higher vaginal IgA titers against the heterologous protective antigen and higher levels of antigen-specific IgA secretion cells in lungs. In Salmonella vaccine strains with RDAS, the strain with the ⌬(wza-wcaM)8 mutation resulted in higher levels of protective antigen production during in vitro growth. Mice immunized with this strain developed higher serum IgG and mucosal IgA antibody responses at 2 weeks. This strain also resulted in better gamma interferon (IFN-␥) responses than the strain without this deletion at doses of 10 8 and 10 9 CFU. Thus, the mutation ⌬(wza-wcaM)8 will be included in various recombinant attenuated Salmonella vaccine (RASV) strains with RDAS derived from Salmonella enterica serovar Paratyphi A and Salmonella enterica serovar Typhi to induce protective immunity against bacterial pathogens.

Genomic and Transcriptomic Analysis of Escherichia coli Strains Associated with Persistent and Transient Bovine Mastitis and the Role of Colanic Acid

“…Our subsequent genome sequencing determined that a significant portion of the operon (wca) responsible for colanic acid synthesis is missing in the transient-infection strains. Previous work has shown a connection between motility and colanic acid synthesis (15). In that work, the Rcs signaling system was found to positively regulate colanic acid synthesis and negatively regulate motility.…”

Colanic Acid Intermediates Prevent De Novo Shape Recovery of Escherichia coli Spheroplasts, Calling into Question Biological Roles Previously Attributed to Colanic Acid

“…Therefore, the observed phenotypes may have arisen either because CA was absent or because the mutants accumulated metabolic intermediates that impeded growth so that the cells were less able to survive the test conditions. To our knowledge, only one virulence experiment has used a mutant lacking the entire CA operon, in Salmonella enterica serovar Typhimurium (52). In this case, the loss of CA caused no difference at all in virulence (52), supporting the idea that CA itself may play no role in these situations.…”

“…To our knowledge, only one virulence experiment has used a mutant lacking the entire CA operon, in Salmonella enterica serovar Typhimurium (52). In this case, the loss of CA caused no difference at all in virulence (52), supporting the idea that CA itself may play no role in these situations. In any event, CA cannot be said to contribute to virulence unless appropriate mutants are created and retested.…”

Multiple antigens of Yersinia pestis delivered by live recombinant attenuated Salmonella vaccine strains elicit protective immunity against plague

“…The 20 gene Δ( wza-wcaM ) -8 deletion precludes synthesis of colanic acid (as does the Δ( gmd-fcl ) -26 ) but also the O-antigen capsule to further reduce biofilm formation. Furthermore, the Δ( wza-wcaM ) - 8 mutation increases the level of protective antigen synthesis and thus, enhances immune responses [25]. The ΔP fur81 ::TT araC P BAD fur mutation was replaced by the ΔP fur33 ::TT araC P BAD fur mutation since strains with the latter mutation colonize better and induce higher immune responses [26].…”