Protection against neonatal Escherichia coli diarrhea by vaccination of sows with a novel multivalent vaccine candidate expressing E. coli adhesins associated with neonatal pig colibacillosis

Oral Immunization with Attenuated Salmonella Choleraesuis Expressing the FedF Antigens Protects Mice against the Shiga-Toxin-Producing Escherichia coli Challenge

Edema disease (ED) is a severe and lethal infectious ailment in swine, stemming from Shiga-toxin-producing Escherichia coli (STEC). An efficient, user-friendly, and safe vaccine against ED is urgently required to improve animal welfare and decrease antibiotic consumption. Recombinant attenuated Salmonella vaccines (RASV) administered orally induce both humoral and mucosal immune responses to the immunizing antigen. Their potential for inducing protective immunity against ED is significant through the delivery of STEC antigens. rSC0016 represents an enhanced recombinant attenuated vaccine vector designed for Salmonella enterica serotype Choleraesuis. It combines sopB mutations with a regulated delay system to strike a well-balanced equilibrium between host safety and immunogenicity. We generated recombinant vaccine strains, namely rSC0016 (pS-FedF) and rSC0016 (pS-rStx2eA), and assessed their safety and immunogenicity in vivo. The findings demonstrated that the mouse models immunized with rSC0016 (pS-FedF) and rSC0016 (pS-rStx2eA) generated substantial IgG antibody responses to FedF and rStx2eA, while also provoking robust mucosal and cellular immune responses against both FedF and rStx2eA. The protective impact of rSC0016 (pS-FedF) against Shiga-toxin-producing Escherichia coli surpassed that of rSC0016 (pS-rStx2eA), with percentages of 83.3%. These findings underscore that FedF has greater suitability for vaccine delivery via recombinant attenuated Salmonella vaccines (RASVs). Overall, this study provides a promising candidate vaccine for infection with STEC.

Salmonella ghosts expressing enterotoxigenic Escherichia coli k88ab, k88ac, k99, and fasa fimbrial antigens induce robust immune responses in a mouse model

BACKGROUND

Bacterial ghosts can be developed as safe and effective vaccines against bacterial infectious disease such as enterotoxigenic Escherichia coli (ETEC)-induced diarrhea in neonatal piglets.

OBJECTIVE

Immune responses against a Salmonella ghost expressing ETEC K88ab, K88ac, K99, and FasA antigens with various adjuvants and inoculation routes were evaluated in mice.

ANIMALS AND METHODS

A ghost cell expressing K88ab, K88ac, K99, and FasA fimbrial antigens of ETEC on the envelope of △asd Salmonella typhimurium was constructed as a candidate vaccine against ETEC infection. To optimize the immunization strategy, 6-week-old female BALB/c mice were inoculated with the ghost and various adjuvants, and the immune responses against the individual fimbrial antigens were measured. Blood samples from caudal vein to evaluate serum IgG concentrations and fecal samples to evaluate mucosal IgA concentrations were collected up to 14 weeks post-prime immunization.

RESULTS

All groups with single, double, and triple inoculations of the ghost showed higher humoral and mucosal immune responses than the control group. In particular, the groups with intramuscular double and triple inoculations showed significantly higher immune responses. In addition, oral inoculation with a combination of the ghost and MONTANIDE IMS 1113 (MI1113) resulted in high and prolonged induction of intestinal IgA levels.

CONCLUSION

These results indicated that both systemic and mucosal immunity against ETEC fimbrial antigens expressed by the ghost are induced by intramuscular booster inoculation with the ghost, and that addition of M1113 to the ghost was found to result in prominent induction of mucosal immunity through oral inoculation.