Antigenicity and immunogenicity of fused B-subunit of heat labile toxin of Escherichia coli and colonization factor antigen I polyepitopes

Oral immunization with a plant-derived chimeric protein in mice: Toward the development of a multipotent edible vaccine against E. coli O157: H7 and ETEC

The most bacterial cause of infectious diseases associated with diarrhea are enterotoxigenic and enterohemorrhagic Escherichia coli (ETEC and EHEC, respectively). These strains use colonization factors for the attachment to the human intestinal mucosa, followed by enterotoxins production that could induce more host damage. The Heat-labile enterotoxin (LT) and colonization factors (CFs) are momentous factors for the pathogenesis of ETEC. Also, Intimin and Shiga like toxin (STX) are the main pathogenic factors expressed by EHEC. Because of mucosal surfaces are the major entry site for these pathogens, oral immunization with providing the protective secretary IgA antibody (sIgA) responses in the mucosa, could prevent the bacterial adherence to the intestine. In this study oral immunogenicity of a synthetic recombinant protein containing StxB, Intimin, CfaB and LtB (SICL) was investigated. For specific expression in canola seeds, the optimized gene was cloned in to plant expression vector containing the Fatty Acid Elongase (FAE) promoter. The evaluation of the expression level in canola seeds was approximately 0.4% of total soluble protein (TSP). Following to oral immunization of mice, serum IgG and fecal IgA antibody responses induced. Caco-2 cell binding assay with ETEC shows that the sera from immunized mice could neutralize the attachment properties of toxigenic E. coli. The reduction of bacterial shedding after the challenge of immunized mice with E. coli O157:H7 was significant. The sera from immunized mice in the rabbit ileal loop experiment exhibited a significant decrease in the fluid accumulation compared to the control. The results indicate efficacy of the recombinant chimeric protein SICL in transgenic canola seed as an effective immunogen, which elicits both systemic and mucosal immune responses as well as protection against EHEC and ETEC adherence and toxicity.

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.