Vaccination with killed whole-cells of Escherichia coli O157:H7 hha mutant emulsified with an adjuvant induced vaccine strain-specific serum antibodies and reduced E. coli O157:H7 fecal shedding in cattle.

Escherichia coli O157:H7 (O157) can cause from a mild diarrheal illness to hemorrhagic colitis and hemolytic uremic syndrome in humans. Cattle are the primary reservoir for O157 and fecal shedding of O157 by these animals is a major risk factor in contamination of cattle hides and carcasses at slaughter. Vaccination is an important strategy to reduce fecal shedding of O157 in cattle. In this study, we evaluated the immunogenicity and efficacy of an inactivated vaccine strain of O157 formulated with an adjuvant. This vaccine strain was deleted of the hha gene enabling high level expression of the locus of enterocyte effacement (LEE) encoded proteins required for O157 colonization in cattle. The inactivated vaccine strain emulsified with the adjuvant or suspended in the phosphate-buffered saline (PBS) was injected in the neck muscles of two groups of weaned calves followed by a booster three weeks later with the corresponding formulation. Animals in groups 3 and 4 were injected similarly with the adjuvant and PBS, respectively. All animals were orally inoculated three weeks post-booster vaccination with a live culture of O157. The animals vaccinated with the adjuvanted vaccine showed higher serum antibody titers to the vaccine strain and shed O157 for a shorter duration and at lower numbers compared to the animals vaccinated with the non-adjuvanted vaccine, adjuvant-only, or PBS. Western blotting of the vaccine strain lysates showed higher immunoreactivity of serum IgG in vaccinated animals to several O157-specific proteins and lipopolysaccharides (LPS). The vaccination induced IgG showed specificity to LEE-encoded proteins and outer membrane LPS as LEE and waaL deletion mutants, unable to produce LEE proteins and synthesize high molecular weight LPS, respectively, yielded significantly lower antibody titers compared to the parent vaccine strain. The positive reactivity of the immune serum was also observed for purified LEE-encoded proteins EspA and EspB. In conclusion, the results of this animal study showed that a two-dose regimen of an adjuvanted vaccine is capable of inducing O157-specific immune response that directly or indirectly reduced fecal shedding of O157 in cattle.

Sharma VK ，Schaut RG ，Loving CL 《-》

Evaluation of hha and hha sepB mutant strains of Escherichia coli O157:H7 as bacterins for reducing E. coli O157:H7 shedding in cattle.

Escherichia coli O157:H7 colonizes cattle intestines by using the locus of enterocyte effacement (LEE)-encoded proteins. The induction of systemic immune response against LEE-encoded proteins, therefore, will prove effective in reducing E. coli O157:H7 colonization in cattle. The previous studies have demonstrated that a hha (encodes for a hemolysin expression modulating protein) deletion enhances expression of LEE-encoded proteins and a sepB (encodes an ATPase required for the secretion of LEE-encoded proteins) deletion results in intracellular accumulation of LEE proteins. In this study, we demonstrate the efficacy of the hha and hha sepB deletion mutants as bacterins for reducing fecal shedding of E. coli O157:H7 in experimentally inoculated weaned calves. The weaned calves were injected intramuscularly with the bacterins containing 10(9) heat-killed cells of the hha(+) wild-type or hha or hha sepB isogenic mutants, and boosted with the same doses 2- and 4-weeks later. The evaluation of the immune response two weeks after the last booster immunization revealed that the calves vaccinated with the hha mutant bacterin had higher antibody titers against LEE proteins compared to the titers for these antibodies in the calves vaccinated with the hha sepB mutant or hha(+) wild-type bacterins. Following oral inoculations with 10(10) CFU of the wild-type E. coli O157:H7, the greater numbers of calves in the group vaccinated with the hha or hha sepB mutant bacterins stopped shedding the inoculum strain within a few days after the inoculations compared to the group of calves vaccinated with the hha(+) wild-type bacterin or PBS sham vaccine. Thus, the use of bacterins prepared from the hha and hha sepB mutants for reducing colonization of E. coli O157:H7 in cattle could represent a potentially important pre-harvest strategy to enhance post-harvest safety of bovine food products, water and produce.

Sharma VK ，Dean-Nystrom EA ，Casey TA 《-》

Efficacy of a recombinant Intimin, EspB and Shiga toxin 2B vaccine in calves experimentally challenged with Escherichia coli O157:H7.

Escherichia coli O157:H7 is a zoonotic pathogen of global importance and the serotype of Shiga toxin-producing E.coli (STEC) most frequently associated with Hemolytic Uremic Syndrome (HUS) in humans. The main STEC reservoir is cattle. Vaccination of calves with the carboxy-terminal fraction of Intimin γ (IntC280) and EspB can reduce E.coli O157:H7 fecal shedding after experimental challenge. Shiga toxin (Stx) exerts local immunosuppressive effects in the bovine intestine and Stx2B fused to Brucella lumazine synthase (BLS-Stx2B) induces Stx2-neutralizing antibodies. To determine if an immune response against Stx could improve a vaccine's effect on fecal shedding, groups of calves were immunized with EspB + IntC280, with EspB + IntC280 + BLS-Stx2B, or kept as controls. At 24 days post vaccination calves were challenged with E.coli O157:H7. Shedding of E.coli O157:H7 was assessed in recto-anal mucosal swabs by direct plating and enrichment followed by immunomagnetic separation and multiplex PCR. Calves were euthanized 15 days after the challenge and intestinal segments were obtained to assess mucosal antibodies. Vaccination induced a significant increase of IntC280 and EspB specific antibodies in serum and intestinal mucosa in both vaccinated groups. Antibodies against Stx2B were detected in serum and intestinal mucosa of animals vaccinated with 3 antigens. Sera and intestinal homogenates were able to neutralize Stx2 verocytotoxicity compared to the control and the 2-antigens vaccinated group. Both vaccines reduced E.coli O157:H7 shedding compared to the control group. The addition of Stx2B to the vaccine formulation did not result in a superior level of protection compared to the one conferred by IntC280 and EspB alone. It remains to be determined if the inclusion of Stx2B in the vaccine alters E.coli O157:H7 shedding patterns in the long term and after recurrent low dose exposure as occurring in cattle herds.

Martorelli L ，Garimano N ，Fiorentino GA ，Vilte DA ，Garbaccio SG ，Barth SA ，Menge C ，Ibarra C ，Palermo MS ，Cataldi A ... -  《-》

Vaccination with attenuated Salmonella enterica Dublin expressing E coli O157:H7 outer membrane protein Intimin induces transient reduction of fecal shedding of E coli O157:H7 in cattle.

Khare S ，Alali W ，Zhang S ，Hunter D ，Pugh R ，Fang FC ，Libby SJ ，Adams LG ... -  《-》

Reduced faecal shedding of Escherichia coli O157:H7 in cattle following systemic vaccination with γ-intimin C₂₈₀ and EspB proteins.

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 is the most prevalent EHEC serotype that has been recovered from patients with haemolytic uremic syndrome (HUS) worldwide. Vaccination of cattle, the main reservoir of EHEC O157:H7, could be a logical strategy to fight infection in humans. This study evaluated a vaccine based on the carboxyl-terminal fragment of 280 amino acids of γ-intimin (γ-intimin C₂₈₀) and EspB, two key colonization factors of E. coli O157:H7. Intramuscular immunization elicited significantly high levels of serum IgG antibodies against both proteins. Antigen-specific IgA and IgG were also induced in saliva, but only the IgA response was significant. Following experimental challenge with E. coli O157:H7, a significant reduction in bacterial shedding was observed in vaccinated calves, compared to control group. These promising results suggest that systemic immunization of cattle with intimin and EspB could be a feasible strategy to reduce EHEC O157:H7 faecal shedding in cattle.

Vilte DA ，Larzábal M ，Garbaccio S ，Gammella M ，Rabinovitz BC ，Elizondo AM ，Cantet RJ ，Delgado F ，Meikle V ，Cataldi A ，Mercado EC ... -  《-》