Immune Response in Calves Vaccinated with Type Three Secretion System Antigens and Shiga Toxin 2B Subunit of Escherichia coli O157:H7

Abstract

Ruminants are the primary reservoir of Shiga-toxin producing Escherichia coli (STEC) O157:H7 and the main source of infection for humans. The aim of this study was to assess the immunogenic properties of a candidate vaccine consisting on the recombinant proteins of E. coli O157:H7 IntiminC280, the carboxy-terminal fraction of Intimin γ, EspB and the fusion protein between the B subunit of Stx2 and Brucella Lumazine Synthase (BLS)(BLS-Stx2B), in Holstein Fresian calves.To accomplish this goal we vaccinated calves with two doses of different vaccine formulations: 2 antigens (IntiminC280, EspB), 3 antigens (IntiminC280, EspB, BLS-Stx2B), BLS-Stx2B alone and a control non-vaccinated group. All antigens were expressed as recombinant proteins in E. coli. Specific IgG titres increased in vaccinated calves and the inclusion of BLS-Stx2B in the formulation seems to have a stimulatory effect on the humoral response to IntiminC280 and EspB after the booster. The neutralizing activity of antibodies against these two antigens was assessed in Red Blood Cell lysis assays and adherence to Hep-2 cells as a correlate of T3SS activity. Both sera from animals vaccinated with 2 or 3 antigens inhibited both virulence properties. Serological response to Stx2 was observed in animals vaccinated only with BLS-Stx2B and with 3 antigens and neutralization of Stx2 cytotoxicity was also observed in both groups. In conclusion, immunization of calves with BLS-Stx2B, IntiminC280 and EspB elicited a potent humoral response able to neutralize Shiga toxin 2 cytotoxity and the T3SS virulence properties in vitro. These results suggest that this formulation is a good candidate vaccine to reduce STEC shedding in cattle and needs to be further assessed in vivo.

Antibiotic‐resistant Shiga toxin‐producing Escherichia coli: An overview of prevalence and intervention strategies

“…In a commercial feedlot, the SRP vaccine demonstrated 53% efficacy in reducing O157 prevalence and 73% efficacy in reducing prevalence of high shedders among cattle (Cull et al, 2012). Overall, these studies support cattle vaccination can effectively reduce STEC shedding (Varela et al, 2013) and researchers are experimentally evaluating new formulations that may improve efficacy or provide alternatives to existing vaccines (Martorelli et al, 2017;Saeedi, Yazdanparast, & Behzadi, 2017;Schmidt et al, 2018).…”

“…In a commercial feedlot, the SRP vaccine demonstrated 53% efficacy in reducing O157 prevalence and 73% efficacy in reducing prevalence of high shedders among cattle (Cull et al, ). Overall, these studies support cattle vaccination can effectively reduce STEC shedding (Varela et al, ) and researchers are experimentally evaluating new formulations that may improve efficacy or provide alternatives to existing vaccines (Martorelli et al, ; Saeedi, Yazdanparast, & Behzadi, ; Schmidt et al, ). However, farmers in the United States and Canada have shown little interest in vaccinating their cattle against bacteria that cause no disease in these animals without any incentives or regulatory mandates (Matthews et al, ; Smith, ).…”

Animal Models of Type III Secretion System-Mediated Pathogenesis

“…Industrial animals such as pigs, chickens, and cattle are of importance because they are often carriers of pathogens such as Salmonella and E. coli [75,76,[81][82][83]94,95]. The food industry often uses antibiotics to prevent infection and for growth promotion.…”

“…These assays are used to obtain a competitive index (CI) in order to compare the virulence of different strains. CIs are calculated as the ratio of mutant to wild-type bacteria in the animal, divided by the ratio of mutant to wild-type bacteria originally used to infect the animal [81,94,141]. A CI greater than 1 means that the mutant strain is more virulent, and a CI less than 1 means it is less virulent than the wild-type.…”

“…Vaccination studies are commonly done in mice [40,42,49], rabbits [65,66], cattle [81], and primates [86,91,93]. These studies can demonstrate the power of inhibiting the T3SS by using antibodies that recognize T3SS effectors or structural components.…”