DEVELOPMENT OF PREFAENA VACCINES FOR THE CONTROL OF SHIGA TOXIN-PRODUCING Escherichia coli COLONIZATION IN THE INTESTINE OF COWS

DUARTE CM; ROSET MS; BRIONES G

Virtual

Congreso; CONGRESO CONJUNTO SAIB-SAMIGE 2021; 2021

Shiga toxin-producing Escherichia coli or STEC (for its abbreviation in English) is a bacterial pathogen responsible for a zoonosis of local importance, characterized by the Hemolytic Uremic Syndrome (HUS). Cow intestine is the reservoir of STEC, and development of prophylactic bovine vaccines that controls bacterial colonization and consequently reduce the STEC shedding in the feces (prefaena vaccines) is critical to avoid contamination of meat derivatives with STEC. Immunity based on antibodies directed against E. coli O157: H7 surface antigens (type III secretion system proteins and other membrane complexes) has been shown to interfere with intestinal colonization in cows, reducing bacterial fecal load feces. Thus, our vaccine preparation consists in a chimeric protein containing antigens Tir, Intimin, SpA and flagella (EITH7). The synthetic EITH7 gene was cloned into the host broad-range plasmid pBBR1MCS-4, which under the control of the Ptrc promoter drives the strong and constitutive expression of EITH7 antigen. Furthermore, since the EITH7 gene sequence was fused to the β-lactamase signal sequence, EITH7 was secreted into the bacterial periplasm where this protein can be purified easily, in a simple step by osmotic shock from E. coli BL21 strain. Periplasmic preparation was used to immunize mice and evaluate its antigenicity. The production of anti-EITH7 antibodies was evaluated after three antigenic doses by ELISA, observing an increase in the titer after the second immunization dose. These antibodies were evaluated in its neutralizing capacity to inhibit adhesion and pedestal formation of pedestals elicited by EPEC E. coli strain that shares with STEC an identical type three protein secretion system, Anti-EITH7 induced antibodies inhibit the interaction of these strains in an in vitro assay. Similarly, mice immunized with EITH7-enriched periplasmic fraction were able to control a challenge infection with E. coli O157: H7. These results indicate that our vaccine preparation based on the EITH7 antigen generates an optimal specific response without the requirement of any adjuvants, allowing the control of EDL933 experimental infection. Our future perspective is to immunize a small group of cattle with this preparation in order to and evaluate its effectivity as a prefaena vaccine.