Abstract
Infection with Escherichia coli O157:H7 may develop into hemorrhagic colitis, or hemolytic uremic syndrome (HUS), which usually causes kidney failure or even death. The adhesion and toxins are the important virulent factors. In this study, a novel vaccine candidate rSOBGs was constructed based on the bacterial ghost (BG). rSOBGs maintained the integrity of cellular morphology and displayed the linear Stx2Am-Stx1B antigen on the surface of outer membrane. rSOBGs induced Stxs-specific IgA/IgG antibodies and stronger intimin-specific IgA/IgG antibodies effectively in sera in this study. In vivo, the rSOBGs provided the higher protection rate (52%) than native bacterial ghost-OBGs (12%) when challenged intragastricly with high dose (500 LD50) viable E. coli O157:H7. Meanwhile, the rSOBGs provided higher protection rate (73.33%) than OBGs when challenged with 2 LD50 even to 5 LD50 lysed E. coli O157:H7. In vitro, the rSOBGs-immunized sera possessed neutralizing activity to lysed pathogenic bacteria. Furthermore, the results of histopathology also displayed that the administration of rSOBGs have the ability to reduce or inhibit the adhesion lesions and toxins damages of organs. The novel vaccine candidate rSOBGs induced both anti-toxin and anti-adhesion immune protection, suggesting the possibility to prevent the infectious diseases caused by Escherichia coli O157:H7.
Highlights
E. coli O157:H7 produces one or both of two types of Shiga toxins (Stxs) which are responsible for HUS and are categorized into two distinct groups, Stx[1] and Stx[2]
The linear Stx2Am-Stx1B antigen was displayed on the surface of E. coli O157:H7 Bacterial ghost (BG) based on a sandwich vector pSOmpA28–31 which was constructed by the partial out membane protein A (OmpA) of Shigella dysenteriae and partial OmpA of E. coli to construct a novel candidate vaccine named rSOBGs
Outer membrane protein intimin could be confirmed in both rSOBGs and OBGs by flow cytometry, but the Stx2A and Stx1B were detected only on the surface of rSOBGs (Fig. 1A)
Summary
E. coli O157:H7 produces one or both of two types of Shiga toxins (Stxs) which are responsible for HUS and are categorized into two distinct groups, Stx[1] and Stx[2]. Wen et al and others have demonstrated genetic toxoids of Stxs protect mice against homologous but not heterologous toxin challenge[9,10]. It can be assumed that vaccine-induced antibodies against these surface antigens would effectively hamper the adherence of the challenge bacteria to the target cells[18,19]. The linear Stx2Am-Stx1B antigen was displayed on the surface of E. coli O157:H7 BGs based on a sandwich vector pSOmpA28–31 which was constructed by the partial out membane protein A (OmpA) of Shigella dysenteriae and partial OmpA of E. coli to construct a novel candidate vaccine named rSOBGs. The immunogenicity, protection ability and immunologic mechanism against the challenge of E. coli O157:H7 were described subsequently
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