Expression of Helicobacter pylori urease B on the surface of Bacillus subtilis spores

Abstract

Helicobacter pylori infection is a major risk factor for chronic gastritis, digestive ulcers, gastric adenocarcinoma and lymphoma. Due to the decreasing efficacy of anti-H. pylori antibiotic therapy in clinical practice, there is renewed interest in the development of anti-H. pylori vaccines. Bacillus subtilis is non-pathogenic and can produce endospores, which can survive under extreme conditions. These features make the B. subtilis spore an ideal vehicle for delivery of heterologous antigens to extreme environments such as the gastrointestinal tract. In this study, we displayed H. pylori urease B protein on the B. subtilis spore coat using the spore coat protein CotC as a fusion partner. Western blot analyses were used to verify urease B surface expression on spores. Recombinant spores displaying the urease B antigen were used for oral immunization and were shown to generate humoral response in mice. Urease B-specific secretory IgA in faeces and IgG in serum reached significant levels 2 weeks after oral dosing. In addition, oral immunization of recombinant urease B spores induced a significant reduction (84 %) in the stomach bacterial load (0.25±0.13¾10 6 c.f.u.) compared to that in the non-recombinant spores treated group (1.56±0.3¾10 6 c.f.u.; P,0.01). This report shows that urease B expressed on B. subtilis spores was immunogenic, and oral administration of urease B spores can provide protection against H. pylori infection. INTRODUCTIONHelicobacter pylori is a Gram-negative bacterium that colonizes the stomach in approximately half the world's population. Infection may progress to pathological states, such as peptic ulcer disease and gastric adenocarcinoma, resulting in significant morbidity and mortality worldwide (de Martel et al., 2012;Nakamura et al., 2012;Toller et al., 2011; Uemura et al., 2001; You et al., 2012). Current regimens for treatment of H. pylori infection consist of a proton pump inhibitor (PPI) and antibiotics including amoxicillin, clarithromycin and metronidazole. Despite an eradication rate greater than 80 %, there are some limitations to the PPI-based triple therapy, such as poor patient compliance, emerging antibiotic resistance, frequent reinfection and high cost (Lee et al., 2013;Su et al., 2013). Vaccination would therefore be a suitable alternative or complement to antibiotic treatment to eradicate the bacterium and prevent reinfection (Czinn & Blanchard, 2011).Identification of antigens that can induce effective immune responses is a crucial step in vaccine development. Many protein molecules expressed by H. pylori have been shown to possess immunogenicity, including urease, cytotoxinassociated antigen, neutrophil-activating protein A, H. pylori adhesin A, vacuolating toxin A, catalase and outermembrane protein (Czinn & Blanchard, 2011;Liu et al., 2011).Among these antigens the B subunit of the urease protein (urease B), a 61 kDa protein encoded by a 1.7 kbp gene, is the most promising one. H. pylori produces a large amount of urease, which is essential for the survival and path...

Oral administration of recombinant Bacillus subtilis spores expressing mutant staphylococcal enterotoxin B provides potent protection against lethal enterotoxin challenge

“…To assess SEB-speci c antibody level from colorectal secretions and serum, we assessed fecal and serum samples from 2 weeks after oral immunization (weeks 2, 4, 6) by ELISA. Consistent with our previous study (Zhou et al 2015), antigen speci c IgA and IgG responses were induced in both the mucosa and serum. Two weeks after the mice were treated with recombinant spores, a signi cant increase in SEB-speci c IgA levels was observed in the feces of mSEB spore-treated mice compared with those in the naïve and CotC groups (p < 0.01) (Fig.…”

“…Our previous study successfully delivered heterologous proteins, such as UreB and CTB-NAP, to B. subtilis surfaces (Dong et al 2017;Zhou et al 2015). The current study used recombinant methods to construct a recombinant plasmid expressing mSEB, which was transformed into B. subtilis WB600 using Spizizen competent transformation.…”

Oral Immunization with Nontoxigenic Clostridium difficile Strains Expressing Chimeric Fragments of TcdA and TcdB Elicits Protective Immunity against C. difficile Infection in Both Mice and Hamsters

“…C. difficile exists environmentally as spore forms. The unique multilayered structure of spores can allow them to survive under extreme temperatures, pHs, and humidity levels; in that regard, spores can serve as an effective oral delivery vehicle (36)(37)(38). By engineering nontoxigenic C. difficile strains to express mTcd138, i.e., NTCD_mTcd138, we combined two independent methods of CDI prevention in one treatment.…”

Recombinant Bacillus subtilis Spores Elicit Th1/Th17-Polarized Immune Response in a Murine Model of Helicobacter pylori Vaccination

“…Interestingly, B. subtilis spores presenting UreB of H. pylori have recently been shown by Zhou et al to be efficient in protecting of orally immunized mice against infection with this bacterium [ 33 ]. This observation does not line up with our previous [ 12 ] and current results, since we observed no immune response elicited by BKH108 spores administered without any adjuvant.…”