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Helicobacter pylori (H. pylori) colonizes the stomach epithelium of half the world's population and is responsible for various digestive diseases and even stomach cancer. Vaccine-mediated protection against H. pylori infection depends primarily on the specific mucosal and T-cell responses. In this study, the synthetic lipopeptide vaccines, Hp4 (Pam 2 Cys modified UreB T-cell epitope) and Hp10 (Pam 2 Cys modified CagA T/B cell combined epitope), not only induce the bone marrow derived dendritic cells (BMDCs) maturation by activating a variety of pattern-recognition receptors (PRRs) such as Toll-like receptor (TLR), Nod-like receptor (NLR), and retinoic acid-inducing gene (RIG) I-like receptor (RLR), and but also stimulate BMDCs to secret cytokines that have the potential to modulate T-cell activation and differentiation. Although intranasal immunization with Hp4 or Hp10 elicits robust epitope-specific T-cell responses in mice, only Hp10 confers protection against H. pylori infection, possibly due to the fact that Hp10 also induces substantial specific sIgA response at mucosal sites. Interestingly, Hp4 elevates the protective response against H. pylori infection of Hp10 when administrated in combination, characterized by better protective effect and enhanced specific T-cell and mucosal antibody responses. The results suggest that synthetic lipopeptide vaccines based on the epitopes derived from the protective antigens are promising candidates for protection against H. pylori infection., (© 2023 Wiley-VCH GmbH.)

Over fifty percent of the people around the world is infected with Helicobacter pylori ( H. pylori ), which is the main cause of gastric diseases such as chronic gastritis and stomach cancer. H. pylori adhesin A (HpaA), which is a surface-located lipoprotein, is essential for bacterial colonization in the gastric mucosa. HpaA had been proposed to be a promising vaccine candidate against H. pylori infection. However, the effect of non-lipidated recombinant HpaA (rHpaA) to stimulate immune response was not very ideal, and the protective effect against H. pylori infection was also limited. Here, we hypothesized that low immunogenicity of rHpaA may attribute to lacking the immunostimulatory properties endowed by the lipid moiety. In this study, two novel lipopeptides, LP1 and LP2, which mimic the terminal structure of the native HpaA (nHpaA), were synthesized and TLR2 activation activity was confirmed in vitro . To investigate whether two novel lipopeptides could improve the protective effect of rHpaA against the infection of H. pylori , groups of mice were immunized either intramuscularly or intranasally with rHpaA together with LP1 or LP2. Compared with rHpaA alone, the bacterial colonization of the mice immunized with rHpaA plus LP2 via intranasal route was significantly decreased and the expression levels of serum IgG2a, IFN-γ, and IL-17 cytokines in spleen lymphocyte culture supernatant increased obviously, indicating that the enhanced protection of LP2 may be associated with elevated specific Th1 and Th17 responses. In conclusion, LP2 has been shown to improve the protective effect of rHpaA against H. pylori infection, which may be closely related to its ability in activating TLR2 by mimicking the terminal structure of nHpaA.

Some plant polysaccharides (PPSs) had been used as the adjuvants for systemic vaccination. In this study, we investigated whether PPSs could exhibit adjuvant effect at the mucosa. Groups of mice were intranasally immunized with Epimedium Polysaccharide (EPS), Trollius chinensis polysaccharide (TCPS), Siberian solomonseal rhizome polysaccharide (SSRPS) and Astragalus polysaccharides (APS) together with ovalbumin (OVA). Significantly higher levels of OVA-specific IgG in serum and secretory IgA in saliva, vaginal wash and intestinal lavage fluid were induced after immunization with OVA plus one of the four PPSs compared to OVA alone. Antigen absorption and TLR2 (Toll-like receptor 2) activation may be related to their mucosal adjuvant effect. Of note, when APS used as an adjuvant, intranasally vaccination with recombination UreB (rUreB, Urease subunit B) conferred more robust protection against Helicobacter pylori (H. pylori). Immunized with rUreB in combination APS resulted in mixed specific Th1 and Th17 immune response, which may contribute to the inhibition of H. pylori colonization. Though specific Th2-dominant responses were elicited when the other three PPS intranasally immunized with rUreB, no significant difference in the protective effect were found between those groups and rUreb alone group. Taken together, the four PPSs may be promising candidates for mucosal adjuvant, and APS could enhance rUreB-specific protective immunity against H. pylori infection., (Copyright © 2019 Elsevier Ltd. All rights reserved.)