Helicobacter pylori (H. pylori) infects more than half of the world’s population, causing chronic gastritis, peptic ulcers and gastric cancer. Urease B subunit (UreB), a conserved protein of H. pylori, is capable of inducing specific CD4+ T-cell responses and provides protection against this infection. Previous studies have confirmed the effectiveness of rUreB subunit vaccines in generating CD4+ T-cell-mediated protection, but less is known regarding the roles of different subtypes of T-cell immunity, such as Th1, Th2 and Th17, particularly the immunodominant epitopes inducing specific CD4+ T-cell responses, in vaccine-mediated protection. In this study, we demonstrated that the vaccination of BALB/c mice with rUreB resulted in significant antigen-specific Th1 and Th17 immune responses. Importantly, two novel Th epitopes, UreB317–329 and UreB409–421, which are recognized by a major population of CD4+ T cells, were identified in immunized mice. Our results demonstrated that two novel epitopes can simultaneously induce Th1 and Th17 immune responses; however, only the epitope vaccine-induced CD4+ T-cells secreting IFN-γ mediated the protection against H. pylori; cells secreting IL-17A did not. Taken together, our results suggest that two novel immunodominant epitopes can induce Th1 and Th17 immune responses, but only the induced Th1 lymphocytes mediate protection against H. pylori.

No vaccine against methicillin-resistant Staphylococcus aureus (MRSA) has been currently approved for use in humans. Staphylococcus enterotoxin B (SEB) is one of the most potent MRSA exotoxins. In the present study, we evaluated the efficacy and immunologic mechanisms of an SEB multiple B-cell epitope vaccine against MRSA infection. Synthetic overlapping peptide ELISA identified three novel B-cell immunodominant SEB epitopes (in addition to those previously known): SEB31–48, SEB133–150, and SEB193–210. Six B-cell immunodominant epitopes (amino acid residues 31–48, 97–114, 133–150, 193–210, 205–222, and 247–261) were sufficient to induce robust IgG1/IgG2b-specific protective responses against MRSA infection. Therefore, we constructed a recombinant MRSA SEB-specific multiple B-cell epitope vaccine Polypeptides by combining the six SEB immunodominant epitopes and demonstrated its ability to induce a robust SEB-specific IgG1 response to MRSA, as well as a Th2-directing isotype response. Moreover, Polypeptides-induced antisera stimulated synergetic opsonophagocytosis killing of MRSA. Most importantly, Polypeptides was more effective at clearing the bacteria in MRSA-infected mice than the whole SEB antigen, and was able to successfully protect mice from infection by various clinical MRSA isolates. Altogether, these results support further evaluation of the SEB multiple B-cell epitope-vaccine to address MRSA infection in humans.

In mice, antigen-specific CD4+ T cell response is indispensible for the protective immunity against Helicobacter pylori (H. pylori). It has been demonstrated that neuraminyllactose-binding hemagglutinin (HpaA) immunization protected mice from H. pylori infection in a CD4+ T cell dependent manner. However, much remains unclear concerning the human CD4+ T cell responses to HpaA. We conducted a systematic study here to explore the immunodominant, HpaA-specific CD4+ T cell responses in H. pylori infected individuals. We found that HpaA-specific CD4+ T cell responses varied remarkably in their magnitude and had broad epitope-specificity. Importantly, the main responses focused on two regions: HpaA76-105 and HpaA130-159. The HLA-DRB1*0901 restricted HpaA142-159 specific CD4+ T cell response was the most immunodominant response at a population level. The immunodominant epitope HpaA142-159 was naturally presented and highly conserved. We also demonstrated that it was not the broad peptide specificity, but the strength of HpaA specific CD4+ T cell responses associated with gastric diseases potentially caused by H. pylori infection. Such investigation will aid development of novel vaccines against H. pylori infection.

Background and aims Although Helicobacter pylori is recognized as an extracellular infection bacterium, it can lead to an increase in the number of CD8+ T cells after infection. At present, the characteristics of H. pylori antigen‐specific CD8+ T cells and the epitope response have not been elucidated. This study was focused on putative protective antigen UreB to detect specific CD8+ T‐cell responses in vitro and screen for predominant response epitopes. Methods The PBMCs collected from H. pylori‐infected individuals were stimulated by UreB peptide pools in vitro to identify the immunodominant CD8+ T‐cell epitopes. Furthermore, their HLA restriction characteristics were detected accordingly by NGS. Finally, the relationship between immunodominant responses and appearance of gastric symptoms after H. pylori infection was conducted. Results UreB‐specific CD8+ T‐cell responses were detected in H. pylori‐infected individuals. Three of UreB dominant epitopes (A‐2 (UreB443–451: GVKPNMIIK), B‐4 (UreB420–428: SEYVGSVEV), and C‐1 (UreB5–13: SRKEYVSMY)) were firstly identified and mainly presented by HLA‐A*1101, HLA‐B*4001 and HLA‐C*0702 alleles, respectively. C‐1 responses were mostly occurred in H. pylori‐infected subjects without gastric symptoms and may alleviate the degree of gastric inflammation. Conclusions The UreB dominant epitope‐specific CD8+ T‐cell response was closely related to the gastric symptoms after H. pylori infection, and the C‐1 (UreB5‐13) dominant peptides may be protective epitopes.