Search

Background Tissue-resident memory T cells accelerate the clearance of pathogens during recall response. However, whether CD4+ TRM cells themselves can provide gastric immunity is unclear. Materials and methods We established a parabiosis model between the enhanced green fluorescent protein and wild-type mice that the circulation system was shared, and the wild-type partner was vaccinated with H pylori vaccine composed of CCF and silk fibroin in gastric subserous layer to induce gastric EGFP+ CD4+ TRM cells. Antigen-specific EGFP+ CD4+ T cells and proliferous TRM cells were analyzed by flow cytometry. The colonization of H pylori was detected by quantitative real-time PCR. EGFP+ CD4+ TRM cells and the inflammation of the stomach were observed by histology. Results A parabiosis animal model was employed to identify the cells that introduced by vaccination in GSL. Antigen-specific EGFP+ CD4+ T cells could be detected at day 7 post-vaccination. Thirty days later, EGFP+ CD4+ TRM cells were established with a phenotype of CD69+ CD103- . Of note, we found that when circulating lymphocytes were depleted by FTY720 administration, these TRM cells could proliferate in situ and differentiate into effector Th1 cells after H pylori challenge. A decrease in H pylori colonization was observed in the vaccinated mice but not unvaccinated mice. Further, we found that although FTY720 was administrated, mounted pro-inflammatory myeloid cells still emerged in the stomach of the vaccinated mice, which might contribute to the reduction of H pylori colonization. Conclusions Our study reveals that H pylori vaccine-induced CD4+ TRM cells can proliferate and differentiate in situ to enhance gastric local immunity during recall response.

BACKGROUND Toxic adjuvant is considered as an indispensable constituent for oral Helicobacter pylori (H. pylori) vaccines. However, the elaborate role of toxic adjuvant in the initiation of adaptive immune response is largely undescribed. MATERIALS AND METHODS We employed an acid-resistant HP55/PLGA nanoparticles (NPs) delivery system encapsulating three antigens (Hsp, Nap, and Lpp20) from H. pylori and accompanied with three adjuvants (LPS, CpG, and chimeric flagellum (CF)) to explore the underlying mechanism of the adjuvant constituent. H. pylori-specific antibody responses were detected by ELISA. Gastric inflammatory and Th1/Th17 responses were analyzed by flow cytometry. Expressions of inflammatory cytokines were measured by quantitative real-time PCR. RESULTS In bone marrow-derived dendritic cells' (BMDCs) model, the addition of toxic adjuvants is responsible for the proinflammatory function, but not the mature phenotype of BMDCs. In vivo, intestinal loop injection with NPs + LPS, rather than NPs alone, altered the dendritic cell (DC) phenotypes in mesenteric lymph nodes and drove a local proinflammatory microenvironment. In a prophylactic vaccination model, mice immunized with NPs + adjuvants significantly reduced the gastric colonization of H. pylori, induced antigen-specific antibody responses and Th1/Th17 cell responses. After H. pylori challenge, these mice showed potent recall responses involving both neutrophil and inflammatory monocyte infiltration. Additionally, TLR4 knockout mice were immunized with NPs + LPS and NPs + CF, respectively; only the recipients of NPs + CF orchestrated a protective response to control bacterial infection. CONCLUSIONS Our study indicated that toxic adjuvants within oral H.pylori vaccines altered the function and phenotype of dendritic cells and facilitated the establishment of proinflammatory microenvironment to initiate adaptive immune responses.

Background Gram-positive enhancer matrix particles (GEM) produced by Lactococcus lactis can enhance vaccine-induced immune response. However, the mechanism under which this adjuvant mounts the efficacy of orally administered vaccines remains unexplored. Materials and Methods We used a prophylactic mice model to investigate the mechanism of GEM-adjuvanted vaccination. Helicobacter pylori urease-specific antibody response was monitored and detected in murine serum by ELISA. Urease-specific splenic cytokine profile was examined. Gastric inflammatory responses were measured on day 43 or 71 by quantitative real-time PCR, flow cytometry and histology. Results We found that GEM enhanced the efficiency of oral H. pylori vaccine by promoting innate immunity. The vaccine CUE-GEM composed of GEM particles and recombinant antigen CTB-UE provided protection of immunized mice against H. pylori insult. The protective response was associated with induction of postimmunization gastritis and local Th1/Th17 cell-medicated immune response. We showed that innate inflammatory responses including neutrophil chemokines CXCL1-2, neutrophils, and antimicrobial proteins S100A8 and MUC1 were significantly elevated. Within all infected mice, S100A8 and MUC1 levels were negatively correlated with H. pylori burden. Strikingly, mice receiving GEM also show reduction of colonization, possibly through natural host response pathways to recruit CD4+ T cells and promote S100A8 expression. Conclusions These findings suggest that GEM-based vaccine may impact Th1/Th17 immunity to orchestrate innate immune response against H. pylori infection.