BackgroundHepatitis B virus infection remains an important global health concern despite the availability of safe and effective prophylactic vaccines. Limitations to these vaccines include requirement for refrigeration and three immunizations thereby restricting use in the developing world. A new nasal hepatitis B vaccine composed of recombinant hepatitis B surface antigen (HBsAg) in a novel nanoemulsion (NE) adjuvant (HBsAg-NE) could be effective with fewer administrations.Methodology and Principal FindingsPhysical characterization indicated that HBsAg-NE consists of uniform lipid droplets (349+/−17 nm) associated with HBsAg through electrostatic and hydrophobic interactions. Immunogenicity of HBsAg-NE vaccine was evaluated in mice, rats and guinea pigs. Animals immunized intranasally developed robust and sustained systemic IgG, mucosal IgA and strong antigen-specific cellular immune responses. Serum IgG reached ≥106 titers and was comparable to intramuscular vaccination with alum-adjuvanted vaccine (HBsAg-Alu). Normalization showed that HBsAg-NE vaccination correlates with a protective immunity equivalent or greater than 1000 IU/ml. Th1 polarized immune response was indicated by IFN-γ and TNF-α cytokine production and elevated levels of IgG2 subclass of HBsAg-specific antibodies. The vaccine retains full immunogenicity for a year at 4°C, 6 months at 25°C and 6 weeks at 40°C. Comprehensive pre-clinical toxicology evaluation demonstrated that HBsAg-NE vaccine is safe and well tolerated in multiple animal models.ConclusionsOur results suggest that needle-free nasal immunization with HBsAg-NE could be a safe and effective hepatitis B vaccine, or provide an alternative booster administration for the parenteral hepatitis B vaccines. This vaccine induces a Th1 associated cellular immunity and also may provide therapeutic benefit to patients with chronic hepatitis B infection who lack cellular immune responses to adequately control viral replication. Long-term stability of this vaccine formulation at elevated temperatures suggests a direct advantage in the field, since potential excursions from cold chain maintenance could be tolerated without a loss in therapeutic efficacy.

The current study tests the hypothesis that chronic atrophic gastritis from hypochlorhydria in the gastrindeficient mouse predisposes the stomach to gastric cancer. Gross morphology and histology of 12-month-old wildtype (WT), gastrin-deficient (GÀ/À) and somatostatindeficient (SOMÀ/À) mice were examined. Parietal and G cells, Ki67, TUNEL, villin and MUC2 expression were analysed by immunohistochemistry. RUNX3 and STAT3 expression was analysed by Western blot. Anchorageindependent growth was determined by cell cluster formation in soft agar. Compared to the WT and SOMÀ/À mice, hypochlorhydric GÀ/À mice developed parietal cell atrophy, significant antral inflammation and intestinal metaplasia. Areas of metaplasia within the GÀ/ À mouse stomach showed decreased RUNX3 expression with elevated MUC2 and villin expression. Cells isolated from the tumor grew in soft agar. However, the cells isolated from WT, nontransformed GÀ/À and SOMÀ/À gastric tissue did not form colonies in soft agar. Consistent with elevated antral proliferation, tumor tissue isolated from the GÀ/À mice showed elevated phosphorylated STAT3 expression. We then examined the mechanism by which STAT3 was constitutively expressed in the tumor tissue of the GÀ/À mice. We found that IFNc expression was also significantly higher in the tumor tissue of GÀ/À mice compared to WT and SOMÀ/À animals. To determine whether STAT3 was regulated by IFNc, MKN45 cells were cocultured with IFNc or gastrin. IFNc significantly stimulated phosphorylation of STAT3 in the MKN45 cell line, but not gastrin. Therefore, we show here that in the hypochlorhydric mouse stomach, the chronic gastritis, atrophy, metaplasia, dysplasia paradigm can be recapitulated in mice. Moreover, neoplastic transformation of the antral gastric mucosa does not require gastrin.

Chronic inflammation of the gastric epithelium is believed to induce mucosal changes that can eventually develop into gastric cancer. In gastrin-deficient (GÀ/À) mice exhibiting chronic inflammation in the hypochlorhydric stomach, we documented a prominent fundic mucous cell lineage sharing morphological similarity with preneoplastic changes reported in Helicobacter-infected mice. To study the identity and origin of this cell lineage, we screened for different gastric mucosal cell markers. The clusters of large, foamy cells stained for trefoil factor 2 (TFF2/SP), MUC6 and the lectin Griffonia Simplicifolia II (GSII), but not for the intestine-specific transcription factor Cdx2, suggested that they arise from gastric mucous neck cells. Ki67-labeled GSII-positive neck cells in Helicobacter felis-infected, but not GÀ/À stomachs, suggested that mucous neck cell proliferation accounted for expansion of this compartment in the H. felis model of gastritis, but not the GÀ/À model. Using RNase protection assays and quantitative PCR, we found that interferon gamma (IFNc) was the most abundant proinflammatory cytokine in the GÀ/À stomach. We also found that this Th1 cytokine can increase the abundance of mucous neck cells, since its infusion into mice recapitulated the appearance of these cells as observed in both GÀ/À and H. felis-infected mice. Using the human gastric cell line NCI-N87, we showed that IFNc induces the secretion of mucus and expression of MUC6, TFF2 and pepsinogen II, but not of pepsinogen I and intrinsic factor. In conclusion, our results demonstrate that inflammation, specifically the proinflammatory cytokine IFNc, induced expansion of the fundic mucous neck cell compartment, which likely represents both increased mucus production and cell number.

Helicobacter pylori evades host immune defenses and causes chronic gastritis. Immunity against intestinal pathogens is largely mediated by dendritic cells, yet the role of dendritic cells in acute H. pylori infection is largely unknown. We observed the recruitment of dendritic cells to the gastric mucosa of H. pylori-infected mice. Bone marrow-derived dendritic cells from mice responded to live H. pylori by upregulating the expression of proinflammatory cytokine mRNA (i.e., IL-1alpha, IL-1beta, and IL-6). The supernatant from dendritic cells stimulated with H. pylori for 18 h contained twofold higher levels of IL-12p70 than IL-10 and induced the proliferation of syngeneic splenocytes and type 1 T helper cell cytokine release (IFN-gamma and TNF-alpha). These responses were significantly lower compared with those induced by Acinetobacter lwoffi, another gastritis-causing pathogen more susceptible to host defenses. Analysis of whole H. pylori sonicate revealed the presence of a heat-stable factor secreted from H. pylori that specifically inhibited IL-12 but not IL-10 release from dendritic cells activated by A. lwoffi. Our findings suggest that dendritic cells participate in the host immune response against H. pylori and that their suppression by H. pylori may explain why infected hosts fail to prevent bacterial colonization.