Defining the Roles of IFN-γ and IL-17A in Inflammation and Protection against Helicobacter pylori Infection

Abstract

CD4+ T cells have been shown to be essential for vaccine-induced protection against Helicobacter pylori infection. However, the effector mechanisms leading to reductions in the gastric bacterial loads of vaccinated mice remain unclear. We have investigated the function of IFN-γ and IL-17A for vaccine-induced protection and inflammation (gastritis) using IFN-γ-gene-knockout (IFN-γ-/-) mice, after sublingual or intragastric immunization with H. pylori lysate antigens and cholera toxin. Bacteria were enumerated in the stomachs of mice and related to the gastritis score and cellular immune responses. We report that sublingually and intragastrically immunized IFN-γ-/- mice had significantly reduced bacterial loads similar to immunized wild-type mice compared to respective unimmunized infection controls. The reduction in bacterial loads in sublingually and intragastrically immunized IFN-γ-/- mice was associated with significantly higher levels of IL-17A in stomach extracts and lower gastritis scores compared with immunized wild-type mice. To study the role of IL-17A for vaccine-induced protection in sublingually immunized IFN-γ-/- mice, IL-17A was neutralized in vivo at the time of infection. Remarkably, the neutralization of IL-17A in sublingually immunized IFN-γ-/- mice completely abolished protection against H. pylori infection and the mild gastritis. In summary, our results suggest that IFN-γ responses in the stomach of sublingually immunized mice promote vaccine-induced gastritis, after infection with H. pylori but that IL-17A primarily functions to reduce the bacterial load.

The frequency of circulating integrin α4β7+ cells correlates with protection against Helicobacter pylori infection in immunized mice

“…Indeed, we have observed a significantly higher frequency of IL‐17A + cells in the stomach after infection with H pylori in sublingually immunized mice compared with intragastrically immunized mice . We also observed an increase in frequency of CD11b + Ly6G − inflammatory monocytes in the circulation after vaccination particularly after IG route of immunization in accordance with the study by Moyat et al Furthermore, we have previously reported the dependence of IFNγ on the protective immune response after IG immunization, and thus, the CD11b + Ly6G‐ inflammatory monocytes activated after IG route of vaccination might play a role in the polarization of the CD4 + T‐cell response to a Th1 phenotype . Finally, we saw a decrease in frequency of eosinophils in circulation after vaccination possibly due to their migration to the effector tissues.…”

“…Spleens from mice were collected after the sacrifice, and single‐cell suspensions were prepared and cultured . In short, cells were plated (2 × 10 5 cells per well) in the presence or absence of boiled H pylori strain Hel 305 lysate antigens (0.1 and 1 μg/mL) in complete Iscoves modified Dulbecco medium supplemented with supplemented with 10% heat‐inactivated fetal calf serum (Sigma), 50 µmol/L 2‐mercaptoethanol (Sigma), 1 mmol/L l ‐glutamine (Biochrome), and 50 µg/mL gentamicin (Sigma) and incubated for 72 hours at 37°C in a 5% CO 2 atmosphere.…”

“…Spleens from mice were collected after the sacrifice, and single-cell suspensions were prepared and cultured. 20 In short, cells were plated…”

Induction of mucosal immune responses against Helicobacter pylori infection after sublingual and intragastric route of immunization

“…Our previous studies in the H. pylori immunization model have shown that the sublingual route of immunization is dose sparing for the vaccine antigen and adjuvant compared with immunization via the intragastric route . We now report that, in vitro , when DCs isolated from the CLN or MLN are pulsed with H. pylori antigens and CT and dmLT adjuvants, they are able to effectively activate H. pylori ‐specific CD4 + T cells and induce their cytokine secretion.…”

Interleukin-21 (IL-21) Downregulates Dendritic Cell Cytokine Responses to Helicobacter pylori and Modulates T Lymphocyte IL-17A Expression in Peyer’s Patches during Infection

“…(IFN-␥) and interleukin-17 (IL-17) and regulatory T (Treg) cell development, impact the pathology elicited in response to H. pylori colonization (13)(14)(15)(16)(17)(18)(19).…”