Protection Against Helicobacter pylori Infection Following Immunization Is IL-12-Dependent and Mediated by Th1 Cells

Abstract

The regulatory roles of Th1 and Th2 cells in immune protection against Helicobacter infection are not clearly understood. In this study, we report that a primary H. pylori infection can be established in the absence of IL-12 or IFN-γ. However, IFN-γ, but not IL-12, was involved in the development of gastritis because IFN-γ−/− (GKO) mice exhibited significantly less inflammation as compared with IL-12−/− or wild-type (WT) mice. Both IL-12−/− and GKO mice failed to develop protection following oral immunization with H. pylori lysate and cholera toxin adjuvant. By contrast, Th2-deficient, IL-4−/−, and WT mice were equally well protected. Mucosal immunization in the presence of coadministered rIL-12 in WT mice increased Ag-specific IFN-γ-producing T cells by 5-fold and gave an additional 4-fold reduction in colonizing bacteria, confirming a key role of Th1 cells in protection. Importantly, only protected IL-4−/− and WT mice demonstrated substantial influx of CD4+ T cells in the gastric mucosa. The extent of inflammation in challenged IL-12−/− and GKO mice was much reduced compared with that in WT mice, indicating that IFN-γ/Th1 cells also play a major role in postimmunization gastritis. Of note, postimmunization gastritis in IL-4−/− mice was significantly milder than WT mice, despite a similar level of protection, indicating that immune protection is not directly linked to the degree of gastric inflammation. Only protected mice had T cells that produced high levels of IFN-γ to recall Ag, whereas both protected and unprotected mice produced high levels of IL-13. We conclude that IL-12 and Th1 responses are crucial for H. pylori-specific protective immunity.

Vaccine-Induced Immunity againstHelicobacter pyloriInfection Is Impaired in IL-18-Deficient Mice

“…Of note, however, conflicting data about the necessity of IFN-␥ for protection have recently been reported (19). In contrast, Th2 cells do not appear to be needed for protection, but they may contribute to the severity of postimmunization gastritis, as suggested by observations made in IL-4-deficient mice (18,20). Moreover, Th2 cells increase in number in well-protected mice over time after immunization, perhaps indicating a role in long term protection (6,11).…”

“…Infected patients as well as mice challenged with H. pylori exhibit strong T cell infiltration with a typical Th1 phenotype in the gastric mucosa (13)(14)(15)(16). Immunized and thus protected mice also demonstrate Th1 dominance, and IL-12 and perhaps IFN-␥ are thought to play major roles in protection as well as being responsible for driving Helicobacter-induced gastritis (17)(18)(19). Of note, however, conflicting data about the necessity of IFN-␥ for protection have recently been reported (19).…”

“…Control sections were incubated without specific mAb. Stained sections were scored from 0 to 4 based on the extent of infiltrating T cells (18). Scores were defined as follows: 0, none; 1, a few T cells scattered in the mucosa; 2, moderate numbers of T cells in the gastric mucosa; 3, dense infiltrates in the deep to mid mucosa; and 4, dense, diffuse infiltrates throughout the lamina propria and into the submucosa.…”

“…pylori was grown on selective blood agar plates as described previously (18) and suspended in PBS. The cells were then washed three times in PBS by centrifugation at 6000 rpm for 10 min at 4°C before being disrupted by freeze-pressing with X-press (46).…”

“…pylori growth conditions and challenge H. pylori Sydney strain (SS1) cells were cultured on selective agar plates containing 5% sheep blood and antibiotics under microaerophilic conditions as described previously (18). The bacteria were then harvested and inoculated into Brucella broth (BD Biosciences, Mountain View, CA) supplemented with 5% heat-inactivated FCS (Biochrom, Berlin, Germany) as described previously (18). To assess protection after immunization, mice were challenged with 5 ϫ 10 7 CFU of H. pylori 2 wk after the last immunization and then killed 2 wk postchallenge.…”