Vaccines: an ongoing promise?

A plasmid immunization construct encoding urease B of Helicobacter pylori induces an antigen-specific antibody response and upregulates the expression of beta-defensins and IL-10 in the stomachs of immunized mice

The objectives of this study were to investigate the efficacy of a prototype DNA immunization construct encoding the urease B subunit enzyme of Helicobacter pylori (H. pylori) for inducing adaptive and innate immune responses in mice immunized via intramuscular or subcutaneous routes and to further explore the adjuvant effects of the CpG motifs in the vector. Antibody, cytokine, and beta-defensin profiles were assessed in the stomachs of immunized animals: experiments were terminated 3 months after immunization because there was a significant increase in the anti-H. pylori urease B antibody response at Week 6 in mice immunized with the urease B construct. A long lasting expression of IL-10 mRNA was noted. Furthermore, a marked and sustained increase in the mRNA expression of beta-defensins was also observed, particularly beta1. This study demonstrates that an H. pylori urease B DNA construct can induce innate as well as adaptive immune responses in the stomachs of immunized mice. Upregulation of beta-defensin gene expression followed immunization and we believe that this is the first report of a DNA vaccine inducing innate anti-microbial responses. Such complex molecular interactions that modulate both innate and adaptive immune responses may be of critical importance in the control of mucosal pathogens, such as H. pylori.

Colonization of C57BL/6J and BALB/c wild-type and knockout mice with Helicobacter pylori: effect of vaccination and implications for innate and acquired immunity

The gram-negative bacterial pathogen Helicobacter pylori is a major cause of peptic ulcer disease and a risk factor for gastric cancer in humans. Adapted H. pylori strains, such as strain SS1, are able to infect mice and are a useful model for gastric colonization and vaccination studies. In this study we used a streptomycin-resistant derivative of H. pylori SS1 to analyze the colonization behavior and the success of vaccination in wild-type (wt) and various knockout mice of the BALB/c and C57BL/6J genetic backgrounds. We here report that BALB/c interleukin-4 knockout (IL-4(-/-)) mice are weakly overcolonized compared to the wt strain but that the IL-12(-/-) knockout results in a strong overcolonization (500%). Unexpectedly, in the C57BL/6J background the same knockouts behaved in diametrically opposed manners. The IL-4(-/-) mutation caused a 50% reduction and the IL-12(-/-) knockout caused a 95% reduction compared to the wt colonization rate. For C57BL/6J mice we further analyzed the IL-18(-/-) and Toll-like receptor 2 knockout mutations, which showed reductions to 66 and 57%, respectively, whereas mice with the IL-10(-/-) phenotype were hardly infected at all (5%). In contrast, the tumor necrosis factor receptor knockout (p55(-/-) and p55/75(-/-)) mice showed an overcolonization compared to the C57BL/6J wt strain. With exception of the low-level infected C57BL/6J IL-10(-/-) and IL-12(-/-) knockout mice, all knockout mutants were accessible to a prophylactic vaccination and their vaccination behavior was comparable to that of the wt strains.