Centre for Innate Immunity and Infectious Diseases, Monash Institute of Medical Research, Monash University, Clayton, Australia.
mBio. 2013 Jun 11;4(3):e00609-12. doi: 10.1128/mBio.00609-12.
Helicobacter pylori causes chronic gastritis and avoids elimination by the immune system of the infected host. The commensal bacterium Lactobacillus acidophilus has been suggested to exert beneficial effects as a supplement during H. pylori eradication therapy. In the present study, we applied whole-genome microarray analysis to compare the immune responses induced in murine bone marrow-derived macrophages (BMDMs) stimulated with L. acidophilus, H. pylori, or both bacteria in combination. While L. acidophilus induced a Th1-polarizing response characterized by high expression of interferon beta (IFN-β) and interleukin 12 (IL-12), H. pylori strongly induced the innate cytokines IL-1β and IL-1α. In BMDMs prestimulated with L. acidophilus, H. pylori blocked the expression of L. acidophilus-induced IFN-β and IL-12 and suppressed the expression of key regulators of the Rho, Rac, and Cdc42 GTPases. The inhibition of L. acidophilus-induced IFN-β was independent of H. pylori viability and the virulence factor CagPAI; however, a vacuolating cytotoxin (vacA) mutant was unable to block IFN-β. Confocal microscopy demonstrated that the addition of H. pylori to L. acidophilus-stimulated BMDMs redirects intracellular processing, leading to an accumulation of L. acidophilus in the endosomal and lysosomal compartments. Thus, our findings indicate that H. pylori inhibits the development of a strong Th1-polarizing response in BMDMs stimulated with L. acidophilus by blocking the production of IFN-β in a VacA-dependent manner. We suggest that this abrogation is caused by a redirection of the endocytotic pathway in the processing of L. acidophilus. IMPORTANCE Approximately half of the world's population is infected with Helicobacter pylori. The factors that allow this pathogen to persist in the stomach and cause chronic infections have not yet been fully elucidated. In particular, how H. pylori avoids killing by macrophages, one of the main types of immune cell underlying the epithelium, remains elusive. Here we have shown that the H. pylori virulence factor VacA plays a key role by blocking the activation of innate cytokines induced by the probiotic Lactobacillus acidophilus in macrophages and suppresses the expression of key regulators required for the organization and dynamics of the intracellular cytoskeleton. Our results identify potential targets for the treatment of H. pylori infection and vaccination, since specific inhibition of the toxin VacA possibly allows the activation of an efficient immune response and thereby eradication of H. pylori in the host.
幽门螺杆菌会导致慢性胃炎，并逃避感染宿主的免疫系统的清除。共生细菌嗜酸乳杆菌已被建议作为幽门螺杆菌根除治疗的补充物发挥有益作用。在本研究中，我们应用全基因组微阵列分析比较了刺激鼠骨髓来源的巨噬细胞（BMDM）的嗜酸乳杆菌、幽门螺杆菌或两者组合所诱导的免疫反应。虽然嗜酸乳杆菌诱导了一种 Th1 极化反应，其特征是干扰素-β（IFN-β）和白细胞介素 12（IL-12）的高表达，而幽门螺杆菌则强烈诱导先天细胞因子 IL-1β和 IL-1α。在预先用嗜酸乳杆菌刺激的 BMDM 中，幽门螺杆菌阻断了嗜酸乳杆菌诱导的 IFN-β和 IL-12 的表达，并抑制了 Rho、Rac 和 Cdc42 GTPases 的关键调节剂的表达。嗜酸乳杆菌诱导的 IFN-β的抑制与幽门螺杆菌的活力和毒力因子 CagPAI 无关；然而，空泡细胞毒素（vacA）突变体不能阻断 IFN-β。共聚焦显微镜显示，将幽门螺杆菌添加到嗜酸乳杆菌刺激的 BMDM 中会重新引导细胞内加工，导致嗜酸乳杆菌在内体和溶酶体区室中积累。因此，我们的研究结果表明，幽门螺杆菌通过依赖 VacA 的方式阻断 IFN-β的产生，抑制嗜酸乳杆菌刺激的 BMDM 中强烈的 Th1 极化反应的发展。我们认为，这种阻断是由嗜酸乳杆菌处理过程中内吞途径的重定向引起的。
重要性 世界上大约一半的人口感染了幽门螺杆菌。这种病原体能够在胃中持续存在并引起慢性感染的因素尚未完全阐明。特别是，幽门螺杆菌如何逃避作为上皮下主要免疫细胞之一的巨噬细胞的杀伤仍然难以捉摸。在这里，我们已经表明，幽门螺杆菌的毒力因子 VacA 通过阻断益生菌嗜酸乳杆菌在巨噬细胞中诱导的先天细胞因子的激活发挥关键作用，并抑制了细胞内细胞骨架的组织和动力学所需的关键调节剂的表达。我们的研究结果确定了治疗幽门螺杆菌感染和疫苗接种的潜在靶点，因为毒素 VacA 的特异性抑制可能允许宿主中有效免疫反应的激活，从而根除幽门螺杆菌。
