Early Host Immune Responses in Human Gallbladder to Salmonella Typhi Strains from Patients with Acute and Chronic Infections. Early Host Immune Responses in Human Gallbladder to Salmonella Typhi Strains from Patients with Acute and Chronic Infections

Salmonella enterica serovar Typhi (S. Typhi), a human-restricted pathogen, enters the host through the gut to cause typhoid fever. Recent calculations of the typhoid fever burden estimated that more than 20 million new typhoid fever cases occur in low and middle-income countries, resulting in 129,000-223,000 deaths yearly. Interestingly, upon the resolution of acute disease, 1%-5% of patients become asymptomatic chronic carriers of S. Typhi. Chronically infected hosts are not only critical reservoirs of infection that transmit the disease to naive individuals but are also predisposed to developing gallbladder carcinoma (GBC). Nevertheless, the molecular mechanisms involved in the early interactions between gallbladder epithelial cells and S. Typhi remain largely unknown. Based on our previous studies showing that very closely related S. Typhi strains elicit distinct innate immune responses, we hypothesized that host molecular pathways activated by S. Typhi strains derived from acutely and chronically infected patients will differ. To test this hypothesis, we used a novel human organoid-derived polarized gallbladder monolayer (HODGM) model, and 13 S. Typhi strains derived from acutely (n=6) and chronically (n=7) infected patients. We found that S. Typhi strains derived from acutely and chronically infected patients differentially regulate mitogen-activated protein kinase (MAPK) and S6 transcription factors. This differential regulation impacts, at least in part, the cytokine signaling pathway involved in the production of TNF- and IL-6 and is likely to play a critical role in inducing chronic S. Typhi infection in the gallbladder. Overall design: A human organoid-derived gallbladder monolayer (HODGM) model infected with 13 S. Typhi strains derived from acutely (n=6) and chronically (n=7) infected patients.

伤寒沙门氏菌（Salmonella enterica serovar Typhi, S. Typhi）是一种人类专属病原体，经肠道侵入宿主后可引发伤寒。近期针对伤寒疾病负担的估算显示，中低收入国家每年新增伤寒病例超2000万例，年死亡人数达12.9万至22.3万。值得注意的是，急性疾病康复后，1%~5%的患者会成为伤寒沙门氏菌无症状慢性带菌者。慢性感染宿主不仅是将疾病传播给易感个体的关键感染储存库，同时也更易罹患胆囊癌（gallbladder carcinoma, GBC）。然而，胆囊上皮细胞与伤寒沙门氏菌早期相互作用所涉及的分子机制，目前仍知之甚少。
基于我们此前的研究发现——亲缘关系极近的伤寒沙门氏菌菌株可引发不同的先天免疫反应，我们提出假说：源自急性感染患者与慢性感染患者的伤寒沙门氏菌菌株所激活的宿主分子通路存在差异。为验证该假说，我们采用了新型人源类器官衍生极化胆囊单层上皮（human organoid-derived polarized gallbladder monolayer, HODGM）模型，以及13株分别来自急性（n=6）和慢性（n=7）感染患者的伤寒沙门氏菌菌株。
实验结果显示，源自急性与慢性感染患者的伤寒沙门氏菌菌株可差异性调控丝裂原活化蛋白激酶（mitogen-activated protein kinase, MAPK）与S6转录因子。这种差异性调控至少部分影响了参与TNF-α与IL-6产生的细胞因子信号通路，且可能在诱导胆囊慢性伤寒沙门氏菌感染中发挥关键作用。
整体实验设计：使用13株分别来自急性（n=6）和慢性（n=7）感染患者的伤寒沙门氏菌菌株感染人源类器官衍生胆囊单层上皮（HODGM）模型。