Division of Microbiology, Department of Biology, Friedrich Alexander University Erlangen/Nuremberg, Erlangen, Germany.
Lett Appl Microbiol. 2020 Apr;70(4):326-330. doi: 10.1111/lam.13277. Epub 2020 Feb 11.
The aim of this study was to investigate whether HtrA is responsible for differences in adherence and invasion of Campylobacter jejuni towards human and chicken cell lines. Gentamicin protection assays were performed with either human Caco-2 or chicken 2G4 cells using C. jejuni strain NCTC11168 to compare the adhesion and invasion rates towards these two cell types. The results revealed significant differences in the adhesion and invasion rates between the human and avian cells. Deletion of the Campylobacter htrA gene, coding for the dual function of serine protease and chaperonin with a role in pathogenesis, led to a reduction of the rates in both cell lines. Using a single-amino acid substitution mutant (ΔhtrA/htrA ) that lacked protease activity, but retained chaperonin activity, we show that the first is involved in the invasion of human Caco-2 and chicken 2G4 cells, whereas the latter mutant invaded at lower levels. Adherence towards the chicken cells is higher than towards Caco-2 cells and this is also dependent on HtrA. Together, these data suggest that the proteolytic activity of HtrA is involved in the difference in host response of C. jejuni towards human and chicken-derived cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Campylobacter jejuni is the main cause for bacterial foodborne enterocolitis worldwide. While colonization of the human intestine can lead to severe problems, avian hosts - as the major source of infection - remain unaffected by the bacteria. We showed that the bacterial serine protease and chaperonin HtrA are involved in adhesion and invasion in both species and not responsible for the discrepancy of virulence between the different hosts. In future, HtrA might act as a target for inhibitors to avoid or eradicate colonization in chickens as a less problematic alternative to antibiotics in commercial livestock breeding.
本研究旨在探讨 HtrA 是否是导致空肠弯曲菌对人源和禽源细胞黏附和侵袭差异的原因。使用 NCTC11168 空肠弯曲菌菌株，通过庆大霉素保护实验，在人源 Caco-2 或禽源 2G4 细胞上比较两种细胞类型的黏附和侵袭率。结果表明，人源和禽源细胞之间的黏附和侵袭率存在显著差异。缺失编码具有丝氨酸蛋白酶和分子伴侣双重功能的空肠弯曲菌 htrA 基因（在发病机制中起作用），导致两种细胞系的侵袭率均降低。使用缺乏蛋白酶活性但保留分子伴侣活性的单氨基酸取代突变体（ΔhtrA/htrA），我们表明该酶的前体参与人源 Caco-2 和禽源 2G4 细胞的侵袭，而后者突变体的侵袭水平较低。对禽源细胞的黏附比人源细胞更高，这也依赖于 HtrA。综上所述，这些数据表明 HtrA 的蛋白水解活性参与了空肠弯曲菌对人源和禽源细胞宿主反应的差异。
空肠弯曲菌是全世界细菌性食源性肠炎的主要原因。虽然该细菌在人类肠道中的定植可导致严重问题，但作为主要感染源的禽类宿主不受其影响。我们表明，细菌丝氨酸蛋白酶和分子伴侣 HtrA 参与了两种物种的黏附和侵袭，而不是导致不同宿主之间毒力差异的原因。在未来，HtrA 可能成为抑制剂的作用靶点，以避免或根除鸡群中的定植，这是商业牲畜养殖中替代抗生素的一种较无问题的选择。
