a Department Biologie , Friedrich-Alexander-Universität Erlangen-Nürnberg , Erlangen , Germany.
b Institut für Klinische Mikrobiologie, Immunologie und Hygiene, Universtitätsklinikum Erlangen , Friedrich-Alexander-Universität Erlangen-Nürnberg , Erlangen , Germany.
Virulence. 2019 Dec;10(1):414-428. doi: 10.1080/21505594.2019.1614384.
Seven non-toxigenic C. diphtheriae strains and one toxigenic strain were analyzed with regard to their interaction with murine macrophages (BMM) and human THP-1 macrophage-like cells. Proliferation assays with BMM and THP-1 revealed similar intracellular CFUs for C. diphtheriae strains independent of the host cell. Strain ISS4060 showed highest intracellular CFUs, while the toxigenic DSM43989 was almost not detectable. This result was confirmed by TLR 9 reporter assays, showing a low signal for DSM43989, indicating that the bacteria are not endocytosed. In contrast, the non-pathogenic C. glutamicum showed almost no intracellular CFUs independent of the host cell, but was recognized by TLR9, indicating that the bacteria were degraded immediately after endocytosis. In terms of G-CSF and IL-6 production, no significant differences between BMM and THP-1 were observed. G-CSF production was considerably higher than IL-6 for all C. diphtheriae strains and the C. glutamicum did not induce high cytokine secretion in general. Furthermore, all corynebacteria investigated in this study were able to induce NFκB signaling but only viable C. diphtheriae strains were able to cause host cell damage, whereas C. glutamicum did not. The absence of Mincle resulted in reduced G-CSF production, while no influence on the uptake of the bacteria was observed. In contrast, when MyD88 was absent, both the uptake of the bacteria and cytokine production were blocked. Consequently, phagocytosis only occurs when the TLR/MyD88 pathway is functional, which was also supported by showing that all corynebacteria used in this study interact with human TLR2.
七种非产毒白喉棒状杆菌菌株和一株产毒菌株与鼠源巨噬细胞（BMM）和人 THP-1 巨噬样细胞的相互作用进行了分析。BMM 和 THP-1 的增殖实验表明，白喉棒状杆菌菌株的细胞内 CFU 相似，与宿主细胞无关。菌株 ISS4060 显示出最高的细胞内 CFU，而产毒 DSM43989 几乎无法检测到。TLR 9 报告基因实验证实了这一结果，显示 DSM43989 的信号较低，表明细菌未被内吞。相比之下，非致病性 C. glutamicum 无论宿主细胞如何，其细胞内 CFU 均较低，但被 TLR9 识别，表明细菌在被内吞后立即被降解。就 G-CSF 和 IL-6 的产生而言，BMM 和 THP-1 之间没有观察到显著差异。所有白喉棒状杆菌菌株的 G-CSF 产生均显著高于 IL-6，而一般来说，C. glutamicum 不会诱导高水平细胞因子分泌。此外，本研究中研究的所有棒状杆菌均能诱导 NFκB 信号，但只有存活的白喉棒状杆菌菌株能够导致宿主细胞损伤，而 C. glutamicum 则不能。Mincle 缺失导致 G-CSF 产生减少，而对细菌的摄取没有影响。相反，当 MyD88 缺失时，细菌的摄取和细胞因子的产生都被阻断。因此，只有当 TLR/MyD88 途径功能正常时，吞噬作用才会发生，这也得到了支持，表明本研究中使用的所有棒状杆菌都与人类 TLR2 相互作用。
