Ruangkiattikul Nanthapon, Nerlich Andreas, Abdissa Ketema, Lienenklaus Stefan, Suwandi Abdulhadi, Janze Nina, Laarmann Kristin, Spanier Julia, Kalinke Ulrich, Weiss Siegfried, Goethe Ralph
a Institute for Microbiology , University of Veterinary Medicine Hannover , Hannover , Germany.
b Department of Molecular Immunology , Helmholtz Centre for Infection Research , Braunschweig , Germany.
Virulence. 2017 Oct 3;8(7):1303-1315. doi: 10.1080/21505594.2017.1321191. Epub 2017 Apr 19.
Type I interferons (IFN-I), such as IFN-α and IFN-β are important messengers in the host response against bacterial infections. Knowledge about the role of IFN-I in infections by nontuberculous mycobacteria (NTM) is limited. Here we show that macrophages infected with pathogens of the Mycobacterium avium complex produced significantly lower amounts of IFN-β than macrophages infected with the opportunistic pathogen M. smegmatis. To dissect the molecular mechanisms of this phenomenon, we focused on the obligate pathogen Mycobacterium avium ssp paratuberculosis (MAP) and the opportunistic M. smegmatis. Viability of both bacteria was required for induction of IFN-β in macrophages. Both bacteria induced IFN-β via the cGAS-STING-TBK1-IRF3/7-pathway of IFN-β activation. Stronger phosphorylation of TBK1 and higher amounts of extracellular bacterial DNA in the macrophage cytosol were found in M. smegmatis infected macrophages than in MAP infected macrophages. After intraperitoneal infection of mice, a strong Ifnb induction by M. smegmatis correlated with clearance of the bacteria. In contrast, MAP only induced weak Ifnb expression which correlated with bacterial persistence and increased number of granulomas in the liver. In mice lacking the type I interferon receptor we observed improved survival of M. smegmatis while survival of MAP was similar to that in wildtype mice. On the other hand, treatment of MAP infected wildtype mice with the IFN-I inducer poly(I:C) or recombinant IFN-β impaired the survival of MAP. This indicates an essential role of IFN-I in clearing infections by MAP and M. smegmatis. The expression level of IFN-I is decisive for transient versus persistent NTM infection.
I型干扰素(IFN-I),如IFN-α和IFN-β,是宿主对抗细菌感染反应中的重要信使。关于IFN-I在非结核分枝杆菌(NTM)感染中的作用的了解有限。在此我们表明,与感染机会性病原菌耻垢分枝杆菌的巨噬细胞相比,感染鸟分枝杆菌复合群病原体的巨噬细胞产生的IFN-β量显著更低。为剖析这一现象的分子机制,我们聚焦于专性病原菌副结核分枝杆菌(MAP)和机会性的耻垢分枝杆菌。巨噬细胞中IFN-β的诱导需要两种细菌都具有活性。两种细菌均通过IFN-β激活的cGAS-STING-TBK1-IRF3/7途径诱导IFN-β。在感染耻垢分枝杆菌的巨噬细胞中发现的TBK1磷酸化更强,且巨噬细胞胞质溶胶中的细胞外细菌DNA量比感染MAP的巨噬细胞中的更高。小鼠腹腔感染后,耻垢分枝杆菌强烈诱导Ifnb与细菌清除相关。相比之下,MAP仅诱导较弱的Ifnb表达,这与细菌持续存在及肝脏中肉芽肿数量增加相关。在缺乏I型干扰素受体的小鼠中,我们观察到耻垢分枝杆菌的存活率提高,而MAP的存活率与野生型小鼠相似。另一方面,用IFN-I诱导剂聚肌胞苷酸(poly(I:C))或重组IFN-β治疗感染MAP的野生型小鼠会损害MAP的存活率。这表明IFN-I在清除MAP和耻垢分枝杆菌感染中起重要作用。IFN-I的表达水平对于NTM的短暂感染与持续感染起决定性作用。
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