The Francis Crick Institute, London, United Kingdom.
UCD School of Veterinary Medicine and UCD Conway Institute, University College Dublin, Dublin, Ireland.
PLoS Pathog. 2021 Mar 15;17(3):e1009410. doi: 10.1371/journal.ppat.1009410. eCollection 2021 Mar.
The Mycobacterium tuberculosis complex (MTBC) is a group of related pathogens that cause tuberculosis (TB) in mammals. MTBC species are distinguished by their ability to sustain in distinct host populations. While Mycobacterium bovis (Mbv) sustains transmission cycles in cattle and wild animals and causes zoonotic TB, M. tuberculosis (Mtb) affects human populations and seldom causes disease in cattle. The host and pathogen determinants underlying host tropism between MTBC species are still unknown. Macrophages are the main host cell that encounters mycobacteria upon initial infection, and we hypothesised that early interactions between the macrophage and mycobacteria influence species-specific disease outcome. To identify factors that contribute to host tropism, we analysed blood-derived primary human and bovine macrophages (hMϕ or bMϕ, respectively) infected with Mbv and Mtb. We show that Mbv and Mtb reside in different cellular compartments and differentially replicate in hMϕ whereas both Mbv and Mtb efficiently replicate in bMϕ. Specifically, we show that out of the four infection combinations, only the infection of bMϕ with Mbv promoted the formation of multinucleated giant cells (MNGCs), a hallmark of tuberculous granulomas. Mechanistically, we demonstrate that both MPB70 from Mbv and extracellular vesicles released by Mbv-infected bMϕ promote macrophage multinucleation. Importantly, we extended our in vitro studies to show that granulomas from Mbv-infected but not Mtb-infected cattle contained higher numbers of MNGCs. Our findings implicate MNGC formation in the contrasting pathology between Mtb and Mbv for the bovine host and identify MPB70 from Mbv and extracellular vesicles from bMϕ as mediators of this process.
结核分枝杆菌复合群(MTBC)是一组相关病原体,可导致哺乳动物发生肺结核(TB)。MTBC 物种的区别在于其在不同宿主种群中持续存在的能力。虽然牛分枝杆菌(Mbv)在牛和野生动物中维持传播循环并引起人畜共患性结核病,但结核分枝杆菌(Mtb)则影响人类人群,很少在牛中引起疾病。MTBC 物种之间宿主嗜性的宿主和病原体决定因素尚不清楚。巨噬细胞是在初次感染时遇到分枝杆菌的主要宿主细胞,我们假设巨噬细胞与分枝杆菌之间的早期相互作用会影响特定物种的疾病结果。为了确定导致宿主嗜性的因素,我们分析了感染 Mbv 和 Mtb 的人源和牛源原代巨噬细胞(分别为 hMϕ 或 bMϕ)。我们表明 Mbv 和 Mtb 分别位于不同的细胞区室中,并在 hMϕ 中以不同的方式复制,而 Mbv 和 Mtb 在 bMϕ 中均能有效复制。具体而言,我们表明,在这四种感染组合中,只有 bMϕ 感染 Mbv 才能促进多核巨细胞(MNGC)的形成,这是结核肉芽肿的标志。从机制上讲,我们证明了 Mbv 的 MPB70 和 Mbv 感染的 bMϕ 释放的细胞外囊泡均可促进巨噬细胞多核化。重要的是,我们将体外研究扩展到表明,Mbv 感染而非 Mtb 感染的牛源肉芽肿中含有更多数量的 MNGC。我们的发现表明,MNGC 的形成参与了 Mbv 和 Mtb 对牛宿主的不同病理学表现,并确定了 Mbv 的 MPB70 和 bMϕ 的细胞外囊泡作为该过程的介质。