Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA.
Cell Microbiol. 2013 Aug;15(8):1323-40. doi: 10.1111/cmi.12117. Epub 2013 Feb 28.
Symptomatic infection with Neisseria gonorrhoeae (Gc) promotes inflammation driven by polymorphonuclear leucocytes (PMNs, neutrophils), yet some Gc survive PMN exposure during infection. Here we report a novel mechanism of gonococcal resistance to PMNs: Gc phagosomes avoid maturation into phagolysosomes by delayed fusion with primary (azurophilic) granules, which contain antimicrobial components including serine proteases. Reduced phagosome-primary granule fusion was observed in gonorrheal exudates and human PMNs infected ex vivo. Delayed phagosome-granule fusion could be overcome by opsonizing Gc with immunoglobulin. Using bacterial viability dyes along with antibodies to primary granules revealed that Gc survival in PMNs correlated with early residence in primary granule-negative phagosomes. However, when Gc was killed prior to PMN exposure, dead bacteria were also found in primary granule-negative phagosomes. These results suggest that Gc surface characteristics, rather than active bacterial processes, influence phagosome maturation and that Gc death inside PMNs occurs after phagosome-granule fusion. Ectopically increasing primary granule-phagosome fusion, by immunoglobulin opsonization or PMN treatment with lysophosphatidylcholine, reduced intracellular Gc viability, which was attributed in part to serine protease activity. We conclude that one method for Gc to avoid PMN clearance in acute gonorrhoea is by delaying primary granule-phagosome fusion, thus preventing formation of a degradative phagolysosome.
淋病奈瑟菌（Gc）的症状感染会引发多形核白细胞（PMNs，中性粒细胞）驱动的炎症，但在感染过程中，有些 Gc 能够在 PMN 暴露下存活。在这里，我们报告了一种淋病奈瑟球菌抵抗 PMN 的新机制：Gc 吞噬体通过延迟与初级（嗜天青）颗粒融合来避免成熟为吞噬溶酶体，初级颗粒包含包括丝氨酸蛋白酶在内的抗菌成分。在淋病渗出物和体外感染的人 PMN 中观察到吞噬体与初级颗粒融合减少。用免疫球蛋白对 Gc 进行调理可以克服吞噬体-颗粒融合延迟。使用细菌存活染料以及针对初级颗粒的抗体表明，Gc 在 PMN 中的存活与早期存在于初级颗粒阴性吞噬体中相关。然而，当 Gc 在暴露于 PMN 之前被杀死时，也在初级颗粒阴性吞噬体中发现了死亡细菌。这些结果表明，Gc 表面特征而非活跃的细菌过程会影响吞噬体成熟，并且 Gc 在 PMN 内死亡发生在吞噬体-颗粒融合之后。通过免疫球蛋白调理或用溶血磷脂酰胆碱处理 PMN 异位增加初级颗粒-吞噬体融合，降低了细胞内 Gc 的活力，这部分归因于丝氨酸蛋白酶活性。我们得出结论，Gc 在急性淋病中避免 PMN 清除的一种方法是延迟初级颗粒-吞噬体融合，从而防止形成降解性吞噬溶酶体。
