Majkowska-Skrobek Grazyna, Latka Agnieszka, Berisio Rita, Squeglia Flavia, Maciejewska Barbara, Briers Yves, Drulis-Kawa Zuzanna
Department of Pathogen Biology and Immunology, Institute of Genetics and Microbiology, University of Wrocław, Wrocław, Poland.
Laboratory of Applied Biotechnology, Department of Biotechnology, Ghent University, Ghent, Belgium.
Front Microbiol. 2018 Oct 23;9:2517. doi: 10.3389/fmicb.2018.02517. eCollection 2018.
produces capsular polysaccharides that are a crucial virulence factor protecting bacteria against innate response mechanisms of the infected host. Simultaneously, those capsules are targeted by specific bacteriophages equipped with virion-associated depolymerases able to recognize and degrade these polysaccharides. We show that phage KP32 produces two capsule depolymerases, KP32gp37 and KP32gp38, with a high specificity for the capsular serotypes K3 and K21, respectively. Together, they determine the host spectrum of bacteriophage KP32, which is limited to strains with serotype K3 and K21. Both depolymerases form a trimeric β-structure, display moderate thermostability and function optimally under neutral to alkaline conditions. We show that both depolymerases strongly affect the virulence of with the corresponding K3 and K21 capsular serotypes. Capsule degradation renders the otherwise serum-resistant cells more prone to complement-mediated killing with up to four log reduction in serum upon exposure to KP32gp37. Decapsulated strains are also sensitized for phagocytosis with a twofold increased uptake. In addition, the intracellular survival of phagocytized cells in macrophages was significantly reduced when bacteria were previously exposed to the capsule depolymerases. Finally, depolymerase application considerably increases the lifespan of larvae infected with in a time- and strain-dependent manner. In sum, capsule depolymerases are promising antivirulence compounds that act by defeating a major resistance mechanism of against the innate immunity.
产生荚膜多糖，这是一种关键的毒力因子，可保护细菌免受受感染宿主的固有反应机制的影响。同时，这些荚膜被配备有病毒体相关解聚酶的特定噬菌体靶向，这些解聚酶能够识别并降解这些多糖。我们表明噬菌体KP32产生两种荚膜解聚酶，KP32gp37和KP32gp38，分别对荚膜血清型K3和K21具有高度特异性。它们共同决定了噬菌体KP32的宿主谱，该宿主谱仅限于血清型K3和K21的菌株。两种解聚酶均形成三聚体β结构，具有适度的热稳定性，并且在中性至碱性条件下功能最佳。我们表明，两种解聚酶都强烈影响具有相应K3和K21荚膜血清型的细菌的毒力。荚膜降解使原本抗血清的细胞更容易受到补体介导的杀伤，暴露于KP32gp37后血清中的细菌数量最多可减少四个对数。去荚膜菌株对吞噬作用也更敏感，摄取量增加了两倍。此外，当细菌先前暴露于荚膜解聚酶时，巨噬细胞中吞噬细胞的细胞内存活率显着降低。最后，解聚酶的应用以时间和菌株依赖性方式显着延长了感染细菌的幼虫的寿命。总之，荚膜解聚酶是有前途的抗毒力化合物，其作用是克服细菌对先天免疫的主要抵抗机制。
