Department of Molecular Genetics and Infection Biology, University of Greifswald, Greifswald, Germany.
Department of Functional Genomics, University Medicine Greifswald, Greifswald, Germany.
J Biomed Sci. 2024 Feb 27;31(1):26. doi: 10.1186/s12929-024-01014-9.
Streptococcus pyogenes (group A streptococcus, GAS) causes a variety of diseases ranging from mild superficial infections of the throat and skin to severe invasive infections, such as necrotizing soft tissue infections (NSTIs). Tissue passage of GAS often results in mutations within the genes encoding for control of virulence (Cov)R/S two component system leading to a hyper-virulent phenotype. Dendritic cells (DCs) are innate immune sentinels specialized in antigen uptake and subsequent T cell priming. This study aimed to analyze cytokine release by DCs and other cells of monocytic origin in response to wild-type and natural covR/S mutant infections.
Human primary monocyte-derived (mo)DCs were used. DC maturation and release of pro-inflammatory cytokines in response to infections with wild-type and covR/S mutants were assessed via flow cytometry. Global proteome changes were assessed via mass spectrometry. As a proof-of-principle, cytokine release by human primary monocytes and macrophages was determined.
In vitro infections of moDCs and other monocytic cells with natural GAS covR/S mutants resulted in reduced secretion of IL-8 and IL-18 as compared to wild-type infections. In contrast, moDC maturation remained unaffected. Inhibition of caspase-8 restored secretion of both molecules. Knock-out of streptolysin O in GAS strain with unaffected CovR/S even further elevated the IL-18 secretion by moDCs. Of 67 fully sequenced NSTI GAS isolates, 28 harbored mutations resulting in dysfunctional CovR/S. However, analyses of plasma IL-8 and IL-18 levels did not correlate with presence or absence of such mutations.
Our data demonstrate that strains, which harbor covR/S mutations, interfere with IL-18 and IL-8 responses in monocytic cells by utilizing the caspase-8 axis. Future experiments aim to identify the underlying mechanism and consequences for NSTI patients.
酿脓链球菌（A 组链球菌，GAS）可引起多种疾病，从轻度的咽喉和皮肤浅表感染到严重的侵袭性感染，如坏死性软组织感染（NSTI）。GAS 的组织穿透通常会导致控制毒力（Cov）R/S 双组分系统的基因发生突变，导致高毒力表型。树突状细胞（DCs）是专门摄取抗原并随后启动 T 细胞的先天免疫哨兵。本研究旨在分析 DCs 和其他单核来源细胞对野生型和天然 covR/S 突变体感染的细胞因子释放。
使用人原代单核细胞衍生的（mo）DCs。通过流式细胞术评估 DC 成熟和感染野生型和 covR/S 突变体后促炎细胞因子的释放。通过质谱法评估全蛋白质组变化。作为原理验证，测定了人原代单核细胞和巨噬细胞的细胞因子释放。
与野生型感染相比，moDCs 和其他单核细胞体外感染天然 GAS covR/S 突变体导致 IL-8 和 IL-18 的分泌减少。相反，moDC 成熟不受影响。半胱天冬酶-8 的抑制恢复了这两种分子的分泌。在不影响 CovR/S 的 GAS 菌株中敲除链球菌溶血素 O 甚至进一步提高了 moDCs 的 IL-18 分泌。在 67 株完全测序的 NSTI GAS 分离株中，有 28 株携带有导致 CovR/S 功能障碍的突变。然而，对血浆 IL-8 和 IL-18 水平的分析与这些突变的存在与否没有相关性。
我们的数据表明，携带 covR/S 突变的菌株通过利用半胱天冬酶-8 轴干扰单核细胞中 IL-18 和 IL-8 的反应。未来的实验旨在确定 NSTI 患者的潜在机制和后果。
