Department of Biochemistry, University of Veterinary Medicine Hannover, Hannover, Germany.
Research Center for Emerging Infections and Zoonoses (RIZ), University of Veterinary Medicine Hannover, Hannover, Germany.
Front Immunol. 2022 May 10;13:879157. doi: 10.3389/fimmu.2022.879157. eCollection 2022.
During the COVID-19 pandemic, vaccination is the most important countermeasure. Pharmacovigilance concerns however emerged with very rare, but potentially disastrous thrombotic complications following vaccination with ChAdOx1. Platelet factor-4 antibody mediated vaccine-induced immune thrombotic thrombocytopenia (VITT) was described as an underlying mechanism of these thrombotic events. Recent work moreover suggests that mechanisms of immunothrombosis including neutrophil extracellular trap (NET) formation might be critical for thrombogenesis during VITT. In this study, we investigated blood and thrombus specimens of a female patient who suffered severe stroke due to VITT after vaccination with ChAdOx1 in comparison to 13 control stroke patients with similar clinical characteristics. We analyzed cerebral thrombi using histological examination, staining of complement factors, NET-markers, DNase and LL-37. In blood samples at the hyper-acute phase of stroke and 7 days later, we determined cell-free DNA, myeloperoxidase-histone complexes, DNase activity, myeloperoxidase activity, LL-37 and inflammatory cytokines. NET markers were identified in thrombi of all patients. Interestingly, the thrombus of the VITT-patient exclusively revealed complement factors and high amounts of DNase and LL-37. High DNase activity was also measured in blood, implying a disturbed NET-regulation. Furthermore, serum of the VITT-patient inhibited reactive oxygen species-dependent NET-release by phorbol-myristate-acetate to a lesser degree compared to controls, indicating either less efficient NET-inhibition or enhanced NET-induction in the blood of the VITT-patient. Additionally, the changes in specific cytokines over time were emphasized in the VITT-patient as well. In conclusion, insufficient resolution of NETs, e.g. by endogenous DNases or protection of NETs against degradation by embedded factors like the antimicrobial peptide LL-37 might thus be an important factor in the pathology of VITT besides increased NET-formation. On the basis of these findings, we discuss the potential implications of the mechanisms of disturbed NETs-degradation for diagnostic and therapeutic approaches in VITT-related thrombogenesis, other auto-immune disorders and beyond.
在 COVID-19 大流行期间，接种疫苗是最重要的对策。然而，在接种 ChAdOx1 后，出现了非常罕见但可能具有灾难性的血栓并发症，引起了药物警戒关注。血小板因子-4 抗体介导的疫苗诱导免疫性血栓性血小板减少症（VITT）被描述为这些血栓事件的潜在机制。最近的研究还表明，包括中性粒细胞胞外诱捕网（NET）形成在内的免疫血栓形成机制可能对 VITT 期间的血栓形成至关重要。在这项研究中，我们对一名女性患者的血液和血栓标本进行了研究，该患者在接种 ChAdOx1 后因 VITT 而遭受严重中风，与 13 名具有相似临床特征的对照中风患者进行了比较。我们使用组织学检查、补体因子染色、NET 标志物、DNase 和 LL-37 分析脑血栓。在中风的超急性期和 7 天后的血液样本中，我们测定了无细胞 DNA、髓过氧化物酶-组蛋白复合物、DNase 活性、髓过氧化物酶活性、LL-37 和炎症细胞因子。所有患者的血栓中均发现了 NET 标志物。有趣的是，VITT 患者的血栓仅显示补体因子和大量的 DNase 和 LL-37。血液中也检测到高 DNase 活性，这意味着 NET 调节失调。此外，与对照组相比，VITT 患者的血清对依赖活性氧物质的 NET 释放的抑制作用较弱，这表明在 VITT 患者的血液中，要么 NET 抑制效率较低，要么 NET 诱导增强。此外，VITT 患者的特定细胞因子随时间的变化也很明显。总之，NET 无法充分解决，例如，内源性 DNase 或嵌入因子（如抗微生物肽 LL-37）对 NET 的保护可能是 VITT 病理的一个重要因素，而不是 NET 形成的增加。基于这些发现，我们讨论了 NET 降解机制紊乱对 VITT 相关血栓形成、其他自身免疫性疾病等的诊断和治疗方法的潜在影响。
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