Department of Physiological Sciences, Faculty of Science, Stellenbosch University, Private Bag X1 Matieland, Stellenbosch, 7602, South Africa.
Central Analytical Facility, Mass Spectrometry Stellenbosch University, Tygerberg Campus, Room 6054, Clinical Building, Francie Van Zijl Drive, Tygerberg, Cape Town, 7505, South Africa.
Cardiovasc Diabetol. 2022 Sep 21;21(1):190. doi: 10.1186/s12933-022-01623-4.
Post-acute sequelae of COVID-19 (PASC), also now known as long COVID, has become a major global health and economic burden. Previously, we provided evidence that there is a significant insoluble fibrin amyloid microclot load in the circulation of individuals with long COVID, and that these microclots entrap a substantial number of inflammatory molecules, including those that might prevent clot breakdown. Scientifically, the most challenging aspect of this debilitating condition is that traditional pathology tests such as a serum CRP (C-reactive protein) may not show any significant abnormal inflammatory markers, albeit these tests measure only the soluble inflammatory molecules. Elevated, or abnormal soluble biomarkers such as IL-6, D-Dimer or fibrinogen indicate an increased risk for thrombosis or a host immune response in COVID-19. The absence of biomarkers in standard pathology tests, result in a significant amount of confusion for patients and clinicians, as patients are extremely sick or even bed-ridden but with no regular identifiable reason for their disease. Biomarkers that are currently available cannot detect the molecules present in the microclots we identified and are therefore unable to confirm their presence or the mechanisms that drive their formation.
Here we analysed the protein content of double-digested microclots of 99 long COVID patients and 29 healthy controls. The patients suffering from long COVID reported their symptoms through a questionnaire completed by themselves or their attending physician.
Our long COVID cohort's symptoms were found to be in line with global findings, where the most prevalent symptoms were constant fatigue (74%,) cognitive impairment (71%) and depression and anxiety (30%). Our most noteworthy findings were a reduced level of plasma Kallikrein compared to our controls, an increased level of platelet factor 4 (PF4) von Willebrand factor (VWF), and a marginally increased level of α-2 antiplasmin (α-2-AP). We also found a significant presence of antibodies entrapped inside these microclots.
Our results confirm the presence of pro-inflammatory molecules that may also contribute to a failed fibrinolysis phenomenon, which could possibly explain why individuals with long COVID suffer from chronic fatigue, dyspnoea, or cognitive impairment. In addition, significant platelet hyperactivation was noted. Hyperactivation will result in the granular content of platelets being shed into the circulation, including PF4. Overall, our results provide further evidence of both a failed fibrinolytic system in long COVID/PASC and the entrapment of many proteins whose presence might otherwise go unrecorded. These findings might have significant implications for individuals with pre-existing comorbidities, including cardiovascular disease and type 2 diabetes.
COVID-19 的急性后期后遗症（也称为长新冠）已成为全球主要的健康和经济负担。此前，我们已经提供了证据表明，长新冠患者的循环中存在大量不可溶性纤维蛋白淀粉样微栓负荷，这些微栓会捕获大量炎症分子，包括可能阻止血栓分解的分子。从科学角度来看，这种使人虚弱的病症最具挑战性的方面是，传统的病理学检测，如血清 CRP（C 反应蛋白）可能不会显示任何显著的异常炎症标志物，尽管这些检测仅测量可溶性炎症分子。升高或异常的可溶性生物标志物，如 IL-6、D-二聚体或纤维蛋白原，表明 COVID-19 患者存在血栓形成或宿主免疫反应的风险增加。标准病理学检测中缺乏生物标志物，导致患者和临床医生感到非常困惑，因为患者病情非常严重，甚至卧床不起，但没有明确的病因。目前可用的生物标志物无法检测到我们所识别的微栓中存在的分子，因此无法确认它们的存在或驱动其形成的机制。
在这里，我们分析了 99 名长新冠患者和 29 名健康对照者的双消化微栓的蛋白质含量。患有长新冠的患者通过自己或主治医生填写的问卷报告了他们的症状。
我们发现，长新冠患者的症状与全球发现的症状一致，最常见的症状是持续疲劳（74%）、认知障碍（71%）和抑郁和焦虑（30%）。我们最值得注意的发现是与对照组相比，血浆激肽释放酶水平降低，血小板因子 4（PF4）、血管性血友病因子（VWF）水平升高，α-2 抗纤溶酶（α-2-AP）水平略有升高。我们还发现这些微栓中存在大量抗体。
我们的结果证实了存在促炎分子，这些分子也可能导致纤溶失败现象，这可能可以解释为什么长新冠患者会患有慢性疲劳、呼吸困难或认知障碍。此外，还观察到血小板显著过度激活。过度激活会导致血小板的颗粒内容物释放到循环中，包括 PF4。总的来说，我们的结果进一步证明了长新冠/急性后期 COVID 中存在纤溶系统失败以及许多蛋白质的捕获，否则这些蛋白质可能不会被记录下来。这些发现可能对患有心血管疾病和 2 型糖尿病等预先存在的合并症的个体具有重要意义。
