Proteomics of serum samples from COVID-19 ARDS and bacterial ARDS patients

SARS-CoV-2 is a novel coronavirus that causes acute respiratory distress syndrome (ARDS), death and long-term sequelae. Innate immune cells are critical for host defense but are also the primary drivers of ARDS. The relationships between innate cellular responses in ARDS resulting from COVID-19 compared to other causes of ARDS, such as bacterial sepsis is unclear. Moreover, the beneficial effects of dexamethasone therapy during severe COVID-19 remain speculative, but understanding the mechanistic effects could improve evidence-based therapeutic interventions. To interrogate these relationships, we developed an scRNAseq atlas that is freely accessible (biernaskielab.ca/COVID_neutrophil). We discovered that compared to bacterial ARDS, COVID-19 was associated with distinct neutrophil polarization characterized by either interferon (IFN) or prostaglandin (PG) active states. Neutrophils from bacterial ARDS had higher expression of antibacterial molecules such as PLAC8 and CD83. Dexamethasone therapy in COVID patients rapidly altered the IFNactive state, downregulated interferon responsive genes, and activated IL1R2+ve neutrophils. Dexamethasone also induced the emergence of immature neutrophils expressing immunosuppressive molecules ARG1 and ANXA1, which were not present in healthy controls. Moreover, dexamethasone remodeled global cellular interactions by changing neutrophils from information receivers into information providers. Importantly, male patients had higher proportions of IFNactive neutrophils and a greater degree of steroid-induced immature neutrophil expansion. Indeed, the highest proportion of IFNactive neutrophils was associated with mortality. These results define neutrophil states unique to COVID-19 when contextualized to other life-threatening infections, thereby enhancing the relevance of our findings at the bedside. Furthermore, the molecular benefits of dexamethasone therapy are also defined. The identified molecular pathways can now be targeted to develop improved therapeutics.

严重急性呼吸综合征冠状病毒2（SARS-CoV-2）是一种新型冠状病毒，可引发急性呼吸窘迫综合征（ARDS）、死亡及长期后遗症。固有免疫细胞在宿主防御中发挥关键作用，同时也是ARDS的主要致病驱动因素。相较于细菌性脓毒症等其他病因引发的ARDS，新冠病毒感染所致ARDS中的固有免疫细胞应答之间的关联尚不明确。此外，地塞米松疗法对重症新冠患者的获益仍有待进一步证实，但阐明其作用机制可助力优化循证治疗干预方案。为探究上述关联，我们构建了一套可公开获取的单细胞RNA测序（scRNAseq）图谱（访问地址：biernaskielab.ca/COVID_neutrophil）。研究发现，与细菌性ARDS相比，新冠病毒感染呈现出独特的中性粒细胞极化特征，具体表现为干扰素（IFN）或前列腺素（PG）活化状态。细菌性ARDS患者的中性粒细胞高表达PLAC8、CD83等抗菌分子。对新冠患者施以地塞米松疗法后，可快速改变干扰素活化状态，下调干扰素应答基因，并激活IL1R2阳性中性粒细胞。地塞米松还可诱导表达免疫抑制分子ARG1与ANXA1的未成熟中性粒细胞出现，这类细胞在健康对照人群中未被检出。此外，地塞米松通过将中性粒细胞从信息接收者重塑为信息提供者，重构了全局细胞互作网络。值得注意的是，男性患者体内干扰素活化中性粒细胞的占比更高，且类固醇诱导的未成熟中性粒细胞扩增程度更为显著。事实上，干扰素活化中性粒细胞的最高占比与患者死亡率密切相关。本研究明确了相较于其他危及生命的感染，新冠病毒感染特有的中性粒细胞状态，从而提升了本研究结果在临床实践中的应用价值。此外，本研究还阐明了地塞米松疗法的分子获益机制。本研究鉴定出的分子通路可作为靶点，用于开发更优化的治疗手段。