Effect of pulsed corticosteroids and tocilizumab on hyperinflammation in COVID-19 patients with acute respiratory distress syndrome

Objective:To compare the efficacy of pulsed-dose corticosteroids(≥250 mg methylprednisolone,3 days)and tocilizumab in treating COVID-19-related hyperinflammation.Methods:This prospective observational study included RT-PCR positive COVID-19 patients with acute respiratory distress syndrome,who were admitted to the COVID-19 Adult Intensive Care Unit of Prof Dr.Murat Dilmener Emergency Hospital(Istanbul,Turkey)between December 1,2020 and February 28,2021.Clinical,laboratory and radiological examinations were used to diagnose COVID-19 associated hyperinflammation.Three cohort groups were formed:the pulsed-dose corticosteroids group(250 mg methylprednisolone for 3 days),the tocilizumab group(8 mg/day single dose or 400 mg/day for 2 days),and the combined group(pulsed-dose corticosteroid+tocilizumab).The difference in mortality rates among the groups was compared primarily.The most common cause(s)of death was determined.Furthermore,adverse events(secondary infection,acute kidney injury,arrhythmia,gastrointestinal system bleeding)for 28 days were recorded.Results:A total of 60 patients were included in this study,with 20 patients in each group.There was no statistically significant difference between the 3 groups in mortality rates(55%in the pulsed corticosteroid group,60%in the tocilizumab group,50%in the combined group,χ2=0.404,P=0.817).Infectious causes were found to be the most common cause of mortality in all the three groups,and no difference was found between them(χ2=0.404,P=0.817).There was also no difference in the development of adverse events such as secondary infection,acute kidney injury,arrhythmia,and gastrointestinal bleeding among the groups(P>0.05).Conclusions:Corticosteroids can be used instead of tocilizumab to treat hyperinflammation in COVID-19 patients with acute respiratory distress syndrome.

The Cell Biology of Systemic Hyperinflammation Resulting from Failed Cytolytic Target Cell Killing

Mutations in genes encoding a key component of cytotoxic granules, or the machinery for their release, underlie the systemic hyperiflammatory symptoms of familial hemophagocytic lymphohistiocytosis (FHL), a typically pediatric onset autosomal recessive disorder with five known genetic subtypes (FHL1 - 5). FHL1 mutations have been mapped to chromosome 9, while the respective genes mutated in FHL2 (PRF1), FHL3 (UNC13D/Munc13-4), FHL4 (STX11) and FHL5 (STXBP2/ Munc18b/Munc18-2) have been identified. Perforin gene mutation directly affected the cytolytic activity of the cytotoxic granules. All the other FHL mutations appear to affect some aspect of cytotoxic granule exocytosis, resulting in impaired target cell killing by cytolytic T lymphocytes (CTLs) and/or natural killer (NK) cells. Recent findings suggest that failure to kill and detach from target cells, and prolonged synapse connection time, promote cytokine hypersecretion by the defective CTLs and NKs, which in turn result in systemic inflammation. Deciphering the genetics of FHL has contributed towards our understanding of the cell biology of hyperinflammatory responses and hemophagocytic lymphohistiocytosis accompanying pathological conditions such as cancer and viral infections.

Molecular mechanisms implicated in SARS-CoV-2 liver tropism

The coronavirus disease 2019(COVID-19)pandemic is caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2).Hepatic involvement is common in SARS-CoV-2-infected individuals.It is currently accepted that the direct and indirect hepatic effects of SARS-CoV-2 infection play a significant role in COVID-19.In individuals with pre-existing infectious and non-infectious liver disease,who are at a remarkably higher risk of developing severe COVID-19 and death,this pathology is most medically relevant.This review emphasizes the current pathways regarded as contributing to the gastrointestinal and hepatic ailments linked to COVID-19-infected patients due to an imbalanced interaction among the liver,systemic inflammation,disrupted coagulation,and the lung.

Pregnancy・lnduced Hemophagocytic Lymphohistiocytosis: A Case Report and Literature Review

Hemophagocytic lymphohistiocytosis(HLH)is a rare but devastating disease characterized by dysregulated immune response and hyp er inflammation.To our knowledge,pregnancy-induced HLH has been rarely reported in the literature.A 30-year・old pregnant woman presented persistent fever for 21 days since 17 weeks of pregnancy.The possible etiologies such as infection,autoimmune disorder,and malignancy had been ruled out based on a series of exhaustive examinations.The disease progressed despite the use of broadspectrum antibiotics and dexamethasone.The patient was diagnosed as pregnancy-induced HLH,and finally recovered completely after termination of pregnancy by caesarean and the continuous use of glucocorticoid which played a crucial part in controlling hyp er inflammation.Pregnancy-induced HLH could be fatal if effective treatment was not initiated timely.Further studies are needed to improve early diagnosis and etiology identification of HLH.

SARS-CoV-2 spike protein as a bacterial lipopolysaccharide delivery system in an overzealous inflammatory cascade

Accumulating evidence indicates a potential role for bacterial lipopolysaccharide(LPs)in the overactivation of the immune response during SARS-CoV-2 infection.LPS is recognized by Toll-like receptor 4,mediating proinflammatory effects.We previously reported that LPS directly interacts with SARS-CoV-2 spike(S)protein and enhances proinflammatory activities.Using native gel electrophoresis and hydrogen-deuterium exchange mass spectrometry,we showed that LPS binds to multiple hydrophobic pockets spanning both the S1 and S2 subunits of the S protein.Molecular simulations validated by a microscale thermophoresis binding assay revealed that LPS binds to the S2 pocket with a lower affinity compared to S1,suggesting a role as an intermediate in LPS transfer.Congruently,nuclear factor-kappa B(NF-kB)activation in monocytic THP-1 cells is strongly boosted by S2.Using NF-kB reporter mice followed by bioimaging,a boosting effect was observed for both S1 and S2,with the former potentially facilitated by proteolysis.The Omicron S variant binds to LPS,but with reduced affinity and LPS boosting in vitro and in vivo.Taken together,the data provide a molecular mechanism by which S protein augments LPS-mediated hyperinflammation.