COVID-19 and Sepsis

The COVID-19 pandemic has created a major alteration in the medical literature including the sepsis discussion. From the outset of the pandemic, various reports have indicated that although there are some unique features pertinent to COVID-19, many of its acute manifestations are similar to sepsis caused by other pathogens. As a consequence, the old definitions now require consideration of this new etiologic agent, namely SARS-CoV-2. Although the pathogenesis of COVID-19 has not been fully explained, the data obtained so far in hospitalized patients has revealed that serum cytokine and chemokine levels are high in severe COVID-19 patients, similar to those found with sepsis. COVID-19 may involve multiple organ systems. In addition to the lungs, the virus has been isolated from blood, urine, faeces, liver, and gallbladder. Results from autopsy series in COVID-19 patients have demonstrated a wide range of findings, including vascular involvement, congestion, consolidation, and hemorrhage as well as diffuse alveolar damage in lung tissue consistent with acute respiratory distress syndrome (ARDS). The presence of viral cytopathic-like changes, infiltration of inflammatory cells (mononuclear cells and macrophages), and viral particles in histopathological samples are considered a consequence of both direct viral infection and immune hyperactivation. Thromboembolism and hyper-coagulopathy are other components in the pathogenesis of severe COVID-19. Although the pathogenesis of hypercoagulability is not fully understood, it has been pointed out that all three components of Virchow's triad (endothelial injury, stasis, and hypercoagulable state) play a major role in contributing to clot formation in severe COVID-19 infection. In severe COVID-19 cases, laboratory parameters such as hematological findings, coagulation tests, liver function tests, D-dimer, ferritin, and acute phase reactants such as CRP show marked alterations, which are suggestive of a cytokine storm. Another key element of COVID-19 pathogenesis in severe cases is its similarity or association with hemophagocytic lymphohistiocytosis (HLH). SARS-CoV-2 induced cytokine storm has significant clinical and laboratory findings overlapping with HLH. Viral sepsis has some similarities but also some differences when compared to bacterial sepsis. In bacterial sepsis, systemic inflammation affecting multiple organs is more dominant than in COVID-19 sepsis. While bacterial sepsis causes an early and sudden onset clinical deterioration, viral diseases may exhibit a relatively late onset and chronic course. Consideration of severe COVID-19 disease as a sepsis syndrome has relevance and may assist in terms of determining treatments that will modulate the immune response, limit intrinsic damage to tissue and organs, and potentially improve outcome.

Is COVID-19-associated cytokine storm distinct from non-COVID-19 secondary hemophagocytic lymphohistiocytosis?

Cytokine storm is an umbrella term that describes an inflammatory syndrome characterized by elevated levels of circulating cytokines and hyperactivation of innate and/or adaptive immune cells. One type of cytokine storm is hemophagocytic lymphohistiocytosis (HLH), which can be either primary or secondary. Severe COVID-19-associated pneumonia and acute respiratory distress syndrome (ARDS) can also lead to cytokine storm/cytokine release syndrome (CS/CRS) and, more rarely, meet criteria for the diagnosis of secondary HLH. Here, we review the immunobiology of primary and secondary HLH and examine whether COVID-19-associated CS/CRS can be discriminated from non-COVID-19 secondary HLH. Finally, we review differences in immunobiology between these different entities, which may inform both clinical diagnosis and treatment of patients.

Perforin, COVID-19 and a possible pathogenic auto-inflammatory feedback loop.

During COVID-19 infection, reduced function of natural killer (NK) cells can lead to both compromised viral clearance and dysregulation of the immune response. Such dysregulation leads to overproduction of cytokines, a raised neutrophil/lymphocyte ratio and monocytosis. This in turn increases IL-6 expression, which promotes scar and thrombus formation. Excess IL-6 also leads to a further reduction in NK function through downregulation of perforin expression, therefore forming a pathogenic auto-inflammatory feedback loop. The perforin/granzyme system of cytotoxicity is the main mechanism through which NK cells and cytotoxic T lymphocytes eliminate virally infected host cells, as well as being central to their role in regulating immune responses to microbial infection. Here, we present epidemiological evidence suggesting an association between perforin expression and resistance to COVID-19. In addition, we outline the manner in which a pathogenic auto-inflammatory feedback loop could operate and the relationship of this loop to genes associated with severe COVID-19. Such an auto-inflammatory loop may be amenable to synergistic multimodal therapy.

Cytokine Storms in the Course of COVID-19 and Haemophagocytic Lymphohistiocytosis in Pregnant and Postpartum Women.

The term 'cytokine storm' (CS) applies to a pathological autoimmune reaction when the interactions that lead to cytokine production are destabilised and may even lead to death. CS may be induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In this study, we present our analysis of certain pathological processes that induce a CS in pregnant and postpartum women. We draw our attention to the similarities between the severe course of Coronavirus Disease 2019 (COVID-19) and haemophagocytic lymphohistiocytosis (HLH). It is noteworthy that many of the criteria used to diagnose HLH are described as COVID-19 mortality predictors. Cytokine storms are considered to be an important cause of death in patients with the severe course of SARS-CoV-2 infection. Due to the fact that pregnant women are in an immunosuppressive state, viral pulmonary infections are more perilous for them-possible risks include miscarriage, intrauterine growth restriction or birth before the term; sometimes ventilation support is needed. HLH should be considered in pregnant and puerperal women suffering from moderately severe to severe COVID-19 and presenting with: fever unresponsive to antibiotic therapy, cytopenia, hepatitis and hyperferritinaemia. The HLH disorder is rare and difficult to diagnose; however, its early detection could reduce patient mortality.

Humoral immune mechanisms involved in protective and pathological immunity during COVID-19.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing COVID-19 is associated with excessive inflammation, as a main reason for severe condition and death. Increased inflammatory cytokines and humoral response to SARS-CoV-2 correlate with COVID-19 immunity and pathogenesis. Importantly, the levels of pro-inflammatory cytokines that increase profoundly in systemic circulation appear as part of the clinical pictures of two overlapping conditions, sepsis and the hemophagocytic syndromes. Both conditions can develop lethal inflammatory responses that lead to tissue damage, however, in many patients hemophagocytic lymphohistiocytosis (HLH) can be differentiated from sepsis. This is a key issue because the life-saving aggressive immunosuppressive treatment, required in the HLH therapy, is absent in sepsis guidelines. This paper aims to describe the pathophysiology and clinical relevance of these distinct entities in the course of COVID-19 that resemble sepsis and further highlights two effector arms of the humoral immune response (inflammatory cytokine and immunoglobulin production) during COVID-19 infection.

Cytokine storm in severe COVID-19 pneumonia.

In this study, laboratorial parameters of hospitalized novel coronavirus (COVID-19) patients, who were complicated with severe pneumonia, were compared with the findings of cytokine storm developing in macrophage activation syndrome (MAS)/secondary hemophagocytic lymphohistiocytosis (sHLH). Severe pneumonia occurred as a result of cytokine storm in some patients who needed intensive care unit (ICU), and it is aimed to determine the precursive parameters in this situation. Also in this study, the aim is to identify laboratory criteria that predict worsening disease and ICU intensification, as well as the development of cytokine storm. This article comprises a retrospective cohort study of patients admitted to a single institution with COVID-19 pneumonia. This study includes 150 confirmed COVID-19 patients with severe pneumonia. When they were considered as severe pneumonia patients, the clinic and laboratory parameters of this group are compared with H-score criteria. Patients are divided into two subgroups; patients with worsened symptoms who were transferred into tertiary ICU, and patients with stable symptoms followed in the clinic. For the patients with confirmed COVID-19 infection, after they become complicated with severe pneumonia, lymphocytopenia (55.3%), anemia (12.0%), thrombocytopenia (19.3%), hyperferritinemia (72.5%), hyperfibrinogenemia (63.7%) and elevated lactate dehydrogenase (LDH) (90.8%), aspartate aminotransaminase (AST) (31.3%), alanine aminotransaminase (ALT) (20.7%) are detected. There were no significant changes in other parameters. Blood parameters between the pre-ICU period and the ICU period (in which their situation had been worsened and acute respiratory distress syndrome [ARDS] was developed) were also compared. In the latter group lymphocyte levels were found significantly reduced (p = 0.01), and LDH, highly sensitive troponin (hs-troponin), procalcitonin, and triglyceride levels were significantly increased (p < 0.05). In addition, there was no change in hemoglobin, leukocyte, platelet, ferritin, and liver function test levels, including patients who developed ARDS, similar to the cytokine storm developed in MAS/sHLH. COVID-19 pneumonia has similar findings as hyperinflammatory syndromes but does not seem to have typical features as in cytokine storm developed in MAS/sHLH. In the severe patient group who has started to develop ARDS signs, a decrease in lymphocyte level in addition to the elevated LDH, hs-troponin, procalcitonin, and triglyceride levels can be a predictor in progression to ICU admission and could help in the planning of anti-cytokine therapy.

Immunopathogenesis of Coronavirus-Induced Acute Respiratory Distress Syndrome (ARDS): Potential Infection-Associated Hemophagocytic Lymphohistiocytosis.

The outbreak of coronavirus disease 2019 (COVID-19) in December 2019 in Wuhan, China, introduced the third highly pathogenic coronavirus into humans in the 21st century. Scientific advance after the severe acute respiratory syndrome coronavirus (SARS-CoV) epidemic and Middle East respiratory syndrome coronavirus (MERS-CoV) emergence enabled clinicians to understand the epidemiology and pathophysiology of SARS-CoV-2. In this review, we summarize and discuss the epidemiology, clinical features, and virology of and host immune responses to SARS-CoV, MERS-CoV, and SARS-CoV-2 and the pathogenesis of coronavirus-induced acute respiratory distress syndrome (ARDS). We especially highlight that highly pathogenic coronaviruses might cause infection-associated hemophagocytic lymphohistiocytosis, which is involved in the immunopathogenesis of human coronavirus-induced ARDS, and also discuss the potential implication of hemophagocytic lymphohistiocytosis therapeutics for combating severe coronavirus infection.

Case Report: Systemic Inflammatory Response and Fast Recovery in a Pediatric Patient With COVID-19.

We report a case of an 8-year-old girl who underwent a SARS-CoV-2 infection manifesting with atypical symptoms spearheaded by abdominal discomfort and systemic inflammation and partially mimicking hemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (MAS), which however did not fulfill the HLH/MAS diagnostic criteria. In this case of what has since been described as Pediatric Inflammatory Multisystem Syndrome Temporally associated with SARS-COV-2 (PIMS-TS) we documented excellent clinical response to immunosuppression with systemic corticosteroids and intravenous immunoglobulins. We show a detailed longitudinal development of neutrophil immunophenotype which suggests activation and engagement of neutrophils during PIMS-TS with compensatory contraction of the response and contra-regulation of neutrophil phenotype during recovery.

Fatal outcome of anti-MDA5 juvenile dermatomyositis in a paediatric COVID-19 patient: a case report.

Anti-melanoma differentiation-associated gene 5 juvenile dermatomyositis (anti-MDA5 JDM) is associated with high risk of developing rapidly progressive interstitial lung disease (RP-ILD). Here we report an 11-year-old girl with anti-MDA5 JDM and RP-ILD which led to a fatal outcome, further aggravated by SARS-CoV-2 infection. She was referred to our hospital after being diagnosed with anti-MDA5 JDM and respiratory failure due to RP-ILD. On admission, fibrobronchoscopy with bronchoalveolar lavage (BAL) revealed Pneumocystis jirovecii infection so treatment with intravenous trimethoprim-sulfamethoxazole was initiated. Due to RP-ILD worsening, immunosuppressive therapy was intensified using methylprednisolone pulses, cyclophosphamide, tofacitinib and intravenous immunoglobulin without response. She developed severe hypoxemic respiratory failure, pneumomediastinum and pneumothorax, further complicated with severe RP-ILD and cervical subcutaneous emphysema. Three real-time RT-PCR for SARS-CoV-2 were made with a negative result. In addition, she was complicated with a secondary hemophagocytic lymphohistiocytosis and a fourth real-time PCR for SARS-CoV-2 performed in BAS sample was positive. Despite aggressive treatment of RP-ILD due to anti-MDA5 JDM, there was no improvement of respiratory failure in the following days and patient developed refractory septic shock and died. Anti-MDA5 JDM patients with RP-ILD have a poor prognosis with a high mortality rate. For this reason, intensive immunosuppressive therapy is essential including the use of promising drugs such as tofacitinib. COVID-19 in children with underlying health conditions like anti-MDA5 JDM may still be at risk for disease and severe complications.

COVID-19: Infection or Autoimmunity.

The clinical and laboratory features of COVID-19 are reviewed with attention to the immunologic manifestations of the disease. Recent COVID-19 publications describe a variety of clinical presentations including an asymptomatic state, pneumonia, a hemophagocytic lymphohistiocytosis like syndrome, Multisystem Inflammatory Syndrome in Children (MIS-C) but, also called Pediatric Inflammatory Multisystem Syndrome-Toxic Shock (PIMS-TS), Kawasaki Disease, and myocarditis. A common theme amongst multiple reports suggests an overexuberant autoimmune component of the disease but a common pathophysiology to explain the variations in clinical presentation has been elusive. Review of the basic science of other viral induced autoimmune disorders may give clues as to why immunosuppressive and immunomodulating regimens now appear to have some efficacy in COVID-19. Review of the immunopathology also reveals other therapies that have yet to be explored. There is potential use of T cell depleting therapies and possibly anti-CD20 therapy for COVID-19 and clinical research using these medications is warranted.

Epstein-Barr Virus Versus Novel Coronavirus-Induced Hemophagocytic Lymphohistocytosis: The Uncharted Waters.

Hemophagocytic lymphohistocytosis (HLH) is a hyperinflammatory syndrome characterized by fever, hepatosplenomegaly, and pancytopenia. It may be associated with genetic mutations or viral/bacterial infections, most commonly Epstein-Barr virus (EBV) and cytomegalovirus. As for the novel coronavirus, severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), also known as COVID-19 (coronavirus disease-2019), the cytokine storm it triggers can theoretically lead to syndromes similar to HLH. In this article, we report a case of a 28-year-old female who presented with high-grade fevers, found to have both SARS-CoV-2 and EBV infections, and eventually began to show signs of early HLH. To our knowledge, this is the first case reported in literature that raises the possibility of SARS-CoV-2-related HLH development.

A complex COVID-19 case with rheumatoid arthritis treated with tocilizumab.

Recurrences of COVID-19 were observed in a patient with long-term usage of hydroxychloroquine, leflunomide, and glucocorticoids due to her 30-year history of rheumatoid arthritis (RA). Tocilizumab was applied and intended to target both COVID-19 and RA. However, disease of this patient aggravated after usage of tocilizumab. After the discussion of a multiple disciplinary team (MDT) including rheumatologists, antimicrobial treatments were applied to target the potential opportunistic infections (Pneumocystis jirovecii and Aspergillus fumigatus), which were authenticated several days later via high throughput sequencing. As an important cytokine in immune responses, IL-6 can be a double-edged sword: interference in the IL-6-IL-6 receptor signaling may save patients from cytokine release storm (CRS), but can also weaken the anti-infectious immunity, particularly in rheumatic patients, who may have received a long-term treatment with immunosuppressive/modulatory agents. Thus, we suggest careful considerations before and close monitoring in the administration of tocilizumab in rheumatic patients with COVID-19. Besides tocilizumab, several disease-modifying antirheumatic drugs (DMARDs) can also be applied in the treatment of COVID-19. Therefore, we also reviewed and discussed the application of these DMARDs in COVID-19 condition.

Cytokine storm in COVID-19: pathogenesis and overview of anti-inflammatory agents used in treatment.

COVID-19 infection has a heterogenous disease course; it may be asymptomatic or causes only mild symptoms in the majority of the cases, while immunologic complications such as macrophage activation syndrome also known as secondary hemophagocytic lymphohistiocytosis, resulting in cytokine storm syndrome and acute respiratory distress syndrome, may also occur in some patients. According to current literature, impairment of SARS-CoV-2 clearance due to genetic and viral features, lower levels of interferons, increased neutrophil extracellular traps, and increased pyroptosis and probable other unknown mechanisms create a background for severe disease course complicated by macrophage activation syndrome and cytokine storm. Various genetic mutations may also constitute a risk factor for severe disease course and occurrence of cytokine storm in COVID-19. Once, immunologic complications like cytokine storm occur, anti-viral treatment alone is not enough and should be combined with appropriate anti-inflammatory treatment. Anti-rheumatic drugs, which are tried for managing immunologic complications of COVID-19 infection, will also be discussed including chloroquine, hydroxychloroquine, JAK inhibitors, IL-6 inhibitors, IL-1 inhibitors, anti-TNF-α agents, corticosteroids, intravenous immunoglobulin (IVIG), and colchicine. Early recognition and appropriate treatment of immunologic complications will decrease the morbidity and mortality in COVID-19 infection, which requires the collaboration of infectious disease, lung, and intensive care unit specialists with other experts such as immunologists, rheumatologists, and hematologists.