Differentiation and activation of eosinophils in the human bone marrow during experimental human endotoxemia

Myeloid-specific deletion of group VIA calcium-independent phospholipase A2 induces pro-inflammatory LPS response predominantly in male mice via MIP-1α activation

Polymorphisms of group VIA calcium-independent phospholipase A2 (PLA2G6) are associated with blood C-reactive protein suggesting its role in inflammation. We showed that myeloid-specific Pla2g6-deficiency in Pla2g6M-/- mice led to exaggerated inflammation and fibrosis in a lean fatty liver model. We here investigated whether these mutants display alteration in immune response after treatment with E. coli lipopolysaccharides (LPS) under acute (a single dose) and persistent (four doses) conditions. Without LPS treatment, male Pla2g6M-/- (but not Flox) mice at 12 months of age exhibited splenomegaly and hepatic necrosis, and ~ 30 % of them exhibited autoimmune hepatitis showing lymphoplasma cells with CD3(+) and CD45R(+) staining. Under acute LPS, male mutants showed an elevation of plasma MIP-1α and immunoglobulinA as well as upregulation of hepatic apoptosis and fibrosis PARP-1, Bax, MCP-1, α-SMA, and collagen I proteins. Their bone-marrow-derived macrophages also showed an elevation of MIP-1α release upon LPS stimulation in vitro. Female mutants under acute LPS showed a moderate increase in plasma KC/CXCL1, MCP-1, and IL10, and they showed no remarkable increase in hepatic fibrosis under acute or persistent LPS. Male mutants under persistent LPS displayed an elevation of aspartate aminotransferase, blood eosinophils, and hepatic apoptosis. Moreover, ~30 % of these mutants exhibited eosinophilic sclerosing portal hepatitis associated with an upregulated protein expression of hepatic CD8α, CD68, eosinophilic cationic protein, and Ly6G. Thus, myeloid-PLA2G6 deficiency led to an autoimmune and LPS-induced inflammatory liver disease via MIP-1α in a male-predominant manner. Our results may be applicable to patients with PLA2G6 mutations who undergo bacterial infection and sepsis.

Changes in leukocytes and CRP in different stages of major depression

Background

We recently reported increased levels of neutrophils, monocytes and C-reactive protein (CRP) correlated with symptom severity in acute schizophrenia. Here, we investigated if a similar pattern of innate immune system activation occurs in major depression (MD).

Methods

We assessed differential blood counts, CRP, depression symptoms (HAMD-21) and psychosocial functioning (GAF) in controls (n = 129) and patients with first (FEMD: n = 82) or recurrent (RMD: n = 47) disease episodes of MD at baseline (T0; hospital admission) and after 6-weeks treatment (T6).

Results

Considering smoking, BMI and gender as covariates, neutrophils (FEMD: p = 0.034, RMD: p = 0.034) and CRP (FEMD: p < 0.001, RMD: p = 0.021) were higher, and eosinophils (FEMD: p = 0.005, RMD: p = 0.004) lower in patients versus controls at T0. Baseline lymphocyte counts were elevated in RMD (p = 0.003) but not FEMD. Results were confirmed by analyses of nonsmokers. At follow-up, eosinophils rose significantly in FEMD (p = 0.011) but no significant changes were observed in RMD. Improvement in HAMD-21 correlated with T0–T6 changes of neutrophil counts in FEMD (r = 0.364, p = 0.024). Compared with our previous schizophrenia study, raised baseline neutrophil and reduced eosinophil counts in MD had smaller effect sizes and treatment had a weaker association with T0-T6 changes in neutrophils. In addition, lymphocytes were elevated at T0 in recurrent MD but not in schizophrenia patients.

Conclusions

These findings suggest that innate immunity may be involved in early stages of MD, and adaptive immunity may be involved in chronic disease. Thus, further studies may lead to new disease stage-dependent MD treatment strategies targeting different aspects of immune system activation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02429-7.

Identification of inflammatory markers in eosinophilic cells of the immune system: fluorescence, Raman and CARS imaging can recognize markers but differently

Eosinophils (Eos) play an important role in the immune system’s response releasing several inflammatory factors and contributing to allergic rhinitis, asthma, or atopic dermatitis. Since Eos have a relatively short lifetime after isolation from blood, usually eosinophilic cell line (EoL-1) is used to study mechanisms of their activation and to test therapies. In particular, EoL-1 cells are examined in terms of signalling pathways of the inflammatory response manifested by the presence of lipid bodies (LBs). Here we examined the differences in response to inflammation modelled by various factors, between isolated human eosinophils and EoL-1 cells, as manifested in the number and chemical composition of LBs. The analysis was performed using fluorescence, Raman, and coherent anti-Stokes Raman scattering (CARS) microscopy, which recognised the inflammatory process in the cells, but it is manifested slightly differently depending on the method used. We showed that unstimulated EoL-1 cells, compared to isolated eosinophils, contained more LBs, displayed different nucleus morphology and did not have eosinophilic peroxidase (EPO). In EoL-1 cells stimulated with various proinflammatory agents, including butyric acid (BA), liposaccharide (LPS), or cytokines (IL-1β, TNF-α), an increased production of LBs with a various degree of lipid unsaturation was observed in spontaneous Raman spectra. Furthermore, stimulation of EoL-1 cells resulted in alterations of the LBs morphology. In conclusion, a level of lipid unsaturation and eosinophilic peroxidase as well as LBs distribution among cell population mainly accounted for the biochemistry of eosinophils upon inflammation.

Immune dysregulation and system pathology in COVID-19

The coronavirus disease 19 (COVID-19) caused by the novel coronavirus known as SARS-CoV-2 has caused a global public health crisis. As of 7 January 2021, 87,640,402 confirmed cases and 1,891,692 mortalities have been reported worldwide. Studies focusing on the epidemiological and clinical characteristics of COVID-19 patients have suggested a dysregulated immune response characterized by lymphopenia and cytokine storm in these patients. The exaggerated immune response induced by the cytokine storm causes septic shock, acute respiratory distress syndrome (ARDS), and/or multiple organs failure, which increases the fatality rate of patients with SARS-CoV-2 infection. Herein, we review the recent research progress on epidemiology, clinical features, and system pathology in COVID-19. Moreover, we summarized the recent therapeutic strategies, which are either approved, under clinical trial, and/or under investigation by the local or global health authorities. We assume that treatments should focus on the use of antiviral drugs in combination with immunomodulators as well as treatment of the underlying comorbidities.

Differential alterations in peripheral lymphocyte subsets in COVID-19 patients: upregulation of double-positive and double-negative T cells

Background

Viral infections cause alteration in the total number of lymphocytes and their subset distribution. We aimed to study peripheral blood lymphocyte subsets in COVID-19 patients and to correlate these subsets with clinical and laboratory data, which may help in clarifying the pathogenesis to develop novel diagnostic and prognostic biomarkers for COVID-19.

Methods

Twenty-six reverse-transcription polymerase chain reaction (RT-PCR) confirmed COVID-19 patients were subjected to medical history-taking and a thorough clinical examination. Laboratory tests included complete blood count, D dimer, ferritin, and C-reactive protein (CRP). Chest CT was used to diagnose COVID-19 pneumonia. Lymphocyte subsets were compared with those in 20 healthy controls using flow cytometry.

Results

Leucopenia, relative neutrophilia, lymphopenia, eosinopenia together with marked elevation in neutrophil/lymphocyte ratio were observed in our COVID-19 patients. A marked reduction was observed in T cells, including both CD4 and CD8 cells, natural killer (NK), and natural killer T cells (NKT). Double-positive T (DPT) cells, double-negative T (DNT) cells, and B cells were elevated in the patients relative to the other lymphocyte subsets.

Conclusion

Immune-inflammatory parameters are of utmost importance in understanding the pathogenesis and in the provisional diagnosis of COVID-19. Yet, adequate care must be taken during their interpretation because of the vast discrepancies observed between studies even in the same locality. Further studies are needed to clarify the role of B cells, DPT, and DNT cells in the pathogenesis and control of COVID-19.

Eosinophils as Major Player in Type 2 Inflammation: Autoimmunity and Beyond

Eosinophils are a subset of differentiated granulocytes which circulate in peripheral blood and home in several body tissues. Along with their traditional relevance in helminth immunity and allergy, eosinophils have been progressively attributed important roles in a number of homeostatic and pathologic situations. This review aims at summarizing available evidence about eosinophils functions in homeostasis, infections, allergic and autoimmune disorders, and solid and hematological cancers.Their structural and biological features have been described, along with their physiological behavior. This includes their chemokines, cytokines, granular contents, and extracellular traps. Besides, pathogenic- and eosinophilic-mediated disorders have also been addressed, with the aim of highlighting their role in Th2-driven inflammation. In allergy, eosinophils are implicated in the pathogenesis of atopic dermatitis, allergic rhinitis, and asthma. They are also fundamentally involved in autoimmune disorders such as eosinophilic esophagitis, eosinophilic gastroenteritis, acute and chronic eosinophilic pneumonia, and eosinophilic granulomatosis with polyangiitis. In infections, eosinophils are involved in protection not only from parasites but also from fungi, viruses, and bacteria. In solid cancers, local eosinophilic infiltration is variably associated with an improved or worsened prognosis, depending on the histotype. In hematologic neoplasms, eosinophilia can be the consequence of a dysregulated cytokine production or the result of mutations affecting the myeloid lineage.Recent experimental evidence was thoroughly reviewed, with findings which elicit a complex role for eosinophils, in a tight balance between host defense and tissue damage. Eventually, emerging evidence about eosinophils in COVID-19 infection was also discussed.

The Systemic Immune Response in COVID-19 Is Associated with a Shift to Formyl-Peptide Unresponsive Eosinophils

A malfunction of the innate immune response in COVID-19 is associated with eosinopenia, particularly in more severe cases. This study tested the hypothesis that this eosinopenia is COVID-19 specific and is associated with systemic activation of eosinophils. Blood of 15 healthy controls and 75 adult patients with suspected COVID-19 at the ER were included before PCR testing and analyzed by point-of-care automated flow cytometry (CD10, CD11b, CD16, and CD62L) in the absence or presence of a formyl peptide (fNLF). Forty-five SARS-CoV-2 PCR positive patients were grouped based on disease severity. PCR negative patients with proven bacterial (n = 20) or other viral (n = 10) infections were used as disease controls. Eosinophils were identified with the use of the FlowSOM algorithm. Low blood eosinophil numbers (<100 cells/μL; p < 0.005) were found both in patients with COVID-19 and with other infectious diseases, albeit less pronounced. Two discrete eosinophil populations were identified in healthy controls both before and after activation with fNLF based on the expression of CD11b. Before activation, the CD11b^bright population consisted of 5.4% (CI_95% = 3.8, 13.4) of total eosinophils. After activation, this population of CD11b^bright cells comprised nearly half the population (42.21%, CI_95% = 35.9, 54.1). Eosinophils in COVID-19 had a similar percentage of CD11b^bright cells before activation (7.6%, CI_95% = 4.5, 13.6), but were clearly refractory to activation with fNLF as a much lower percentage of cells end up in the CD11b^bright fraction after activation (23.7%, CI_95% = 18.5, 27.6; p < 0.001). Low eosinophil numbers in COVID-19 are associated with refractoriness in responsiveness to fNLF. This might be caused by migration of fully functional cells to the tissue.

Immunological Aspects Related to Viral Infections in Severe Asthma and the Role of Omalizumab

Viral respiratory infections are recognized risk factors for the loss of control of allergic asthma and the induction of exacerbations, both in adults and children. Severe asthma is more susceptible to virus-induced asthma exacerbations, especially in the presence of high IgE levels. In the course of immune responses to viruses, an initial activation of innate immunity typically occurs and the production of type I and III interferons is essential in the control of viral spread. However, the Th2 inflammatory environment still appears to be protective against viral infections in general and in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections as well. As for now, literature data, although extremely limited and preliminary, show that severe asthma patients treated with biologics don't have an increased risk of SARS-CoV-2 infection or progression to severe forms compared to the non-asthmatic population. Omalizumab, an anti-IgE monoclonal antibody, exerts a profound cellular effect, which can stabilize the effector cells, and is becoming much more efficient from the point of view of innate immunity in contrasting respiratory viral infections. In addition to the antiviral effect, clinical efficacy and safety of this biological allow a great improvement in the management of asthma.

The role of peripheral blood eosinophil counts in COVID-19 patients

Background

Coronavirus disease 2019 (COVID‐19) emerged in Wuhan city and rapidly spread globally outside China. We aimed to investigate the role of peripheral blood eosinophil (EOS) as a marker in the course of the virus infection to improve the efficiency of diagnosis and evaluation of COVID‐19 patients.

Methods

227 pneumonia patients who visited the fever clinics in Shanghai General Hospital and 97 hospitalized COVID‐19 patients admitted to Shanghai Public Health Clinical Center were involved in a retrospective research study. Clinical, laboratory, and radiologic data were collected. The trend of EOS level in COVID‐19 patients and comparison among patients with different severity were summarized.

Results

The majority of COVID‐19 patients (71.7%) had a decrease in circulating EOS counts, which was significantly more frequent than other types of pneumonia patients. EOS counts had good value for COVID‐19 prediction, even higher when combined with neutrophil‐to‐lymphocyte ratio. Patients with low EOS counts at admission were more likely to have fever, fatigue, and shortness of breath, with more lesions in chest CT and radiographic aggravation, and longer length of hospital stay and course of disease than those with normal EOS counts. Circulating EOS level gradually increased over the time, and was synchronous with the improvement in chest CT (12 days vs 13 days, P = .07), later than that of body temperature (12 days vs 10 days, P = .014), but earlier than that of the negative conversion of nucleic acid assays (12 days vs 17 days, P = .001).

Conclusion

Peripheral blood EOS counts may be an effective and efficient indicator in diagnosis, Evaluation, and prognosis monitoring of COVID‐19 patients.

Evaluation of eosinopenia as a diagnostic and prognostic indicator in COVID-19 infection

INTRODUCTION

Eosinopenia has been observed during infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19. This study evaluated the role of eosinopenia as a diagnostic and prognostic indicator in COVID-19 infection.

METHODS

Information on 429 patients with confirmed COVID-19, admitted to Apollo Hospitals, Chennai, India between 04 June 2020 to 15 August 2020, was retrospectively collected through electronic records and analysed.

RESULTS

79.25% of the patients included in the study had eosinopenia on admission. The median eosinophil count in COVID-19-positive patients was 0.015 × 10⁹ /L, and in negative patients, it was 0.249 × 10⁹ /L. Eighteen per cent of the positive patients presented with 0 eosinophil count. Eosinopenia for early diagnosis of COVID-19 had a sensitivity of 80.68% and specificity of 100% with an accuracy of 85.24. Role of eosinopenia in prognostication of COVID-19 was found to be insignificant. There was no statistically significant difference between the median eosinophil counts in survivors and nonsurvivors. Eosinophil trends during the course of disease were found to be similar between survivors and nonsurvivors.

CONCLUSIONS

Eosinopenia on admission is a reliable and convenient early diagnostic marker for COVID-19 infection, helping in early identification, triaging and isolation of the patients till nucleic acid test results are available. Role of eosinopenia as a prognostic indicator is insignificant.

Prognostic Assessment of COVID-19 in the Intensive Care Unit by Machine Learning Methods: Model Development and Validation

BACKGROUND

Patients with COVID-19 in the intensive care unit (ICU) have a high mortality rate, and methods to assess patients' prognosis early and administer precise treatment are of great significance.

OBJECTIVE

The aim of this study was to use machine learning to construct a model for the analysis of risk factors and prediction of mortality among ICU patients with COVID-19.

METHODS

In this study, 123 patients with COVID-19 in the ICU of Vulcan Hill Hospital were retrospectively selected from the database, and the data were randomly divided into a training data set (n=98) and test data set (n=25) with a 4:1 ratio. Significance tests, correlation analysis, and factor analysis were used to screen 100 potential risk factors individually. Conventional logistic regression methods and four machine learning algorithms were used to construct the risk prediction model for the prognosis of patients with COVID-19 in the ICU. The performance of these machine learning models was measured by the area under the receiver operating characteristic curve (AUC). Interpretation and evaluation of the risk prediction model were performed using calibration curves, SHapley Additive exPlanations (SHAP), Local Interpretable Model-Agnostic Explanations (LIME), etc, to ensure its stability and reliability. The outcome was based on the ICU deaths recorded from the database.

RESULTS

Layer-by-layer screening of 100 potential risk factors finally revealed 8 important risk factors that were included in the risk prediction model: lymphocyte percentage, prothrombin time, lactate dehydrogenase, total bilirubin, eosinophil percentage, creatinine, neutrophil percentage, and albumin level. Finally, an eXtreme Gradient Boosting (XGBoost) model established with the 8 important risk factors showed the best recognition ability in the training set of 5-fold cross validation (AUC=0.86) and the verification queue (AUC=0.92). The calibration curve showed that the risk predicted by the model was in good agreement with the actual risk. In addition, using the SHAP and LIME algorithms, feature interpretation and sample prediction interpretation algorithms of the XGBoost black box model were implemented. Additionally, the model was translated into a web-based risk calculator that is freely available for public usage.

CONCLUSIONS

The 8-factor XGBoost model predicts risk of death in ICU patients with COVID-19 well; it initially demonstrates stability and can be used effectively to predict COVID-19 prognosis in ICU patients.

Airways exposure of bacterial superantigen SEB enhances bone marrow eosinophil population and facilitates its egress to blood and lung tissue

BACKGROUND

Differentiation of bone marrow eosinophils (BM-EO) and its trafficking to peripheral blood and respiratory mucosa are a hallmark of inflammatory diseases. Staphylococcal enterotoxin B (SEB) has been shown to aggravate airways eosinophilic inflammation. This study aimed to investigate the effects of mouse airways SEB exposure on BM-EO population, as well as its adhesive properties and release of cytokines/chemokines that orchestrate BM-EO trafficking to lungs.

METHODS

Male BALB/c mice were intranasally exposed to SEB (1 μg), and at 4, 16, 24 and 48 h thereafter, bone marrow (BM), circulating blood and bronchoalveolar lavage (BAL) fluid were collected. Levels of cytokines/chemokines and expressions of VLA-4 and CCR3 in BM were evaluated. Adhesion of BM to ICAM-1 and VCAM-1 were also evaluated.

RESULTS

SEB exposure promoted a marked eosinophil influx to BAL at 16 and 24 h after exposure, which was accompanied by significant increases in counts of immature (16 h) and mature (4 to 48 h) forms of eosinophil in BM, along with blood eosinophilia (16 h). In BM, higher levels of eotaxin, IL-5, IL-4, IL-3 and IL-7 were detected at 16 to 48 h. SEB also significantly increased CCR3 expression and calcium levels in BM-EO, and enhanced the cell adhesion to ICAM-1 (24 h) and ICAM-1 (48 h).

CONCLUSION

Airways SEB exposure increases the number of eosinophils in BM by mechanisms involving a network of cytokine and chemokine release, facilitating the BM-EO adhesion to ICAM-1 and VCAM-1 to gain access to the peripheral blood and lung tissues.

A compendium answering 150 questions on COVID-19 and SARS-CoV-2

In December 2019, China reported the first cases of the coronavirus disease 2019 (COVID‐19). This disease, caused by the severe acute respiratory syndrome–related coronavirus 2 (SARS‐CoV‐2), has developed into a pandemic. To date, it has resulted in ~9 million confirmed cases and caused almost 500 000 related deaths worldwide. Unequivocally, the COVID‐19 pandemic is the gravest health and socioeconomic crisis of our time. In this context, numerous questions have emerged in demand of basic scientific information and evidence‐based medical advice on SARS‐CoV‐2 and COVID‐19. Although the majority of the patients show a very mild, self‐limiting viral respiratory disease, many clinical manifestations in severe patients are unique to COVID‐19, such as severe lymphopenia and eosinopenia, extensive pneumonia, a “cytokine storm” leading to acute respiratory distress syndrome, endothelitis, thromboembolic complications, and multiorgan failure. The epidemiologic features of COVID‐19 are distinctive and have changed throughout the pandemic. Vaccine and drug development studies and clinical trials are rapidly growing at an unprecedented speed. However, basic and clinical research on COVID‐19–related topics should be based on more coordinated high‐quality studies. This paper answers pressing questions, formulated by young clinicians and scientists, on SARS‐CoV‐2, COVID‐19, and allergy, focusing on the following topics: virology, immunology, diagnosis, management of patients with allergic disease and asthma, treatment, clinical trials, drug discovery, vaccine development, and epidemiology. A total of 150 questions were answered by experts in the field providing a comprehensive and practical overview of COVID‐19 and allergic disease.

Longitudinal hematologic and immunologic variations associated with the progression of COVID-19 patients in China

BACKGROUND

Crucial roles of hematologic and immunologic responses in progression of coronavirus disease 2019 (COVID-19) remain largely unclear.

OBJECTIVE

We sought to address the dynamic changes in hematologic and immunologic biomarkers and their associations with severity and outcomes of COVID-19.

METHODS

A retrospective study including 548 patients with COVID-19 with clarified outcome (discharged or deceased) from a national cohort in China was performed. Cross-sectional and longitudinal variations were compared and the associations with different severity and outcomes were analyzed.

RESULTS

On admission, the counts of lymphocytes, T-cell subsets, eosinophils, and platelets decreased markedly, especially in severe/critical and fatal patients. Increased neutrophil count and neutrophils-to-lymphocytes ratio were predominant in severe/critical cases or nonsurvivors. During hospitalization, eosinophils, lymphocytes, and platelets showed an increasing trend in survivors, but maintained lower levels or dropped significantly afterwards in nonsurvivors. Nonsurvivors kept a high level or showed an upward trend for neutrophils, IL-6, procalcitonin, D-dimer, amyloid A protein, and C-reactive protein, which were kept stable or showed a downward trend in survivors. Positive correlation between CD8+ T-cell and lymphocytes count was found in survivors but not in nonsurvivors. A multivariate Cox regression model suggested that restored levels of lymphocytes, eosinophils, and platelets could serve as predictors for recovery, whereas progressive increases in neutrophils, basophils, and IL-6 were associated with fatal outcome.

CONCLUSIONS

Hematologic and immunologic impairment showed a significantly different profile between survivors and nonsurvivors in patients with COVID-19 with different severity. The longitudinal variations in these biomarkers could serve to predict recovery or fatal outcome.

Comparison of host immune responses to LPS in human using an immune profiling panel, in vivo endotoxemia versus ex vivo stimulation

Patients that suffer from sepsis exhibit an early hyper-inflammatory immune response which can lead to organ failure and death. In our study, we assessed the immune modulation in the human in vivo endotoxemia model and compared it to ex vivo LPS stimulation using 38 transcriptomic markers. Blood was collected before and after 4 hours of LPS challenge and tested with the Immune Profiling Panel (IPP) using the FilmArray system. The use of IPP showed that markers from the innate immunity dominated the response to LPS in vivo, mainly markers related to monocytes and neutrophils. Comparing the two models, in vivo and ex vivo, revealed that most of the markers were modulated in a similar pattern (68%). Some cytokine markers such as TNF, IFN-γ and IL-1β were under-expressed ex vivo compared to in vivo. T-cell markers were either unchanged or up-modulated ex vivo, compared to a down-modulation in vivo. Interestingly, markers related to neutrophils were expressed in opposite directions, which might be due to the presence of cell recruitment and feedback loops in vivo. The IPP tool was able to capture the early immune response in both the human in vivo endotoxemia model, a translational model mimicking the immune response observed in septic patients.

Eosinophil responses during COVID-19 infections and coronavirus vaccination

Eosinophils are circulating and tissue-resident leukocytes that have potent proinflammatory effects in a number of diseases. Recently, eosinophils have been shown to have various other functions, including immunoregulation and antiviral activity. Eosinophil levels vary dramatically in a number of clinical settings, especially following eosinophil-targeted therapy, which is now available to selectively deplete these cells. There are key coronavirus disease 2019 (COVID-19)-related questions concerning eosinophils whose answers affect recommended prevention and care. First, do patients with eosinophilia-associated diseases have an altered course of COVID-19? Second, do patients with eosinopenia (now intentionally induced by biological drugs) have unique COVID-19 susceptibility and/or disease course? This is a particularly relevant question because eosinopenia is associated with acute respiratory deterioration during infection with the severe acute respiratory syndrome coronavirus 2, the causative agent of COVID-19. Third, do eosinophils contribute to the lung pathology induced during COVID-19 and will they contribute to immunopotentiation potentially associated with emerging COVID-19 vaccines? Herein, we address these timely questions and project considerations during the emerging COVID-19 pandemic.