Effects of severe acute respiratory syndrome (SARS) coronavirus infection on peripheral blood lymphocytes and their subsets

Verbenalin protects against coronavirus pneumonia by promoting host immune homeostasis: Evidences for its mechanism of action

BACKGROUND

Coronavirus has caused high-mortality viral pneumonia worldwide. The pathogenesis is characterized by hyperinflammatory reactions resulting from immune homeostasis dysregulation. Verbenalin, an iridoid glucoside derived from Verbena officinalis L., is widely used in Traditional Chinese Medicine (TCM) clinical practice for its antioxidant, anti-inflammatory and antiviral properties.

PURPOSE

This study aimed to investigate the pharmacological effects and underlying mechanisms of verbenalin on coronavirus pneumonia both in vivo and in vitro.

METHODS

A coronavirus pneumonia mouse model and macrophage injury models, including mouse alveolar macrophage cell line (MH-S) cells and primary macrophages, were established to initially confirm the antiviral effects of verbenalin. Time-resolved proteomic were then employed to uncover proteomic changes and identify potential therapeutic targets for coronavirus treatment. Subsequently, flow cytometry and Western blot were employed to investigate verbenalin's effects on NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome pathway. Additionally, the targeting regulation of phosphatase and tensin homolog-induced putative kinase 1 (PINK1) / E3 ubiquitin ligase Parkin (Parkin) pathway by verbenalin was validated through molecular docking, surface plasmon resonance (SPR), immunofluorescent staining, RNA interference (RNAi), and mitophagy inhibition both in vivo and in vitro.

RESULTS

Verbenalin reduced cell injury and inflammation in Human coronavirus 229E (HCoV-229E)-infected macrophages and improved lung inflammation in mice. Proteomics analysis highlighted the roles of nucleotide-binding oligomerization domain (NOD)-like receptor signaling and mitophagy pathways in coronavirus pneumonia. Verbenalin bound strongly to PINK1 and Parkin proteins, increased mitochondrial membrane potential (MMP), decreased mitochondrial reactive oxygen species (mtROS) levels, reduced the opening of mitochondrial permeability transition pore (MPTP), maintained mitochondrial mass, promoted mitophagy flux, upregulated the expression of PINK1, Parkin, and microtubule-associated protein 1A/1B-light chain 3BII (LC3BII). Additionally, verbenalin inhibited the activation of the NLRP3 inflammasome and downregulated the expression of Interleukin-1 beta (IL-1β), cysteine aspartate-specific protease 1 (caspase-1), and gasdermin D (GSDMD) both in vivo and in vitro. Furthermore, treatment with a mitophagy inhibitor and RNAi attenuated the inhibitory effects of verbenalin on NLRP3 activation, confirming the involvement of the PINK1/Parkin/NLRP3 pathway in verbenalin's protective effects.

CONCLUSION

Verbenalin enhances PINK1/Parkin-mediated mitophagy to suppress NLRP3 activation, thereby promoting immune homeostasis and mitigating HCoV-229E-induced inflammation.

Correlation between peripheral lymphocyte subsets monitoring and COVID-19 pneumonia in kidney transplant recipients

OBJECTIVES

In kidney transplant recipients (KTRs), immune monitoring of peripheral lymphocyte subsets (PLS) reflects the real immune status and aids in the diagnosis of the occurrence and development of infectious diseases, including COVID-19. Exploring the PLS of COVID-19 pneumonia in KTRs is important.

METHODS

In this study, a total of 103 KTRs were divided into mild pneumonia (MP) and severe pneumonia (SP) groups, as well as a stable group. The clinical information and PLS data were assessed via t or Mann-Whitney test and receiver operating curve analysis. Logistic regression was employed to identify the risk factors, and Spearman's correlation analysis was used to identify correlations.

RESULTS

Lymphopenia is a common manifestation of COVID-19 in KTRs, and it is positively related to the severity of COVID-19 pneumonia. The CD3 + T-cell count had the highest AUC between the MP and the SP. Multiple PLS measures were found to be independent risk factors for COVID-19 pneumonia progression in KTRs.

CONCLUSIONS

This study revealed a robust correlation between PLS and severe COVID-19 pneumonia progression in KTRs. PLS monitoring could facilitate real-time diagnosis and therapy for infection, as well as timely and precisive adjustment of immunosuppression instructions, for KTRs with COVID-19.

Comparison of Platelet Indices, Lymphocyte, and Systemic Inflammation Indices on Days 1 and 8 in Surviving and Non-Surviving COVID-19 Patients at Hasan Sadikin General Hospital, Bandung, Indonesia

Purpose

This study aimed to compare platelet count, platelet indices, lymphocyte, and systemic inflammation indices between surviving and non-surviving COVID-19 patients, measured at admission and on the eighth day of hospitalization.

Patients and Methods

A retrospective cohort study was conducted on COVID-19 patients hospitalized at Hasan Sadikin General Hospital, Bandung, from March to December 2020. Patient characteristics and laboratory data were sourced from medical records and the Clinical Pathology Laboratory. Bivariate analysis was performed to determine the comparison of platelet indexes between Surviving and Non-Surviving COVID-19 patients depending on data distribution. Significantly correlated variables in Bivariate analysis were included in the ROC analysis, with the AUC used to identify optimal threshold values for laboratory parameters.

Results

Data from 132 patients were analyzed, with 106 (80.3%) surviving and 32 (19.7%) not surviving. Non-surviving patients had lower platelet count, PLTCT, and lymphocyte levels but higher MPV and PDW compared to survivors. Receiver operating characteristic (ROC) analysis revealed that on day 1, lymphocytes had a higher area under the curve (AUC) than MPV. On day 8, lymphocytes had the highest AUC, followed by platelet count, MPV, PLTCT, and PDW.

Conclusion

Platelet indices, lymphocyte counts, and systemic inflammation index have the potential to distinguish the severity of COVID-19.

T-cell immunobiology and cytokine storm of COVID-19

The 2019 coronavirus illness (COVID 2019) first manifests as a newly identified pneumonia and may quickly escalate to acute respiratory distress syndrome, which has caused a global pandemic. Except for individualized supportive care, no curative therapy has been steadfastly advised for COVID-19 up until this point. T cells and virus-specific T lymphocytes are required to guard against viral infection, particularly COVID-19. Delayed immunological reconstitution (IR) and cytokine storm (CS) continue to be significant barriers to COVID-19 cure. While severe COVID-19 patients who survived the disease had considerable lymphopenia and increased neutrophils, especially in the elderly, their T cell numbers gradually recovered. Exhausted T lymphocytes and elevated levels of pro-inflammatory cytokines, including IL6, IL10, IL2, and IL17, are observed in peripheral blood and the lungs. It implies that while convalescent plasma, IL-6 blocking, mesenchymal stem cells, and corticosteroids might decrease CS, Thymosin α1 and adaptive COVID-19-specific T cells could enhance IR. There is an urgent need for more clinical research in this area throughout the world to open the door to COVID-19 treatment in the future.

Prospective and Longitudinal Analysis of Lymphocyte Subpopulations in SARS-CoV-2 Positive and Negative Pneumonia: Potential Role of Decreased Naïve CD8+ in COVID-19 Patients

Background: During the acute phase of COVID-19, a number of immunological abnormalities have been reported, but few studies longitudinally analyzed the specific subsets of peripheral blood lymphocytes. Methods: In this observational, prospective, and longitudinal study, adult patients developing acute pneumonia during the COVID-19 pandemic have been followed up for 12 months. Peripheral blood lymphocyte subsets were assessed (with a specific focus on the memory markers) at 6 time points after the disease onset until 12 months. Results: A total of 76 patients with acute pneumonia (characterized by a prevalently interstitial pattern of lung inflammation) at the hospital admission (who completed the 12-month follow-up period) were recruited in this study. They were divided into two groups, namely positive (n = 31) and negative (n = 45) patients for the SARS-CoV-2 PCR test. In the acute phase, the general lymphocyte immunophenotyping profile was comparable for most parameters between these groups, except for B cells. When B and T cells were analyzed according to the expression of memory markers, a significant decrease in naïve CD8+ T cells was observed in the SARS-CoV-2-positive pneumonia group during the acute phase. Notably, this aspect was maintained during the follow-up period for at least 9 months. Conclusions: COVID-19 pneumonia seems to be associated with a lower number of naïve CD8+ T cells compared to pneumonia patients negative for this virus. This alteration can persist in the convalescent phase.

Neutrophil-to-Lymphocyte and Platelet Ratio (N/LP Ratio), a Reliable Criterion for Predicting In-Hospital Mortality in Both Genders Infected With SARS-CoV-2

Background: The neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), derived neutrophil-to-lymphocyte ratio (dNLR), neutrophil-to-lymphocyte and platelet ratio (N/LP ratio), aggregate index of systemic inflammation (AISI), systemic inflammation response index (SIRI), and systemic inflammation index (SII) have emerged as noteworthy determinants in evaluating the severity and mortality prognosis of inflammatory diseases. In order to predict mortality rate, this study aimed to assess the impact of systemic inflammatory markers on both men and women who were admitted to the hospital due to SARS-CoV-2 infection. Methods: The laboratory parameters of the 2007 COVID-19 patients were analyzed in a retrospective study (men = 1145 and women = 862). Receiver operating characteristic (ROC) analysis was used to determine the capability of inflammatory markers to differentiate the severity of COVID-19, while survival probability was determined using Kaplan-Meier curves, with the endpoint being death. To prevent any linear bias, the inflammatory indices were assessed separately using univariate analysis for Charlson comorbidity index (CCI), and adjustments were made for confounding factors if p < 0.2. Results: Adjusted-NLR, adjusted-MLR, N/LP ratio, adjusted-dNLR, adjusted-AISI, adjusted-SII, and adjusted-SIRI exhibited remarkably higher values in patients who did not survive as compared to those who did. The multivariate Cox regression models demonstrated significant association between survival and N/LP ratio (HR = 1.564, 95% CI = 1.161 to 2.107, p < 0.01) in men and N/LP ratio (HR = 1.745, 95% CI = 1.230 to 2.477, p < 0.01) and adjusted-SII (HR = 6.855, 95% CI = 1.454 to 32.321, p < 0.05) in women. Conclusion: A reliable predictor in the current study of men and women with COVID-19 was N/LP ratio.

Inflammation, immunity and biomarkers in procoagulant responses of critically ill patients

Understanding the pathobiology of critical illness is essential for patients' prognosis. Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. As part of the host response, procoagulant responses, one of the most primitive reactions in biology, start at the very beginning of diseases and can be monitored throughout the process. Currently, we can achieve near-complete monitoring of the coagulation process, and procoagulant responses serve as indicators of the severity of host response in critically ill patients. However, the rapid interpretation of the complex results of various biomarkers remains a challenge for many clinicians. The indicators commonly used for coagulation assessment are complex, typically divided into three categories for clarity: process index, functional index, and outcome index. Monitoring and understanding these indicators can help manage procoagulant responses. The intervention of procoagulant response should be part of the bundle therapy, alongside the treatment for primary disease, management for hemodynamics, and controlling for host response. Early intervention for procoagulant response mainly includes anti-inflammation, antiplatelet and anticoagulant therapy, as well as management of primary disease. In this review, we systemically introduce the onset, assessment and intervention of procoagulant response.

Pulmonary microbial spectrum in late-stage SARS-CoV-2 infection: a case series

Coronavirus disease 2019 (COVID-19), a kind of respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), primarily spreads through the respiratory tract from human to human. Its extensive and rapid spread has led to a global pandemic, causing great harm to human health and economic development all over the world. Current known evidence indicates that SARS-CoV-2 has evolved accumulating multiple mutations, with altered infectivity and viral replication capacity. A better understanding of the complications of COVID-19 and its relationship with underlying diseases is crucial for the prevention and treatment of SARS-CoV-2. This case series reviewed case data of our 4 recent patients with severe or critical COVID-19, including treatment plan, status of pulmonary infection and their microbiology workup with metagenomic next-generation sequencing with bronchoalveolar lavage fluid. This report shed light on the significance of rapid and accurate clinical diagnosis and treatment on COVID-19.

Early Fluvoxamine Reduces the Risk for Clinical Deterioration in Symptomatic Outpatients with COVID-19: A Real-World, Retrospective, before-after Analysis

Fluvoxamine, a selective serotonin reuptake inhibitor with anti-inflammatory properties, has gained attention as a repurposed drug to treat COVID-19. We aimed to explore the potential benefit of fluvoxamine on outpatients with early SARS-CoV-2 infection. We performed a retrospective study of fluvoxamine adult outpatients with symptomatic COVID-19 disease of early onset (<5 days), in the context of an infectious diseases private practice, between September-December 2021, in Greece. Patients with disease duration ≥5 days, dyspnea and/or hypoxemia with oxygen saturation <94% in room air and pregnancy were excluded from the analysis. In total, 103 patients, 54 males/49 females with a median age of 47 years (39-56), were included in this study. Patient characteristics were balanced before and after the introduction of fluvoxamine. Two patients in the fluvoxamine arm (3.8%; 95% CI 0.4-13) had clinical deterioration compared to 8 patients in the standard of care group (16%; 95% CI 7.2-29.1, p < 0.04). After controlling for age, sex, body mass index > 30 and vaccination status, fluvoxamine was independently associated with a lower risk of clinical deterioration (adj. OR 0.12; 95% CI 0.02-0.70, p < 0.02). Adding on fluvoxamine to treatment for early symptomatic COVID-19 patients may protect them from clinical deterioration and hospitalization, and it is an appealing low-cost, low-toxicity option in the community setting and warrants further investigation.

Evaluation of Laboratory Findings of Patients with Coronavirus Disease 2019 in Kerman, Iran

Background & Objective

Since December 2019 in Wuhan, China there is a new form of pneumonia and after expansion in other countries, World Health Organization (WHO) called it Coronavirus Disease 2019 (COVID-19). Since the clinical laboratory findings have played an important role in the progression of the disease, this study aimed to evaluate the laboratory findings in COVID-19 patients (before vaccination).

Methods

In this case-control study that was conducted from February to August 2020; the laboratory test status in 101 positive COVID-19 patients was evaluated and compared with 101 healthy individuals.

Results

The results of our study showed that 21% of patients had low WBC, 24.75% low RBC, 37.62%, low Hb, 18.81% with low HCT, 29.7%, low Plt, 41.58% had High PT, 71.29% high CRP, 17.82% high urea, 11.88% high CR, 15.84% high LDH, 10.89% low sodium, 14.75% low potassium (K). The quantitative examination of blood factors showed that lymph%, mixed%, PLT, HCT, Hb, and RBC were higher in the control group than in the case group. While Neu%, WBC, PTT, CRP, UREA, LDH, K in the patient group were higher than in the control group.

Conclusion

According to the results of the study, it can be concluded that in the clinical treatment of COVID-19 patients, much attention should be paid to the laboratory indicators to identify and intervene early in critically ill patients.

Dynamic alterations in white blood cell counts and SARS-CoV-2 shedding in saliva: an infection predictor parameter

Introduction

The recent coronavirus (COVID-19) outbreak posed a global threat and quickly escalated to a pandemic. However, accurate information on potential relationships between SARS-CoV-2 shedding in body fluids, especially saliva, and white blood cell (WBC) count is limited. In the present study we investigated the potential correlation between alterations in blood cell counts and viral shedding in saliva in a cohort of COVID-19 patients.

Method

In this preliminary clinical research, 24 age-matched COVID-19 patients without comorbidities, 12 (50%) men and 12 (50%) women, were followed up for a period of 5 days to investigate whether changes in the level of viral shedding in saliva might parallel with temporal alterations in WBC count. Viral shedding in saliva was qualitatively measured by performing SARS-CoV-2 rapid antigen tests on patient saliva samples, using SARS-CoV-2 Rapid Antigen Test Kit (Roche, Basel, Switzerland). These patients were classified into two groups with sputum and non-sputum cough. WBCs counts including leukocyte (LYM), neutrophil (NEU), and LYM counts were recorded for each patient on days 1, 3, and 5.

Results

The results of the present study showed that the levels of WBC, LYM, and NEU as well as erythrocyte sedimentation rate (ESR) increased significantly on the 5th day compared to the first day in both groups with sputum. However, the levels of C-reactive protein (CRP), Neutrophil-to-Lymphocyte Ratio (NLR) and lactate dehydrogenase (LDH) did not show significant changes.

Conclusion

This study proves that investigating the change in the number of blood LYMs as well as laboratory parameters such as CRP, LDH, and ESR as biomarkers is an accurate indicator to detect the amount of viral shedding in people with sputum and non-sputum. The results of our study denote that the measured parameters exhibit the intensity of viral shedding in people with sputum.

Clinical course and prognostic factors of COVID-19 infection in patients with chronic inflammatory-rheumatic disease: A retrospective, case-control study

OBJECTIVES

This study aims to investigate the prognosis of novel coronavirus disease-2019 (COVID-19) infection in patients with the chronic inflammatory-rheumatic disease and evaluate the effects of immunosuppressive drugs on the prognosis, clinical characteristics, laboratory findings and hospitalization periods of the rheumatic patients with COVID-19 infection.

PATIENTS AND METHODS

Between April 2020 and March 2021, a total of 101 patients (30 males, 71 females; mean age: 48±14.4 years; range, 46 to 48 years) with the rheumatic diseases diagnosed with COVID-19 infection were included. A total of 102 age- and sex-matched patients (35 males, 67 females; mean age: 44±14.4 years; range, 28 to 44 years) who were diagnosed with COVID-19 infection and had no history of rheumatic disease in the same period were included as the control group. Data including demographic characteristics of the patients, presence of any symptoms of COVID-19 disease, laboratory data at the time of diagnosis, and treatments administered were collected.

RESULTS

The rate of hospitalization was higher in 38 (37%) patients without rheumatic diseases than in 31 (31%) patients with rheumatic diseases (p=0.324). The rate of lung infiltration on radiographic examination was higher in patients without rheumatic diseases (40% vs. 49%) (p=0.177). COVID-19 infection symptoms such as anosmia 45 (45%), ageusia 51 (50%), shortness of breath 45(45%), nausea 29 (29%), vomiting 16 (16%), diarrhea 25 (25%) and myalgia-arthralgia 81 (80%) were higher in patients with rheumatic diseases. In terms of laboratory values, lymphocyte count (p=0.031) was statistically higher in patients without rheumatic diseases. Hydroxychloroquine (35%), oseltamivir 10 (10%), antibiotics 27 (26%), acetylsalicylic acid 52 (51%), and supplementary oxygen 25 (25%) treatments which used to cure COVID 19 infection were administered more in patients without rheumatic diseases. The number of treatments administered was higher in patients without rheumatic diseases (p<0.001).

CONCLUSION

Patients with the chronic inflammatory-rheumatic disease have more symptoms due to COVID-19 infection, but the disease course is not poor and hospitalization rates are lower.

T-cell lymphocytopenia: an omnipresent predictor of morbidity and mortality in consequence of SARS-CoV disease and influenza A infections

We proposed T-cell lymphocytopenia as a strategic predictor of serious coronavirus and influenza infections. Our preeminent goal was to determine whether a degree of T-cell lymphopenia would identify a distinct threshold cell count to differentiate between severe and non-severe infections. We codified an Index Severity Score to exploit an association between T-cell cytopenia and the grade of disease activity.

Principal result

A T-cell count of 560 cells/uL or below signified a trend towards advanced disease.

Key findings and conclusions

The T-cell threshold >560 cells/uL discriminated 85.7% specificity of the lesser viral infections and <=560 cells/uL identified 100% sensitivity of severe infections or death. The positive predictive value of this threshold test was 92.9%.•

T-cell apoptosis and sequestration are two of the primary mechanisms of T-cell lymphodepletion.

•

There is potential for the T-cell threshold at <=560 cells/uL to become a standard to differentiate disease severity.

•

Future research should explore correlations between the T-cell threshold, medical outcomes of treatment, Cytokine Release Syndromes, cytokine levels, inflammatory and coagulation markers.

Remdesivir Influence on SARS-CoV-2 RNA Viral Load Kinetics in Nasopharyngeal Swab Specimens of COVID-19 Hospitalized Patients: A Real-Life Experience

There are still conflicting data on the virological effects of the SARS-CoV-2 direct antivirals used in clinical practice, in spite of the documented clinical efficacy. The aim of this monocentric retrospective study was to compare virologic and laboratory data of patients admitted due to SARS-CoV-2 infection from March to December 2020 treated with either remdesivir (R), a protease inhibitor (lopinavir or darunavir/ritonavir (PI)) or no direct antiviral drugs (NT). Viral load variation was indirectly assessed through PCR cycle threshold (Ct) values on the nasopharyngeal swab, analyzing the results from swabs obtained at ward admission and 7 (±2) days later. Overall, 253 patients were included: patients in the R group were significantly older, more frequently males with a significantly higher percentage of severe COVID-19, requiring more often intensive care admission, compared to the other groups. Ct variation over time did not differ amongst the three treatment groups and did not seem to be influenced by corticosteroid use, even after normalization of the treatment groups for disease severity. Non-survivors had lower Ct on admission and showed a significantly slower viral clearance compared to survivors. CD4 T-lymphocytes absolute count assessed at ward admission correlated with a reduced Ct variation over time. In conclusion, viral clearance appears to be slower in COVID-19 non-survivors, while it seems not to be influenced by the antiviral treatment received.

Are bacterial coinfections really rare in COVID-19 intensive care units?

OBJECTIVES

There are limited data about nosocomial coinfections of COVID-19 cases monitored in the intensive care unit. This study aims to investigate coinfections in COVID-19 patients followed in an intensive care unit of a university hospital.

METHODS

This study analyzed retrospectively the data of coinfections of 351 COVID-19 patients in the period 28.02.2020-15.01.2021 in a tertiary care intensive care unit in a university hospital.

RESULTS

Bacterial coinfections were present in 216 of the 351 cases. One hundred and thirty of these cases were evaluated as nosocomial infections. On the third day the Sequential Organ Failure Assessment Score, usage of invasive mechanical ventilation and presence of septic shock were significantly higher in the coinfected group. The neutrophil/lymphocyte ratio, polymorphonuclear leukocyte count, procalcitonin, ferritin, and blood urea nitrogen values were significantly higher in the coinfection group. White blood cells (WBC) (OR: 1.075, 95% CI 1.032-1.121, p = 0.001) and ICU hospitalization day (OR: 1.114, 95% CI 1.063-1.167, p < 0.001) were found to be independent risk factors for coinfection in the multivariate logistic regression analysis. The rates of hospitalization day on the day of arrival, the 21st day, as well as total mortality (p = 0.004), were significantly higher in the coinfected group.

CONCLUSION

Bacterial coinfections of COVID-19 patients in the intensive care unit remain a problem. Identifying the infectious agent, classifying colonizations and infections, and using the proper treatment of antibiotics are of great importance in the case management of COVID-19 patients in the intensive care unit.

Immunophenotyping characteristics of COVID-19 patients: Peripheral blood CD8+ HLA-DR+ T cells as a biomarker for mortality outcome

INTRODUCTION

The goal of this study was to identify biomarker(s) to assign risk of mortality in COVID-19 patients to improve intensive care unit (ICU) and coronary care unit  management. A total of 100 confirmed COVID-19 patients admitted at Imam Khomeini Hospital in Tehran, were compared to 70 control subjects. Peripheral blood leukocyte was studied using staining reagents included CD3, CD4, CD8, HLA-DR, CD19, CD16, and CD56. The immunophenotyping analysis was evaluated using the FACSCalibur instrument. To investigate the cell density of lung infiltrating T cells, postmortem slides of needle necropsies taken from the lung tissue of 3 critical patients were evaluated by immunohistochemistry staining. The number of lymphocyte subpopulations was significantly lower in COVID-19 patients than in the control group. Regarding the disease severity, the absolute count of T, NK, and HLA-DR+ T cells were significantly reduced in severe patients compared to the moderate ones. The critical patients had a significantly lower count of CD8-HLA-DR+ T cells than the moderate cases. Regarding the disease mortality, based on univariate analysis, the count of HLA-DR+ T, CD8- HLA-DR+ T, and CD8+ HLA-DR+ T cells was associated with mortality in COVID-19 patients. Receiver operating characteristic curve analysis showed the count of CD8+ HLA-DR+ T cells is the best candidate as a biomarker for mortality outcome. Furthermore, pulmonary infiltration of T cells in the lung tissue showed only slight infiltrations of CD3+ T cells, with an equal percentage of CD4+ and CD8+ T cell subpopulation in the lung tissue. These findings suggest that close monitoring of the value of CD8+ HLA-DR+ T cells in COVID-19 patients may be helpful to identify high-risk patients. However, further studies with larger sample size are needed.

CD4 and IL-2 mediated NK cell responses after COVID-19 infection and mRNA vaccination in adults

A detailed understanding of protective immunity against SARS-CoV-2 is incredibly important in fighting the pandemic. Central to protective immunity is the ability of the immune system to recall previous exposures. Although antibody and T cell immunity have gained considerable attention, the contribution of the NK cell compartment to immune recall and protection from SARS-CoV-2 has not been explored. In this study, we investigate the NK cell responses to stimulation with SARS-CoV-2 in previously exposed and non-exposed individuals. We show that NK cells demonstrate an enhanced CD4+ T cell dependent response when re-exposed to SARS-CoV-2 antigen. The enhanced response is dependent on T cells and correlates with the number of SARS-CoV-2 specific CD4 T cells. We find that IL-2 is a critical mediator of NK cell function. These findings suggest that NK cells contribute to the protective responses against SARS-CoV-2 through a cooperation with antigen-specific CD4 T cells and have significant implications on our understanding of protective immunity in SARS-CoV-2.

Clinical profile and severity predictors of coronavirus disease 19 infection in a reference center from southern Brazil: a cross-sectional study

OBJECTIVES

The coronavirus disease pandemic has become a major global health crisis since 2019. Recent data show the association of diabetes, hypertension, and obesity with poor related outcomes in coronavirus disease infection. This descriptive study aimed to identify the clinical and laboratory parameters in patients with acute respiratory syndrome and confirmed severe acute respiratory syndrome coronavirus 2 infection.

METHODS

In this cross-sectional study, we analyzed data of 409 patients admitted to a referral hospital in Rio Grande do Sul, Brazil, with coronavirus disease infection confirmed by reverse transcription polymerase chain reaction. Clinical, laboratory, and imaging data were collected retrospectively from electronic medical records using a template with the variables of interest.

RESULTS

The average age was 64 years (52-73), and the body mass index was 27 kg/m² (22.1-31.2). Hypertension, diabetes, and obesity were observed in 58, 33, and 32% of the patients, respectively. Patients admitted to an intensive care unit were older [66 years (53-74) vs. 59 years (42.2-71.7)], with significantly higher impairment on chest computed tomography [75% (50-75) vs. 50% (25-60)] and received higher doses of corticosteroid therapy [39.4 mg (14.3-70.3) vs. 6 mg (6-14.7)]. Hematological parameters were lower in critically ill patients, with greater differences observed on the fifth day of hospitalization [hemoglobin 11.5 g/dL (9.5-13.1) vs. 12.8 g/dL (11.5-14.2), platelets 235,000 μL (143,000-357,000) vs. 270,000 μL (192,000-377,000), and lymphocytes 900 μL (555-1,500) vs. 1,629 μL (1,141-2,329)]. C-reactive protein levels and kidney function were also worse in intensive care unit patients. The mortality rate was significantly higher in the intensive care unit compared to the basic care unit (62.8 vs. 12.2%).

CONCLUSION

Our findings suggest that metabolic and cardiovascular comorbidities, as well as abnormal hematological parameters, are common findings among patients with severe respiratory syndrome related to coronavirus disease.

Exploiting Signal Joint T Cell Receptor Excision Circle to Investigate the Impact of COVID-19 and Autoimmune Diseases on Age Prediction and Immunosenescence

Signal joint T cell receptor excision circles (sjTRECs) are a promising marker for age estimation and immunosenescence in different ethnic groups. Several limitations are expected to overshadow their use as accurate markers for age prediction. The current study was conducted to determine the influence of immunologic disorders, such as autoimmune diseases and COVID-19, on the accuracy of sjTRECs as molecular markers for age estimation and immunosenescence among living Egyptians. Peripheral blood sjTRECs level was measured by qPCR in 90 autoimmune patients, 58 COVID-19 patients, and 85 healthy controls. The mean dCt values were significantly (p = 0.0002) different between the three groups, with the highest values in healthy subjects, followed by autoimmune and COVID-19 patients. A significant negative correlation was identified between the sjTRECs levels and ages in all studied cases. There were significant positive correlations between chronological age and predicted age for healthy individuals, autoimmune, and COVID-19 patients with mean absolute deviations (MAD) of 9.40, 11.04, and 9.71, respectively. The two patients' groups exhibited early immunosenescence, which was more noticeable among the young adults with COVID-19 and autoimmune patients of age range (18-49 years). Autoimmunity may represent a critical factor impacting the accuracy of sjTRECs quantitation for age prediction.

Pandemic influenza A (H1N1) virus causes abortive infection of primary human T cells

Influenza A virus still represents a noticeable epidemic risk to international public health at present, despite the extensive use of vaccines and anti-viral drugs. In the fight against pathogens, the immune defence lines consisting of diverse lymphocytes are indispensable for humans. However, the role of virus infection of lymphocytes and subsequent abnormal immune cell death remains to be explored. Different T cell subpopulations have distinct characterizations and functions, and we reveal the high heterogeneity of susceptibility to viral infection and biological responses such as apoptosis in various CD4+ T and CD8+ T cell subsets through single-cell transcriptome analyses. Effector memory CD8+ T cells (CD8+ TEM) that mediate protective memory are identified as the most susceptible subset to pandemic influenza A virus infection among primary human T cells. Non-productive infection is established in CD8+ TEM and naïve CD8+ T cells, which indicate the mechanism of intracellular antiviral activities for inhibition of virus replication such as abnormal viral splicing efficiency, incomplete life cycles and up-regulation of interferon-stimulated genes in human T cells. These findings provide insights into understanding lymphopenia and the infectious mechanisms of pandemic influenza A virus and broad immune host-pathogen interactional atlas in primary human T cells.

Early Short-Term Use of Different Doses of Corticosteroid in Hospitalized Pediatric Patients with Coronavirus Disease 2019 Pneumonia

Objective Encouraged by reports of favorable outcomes following the use of corticosteroids in patients with moderate-to-severe coronavirus 2019 (COVID-19) pneumonia, we aimed to present our experience with early short-term corticosteroid use at our center in pediatric patients with COVID-19 pneumonia.

Methods One hundred and twenty-nine pediatric patients were included in the study. Patients were divided into four groups according to the type and dose of corticosteroids given: Group 1 (those receiving dexamethasone 0.15 mg/kg/d); Group 2 (those receiving methylprednisolone 1 mg/kg/d); Group 3 (those receiving methylprednisolone 2 mg/kg/d); and Group 4 (those receiving pulse methylprednisolone 10–30 mg/kg/d).

Results Of 129 patients, 19 (14.7%) patients were assigned to Group 1, 30 (23.3%) patients to Group 2, 30 (23.3%) patients to Group 3, and 50 (38.8%) patients to Group 4. Thirty-two (24.8%) patients were followed in the pediatric intensive care unit (PICU), of whom 13 (10%) required mechanical ventilation, and 7 (%5.4) died. In Group 4, the hospitalization length was significantly longer than in other groups (p < 0.001, p < 0.001). No significant difference was found among the groups in terms of mortality (p = 0.15). The most common comorbidity was obesity (33%). A significant association was found between the presence of comorbidity and mortality (p < 0.001). All patients who died had an underlying disease. Cerebral palsy was the most common underlying disease among the patients who died. Worsening of lymphopenia was significant in patients with severe COVID-19 pneumonia at the time of transfer to the PICU (p = 0.011).

Conclusion Although children usually have a milder course of COVID-19 than adults, underlying diseases and obesity increase the severity of disease manifestations also in children. Further studies are needed to define the exact role of corticosteroids in COVID-19 patients.

Evaluation of Hematological Parameters in Predicting Intensive Care Unit Admission in COVID-19 Patients

Hematological parameters like total leukocyte count (TLC), neutrophil, lymphocyte, and absolute eosinophil counts (AEC), and neutrophil-to-lymphocyte ratio (NLR) are known to predict the severity of novel coronavirus disease 2019 (COVID-19) patients. In the present study, we aimed to study the role of complete blood count parameters in triaging these patients requiring intensive care unit (ICU) admission. A retrospective study was done over a period of 2 months. Patients, who were ≥ 18 years of age with COVID-19 confirmed on SARS-CoV-2 reverse transcription-polymerase chain reaction (RT-PCR) and whose routine hematology counts were sent within 24 h of admission, were included in the study. Cut-off values of 47.5 years for age, 11.3 × 10⁹/L for TLC, and 9.1 for NLR were predictive of disease severity among COVID-19 patients. Relative neutrophilia ≥ 70% (p < 0.007), relative lymphopenia ≤ 20% (p < 0.002), AEC ≤ 40/cumm (p < 0.001), and NLR ≥ 9.1 (p < 0.001) were significantly associated with ICU admission. Routine hematological parameters are cost-effective and fast predictive markers for severe COVID-19 patients, especially in resource-constrained health care settings to utilize limited ICU resources more effectively.

D-dimer levels and characteristics of lymphocyte subsets, cytokine profiles in peripheral blood of patients with severe COVID-19: A systematic review and meta-analysis

Purpose

A series of complications caused by severe COVID-19 can significantly affect short-term results. Therefore, early diagnosis is essential for critically COVID-19 patients. we aimed to investigate the correlation among D-dimer levels, lymphocyte subsets, cytokines, and disease severity in COVID-19 patients.

Methods

Systematic review and meta- analysis of PubMed, Scopus, Web of Science, Cochrane Central Register of Controlled Trials, Embase, clinical trials, and China National Knowledge Infrastructure (CNKI) until 1 August 2022. We considered case-control, and cohort studies that compared laboratory parameters between patients with severe or non-serious diseases or between survivors and non-survivors. Pooled data was assessed by use of a random-effects model and used I 2 to test heterogeneity. We assessed the risk of bias using the Newcastle- Ottawa Scale.

Results

Of the 5,561 identified studies, 32 were eligible and included in our analysis (N = 3,337 participants). Random-effect results indicated that patients with COVID-19 in severe group had higher levels for D-dimer (WMD = 1.217 mg/L, 95%CI=[0.788, 1.646], P < 0.001), neutrophil-to-lymphocyte ratio (NLR) (WMD = 6.939, 95%CI = [4.581, 9.297], P < 0.001), IL-2 (WMD = 0.371 pg/ml, 95%CI = [-0.190, 0.932], P = 0.004), IL-4 (WMD = 0.139 pg/ml, 95%CI = [0.060, 0.219], P = 0.717), IL-6 (WMD = 44.251 pg/ml, 95%CI = [27.010, 61.493], P < 0.001), IL-10 (WMD = 3.718 pg/ml, 95%CI = [2.648, 4.788], P < 0.001) as well as lower levels of lymphocytes (WMD = -0.468( × 109/L), 95%CI = [-0.543, -0.394], P < 0.001), T cells (WMD = -446.746(/μL), 95%CI = [-619.607, -273.885], P < 0.001), B cells (WMD = -60.616(/μL), 95%CI = [-96.452, -24.780], P < 0.001), NK cells (WMD = -68.297(/μL), 95%CI = [-90.600, -45.994], P < 0.001), CD3+T cells (WMD = -487.870(/μL), 95%CI = [-627.248, -348.492], P < 0.001), CD4+T cells (WMD = -290.134(/μL), 95%CI = [-370.834, -209.435], P < 0.001), CD8+T cells (WMD = -188.781(/μL), 95%CI = [-227.806, -149.757], P < 0.001).

Conclusions

There is a correlation among higher levels of D-dimer, cytokines, lower levels of lymphocyte subsets, and disease severity in COVID-19 patients. These effective biomarkers may help clinicians to evaluate the severity and prognosis of COVID-19. This study is registered with PROSPERO, number CRD42020196659.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=196659; PROSPERO registration number: CRD42020196659.

Inflammatory and blood gas markers of COVID-19 delirium compared to non-COVID-19 delirium: a cross-sectional study

OBJECTIVES

We aimed to find the association of inflammation and respiratory failure with delirium in COVID-19 patients. We compare the inflammatory and arterial blood gas markers between patients with COVID-19 delirium and delirium in other medical disorders.

METHODS

This cross-sectional study used the CHART-DEL, a validated research tool, to screen patients for delirium retrospectively from clinical notes. Inflammatory markers C-reactive protein (CRP) and white cell count (WBC), and the partial pressures of oxygen (PO₂) and carbon dioxide (PCO₂) were compared between patients with COVID-19 delirium and delirium in other medical disorders.

RESULTS

In bivariate analysis, CRP (mg/L) was significantly higher in the COVID-19 group, (81.7 ± 80.0 vs. 58.8 ± 87.7, p = 0.04), and WBC (10⁹/L) was significantly lower (7.44 ± 3.42 vs. 9.71 ± 5.45, p = 0.04). The geometric mean of CRP in the COVID-19 group was 140% higher in multiple linear regression (95% CI = 7-439%, p = 0.03) with age and sex as covariates. There were no significant differences in pO₂ or pCO₂ across groups.

CONCLUSION

The association between higher CRP and COVID-19 in patients with delirium may suggest an inflammatory basis for delirium in COVID-19. Our findings may assist clinicians in establishing whether delirium is due to COVID-19, which may improve management and outcomes of infected patients.

IL-6 drives T cell death to participate in lymphopenia in COVID-19

Lymphopenia is a common observation in patients with COVID-19. To explore the cause of T cell lymphopenia in the disease, laboratory results of 64 hospitalized COVID-19 patients were retrospectively analyzed and six patients were randomly selected to trace their changes of T lymphocytes and plasma concentration of IL-6 for the course of disease. Results confirmed that the T-cell lymphopenia, especially CD4⁺ T cell reduction in COVID-19 patients, was a reliable indicator of severity and hospitalization in infected patients. And CD4⁺ T cell count below 200 cells/μL predicts critical illness in COVID-19 patients. In vitro assay supported that exposure to key contributors (IL-1β, IL-6, TNF-α and IFN-γ) of COVID-19 cytokine storm caused substantial death of activated T cells. Among these contributors, IL-6 level was found to probably reversely correlate with T cell counts in patients. And IL-6 alone was potent to induce T cell reduction by gasderminE-mediated pyroptosis, inferring IL-6 took a part in affecting the function and status of T cells in COVID-19 patients. Intervention of IL-6 mediated T cell pryprotosis may effectively delay disease progression, maintain normal immune status at an early stage of infection.

SARS-CoV-2 infection: Pathogenesis, Immune Responses, Diagnosis

COVID-19 has emerged as the most alarming infection of the present time instigated by the virus SARS-CoV-2. In spite of advanced research technologies, the exact pathophysiology and treatment of the condition still need to be explored. However, SARS-CoV-2 has several structural and functional similarities that resemble SARS-CoV and MERS-CoV which may be beneficial in exploring the possible treatment and diagnostic strategies for SARS-CoV-2. This review discusses the pathogen phenotype, genotype, replication, pathophysiology, elicited immune response and emerging variants of SARS-CoV-2 and their similarities with other similar viruses. SARS-CoV-2 infection is detected by a number of diagnostics techniques, their advantages and limitations are also discussed in detail. The review also focuses on nanotechnology-based easy and fast detection of SARS-CoV-2 infection. Various pathways which might play a vital role during SARS-CoV-2 infection have been elaborately discussed since immune response plays a major role during viral infections.

Factors that predict severity of infection and seroconversion in immunocompromised children and adolescents with COVID-19 infection

Objectives

We aimed to study the outcomes, severity, and seroconversion post SARS-CoV-2 infection in immunocompromised children and adolescents treated at our center.

Method

For this observational study, all pediatric patients who had COVID-19 infection from Sep-22-2020 to Nov-10-2021were identified by reviewing our laboratory records. Their charts were reviewed to determine clinical severity and outcome. Blood samples were drawn for anti-SARS-CoV-2 antibody assay. Serious COVID-19 infection (SVI) was defined if the patient had moderate, severe, or critical illness. A cutoff of 100 U/mL anti-SARS-CoV-2 antibodies was used to categorize low and high titer seroconversion.

Results

We identified 263 pediatric patients with COVID-19; most (68%) were symptomatic: 5% had severe or critical infection, 25% were hospitalized, 12 required respiratory support, 12 were admitted to the ICU, and five patients (2%) died. Multivariable analysis revealed several factors that predict SVI: Age above 12 years (p=0.035), body mass index above 95th percentile (p=0.034), comorbid conditions (p=0.025), absolute neutrophil count ≤500(p=0.014) and absolute lymphocyte count ≤300 (p=0.022). Levels of anti-SARS-CoV-2 spike antibodies were obtained for 173 patients at a median of 94 days (range, 14–300) after PCR diagnosis; of them 142 (82%) patients seroconverted; the lowest seroconversion rate was observed in patients with hematological malignancies (79%). Our univariable model showed that the following factors were predictive of low titer: lower ANC, p=0.01; hematologic malignancy, p=0.023; receiving steroids in the last 14 days, p=0.032; time since last chemotherapy or immunosuppressive therapy less than 30 days, p=0.002; and being on active chemotherapy in the last 3 months prior to infection, p&lt;0.001.

Conclusions

SARS-CoV-2 antibodies developed in most immunocompromised patients with COVID-19 infection in our study. Mortality was relatively low in our patients. Our univariable and multivariable models showed multiple variables that predict severity of infections and antibody response post COVID-19 infection. These observations may guide choice of active therapy during infection and the best timing of vaccination in this high-risk population.

Clinical characteristics of 310 SARS-CoV-2 Omicron variant patients and comparison with Delta and Beta variant patients in China

Although the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has spread, data on the clinical characteristics of infected patients are limited. In this study, the demographic, clinical characteristics, and laboratory data of 310 SARS-CoV-2 Omicron variant patients treated at Haihe Hospital of Tianjin were collected and analyzed. Information on these patients was compared to 96 patients with the Delta variant of concern (VOC) and 326 patients with the Beta VOC during the previous coronavirus disease 2019 (COVID-19) outbreak in Harbin. Of the 310 patients infected with the Omicron variant, the median age was 35 years. Most patients were clinically classified as mild (57.74%), and the most common symptoms were cough (48.71%), fever (39.35%), and sore throat (38.26%). The results for different vaccination groups in the Omicron group showed that the median of “SARS-CoV-2 specific IgG” after 2 or 3 doses of vaccination was higher than the unvaccinated group (all Ps ​< ​0.05). Older age was associated with a higher proportion of moderate cases and lower asymptomatic and mild cases based on clinical classifications. Compared to the Delta and Beta groups, the median age of the Omicron group was younger. The total number of asymptomatic patients and mild patients in the Omicron virus group was higher than the Delta and Beta groups (60.97% vs. 54.17% vs. 47.55%). This study presented the clinical characteristics of the first group of patients infected with the Omicron variant in Tianjin, China, and compared their clinical features with patients infected by the Delta and Beta variants, which would increase our understanding of the characteristics of SARS-CoV-2 Omicron variant.

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Clinical features of the Chinese first group of patients infected Omicron variants were studied.

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The effects of vaccine and age on Omicron group were analyzed.

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Compared with the Delta and Beta groups, the symptoms in Omicron group were less severe.

NK cell dysfunction is linked with disease severity in SARS-CoV-2 patients

SARS-CoV-2 first raised from Wuhan City, Hubei Province in November 2019. The respiratory disorder, cough, weakness, fever are the main clinical symptoms of coronavirus disease 2019 (COVID-19) patients. Natural Killer (NK) cells as a first defense barrier of innate immune system have an essential role in early defense against pulmonary virus. They kill the infected cells by inducing apoptosis or the degranulation of perforin and granzymes. Collectively, NK cells function are coordinated by the transmitted signals from activating and inhibitory receptors. It is clear that the cytotoxic function of NK cells is disrupted in COVID-19 patients due to the dysregulation of activating and inhibitory receptors. Therefore, better understanding of the activating and inhibitory receptors mechanism could facilitate the treatment strategy in clinic. To improve the efficacy of immunotherapy in COVID-19 patients, the functional detail of NK cell and manipulation of their key checkpoints are gathered in current review.

Exploring the Immunomodulatory Aspect of Mesenchymal Stem Cells for Treatment of Severe Coronavirus Disease 19

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is an enveloped, positive sense, single stranded RNA (+ssRNA) virus, belonging to the genus Betacoronavirus and family Coronaviridae. It is primarily transmitted from infected persons to healthy ones through inhalation of virus-laden respiratory droplets. After an average incubation period of 2–14 days, the majority of infected individuals remain asymptomatic and/or mildly symptomatic, whereas the remaining individuals manifest a myriad of clinical symptoms, including fever, sore throat, dry cough, fatigue, chest pain, and breathlessness. SARS-CoV-2 exploits the angiotensin converting enzyme 2 (ACE-2) receptor for cellular invasion, and lungs are amongst the most adversely affected organs in the body. Thereupon, immune responses are elicited, which may devolve into a cytokine storm characterized by enhanced secretion of multitude of inflammatory cytokines/chemokines and growth factors, such as interleukin (IL)-2, IL-6, IL-7, IL-8, IL-9, tumor necrosis factor alpha (TNF-α), granulocyte colony-stimulating factor (GCSF), basic fibroblast growth factor 2 (bFGF2), monocyte chemotactic protein-1 (MCP1), interferon-inducible protein 10 (IP10), macrophage inflammatory protein 1A (MIP1A), platelet-derived growth factor subunit B (PDGFB), and vascular endothelial factor (VEGF)-A. The systemic persistence of inflammatory molecules causes widespread histological injury, leading to functional deterioration of the infected organ(s). Although multiple treatment modalities with varying effectiveness are being employed, nevertheless, there is no curative COVID-19 therapy available to date. In this regard, one plausible supportive therapeutic modality may involve administration of mesenchymal stem cells (MSCs) and/or MSC-derived bioactive factors-based secretome to critically ill COVID-19 patients with the intention of accomplishing better clinical outcome owing to their empirically established beneficial effects. MSCs are well established adult stem cells (ASCs) with respect to their immunomodulatory, anti-inflammatory, anti-oxidative, anti-apoptotic, pro-angiogenic, and pro-regenerative properties. The immunomodulatory capabilities of MSCs are not constitutive but rather are highly dependent on a holistic niche. Following intravenous infusion, MSCs are known to undergo considerable histological trapping in the lungs and, therefore, become well positioned to directly engage with lung infiltrating immune cells, and thereby mitigate excessive inflammation and reverse/regenerate damaged alveolar epithelial cells and associated tissue post SARS-CoV-2 infection. Considering the myriad of abovementioned biologically beneficial properties and emerging translational insights, MSCs may be used as potential supportive therapy to counteract cytokine storms and reduce disease severity, thereby facilitating speedy recovery and health restoration.

Major bat-borne zoonotic viral epidemics in Asia and Africa: A systematic review and meta-analysis

Bats are the natural reservoir host for many pathogenic and non-pathogenic viruses, potentially spilling over to humans and domestic animals directly or via an intermediate host. The ongoing COVID-19 pandemic is the continuation of virus spillover events that have taken place over the last few decades, particularly in Asia and Africa. Therefore, these bat-associated epidemics provide a significant number of hints, including respiratory cellular tropism, more intense susceptibility to these cell types, and overall likely to become a pandemic for the next spillover. In this systematic review, we analysed data to insight, through bat-originated spillover in Asia and Africa. We used STATA/IC-13 software for descriptive statistics and meta-analysis. The random effect of meta-analysis showed that the pooled estimates of case fatality rates of bat-originated viral zoonotic diseases were higher in Africa (61.06%, 95%CI: 50.26 to 71.85, l2 % = 97.3, p < 0.001). Moreover, estimates of case fatality rates were higher in Ebola (61.06%; 95%CI: 50.26 to 71.85, l2 % = 97.3, p < 0.001) followed by Nipah (55.19%; 95%CI: 39.29 to 71.09, l2 % = 94.2, p < 0.001), MERS (18.49%; 95%CI: 8.19 to 28.76, l2 % = 95.4, p < 0.001) and SARS (10.86%; 95%CI: 6.02 to 15.71, l2 % = 85.7, p < 0.001) with the overall case fatality rates of 29.86 (95%CI: 29.97 to 48.58, l2 % = 99.0, p < 0.001). Bat-originated viruses have caused several outbreaks of deadly diseases, including Nipah, Ebola, SARS and MERS in Asia and Africa in a sequential fashion. Nipah virus emerged first in Malaysia, but later, periodic outbreaks were noticed in Bangladesh and India. Similarly, the Ebola virus was detected in the African continent with neurological disorders in humans, like Nipah, seen in the Asian region. Two important coronaviruses, MERS and SARS, were introduced, both with the potential to infect respiratory passages. This paper explores the dimension of spillover events within and/or between bat-human and the epidemiological risk factors, which may lead to another pandemic occurring. Further, these processes enhance the bat-originated virus, which utilises an intermediate host to jump into human species.

Natural Killer Cells in SARS-CoV-2 Infection: Pathophysiology and Therapeutic Implications

Natural Killer (NK) cells are lymphocytes of the innate immunity that play a crucial role in the control of viral infections in the absence of a prior antigen sensitization. Indeed, they display rapid effector functions against target cells with the capability of direct cell killing and antibody-dependent cell-mediated cytotoxicity. Furthermore, NK cells are endowed with immune-modulatory functions innate and adaptive immune responses via the secretion of chemokines/cytokines and by undertaking synergic crosstalks with other innate immune cells, including monocyte/macrophages, dendritic cells and neutrophils. Recently, the Coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread globally. Although the specific role of NK cells in COVID-19 pathophysiology still need to be explored, mounting evidence indicates that NK cell tissue distribution and effector functions could be affected by SARS-CoV-2 infection and that a prompt NK cell response could determine a good clinical outcome in COVID-19 patients. In this review, we give a comprehensive overview of how SARS-CoV-2 infection interferes with NK cell antiviral effectiveness and their crosstalk with other innate immune cells. We also provide a detailed characterization of the specific NK cell subsets in relation to COVID-19 patient severity generated from publicly available single cell RNA sequencing datasets. Finally, we summarize the possible NK cell-based therapeutic approaches against SARS-CoV-2 infection and the ongoing clinical trials updated at the time of submission of this review. We will also discuss how a deep understanding of NK cell responses could open new possibilities for the treatment and prevention of SARS-CoV-2 infection.

The Robustness of Cellular Immunity Determines the Fate of SARS-CoV-2 Infection

Two years after the appearance of the SARS-CoV-2 virus, the causal agent of the current global pandemic, it is time to analyze the evolution of the immune protection that infection and vaccination provide. Cellular immunity plays an important role in limiting disease severity and the resolution of infection. The early appearance, breadth and magnitude of SARS-CoV-2 specific T cell response has been correlated with disease severity and it has been thought that T cell responses may be sufficient to clear infection with minimal disease in COVID-19 patients with X-linked or autosomal recessive agammaglobulinemia. However, our knowledge of the phenotypic and functional diversity of CD8+ cytotoxic lymphocytes, CD4+ T helper cells, mucosal-associated invariant T (MAIT) cells and CD4+ T follicular helper (Tfh), which play a critical role in infection control as well as long-term protection, is still evolving. It has been described how CD8+ cytotoxic lymphocytes interrupt viral replication by secreting antiviral cytokines (IFN-γ and TNF-α) and directly killing infected cells, negatively correlating with stages of disease progression. In addition, CD4+ T helper cells have been reported to be key pieces, leading, coordinating and ultimately regulating antiviral immunity. For instance, in some more severe COVID-19 cases a dysregulated CD4+ T cell signature may contribute to the greater production of pro-inflammatory cytokines responsible for pathogenic inflammation. Here we discuss how cellular immunity is the axis around which the rest of the immune system components revolve, since it orchestrates and leads antiviral response by regulating the inflammatory cascade and, as a consequence, the innate immune system, as well as promoting a correct humoral response through CD4+ Tfh cells. This review also analyses the critical role of cellular immunity in modulating the development of high-affinity neutralizing antibodies and germinal center B cell differentiation in memory and long-lived antibody secreting cells. Finally, since there is currently a high percentage of vaccinated population and, in some cases, vaccine booster doses are even being administered in certain countries, we have also summarized newer approaches to long-lasting protective immunity and the cross-protection of cellular immune response against SARS-CoV-2.

Mechanisms of SARS-CoV-2 Infection-Induced Kidney Injury: A Literature Review

The severe acute respiratory coronavirus 2 (SARS-CoV-2) has become a life-threatening pandemic. Clinical evidence suggests that kidney involvement is common and might lead to mild proteinuria and even advanced acute kidney injury (AKI). Moreover, AKI caused by coronavirus disease 2019 (COVID-19) has been reported in several countries and regions, resulting in high patient mortality. COVID-19-induced kidney injury is affected by several factors including direct kidney injury mediated by the combination of virus and angiotensin-converting enzyme 2, immune response dysregulation, cytokine storm driven by SARS-CoV-2 infection, organ interactions, hypercoagulable state, and endothelial dysfunction. In this review, we summarized the mechanism of AKI caused by SARS-CoV-2 infection through literature search and analysis.

Thymic Dysfunction and Atrophy in COVID-19 Disease Complicated by Inflammation, Malnutrition and Cachexia

Background: The current COVID-19 pandemic has put millions of people, especially children at risk of protein-energy malnutrition (PEM) by pushing them into poverty and disrupting the global food supply chain. The thymus is severely affected by nutritional deficiencies and is known as a barometer of malnutrition. Aim: The present commentary provides a novel perspective on the role of malnutrition-induced thymic dysfunction, involution and atrophy on the risk and severity of disease in children during the COVID-19 pandemic. Methods: A review of pertinent indexed literature including studies examining the effects of malnutrition on the thymus and immune dysfunction in COVID-19. Results: Protein-energy malnutrition and micronutrient deficiencies of zinc, iron and vitamin A are known to promote thymic dysfunction and thymocyte loss in children. Malnutrition- and infection-induced thymic atrophy and immune dysfunction may increase the risk of first, progression of COVID-19 disease to more severe forms including development of multisystem inflammatory syndrome in children (MIS-C); second, slow the recovery from COVID-19 disease; and third, increase the risk of other infections. Furthermore, malnourished children may be at increased risk of contracting SARS-CoV-2 infection due to socioeconomic conditions that promote viral transmission amongst contacts and create barriers to vaccination. Conclusion: National governments and international organizations including WHO, World Food Program, and UNICEF should institute measures to ensure provision of food and micronutrients for children at risk in order to limit the health impact of the ongoing COVID-19 pandemic.

SARS-CoV-2 Envelope (E) Protein Binds and Activates TLR2 Pathway: A Novel Molecular Target for COVID-19 Interventions

This paper presents a molecular characterization of the interaction between the SARS-CoV-2 envelope (E) protein and TLR2. We demonstrated that the E protein, both as a recombinant soluble protein and as a native membrane protein associated with SARS-CoV-2 viral particles, interacts physically with the TLR2 receptor in a specific and dose-dependent manner. Furthermore, we showed that the specific interaction with the TLR2 pathway activates the NF-κB transcription factor and stimulates the production of the CXCL8 inflammatory chemokine. In agreement with the importance of NF-κB in the TLR signaling pathway, we showed that the chemical inhibition of this transcription factor leads to significant inhibition of CXCL8 production, while the blockade of the P38 and ERK1/2 MAP kinases only results in partial CXCL8 inhibition. Overall, our findings propose the envelope (E) protein as a novel molecular target for COVID-19 interventions: either (i) by exploring the therapeutic effect of anti-E blocking/neutralizing antibodies in symptomatic COVID-19 patients, or (ii) as a promising non-spike SARS-CoV-2 antigen candidate for inclusion in the development of next-generation prophylactic vaccines against COVID-19 infection and disease.

The role of unconventional T cells in COVID-19

COVID-19 is a respiratory disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It was first documented in late 2019, but within months, a worldwide pandemic was declared due to the easily transmissible nature of the virus. Research to date on the immune response to SARS-CoV-2 has focused largely on conventional B and T lymphocytes. This review examines the emerging role of unconventional T cell subsets, including γδ T cells, invariant natural killer T (iNKT) cells and mucosal associated invariant T (MAIT) cells in human SARS-CoV-2 infection.Some of these T cell subsets have been shown to play protective roles in anti-viral immunity by suppressing viral replication and opsonising virions of SARS-CoV. Here, we explore whether unconventional T cells play a protective role in SARS-CoV-2 infection as well. Unconventional T cells are already under investigation as cell-based immunotherapies for cancer. We discuss the potential use of these cells as therapeutic agents in the COVID-19 setting. Due to the rapidly evolving situation presented by COVID-19, there is an urgent need to understand the pathogenesis of this disease and the mechanisms underlying its immune response. Through this, we may be able to better help those with severe cases and lower the mortality rate by devising more effective vaccines and novel treatment strategies.

Immune Responses in SARS-CoV-2, SARS-CoV, and MERS-CoV Infections: A Comparative Review

Coronavirus, discovered in the 1960s, is able to infect human hosts and causes mild to serious respiratory problems. In the last two decades, the severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been recognized. It has long been demonstrated that MERS-CoV binds to dipeptidyl peptidase 4 and SARS-CoV binds to angiotensin-converting enzyme 2. A "cytokine storm" is the main pathophysiology of aforementioned viruses. Infiltration of neutrophils at the site of the infection is a risk factor for the development of acute respiratory distress syndrome and death. The new coronavirus, SARS-CoV-2, has infected more people than SARS-Cov and MERS-CoV as it can easily be transmitted from person to person. Epidemiological studies indicate that majority of individuals are asymptomatic; therefore, an effective and an efficient tool is required for rapid testing. Identification of various cytokine and inflammatory factor expression levels can help in outcome prediction. In this study we reviewed immune responses in SARS-CoV, Mers-CoV, and SARS-COV-2 infections and the role of inflammatory cells.

Cardiac surgery outcomes in patients with coronavirus disease 2019 (COVID-19): A case-series report

OBJECTIVE

The impact of coronavirus disease 2019 (COVID-19) on the postoperative course of patients after cardiac surgery is unknown. We experienced a major severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in our cardiac surgery unit, with several patients who tested positive early after surgery. Here we describe the characteristics, postoperative course, and laboratory findings of these patients, along with the fate of the health care workers. We also discuss how we reorganize and reallocate hospital resources to resume the surgical activity without further positive patients.

METHODS

After diagnosis of the first symptomatic patient, surgery was suspended. Nasopharyngeal swabs were performed in all patients and health care workers. Patients who were positive for SARS-CoV-2 were isolated and monitored throughout the in-hospital stay and followed up after discharged until death or clinical recovery.

RESULTS

Twenty patients were found to be positive for SARS-CoV-2 sometime after cardiac surgery (mean age 69 ± 10.4 years; median European System for Cardiac Operative Risk Evaluation II score 3 [interquartile range, 5.1]); the median time from surgery to diagnosis was 15 days (interquartile range, 11). Among the patients, 18 had undergone cardiac surgery and 2 of them transcatheter aortic valve replacement. Overall mortality was 15%. Specific COVID-19-related symptoms were identified in 7 patients (35%). Among the 12 health care workers infected, 1 developed a bilateral mild-grade interstitial pneumonia.

CONCLUSIONS

COVID-19 infection after cardiac surgery, regardless the time of the onset, is a serious condition. The systemic inflammatory state that follows extracorporeal circulation may mask the typical COVID-19 laboratory findings, making the diagnosis more difficult. A strict reorganization of the hospital resources is necessary to safely resume the cardiac surgical activity.

COVID-19-Associated Encephalopathy: Systematic Review of Case Reports

Background and Purpose

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) primarily attacks the respiratory system, but there are also several reports of the involvement of the central nervous system, with one of the manifestations being encephalopathy. The relatively new emergence of COVID-19 means that few studies have investigated the clinical profile of encephalopathy associated with this disease. This study aimed to determine the clinical profile, laboratory, and imaging results of encephalopathy associated with COVID-19.

Methods

Three databases, namely PubMed/MEDLINE, Embase, and Scopus, were systematically searched for case reports and case series related to COVID-19-associated encephalopathy published from January 1, 2019 to July 20, 2020.

Results

This review included 24 studies involving 33 cases. The most-reported neurological symptoms were disorientation/confusion (72.72%), decreased consciousness (54.54%), and seizures (27.27%). Laboratory examinations revealed increases in the C-reactive protein level (48.48%), the lactate dehydrogenase level (30.30%), and lymphopenia (27.27%). Brain imaging did not produce any pathological findings in 51.51% of the cases. Electroencephalography showed generalized slowing in 45.45% of the cases. Elevated protein (42.42%) and lymphocytosis (24.24%) were found in the cerebrospinal fluid. Fifteen patients were reportedly discharged from the hospital in a stable condition, while four cases of mortality were recorded.

Conclusions

The clinical, laboratory, and imaging findings in this review support the hypothesis that cerebral damage in COVID-19-associated encephalopathy is caused by cytokine-immune-mediated inflammation rather than by direct invasion.

T cell counts and IL-6 concentration in blood of North African COVID-19 patients are two independent prognostic factors for severe disease and death

The immune system plays a crucial role in the response against severe acute respiratory syndrome coronavirus 2 with significant differences among patients. The study investigated the relationships between lymphocyte subsets, cytokines, and disease outcomes in patients with coronavirus disease 2019 (COVID-19). The measurements of peripheral blood lymphocytes subsets and cytokine levels were performed by flow cytometry for 57 COVID-19 patients. Patients were categorized into two groups according to the severity of the disease (nonsevere vs. severe). Total lymphocytes, T cells, CD4+ T cells, CD8+ T cells, B cells, and natural killer cells were decreased in COVID-19 patients and statistical differences were found among different severity of illness and survival states (P ˂ 0.01). The levels of IL-6 and IL-10 were significantly higher in severe and death groups and negatively correlated with lymphocyte subsets counts. The percentages of Th17 in the peripheral blood of patients were higher than those of healthy controls whereas the percentages of Th2 were lower. For the severe cases, the area under receiver operating characteristic (ROC) curve of IL-6 was the largest among all the immune parameters (0.964; 95% confidence interval: 0.927-1.000, P < 0.0001). In addition, the preoperative IL-6 concentration of 77.38 pg/ml was the optimal cutoff value (sensitivity: 84.6%, specificity: 100%). Using multivariate logistic regression analysis and ROC curves, IL-6 > 106.44 pg/ml and CD8+ T cell counts <150 cells/μl were found to be associated with mortality. Measuring the immune parameters and defining a risk threshold can segregate patients who develop a severe disease from those with a mild pathology. The identification of these parameters may help clinicians to predict the outcome of the patients with high risk of unfavorable progress of the disease.

Clinical and hematological characteristics of 300 COVID-19 patients in Erbil, Kurdistan Region, Iraq

Background

COVID-19 primarily presents as a respiratory tract infection, but studies indicate that it could be considered a systemic disease that can spread to affect multiple organ systems, including respiratory, cardiovascular, gastrointestinal, hematopoietic, neurological, and immune systems.

Objective

To describe and analyze the clinical and hematological characteristics of 300 hospitalized COVID-19 patients in Erbil, Kurdistan.

Methods

This retrospective study included 300 patients of any age admitted to hospital due to confirmed COVID-19 between September 2020 and February 2021. Cases were diagnosed by reverse transcriptase polymerase chain reaction assays of nasopharyngeal swab specimens.

Results

The highest proportion of patients were aged 21–40 years. The most common symptoms among the patients were myalgia (66.7%), fatigue (62.3%), headache (50.7%), and chest pain (52.7%). Differences in hematological and biochemical parameters were observed between deceased and recovered patients. Only the mid-range absolute count percentage (MID%) was significantly higher in the recovered patients than in the deceased ones (6.41% vs. 4.48, p = 0.019). Death was significantly higher among older patients (>40 years) than younger ones (≤40 years) (6.8% vs. 1.3%, p = 0.015), diabetic than non-diabetic (10.8% vs. 3%, p = 0.047), and those having chronic diseases than those without chronic diseases (10.6% vs. 2.1%, p = 0.006).

Conclusions

Different hematological and biochemical parameter findings were observed among the COVID-19 patients. Low MID%, older age, and presence of diabetes mellitus and chronic disease were significantly associated with death among COVID-19 patients.

COVID-19 immunopathology with emphasis on Th17 response and cell-based immunomodulation therapy: Potential targets and challenges

The role of the immune system against coronavirus disease 2019 (COVID-19) is unknown in many aspects, and the protective or pathologic mechanisms of the immune response are poorly understood. Pro-inflammatory cytokine release and a consequent cytokine storm can lead to acute respiratory distress syndrome (ARDS) and result in multi-organ failure. There are many T cell subsets during anti-viral immunity. The Th17-associated response, as a pro-inflammatory pathway, and its consequent outcomes in many autoimmune disorders play a fundamental role in progression of systemic hyper-inflammation during COVID-19. Therapeutic strategies based on immunomodulation therapy could be helpful for targeting hyper-inflammatory immune responses in COVID-19, especially Th17-related inflammation and hyper-cytokinemia. Cell-based immunotherapeutic approaches including mesenchymal stem cells (MSCs), tolerogenic dendritic cells (tolDCs) and regulatory T cells (Tregs) seem to be promising strategies as orchestrators of the immune response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this review, we highlight Th17-related immunopathology of SARS-CoV-2 infection and discuss cell-based immunomodulatory strategies and their mechanisms for regulation of the hyper-inflammation during COVID-19.

The inflammatory biomarkers profile of hospitalized patients with COVID-19 and its association with patient's outcome: A single centered study

Several reports highlighted the central role of inflammation in the pathogenesis of corona virus disease-19 (COVID-19) disease. Also, the hyper-inflammatory response that is triggered by severe acute respiratory syndrom-Covid-2 (SARS-CoV-2) infection was believed to play an essential role in disease severity and adverse clinical course. For that reason, the classical inflammatory markers were proposed as a possible indicator for COVID-19 severity. However, an extensive analysis of the predictive value of inflammatory biomarkers in large patients' cohorts is still limited and critically needed. In this study we investigated the predictive value of the classical inflammatory biomarkers in a patient cohort consists of 541 COVID-19 patients admitted to Al Kuwait Hospital, Dubai, UAE. A detailed analysis of the association between the essential inflammatory markers and clinical characteristics as well as clinical outcome of the patients were made. In addition, the correlation between those markers and a wide range of laboratory biomarkers and incidence of acute organs injury were investigated. Our results showed a significant elevation of many inflammatory markers including white cell count (WBC) count, neutrophils count, C-reactive protein (CRP), D-Dimer, ferritin, procalcitonin (PCT), and lactate dehydrogenase (LDH) levels in patients with more severe illness. Also, our results highlighted that higher levels of those markers can predict worse patient outcome including the need of ventilation, intensive care unit (ICU) admission, multiple organs dysfunction as well as death. In addition, Our results showed that the presence of lymphopenia and lower absolute lymphocyte count (ALC) at the time of admission were associated with severe to critical COVID-19 illness (P<0.0001), presence of acute respiratory distress syndrome (ARDS) (P<0.0001) and the need for ventilation and ICU admission., Moreover, our results showed a strong association between lower ALC count and multiple organs dysfunction and patient's death (P<0.0001). In conclusion, our results highlighted the possible use of classical inflammatory biomarkers at time of admission as a potential predictive marker for more severe clinical course in COVID-19 patients that might need more aggressive therapeutic approach including the need of ventilators and ICU admission. The presence of such predictive markers might improve patient's stratification and help in the direction of the available resources to patients in need, which in turn help in improving our response to the disease pandemic.

The Immunopathobiology of SARS-CoV-2 Infection

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can lead to coronavirus disease 2019 (COVID-19). Virus-specific immunity controls infection, transmission and disease severity. With respect to disease severity, a spectrum of clinical outcomes occur associated with age, genetics, comorbidities and immune responses in an infected person. Dysfunctions in innate and adaptive immunity commonly follow viral infection. These are heralded by altered innate mononuclear phagocyte differentiation, activation, intracellular killing and adaptive memory, effector, and regulatory T cell responses. All of such affect viral clearance and the progression of end-organ disease. Failures to produce effective controlled antiviral immunity leads to life-threatening end-organ disease that is typified by the acute respiratory distress syndrome. The most effective means to contain SARS-CoV-2 infection is by vaccination. While an arsenal of immunomodulators were developed for control of viral infection and subsequent COVID-19 disease, further research is required to enable therapeutic implementation.

Association of HLA class I and II genes with Middle East respiratory syndrome coronavirus infection in Koreans

Introduction

Middle East Respiratory Syndrome (MERS) caused by MERS‐coronavirus (CoV) is a lower respiratory tract disease characterized by a high mortality rate. MERS‐CoV spread from Saudi Arabia to other countries, including South Korea. Dysfunction of the human leukocyte antigen (HLA) system has many effects due to genetic complexity and its role in the adaptive immune response. We investigated the association of HLA class I and II alleles with MERS‐CoV in 32 patients with MERS.

Methods

HLA‐A, ‐B, ‐C, ‐DRB1, ‐DQB1, and ‐DPB1 were genotyped by polymerase chain reaction sequence‐based typing.

Results

HLA‐DQB1*03:02 are significantly associated with moderate/mild cases of MERS‐CoV. Other alleles are no statistical significance.

Conclusions

Treatment strategies based on current research on the HLA gene and MERS‐CoV will provide potential therapeutic targets.

Thymus Gland: A Double Edge Sword for Coronaviruses

The thymus is the main lymphoid organ that regulates the immune and endocrine systems by controlling thymic cell proliferation and differentiation. The gland is a primary lymphoid organ responsible for generating mature T cells into CD4+ or CD8+ single-positive (SP) T cells, contributing to cellular immunity. Regarding humoral immunity, the thymic plasma cells almost exclusively secrete IgG1 and IgG3, the two main complement-fixing effector IgG subclasses. Deformity in the thymus can lead to inflammatory diseases. Hassall's corpuscles' epithelial lining produces thymic stromal lymphopoietin, which induces differentiation of CDs thymocytes into regulatory T cells within the thymus medulla. Thymic B lymphocytes produce immunoglobulins and immunoregulating hormones, including thymosin. Modulation in T cell and naive T cells decrement due to thymus deformity induce alteration in the secretion of various inflammatory factors, resulting in multiple diseases. Influenza virus activates thymic CD4+ CD8+ thymocytes and a large amount of IFNγ. IFNs limit virus spread, enhance macrophages' phagocytosis, and promote the natural killer cell restriction activity against infected cells. Th2 lymphocytes-produced cytokine IL-4 can bind to antiviral INFγ, decreasing the cell susceptibility and downregulating viral receptors. COVID-19 epitopes (S, M, and N proteins) with ≥90% identity to the SARS-CoV sequence have been predicted. These epitopes trigger immunity for antibodies production. Boosting the immune system by improving thymus function can be a therapeutic strategy for preventing virus-related diseases. This review aims to summarize the endocrine-immunoregulatory functions of the thymus and the underlying mechanisms in the prevention of COVID-19.

Lymphopenia Caused by Virus Infections and the Mechanisms Beyond

Viral infections can give rise to a systemic decrease in the total number of lymphocytes in the blood, referred to as lymphopenia. Lymphopenia may affect the host adaptive immune responses and impact the clinical course of acute viral infections. Detailed knowledge on how viruses induce lymphopenia would provide valuable information into the pathogenesis of viral infections and potential therapeutic targeting. In this review, the current progress of viruses-induced lymphopenia is summarized and the potential mechanisms and factors involved are discussed.

Distinct mitochondria-mediated T cells apoptosis responses in children and adults with COVID-19

BACKGROUND

Lymphopenia is a key feature for adult patients with coronavirus disease 2019 (COVID-19), while it is rarely observed in children. The underlying mechanism remains unclear.

METHODS

Immunohistochemical and flow cytometric analyses were used to compare the apoptotic rate of T cells from COVID-19 adults and children and apoptotic responses of adult and child T cells to COVID-19 pooled plasma. Biological properties of caspases and reactive oxygen species were assessed in T cells treated by COVID-19 pooled plasma.

RESULTS

Mitochondria apoptosis of peripheral T cells were identified in COVID-19 adult patient samples, but not in the children. Furthermore, increased TNF-α and IL-6 in COVID-19 plasma induced mitochondria apoptosis and caused DNA damage by elevating reactive oxygen species levels of the adult T cells. However, the child T cells showed tolerance to mitochondrial apoptosis due to mitochondria autophagy. Activation of autophagy could decrease apoptotic sensitivity of the adult T cells to plasma from COVID-19 patients.

CONCLUSIONS

Our results indicated that the mitochondrial apoptosis pathway was activated in T cells of COVID-19 adult patients specifically, which may shed light on the pathophysiological difference between adults and children infected with SARS-CoV-2.

Xanthine Oxidase-Induced Inflammatory Responses in Respiratory Epithelial Cells: A Review in Immunopathology of COVID-19

Xanthine oxidase (XO) is an enzyme that catalyzes the production of uric acid and superoxide radicals from purine bases: hypoxanthine and xanthine and is also expressed in respiratory epithelial cells. Uric acid, which is also considered a danger associated molecule pattern (DAMP), could trigger a series of inflammatory responses by activating the inflammasome complex path and NF-κB within the endothelial cells and by inducing proinflammatory cytokine release. Concurrently, XO also converts the superoxide radicals into hydroxyl radicals that further induce inflammatory responses. These conditions will ultimately sum up a hyperinflammation condition commonly dubbed as cytokine storm syndrome (CSS). The expression of proinflammatory cytokines and neutrophil chemokines may be reduced by XO inhibitor, as observed in human respiratory syncytial virus (HRSV)-infected A549 cells. Our review emphasizes that XO may have an essential role as an anti-inflammation therapy for respiratory viral infection, including coronavirus disease 2019 (COVID-19).