The Role of the Immune System on the Cardiac Complications Observed in SARS-CoV-2

Abstract An acute respiratory syndrome caused by SARS-CoV2 was declared a pandemic by the World Health Organization. Current data in the world and in Brazil show that approximately 40% of patients who died have some type of cardiac comorbidity. There are also robust reports showing an increase in IL-6 / IL-1B / TNF-alpha and the presence of lymphopenia in patients with COVID-19. Our team and others have shown that increased cytokines are the link between arrhythmias/Left ventricular dysfunction and the immune system in different diseases. In addition, it has been well demonstrated that lymphopenia can not only be a good marker, but also a factor that causes heart failure. Thus, the present review focused on the role of the immune system upon the cardiac alterations observed in the SARS-CoV2 infection. Additionally, it was well described that SARS-CoV-2 is able to infect cardiac cells. Therefore, here it will be reviewed in deep.

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

PURPOSE OF THE RESEARCH: 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.

Lymphopenia in patients affected by SARS-CoV-2 infection is caused by margination of lymphocytes in large bowel: an [18F]FDG PET/CT study.

BACKGROUND: To investigate the cause of lymphopenia in patients with newly diagnosed COVID-19, we measured [18F]FDG uptake in several tissues, including the ileum, right colon, and caecum at diagnosis and after recovery and correlated these measurements with haematological parameters. METHODS: We studied, by [18F]FDG PET/CT, 18 newly diagnosed patients with COVID-19. Regions of interest were drawn over major organs and in the terminal ileum, caecum, and right colon, where the bowel wall was evaluable. Five patients were re-examined after recovery, and three of them also performed a white blood cell scan with 99mTc-HMPAO-WBC on both occasions. Complete blood count was performed on both occasions, and peripheral blood lymphocyte subsets were measured at diagnosis. Data were analysed by a statistician. RESULTS: Patients had moderate severity COVID-19 syndrome. Basal [18F]FDG PET/CT showed focal lung uptake corresponding to hyperdense areas at CT. We also found high spleen, ileal, caecal, and colonic activity as compared to 18 control subjects. At recovery, hypermetabolic tissues tended to normalize, but activity in the caecum remained higher than in controls. Regression analyses showed an inverse correlation between CD4 + lymphocytes and [18F]FDG uptake in the caecum and colon and a direct correlation between CD8 + lymphocytes and [18F]FDG uptake in lungs and bone marrow. WBC scans showed the presence of leukocytes in the caecum and colon that disappeared at recovery. CONCLUSIONS: These findings indicate that lymphopenia in COVID-19 patients is associated with large bowel inflammation supporting the hypothesis that CD4 + lymphocytes migrate to peripheral lymphoid tissues in the bowel.

The mechanism underlying extrapulmonary complications of the coronavirus disease 2019 and its therapeutic implication.

The coronavirus disease 2019 (COVID-19) is a highly transmissible disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that poses a major threat to global public health. Although COVID-19 primarily affects the respiratory system, causing severe pneumonia and acute respiratory distress syndrome in severe cases, it can also result in multiple extrapulmonary complications. The pathogenesis of extrapulmonary damage in patients with COVID-19 is probably multifactorial, involving both the direct effects of SARS-CoV-2 and the indirect mechanisms associated with the host inflammatory response. Recognition of features and pathogenesis of extrapulmonary complications has clinical implications for identifying disease progression and designing therapeutic strategies. This review provides an overview of the extrapulmonary complications of COVID-19 from immunological and pathophysiologic perspectives and focuses on the pathogenesis and potential therapeutic targets for the management of COVID-19.

Mitochondrial Dysfunction Associates With Acute T Lymphocytopenia and Impaired Functionality in COVID-19 Patients.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection results in rapid T lymphocytopenia and functional impairment of T cells. The underlying mechanism, however, remains incompletely understood. In this study, we focused on characterizing the phenotype and kinetics of T-cell subsets with mitochondrial dysfunction (MD) by multicolor flow cytometry and investigating the association between MD and T-cell functionality. While 73.9% of study subjects displayed clinical lymphocytopenia upon hospital admission, a significant reduction of CD4 or CD8 T-cell frequency was found in all asymptomatic, symptomatic, and convalescent cases. CD4 and CD8 T cells with increased MD were found in both asymptomatic and symptomatic patients within the first week of symptom onset. Lower proportion of memory CD8 T cell with MD was found in severe patients than in mild ones at the stage of disease progression. Critically, the frequency of T cells with MD in symptomatic patients was preferentially associated with CD4 T-cell loss and CD8 T-cell hyperactivation, respectively. Patients bearing effector memory CD4 and CD8 T cells with the phenotype of high MD exhibited poorer T-cell responses upon either phorbol 12-myristate-13-acetate (PMA)/ionomycin or SARS-CoV-2 peptide stimulation than those with low MD. Our findings demonstrated an MD-associated mechanism underlying SARS-CoV-2-induced T lymphocytopenia and functional impairment during the acute phase of infection.

Neutrophils and lymphopenia, an unknown axis in severe COVID-19 disease.

The Coronavirus Disease 2019 (COVID-19) is caused by the betacoronavirus Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus that can mediate asymptomatic or fatal infections characterized by pneumonia, acute respiratory distress syndrome (ARDS), and multi-organ failure. Several studies have highlighted the importance of B and T lymphocytes, given that neutralizing antibodies and T cell responses are required for an effective immunity. In addition, other reports have described myeloid cells such as macrophages and monocytes play a major role in the immunity against SARS-CoV-2 as well as dysregulated pro-inflammatory signature that characterizes severe COVID-19. During COVID-19, neutrophils have been defined as a heterogeneous group of cells, functionally linked to severe inflammation and thrombosis triggered by degranulation and NETosis, but also to suppressive phenotypes. The physiological role of suppressive neutrophils during COVID-19 and their implications in severe disease have been poorly studied and is not well understood. Here, we discuss the current evidence regarding the role of neutrophils with suppressive properties such as granulocytic myeloid-derived suppressor cells (G-MDSCs) and their possible role in suppressing CD4+ and CD8+ T lymphocytes expansion and giving rise to lymphopenia in severe COVID-19 infection.

Lymphopenia and lung complications in patients with coronavirus disease-2019 (COVID-19): A retrospective study based on clinical data.

A rapid outbreak of novel coronavirus, coronavirus disease-2019 (COVID-19), has made it a global pandemic. This study focused on the possible association between lymphopenia and computed tomography (CT) scan features and COVID-19 patient mortality. The clinical data of 596 COVID-19 patients were collected from February 2020 to September 2020. The patients' serological survey and CT scan features were retrospectively explored. The median age of the patients was 56.7 ± 16.4 years old. Lung involvement was more than 50% in 214 COVID-19 patients (35.9%). The average blood lymphocyte percentage was 20.35 ± 10.16 (normal range, 20%-50%). Although the levels of C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were high in more than 80% of COVID-19 patients; CRP, ESR, and platelet-to-lymphocyte ratio (PLR) may not indicate the in-hospital mortality of COVID-19. Patients with severe lung involvement and lymphopenia were found to be significantly associated with increased odds of death (odds ratio, 9.24; 95% confidence interval, 4.32-19.78). These results indicated that lymphopenia < 20% along with pulmonary involvement >50% impose a multiplicative effect on the risk of mortality. The in-hospital mortality rate of this group was significantly higher than other COVID-19 hospitalized cases. Furthermore, they meaningfully experienced a prolonged stay in the hospital (p = .00). Lymphocyte count less than 20% and chest CT scan findings with more than 50% involvement might be related to the patient's mortality. These could act as laboratory and clinical indicators of disease severity, mortality, and outcome.

Prolonged SARS-CoV-2 RNA virus shedding and lymphopenia are hallmarks of COVID-19 in cancer patients with poor prognosis.

Patients with cancer are at higher risk of severe coronavirus infectious disease 2019 (COVID-19), but the mechanisms underlying virus-host interactions during cancer therapies remain elusive. When comparing nasopharyngeal swabs from cancer and noncancer patients for RT-qPCR cycle thresholds measuring acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in 1063 patients (58% with cancer), we found that malignant disease favors the magnitude and duration of viral RNA shedding concomitant with prolonged serum elevations of type 1 IFN that anticorrelated with anti-RBD IgG antibodies. Cancer patients with a prolonged SARS-CoV-2 RNA detection exhibited the typical immunopathology of severe COVID-19 at the early phase of infection including circulation of immature neutrophils, depletion of nonconventional monocytes, and a general lymphopenia that, however, was accompanied by a rise in plasmablasts, activated follicular T-helper cells, and non-naive Granzyme B+FasL+, EomeshighTCF-1high, PD-1+CD8+ Tc1 cells. Virus-induced lymphopenia worsened cancer-associated lymphocyte loss, and low lymphocyte counts correlated with chronic SARS-CoV-2 RNA shedding, COVID-19 severity, and a higher risk of cancer-related death in the first and second surge of the pandemic. Lymphocyte loss correlated with significant changes in metabolites from the polyamine and biliary salt pathways as well as increased blood DNA from Enterobacteriaceae and Micrococcaceae gut family members in long-term viral carriers. We surmise that cancer therapies may exacerbate the paradoxical association between lymphopenia and COVID-19-related immunopathology, and that the prevention of COVID-19-induced lymphocyte loss may reduce cancer-associated death.

Immunological Characteristics in Type 2 Diabetes Mellitus Among COVID-19 Patients.

Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT04365634. Context: Diabetes mellitus was associated with increased severity and mortality of disease in COVID-19 pneumonia. So far the effect of type 2 diabetes (T2DM) or hyperglycemia on the immune system among COVID-19 disease has remained unclear. Objective: We aim to explore the clinical and immunological features of type 2 diabetes mellitus (T2DM) among COVID-19 patients. Design and Methods: In this retrospective study, the clinical and immunological characteristics of 306 hospitalized confirmed COVID-19 patients (including 129 diabetic and 177 non-diabetic patients) were analyzed. The serum concentrations of laboratory parameters including cytokines and numbers of immune cells were measured and compared between diabetic and non-diabetic groups. Results: Compared with non-diabetic group, diabetic cases more frequently had lymphopenia and hyperglycemia, with higher levels of urea nitrogen, myoglobin, D-dimer and ferritin. Diabetic cases indicated the obviously elevated mortality and the higher levels of cytokines IL-2R, IL-6, IL-8, IL-10, and TNF-α, as well as the distinctly reduced Th1/Th2 cytokines ratios compared with non-diabetic cases. The longitudinal assays showed that compared to that at week 1, the levels of IL-6 and IL-8 were significantly elevated at week 2 after admission in non-survivors of diabetic cases, whereas there were greatly reductions from week 1 to week 2 in survivors of diabetic cases. Compared with survival diabetic patients, non-survival diabetic cases displayed distinct higher serum concentrations of IL-2R, IL-6, IL-8, IL-10, TNF-α, and lower Th1/Th2 cytokines ratios at week 2. Samples from a subset of participants were evaluated by flow cytometry for the immune cells. The counts of peripheral total T lymphocytes, CD4+ T cells, CD8+ T cells and NK cells were markedly lower in diabetic cases than in non-diabetic cases. The non-survivors showed the markedly declined counts of CD8+ T cells and NK cells than survivors. Conclusion: The elevated cytokines, imbalance of Th1/Th2 cytokines ratios and reduced of peripheral numbers of CD8+ T cells and NK cells might contribute to the pathogenic mechanisms of high mortality of COVID-19 patients with T2DM.

Obesity, glucose intolerance, advanced age, and lymphocytopenia are independent risk factors for oxygen requirement in Japanese patients with Coronavirus disease 2019 (COVID-19).

At the current time of rising demand for hospital beds, it is important to triage COVID-19 patients according to the treatment needed during hospitalization. The need for oxygen therapy is an important factor determining hospital admission of these patients. Our retrospective study was designed to identify risk factors associated with the progression to oxygen requirement in COVID-19 patients. A total of 133 patients with laboratory-confirmed COVID-19 were admitted to our hospital from February 22, 2020, to August 23. After excluding asymptomatic, non-Japanese, pediatric, pregnant patients and also those who needed oxygen immediately at admission, data of the remaining 84 patients were analyzed. The patients were separated into those who required oxygen after admission and those who did not, and their characteristics were compared. Age, body mass index (BMI), lymphocyte count, C-reactive protein (CRP), lactate dehydrogenase, estimated glomerular filtration rate, glucose intolerance, hypertension, and dyslipidemia were significantly different between the two groups. Multivariate analysis identified four significant and independent risk factors of oxygen requirement, including advanced age, obesity, glucose intolerance and lymphocytopenia. Dividing the patients into subgroups according to the number of these risk factors found in each patient indicated that the need for oxygen increased with higher number of these risk factors in the same individual. Our results suggest that the presence of higher number of these risk factors in COVID-19 patients is associated with future oxygen requirement and that this index can be potentially useful in triaging COVID-19 patients staying home in the context of need for hospitalization.

Age cohorts stratified according to age-distributions of COVID-19 morbidity statistics identify uniquely age-dependent CD3+CD8+ T-cell lymphocytopenia in COVID-19 patients without comorbidities on admission.

If age boundaries are arbitrarily or roughly defined, age-related analyses can result in questionable findings. Here, we aimed to delineate the uniquely age-dependent immune features of coronavirus disease 2019 (COVID-19) in a retrospective study of 447 patients, stratified according to age distributions of COVID-19 morbidity statistics into well-defined age-cohorts (2-25y, 26-38y, 39-57y, 58-68y, and 69-79y). Age-dependent susceptibilities and severities of the disease were observed in COVID-19 patients. A comparison of the lymphocyte counts among the five age-groups indicated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection led to age-dependent lymphopenia. Among the lymphocyte subsets, the CD8+ T cell count alone was significantly and age-dependently decreased (520, 385, 320, 172, and 139 n/µl in the five age-groups, respectively). In contrast, the CD4+ T cell, B cell, and natural killer cell counts did not differ among age-cohorts. Age and CD8+ T cell counts (r=‒0.435, p<0.0001) were negatively correlated in COVID-19 patients. Moreover, SARS-CoV-2 infection age-dependently increased the plasma C-reactive protein concentrations (2.0, 5.0, 9.0, 11.6, and 36.1 mg/L in the five age-groups, respectively). These findings can be used to elucidate the role of CD8+ T cells in age-related pathogenesis and to help develop therapeutic strategies for COVID-19.

COVID-19 in children ranging from asymptomatic to a multi-system inflammatory disease: A single-center study.

OBJECTIVES: To identify clinical and laboratory characteristics of the Saudi children with confirmed COVID-19. METHODS: Eighty-eight children (0-14 years) with COVID-19 who were admitted to Prince Sultan Military Medical City (PSMMC), Riyadh, Saudi Arabia from April to June 2020 were recruited. RESULTS: Mean age was 5.74 ± 4.7 years with 41 (49.4%) males and 42 (50.6%) females. The length of hospital stay (LOS) ranged from 1 to 17 days. The main source of infection was infected family members. Mean values of C-reactive protein (CRP), serum ferritin, and lactate dehydrogenase (LDH) were noticeably above normal. Degree of severity and length of stay was significantly correlated with lymphopenia (r= -0.36; p=0.001), whereas it was positively correlated with absolute neutrophil count and with high inflammatory markers, such as CRP, LDH, and others. CONCLUSIONS: Identifying the clinical and laboratory characteristics of the Saudi children with confirmed COVID-19 will improve understanding of this disease's presentation and will help put rapid and proper management strategies into place to face this pandemic. A high index of suspicion is needed for cases presenting with multi-system inflammatory disease, which represented 5.7% of the included study population.

Clinical characteristics and predictors of mortality associated with COVID-19 in elderly patients from a long-term care facility.

Since December 2019, coronavirus disease 2019 (COVID-19) pandemic has spread from China all over the world and many COVID-19 outbreaks have been reported in long-term care facilities (LCTF). However, data on clinical characteristics and prognostic factors in such settings are scarce. We conducted a retrospective, observational cohort study to assess clinical characteristics and baseline predictors of mortality of COVID-19 patients hospitalized after an outbreak of SARS-CoV-2 infection in a LTCF. A total of 50 patients were included. Mean age was 80 years (SD, 12 years), and 24/50 (57.1%) patients were males. The overall in-hospital mortality rate was 32%. At Cox regression analysis, significant predictors of in-hospital mortality were: hypernatremia (HR 9.12), lymphocyte count < 1000 cells/µL (HR 7.45), cardiovascular diseases other than hypertension (HR 6.41), and higher levels of serum interleukin-6 (IL-6, pg/mL) (HR 1.005). Our study shows a high in-hospital mortality rate in a cohort of elderly patients with COVID-19 and hypernatremia, lymphopenia, CVD other than hypertension, and higher IL-6 serum levels were identified as independent predictors of in-hospital mortality. Given the small population size as major limitation of our study, further investigations are necessary to better understand and confirm our findings in elderly patients.

Hematologic disorders associated with COVID-19: a review.

Coronavirus disease 2019 is caused by severe acute respiratory syndrome coronavirus 2. Primarily an infection of the lower respiratory tract, it is now well known to cause multisystem abnormalities. Hematologic manifestations constitute a significant area of concern. Severe acute respiratory syndrome coronavirus 2 infects monocytes and endothelial cells leading to a complex downstream cascade, cytokine storm, and eventual intravascular thrombosis. Coronavirus disease 2019 causes lymphopenia, neutrophilia, and thrombocytopenia. Prophylactic anticoagulation is vital in patients with coronavirus disease 2019, as its effect on the coagulation system is associated with significant morbidity and mortality. The disease can cause both arterial and venous thromboses, especially pulmonary embolism and pulmonary microthrombi. A high index of suspicion is indispensable in recognizing these complications, and timely institution of therapeutic anticoagulation is vital in treating them. Virus-induced disseminated intravascular coagulation is uncommon but shares some similarities to sepsis-induced disseminated intravascular coagulation. Marked elevations in hematologic biomarkers such as lactate dehydrogenase, D-dimer, ferritin, and C-reactive protein are associated with worse outcomes. Understanding the pathophysiology and recognizing factors associated with poor prognosis are crucial in improving patient outcomes with coronavirus disease 2019.

Hyperglycemia associated with lymphopenia and disease severity of COVID-19 in type 2 diabetes mellitus.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has been declared a global pandemic. COVID-19 is more severe in people with diabetes. The identification of risk factors for predicting disease severity in COVID-19 patients with type 2 diabetes mellitus (T2DM) is urgently needed. METHODS: Two hundred and thirty-six patients with COVID-19 were enrolled in our study. The patients were divided into 2 groups: COVID-19 patients with or without T2DM. The patients were further divided into four subgroups according to the severity of COVID-19 as follows: Subgroup A included moderate COVID-19 patients without diabetes, subgroup B included severe COVID-19 patients without diabetes, subgroup C included moderate COVID-19 patients with diabetes, and subgroup D included severe COVID-19 patients with diabetes. The clinical features and radiological assessments were collected and analyzed. We tracked the dynamic changes in laboratory parameters and clinical outcomes during the hospitalization period. Multivariate analysis was performed using logistic regression to analyze the risk factors that predict the severity of COVID-19 with T2DM. RESULTS: Firstly, compared with the nondiabetic group, the COVID-19 with T2DM group had a higher erythrocyte sedimentation rate (ESR) and levels of C-reactive protein (CRP), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and procalcitonin (PCT) but lower lymphocyte counts and T lymphocyte subsets, including CD3+ T cells, CD8+ T cells, CD4+ T cells, CD16 + CD56 cells, and CD19+ cells. Secondly, compared with group A, group C had higher levels of Fasting blood glucose (FBG), IL-6, TNF-α, and neutrophils but lower lymphocyte, CD3+ T cell, CD8+ T cell, and CD4+ T cell counts. Similarly, group D had higher FBG, IL-6 and TNF-α levels and lower lymphocyte, CD3+ T cell, CD8+ T cell, and CD4+ T cell counts than group B. Thirdly, binary logistic regression analysis showed that HbA1c, IL-6, and lymphocyte count were risk factors for the severity of COVID-19 with T2DM. Importantly, COVID-19 patients with T2DM were more likely to worsen from moderate to severe COVID-19 than nondiabetic patients. Of note, lymphopenia and inflammatory responses remained more severe throughout hospitalization for COVID-19 patients with T2DM. CONCLUSION: Our data suggested that COVID-19 patients with T2DM are more likely to develop severe COVID-19 than those without T2DM and that hyperglycemia associated with the lymphopenia and inflammatory responses in COVID-19 patients with T2DM.

Lymphopenia predicted illness severity and recovery in patients with COVID-19: A single-center, retrospective study.

The outbreak of SARS-CoV-2 began in December 2019 and rapidly became a pandemic. The present study investigated the significance of lymphopenia on disease severity. A total of 115 patients with confirmed COVID-19 from a tertiary hospital in Changsha, China, were enrolled. Clinical, laboratory, treatment and outcome data were gathered and compared between patients with and without lymphopenia. The median age was 42 years (1-75). Fifty-four patients (47.0%) of the 115 patients had lymphopenia on admission. More patients in the lymphopenia group had hypertension (30.8% vs. 10.0%, P = 0.006) and coronary heart disease (3.6% vs. 0%, P = 0.029) than in the nonlymphopenia group, and more patients with leukopenia (48.1% vs 14.8%, P<0.001) and eosinopenia (92.6% vs 54.1%, P<0.001) were observed. Lymphopenia was also correlated with severity grades of pneumonia (P<0.001) and C-reactive protein (CRP) level (P = 0.0014). Lymphopenia was associated with a prolonged duration of hospitalization (17.0 days vs. 14.0 days, P = 0.002). Lymphocyte recovery appeared the earliest, prior to CRP and chest radiographs, in severe cases, which suggests its predictive value for disease improvement. Our results demonstrated the clinical significance of lymphopenia for predicting the severity of and recovery from COVID-19, which emphasizes the need to dynamically monitor lymphocyte count.