The majority of severe COVID-19 patients develop anti-cardiac autoantibodies.

Severe cases of COVID-19 are characterized by an inflammatory burst, which is accompanied by multiorgan failure. The elderly population has higher risk for severe or fatal outcome for COVID-19. Inflammatory mediators facilitate the immune system to combat viral infection by producing antibodies against viral antigens. Several studies reported that the pro-inflammatory state and tissue damage in COVID-19 also promotes autoimmunity by autoantibody generation. We hypothesized that a subset of these autoantibodies targets cardiac antigens. Here we aimed to detect anti-cardiac autoantibodies in severe COVID-19 patients during hospitalization. For this purpose, 104 COVID-19 patients were recruited, while 40 heart failure patients with dilated cardiomyopathy and 20 patients with severe aortic stenosis served as controls. Patients were tested for anti-cardiac autoantibodies, using human heart homogenate as a bait. Follow-up samples were available in 29 COVID-19 patients. Anti-cardiac autoantibodies were detected in 68% (71 out of 104) of severe COVID-19 patients. Overall, 39% of COVID-19 patients had anti-cardiac IgG autoantibodies, while 51% had anti-cardiac autoantibodies of IgM isotype. Both IgG and IgM anti-cardiac autoantibodies were observed in 22% of cases, and multiple cardiac antigens were targeted in 38% of COVID-19 patients. These anti-cardiac autoantibodies targeted a diverse set of myocardial proteins, without apparent selectivity. As controls, heart failure patients (with dilated cardiomyopathy) had similar occurrence of IgG (45%, p = 0.57) autoantibodies, while significantly lower occurrence of IgM autoantibodies (30%, p = 0.03). Patients with advanced aortic stenosis had significantly lower number of both IgG (11%, p = 0.03) and IgM (10%, p < 0.01) type anti-cardiac autoantibodies than that in COVID-19 patients. Furthermore, we detected changes in the anti-cardiac autoantibody profile in 7 COVID-19 patients during hospital treatment. Surprisingly, the presence of these anti-cardiac autoantibodies did not affect the clinical outcome and the prevalence of the autoantibodies did not differ between the elderly (over 65 years) and the patients younger than 65 years of age. Our results demonstrate that the majority of hospitalized COVID-19 patients produce novel anti-cardiac IgM autoantibodies. COVID-19 also reactivates resident IgG autoantibodies. These autoantibodies may promote autoimmune reactions, which can complicate post-COVID recuperation, contributing to post-acute sequelae of COVID-19 (long COVID).

SARS-CoV-2 infects human cardiomyocytes promoted by inflammation and oxidative stress.

INTRODUCTION: The respiratory illness triggered by severe acute respiratory syndrome virus-2 (SARS-CoV-2) is often particularly serious or fatal amongst patients with pre-existing heart conditions. Although the mechanisms underlying SARS-CoV-2-related cardiac damage remain elusive, inflammation (i.e. 'cytokine storm') and oxidative stress are likely involved. METHODS AND RESULTS: Here we sought to determine: 1) if cardiomyocytes are targeted by SARS-CoV-2 and 2) how inflammation and oxidative stress promote the viral entry into cardiac cells. We analysed pro-inflammatory and oxidative stress and its impact on virus entry and virus-associated cardiac damage from SARS-CoV-2 infected patients and compared it to left ventricular myocardial tissues obtained from non-infected transplanted hearts either from end stage heart failure or non-failing hearts (donor group). We found that neuropilin-1 potentiates SARS-CoV-2 entry into human cardiomyocytes, a phenomenon driven by inflammatory and oxidant signals. These changes accounted for increased proteases activity and apoptotic markers thus leading to cell damage and apoptosis. CONCLUSION: This study provides new insights into the mechanisms of SARS-CoV-2 entry into the heart and defines promising targets for antiviral interventions for COVID-19 patients with pre-existing heart conditions or patients with co-morbidities.

Profiling of Lactate Dehydrogenase Isoenzymes in COVID-19 Disease.

INTRODUCTION: Serum total lactate dehydrogenase (LDH) activity was elevated and showed a positive correlation with disease severity and outcome in severe COVID-19 disease. However, it is still unknown whether the relative abundance or calculated activity of any LDH isoenzyme is predominately increased in COVID-19 subjects. METHODS: Twenty-two consecutive patients suffered from moderate or severe COVID-19 pneumonia were recruited into this study who showed enhanced total LDH activity. The ratio of LDH isoenzyme activities was further investigated using gel electrophoresis (Hydragel®, Sebia) with densitometric evaluation. Calculated activity values of these isoenzymes were correlated with routine laboratory parameters, the degree of lung parenchymal affection based on chest CT and clinical outcome. RESULTS: Total LDH activity was raised in the range of 272-2141 U/L and significantly correlated with calculated LDH-3 and LDH-4 activities (r=0.765, P=0.0001; and r=0.783, P=0.0001, respectively). In contrast, the relative abundance of neither LDH isoenzyme was exclusively abnormal in COVID-19 patients. Calculated activity of LDH-3 and LDH-4 demonstrated a modest but statistically significant association with serum ferritin (r=0.437, P=0.042; r=0.505, P=0.016, respectively). When the relationship between the severity of pulmonary affection by SARS-CoV-2 infection and relative abundance of LDH isoenzymes was studied, a larger ratio of mid-zone fractions was observed in the presence of ≥ 50% lung parenchymal involvement. Finally, regardless of LDH isoenzyme pattern, abnormal relative ratio of LDH-4 and higher calculated LDH-3 and LDH-4 activity values were detected in subjects with unfavorable outcome. CONCLUSION: No characteristic profile of LDH isoenzymes can be detected in COVID-19 pneumonia, however, elevated activities of LDH-3 and LDH-4 are associated with worse clinical outcomes.

Circulating ACE2 activity predicts mortality and disease severity in hospitalized COVID-19 patients.

OBJECTIVES: Angiotensin-converting enzyme 2 (ACE2) represents the primary receptor for SARS-CoV-2 to enter endothelial cells. Here we investigated circulating ACE2 activity to predict the severity and mortality of COVID-19. METHODS: Serum ACE2 activity was measured in COVID-19 (110 critically ill and 66 severely ill subjects at hospital admission and 106 follow-up samples) and in 32 non-COVID-19 severe sepsis patients. Associations between ACE2, inflammation-dependent biomarkers, pre-existing comorbidities, and clinical outcomes were studied. RESULTS: Initial ACE2 activity was significantly higher in critically ill COVID-19 patients (54.4 [36.7-90.8] mU/L) than in severe COVID-19 (34.5 [25.2-48.7] mU/L; P<0.0001) and non-COVID-19 sepsis patients (40.9 [21.4-65.7] mU/L; P=0.0260) regardless of comorbidities. Circulating ACE2 activity correlated with inflammatory biomarkers and was further elevated during the hospital stay in critically ill patients. Based on ROC-curve analysis and logistic regression test, baseline ACE2 independently indicated the severity of COVID-19 with an AUC value of 0.701 (95% CI [0.621-0.781], P<0.0001). Furthermore, non-survivors showed higher serum ACE2 activity vs. survivors at hospital admission (P<0.0001). Finally, high ACE2 activity (≥45.4 mU/L) predicted a higher risk (65 vs. 37%) for 30-day mortality (Log-Rank P<0.0001). CONCLUSIONS: Serum ACE2 activity correlates with COVID-19 severity and predicts mortality.

Changes in the SARS-CoV-2 cellular receptor ACE2 levels in cardiovascular patients: a potential biomarker for the stratification of COVID-19 patients.

Angiotensin-converting enzyme 2 (ACE2) is essential for SARS-CoV-2 cellular entry. Here we studied the effects of common comorbidities in severe COVID-19 on ACE2 expression. ACE2 levels (by enzyme activity and ELISA measurements) were determined in human serum, heart and lung samples from patients with hypertension (n = 540), heart transplantation (289) and thoracic surgery (n = 49). Healthy individuals (n = 46) represented the controls. Serum ACE2 activity was increased in hypertensive subjects (132%) and substantially elevated in end-stage heart failure patients (689%) and showed a strong negative correlation with the left ventricular ejection fraction. Serum ACE2 activity was higher in male (147%), overweight (122%), obese (126%) and elderly (115%) hypertensive patients. Primary lung cancer resulted in higher circulating ACE2 activity, without affecting ACE2 levels in the surrounding lung tissue. Male sex resulted in elevated serum ACE2 activities in patients with heart transplantation or thoracic surgery (146% and 150%, respectively). Left ventricular (tissular) ACE2 activity was unaffected by sex and was lower in overweight (67%), obese (62%) and older (73%) patients with end-stage heart failure. There was no correlation between serum and tissular (left ventricular or lung) ACE2 activities. Neither serum nor tissue (left ventricle or lung) ACE2 levels were affected by RAS inhibitory medications. Abandoning of ACEi treatment (non-compliance) resulted in elevated blood pressure without effects on circulating ACE2 activities. ACE2 levels associate with the severity of cardiovascular diseases, suggestive for a role of ACE2 in the pathomechanisms of cardiovascular diseases and providing a potential explanation for the higher mortality of COVID-19 among cardiovascular patients. Abandoning RAS inhibitory medication worsens the cardiovascular status without affecting circulating or tissue ACE2 levels.

Human Tissue Angiotensin Converting Enzyme (ACE) Activity Is Regulated by Genetic Polymorphisms, Posttranslational Modifications, Endogenous Inhibitors and Secretion in the Serum, Lungs and Heart.

Objective: Inhibitors of the angiotensin converting enzyme (ACE) are the primarily chosen drugs to treat heart failure and hypertension. Moreover, an imbalance in tissue ACE/ACE2 activity is implicated in COVID-19. In the present study, we tested the relationships between circulating and tissue (lung and heart) ACE levels in men. Methods: Serum, lung (n = 91) and heart (n = 72) tissue samples were collected from Caucasian patients undergoing lung surgery or heart transplantation. ACE I/D genotype, ACE concentration and ACE activity were determined from serum and tissue samples. Clinical parameters were also recorded. Results: A protocol for ACE extraction was developed for tissue ACE measurements. Extraction of tissue-localized ACE was optimal in a 0.3% Triton-X-100 containing buffer, resulting in 260 ± 12% higher ACE activity over detergent-free conditions. SDS or higher Triton-X-100 concentrations inhibited the ACE activity. Serum ACE concentration correlated with ACE I/D genotype (II: 166 ± 143 ng/mL, n = 19, ID: 198 ± 113 ng/mL, n = 44 and DD: 258 ± 109 ng/mL, n = 28, p < 0.05) as expected. In contrast, ACE expression levels in the lung tissue were approximately the same irrespective of the ACE I/D genotype (II: 1423 ± 1276 ng/mg, ID: 1040 ± 712 ng/mg and DD: 930 ± 1273 ng/mg, p > 0.05) in the same patients (values are in median ± IQR). Moreover, no correlations were found between circulating and lung tissue ACE concentrations and activities (Spearman's p > 0.05). In contrast, a significant correlation was identified between ACE activities in serum and heart tissues (Spearman's Rho = 0.32, p < 0.01). Finally, ACE activities in lung and the serum were endogenously inhibited to similar degrees (i.e., to 69 ± 1% and 53 ± 2%, respectively). Conclusion: Our data suggest that circulating ACE activity correlates with left ventricular ACE, but not with lung ACE in human. More specifically, ACE activity is tightly coordinated by genotype-dependent expression, endogenous inhibition and secretion mechanisms.

Level of the SARS-CoV-2 receptor ACE2 activity is highly elevated in old-aged patients with aortic stenosis: implications for ACE2 as a biomarker for the severity of COVID-19.

Coronavirus disease 2019 (COVID-19) has a high mortality in elderly patients with pre-existing cardiovascular diseases. The cellular receptor of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the angiotensin-converting enzyme 2 (ACE2), thereby implicating a link between cardiovascular diseases and SARS-CoV-2 susceptibility. Aortic stenosis (AS) represents a chronic inflammatory state with severe cardiovascular complications in the elderly, a prime condition for COVID-19 mortality. The circulating ACE2 levels were measured in 111 patients with severe AS and compared to patients with hypertension and healthy individuals. About 4 times higher circulating ACE2 activity was found in patients with severe AS than in hypertensives or healthy individuals (88.3 ± 61.6., n = 111, 20.6 ± 13.4, n = 540, and 16.1 ± 7.4 mU/L, n = 46, respectively). Patients with severe AS were older than patients with hypertension (80 ± 6 years vs. 60 ± 15 years, P < 0.05). Serum ACE2 activity correlated negatively with the left ventricular ejection fraction, aortic root area, TAPSE, and positively with the right ventricular systolic pressure, cardiac diameters in patients with AS. In contrast, circulating ACE2 activity was independent of the blood pressure, peak flow velocity at the aortic root, kidney function (GFR), and inflammatory state (CRP). We found no effect of RAAS inhibitory drugs on the serum ACE2 activity in this group of patients. Our results illustrate circulating ACE2 as a potential interface between chronic inflammation, cardiovascular disease, and COVID-19 susceptibility. Elderly patients with AS have markedly elevated ACE2 levels together with altered left and right ventricular functions, which may pose higher risks during COVID-19. Our clinical data do not support a role for RAAS inhibitors in regulating circulating ACE2 levels.

A dramatic rise in serum ACE2 activity in a critically ill COVID-19 patient.

Endothelial cells express surface angiotensin-converting enzyme 2 (ACE2), the main receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that promotes the infection of endothelial cells showing activation and damage. Bronchoalveolar lavage fluid from coronavirus disease-2019 (COVID-19) subjects showed a critical imbalance in the renin-angiotensin-aldosterone system with the upregulated expression of ACE2. Recently, intravenous recombinant ACE2 was reported as an effective therapy in severe COVID-19 by blocking the viral entry to target cells. Here, we present a case of a critically ill COVID-19 patient with acute respiratory distress syndrome where circulating ACE2 was first measured to monitor disease prognosis. ACE2 activity increased about 40-fold over the normal range and showed a distinct time course as compared to 2-3-fold higher levels of endothelium biomarkers. Although the level of soluble E-selectin followed the clinical status of our patient similar to ferritin and IL-6 levels, the dramatic rise in serum ACE2 activity may act as an endogenous nonspecific protective mechanism against SARS-CoV-2 infection that preceded the recovery of our patient.