Mechanisms of Atrial Fibrillation in Covid-19

Atrial fibrillation (AF) is the most frequent form of cardiac arrhythmia in COVID-19 infected patients. The occurrence of AF paroxysms is often associated with the acute period of infection in time. At the same time, the pathophysiological mechanisms of the occurrence of AF associated with COVID-19 remain insufficiently studied. The review considers the available literature data on the influence of factors such as reduced availability of angiotensin-converting enzyme 2 receptors, interaction of the virus with the cluster of differentiation 147 and sialic acid, increased inflammatory signaling, "cytokine storm", direct viral damage to the endothelium, electrolyte and acid-alkaline balance in the acute phase of severe illness and increased sympathetic activity.Copyright © Autors 2023.

The mechanisms of action of ivermectin against SARS-CoV-2-an extensive review

Considering the urgency of the ongoing COVID-19 pandemic, detection of new mutant strains and potential re-emergence of novel coronaviruses, repurposing of drugs such as ivermectin could be worthy of attention. This review article aims to discuss the probable mechanisms of action of ivermectin against SARS-CoV-2 by summarizing the available literature over the years. A schematic of the key cellular and biomolecular interactions between ivermectin, host cell, and SARS-CoV-2 in COVID-19 pathogenesis and prevention of complications has been proposed.Copyright © 2022 Japan Antibiotics Research Association. All rights reserved.

POST-GAM-COVID-VAC COMBINED VECTOR VACCINE CELLULAR AND HUMORAL IMMUNE RESPONSE.

Currently, as the SARS-CoV-2 pandemic evolves, there has been increasingly more attention paid to building natural and vaccine-induced immunity against SARS-CoV-2 and related disease known as COVID-19. Widespread preventive vaccination plays an important role in effectively protecting people from viral infections and can reduce national economic costs. Purpose - to study peripheral blood cell subset composition and magnitude of humoral response in vaccinated Gam-COVID-Vac subjects. The prospective study included 352 patients, of which 194 (119 women and 75 men) underwent an immunogram study and assessed level of anti-SARS-CoV-2 antibodies. In patients, the study of the lymphocyte subset composition and estimation of anti-SARS-CoV-2 antibodies was carried out at two time points - prior to vaccination and 90 days after inoculated component 1 of the Gam-COVID-Vac vaccine. In general, vaccination was well tolerated by patients, with no serious adverse events after immunization. The reaction to the vaccine (fever, malaise, headache, local reactions) was short-term (1-2 days) and more often noted after inoculated vaccine component 2. Comparatively analyzed immunogram parameters in females before and after vaccination revealed increased relative level of T-lymphocytes (CD3+), T-helper cell subset (CD3+CD4+), increased absolute and relative level of activated CD3+CD25+ T-lymphocytes, but decreased absolute and relative level of natural killer (CD3-CD56+CD16+) and natural killer T-cell (CD3+CD56+CD16+) cell subsets as well as decreased CD147 receptor expression on T-lymphocytes. Similar patterns were also found while examining the immunogram in males exepting increased level of lymphocytes and lowered CD147 expression on both T- and B-lymphocytes. No changes in the parameters of the immune T-cell arm was found. The high efficacy of the vaccine was confirmed by development of SARS-CoV-2-specific class G antiviral antibodies in 97.5% and 92.3% of vaccinated females and males, respectively. The data obtained evidence that: 1) vaccination induces a specific humoral immune response determined three months post-vaccination, and 2) it caused no serious disturbances in the immune system functioning, which could be reflected in the peripheral blood lymphocyte subset composition. Thus, the data presented allow to conclude that Gam-COVID-Vac is effective vaccine against SARS-CoV-2 infection.Copyright © 2022 Saint Petersburg Pasteur Institute. All rights reserved.

POST-GAM-COVID-VAC COMBINED VECTOR VACCINE CELLULAR AND HUMORAL IMMUNE RESPONSE

Currently, as the SARS-CoV-2 pandemic evolves, there has been increasingly more attention paid to building natural and vaccine-induced immunity against SARS-CoV-2 and related disease known as COVID-19. Widespread preventive vaccination plays an important role in effectively protecting people from viral infections and can reduce national economic costs. Purpose - to study peripheral blood cell subset composition and magnitude of humoral response in vaccinated Gam-COVID-Vac subjects. The prospective study included 352 patients, of which 194 (119 women and 75 men) underwent an immunogram study and assessed level of anti-SARS-CoV-2 antibodies. In patients, the study of the lymphocyte subset composition and estimation of anti-SARS-CoV-2 antibodies was carried out at two time points - prior to vaccination and 90 days after inoculated component 1 of the Gam-COVID-Vac vaccine. In general, vaccination was well tolerated by patients, with no serious adverse events after immunization. The reaction to the vaccine (fever, malaise, headache, local reactions) was short-term (1-2 days) and more often noted after inoculated vaccine component 2. Comparatively analyzed immunogram parameters in females before and after vaccination revealed increased relative level of T-lymphocytes (CD3+), T-helper cell subset (CD3+CD4+), increased absolute and relative level of activated CD3+CD25+ T-lymphocytes, but decreased absolute and relative level of natural killer (CD3-CD56+CD16+) and natural killer T-cell (CD3+CD56+CD16+) cell subsets as well as decreased CD147 receptor expression on T-lymphocytes. Similar patterns were also found while examining the immunogram in males exepting increased level of lymphocytes and lowered CD147 expression on both T- and B-lymphocytes. No changes in the parameters of the immune T-cell arm was found. The high efficacy of the vaccine was confirmed by development of SARS-CoV-2-specific class G antiviral antibodies in 97.5% and 92.3% of vaccinated females and males, respectively. The data obtained evidence that: 1) vaccination induces a specific humoral immune response determined three months post-vaccination, and 2) it caused no serious disturbances in the immune system functioning, which could be reflected in the peripheral blood lymphocyte subset composition. Thus, the data presented allow to conclude that Gam-COVID-Vac is effective vaccine against SARS-CoV-2 infection.

POST-GAM-COVID-VAC COMBINED VECTOR VACCINE CELLULAR AND HUMORAL IMMUNE RESPONSE.

Currently, as the SARS-CoV-2 pandemic evolves, there has been increasingly more attention paid to building natural and vaccine-induced immunity against SARS-CoV-2 and related disease known as COVID-19. Widespread preventive vaccination plays an important role in effectively protecting people from viral infections and can reduce national economic costs. Purpose - to study peripheral blood cell subset composition and magnitude of humoral response in vaccinated Gam-COVID-Vac subjects. The prospective study included 352 patients, of which 194 (119 women and 75 men) underwent an immunogram study and assessed level of anti-SARS-CoV-2 antibodies. In patients, the study of the lymphocyte subset composition and estimation of anti-SARS-CoV-2 antibodies was carried out at two time points - prior to vaccination and 90 days after inoculated component 1 of the Gam-COVID-Vac vaccine. In general, vaccination was well tolerated by patients, with no serious adverse events after immunization. The reaction to the vaccine (fever, malaise, headache, local reactions) was short-term (1-2 days) and more often noted after inoculated vaccine component 2. Comparatively analyzed immunogram parameters in females before and after vaccination revealed increased relative level of T-lymphocytes (CD3+), T-helper cell subset (CD3+CD4+), increased absolute and relative level of activated CD3+CD25+ T-lymphocytes, but decreased absolute and relative level of natural killer (CD3-CD56+CD16+) and natural killer T-cell (CD3+CD56+CD16+) cell subsets as well as decreased CD147 receptor expression on T-lymphocytes. Similar patterns were also found while examining the immunogram in males exepting increased level of lymphocytes and lowered CD147 expression on both T- and B-lymphocytes. No changes in the parameters of the immune T-cell arm was found. The high efficacy of the vaccine was confirmed by development of SARS-CoV-2-specific class G antiviral antibodies in 97.5% and 92.3% of vaccinated females and males, respectively. The data obtained evidence that: 1) vaccination induces a specific humoral immune response determined three months post-vaccination, and 2) it caused no serious disturbances in the immune system functioning, which could be reflected in the peripheral blood lymphocyte subset composition. Thus, the data presented allow to conclude that Gam-COVID-Vac is effective vaccine against SARS-CoV-2 infection. Copyright © 2022 Saint Petersburg Pasteur Institute. All rights reserved.

EFFECT OF COVID-19 VACCINATION ON THE IMMUNE STATUS AND AUTOANTIBODY PROFILE IN WOMEN OF REPRODUCTIVE AGE.

In the context of the COVID-19 pandemic, scientific interest is growing in studying the impact of the proposed vaccination on women's reproductive health. As is known, alterations in the state of the immune system and activation of an autoimmune response can lead to reproductive failure in women and potential complications of subsequent pregnancy. Objective(s): to evaluate the effect of the "Gam-COVID-Vac" on the immune status parameters, the relationship of their changes and the specific immune response to vaccination with the dynamics of the level of autoantibodies in women of reproductive age. The prospective study included 120 women who were vaccinated against COVID-19 with the "Gam-COVID-Vac". The criteria for inclusion in the study were: the age from 18 to 49 years, the absence of COVID-19 in the anamnesis, a negative result of a study on SARS-CoV-2 by PCR and negative results of tests for antibodies of classes G and M to SARS-CoV-2 before vaccination, the absence of pregnancy and serious somatic diseases. The patients were examined twice: immediately before vaccination and 90-100 days after the introduction of the 1st component of the vaccine. The level of IgG antibodies to SARS-CoV-2 after vaccination was assessed using ELISA. Before and after vaccination, the levels of antiphospholipid, anti-nuclear, organ-specific and antihormonal autoantibodies were determined, peripheral blood lymphocytes were immunophenotyped to determine the main subpopulations (CD3, CD4, CD8, CD19, CD5, CD16, CD56), as well as the expression of activation markers of lymphocytes (HLA-DR, CD25, CD147) using monoclonal antibodies. The effectiveness and safety of the combined vector vaccine against COVID-19 were high. Specific IgG antibodies to SARS-CoV-2 were produced in 98.3% of vaccinated women, no serious adverse reactions were observed. After vaccination, there was an increase in the level of some autoantibodies within the reference ranges, only IgM antibodies to phosphatidylethanolamine (PE) and IgG antibodies to DNA increased above the reference values. However, this increase was transient. After vaccination, the following changes in the parameters of the immunogram were observed: an increase in the content of cells with CD3+CD25+, CD19+ phenotype in peripheral blood and a decrease in the content of cells with CD56+CD16+ phenotype within the reference ranges, a decrease in CD147+/CD3+. Weak correlations were noted between these changes in immunogram parameters and the levels of some autoantibodies. The specific antiviral immune response to vaccination did not correlate with the autoimmune response. Vaccination with "Gam-COVID-Vac" is effective and safe and does not lead to disorders in the immune system. The observed increase in the level of autoantibodies to PE and DNA is transient. Changes in the parameters of the immune status within the reference ranges may be due to vaccination and the development of a specific antiviral immune response. Copyright © 2022, SPb RAACI.

EFFECT OF COVID-19 VACCINATION ON THE IMMUNE STATUS AND AUTOANTIBODY PROFILE IN WOMEN OF REPRODUCTIVE AGE

In the context of the COVID-19 pandemic, scientific interest is growing in studying the impact of the proposed vaccination on women's reproductive health. As is known, alterations in the state of the immune system and activation of an autoimmune response can lead to reproductive failure in women and potential complications of subsequent pregnancy. Objective: to evaluate the effect of the "Gam-COVID-Vac” on the immune status parameters, the relationship of their changes and the specific immune response to vaccination with the dynamics of the level of autoantibodies in women of reproductive age. The prospective study included 120 women who were vaccinated against COVID-19 with the "Gam-COVID-Vac”. The criteria for inclusion in the study were: the age from 18 to 49 years, the absence of COVID-19 in the anamnesis, a negative result of a study on SARS-CoV-2 by PCR and negative results of tests for antibodies of classes G and M to SARS-CoV-2 before vaccination, the absence of pregnancy and serious somatic diseases. The patients were examined twice: immediately before vaccination and 90-100 days after the introduction of the 1st component of the vaccine. The level of IgG antibodies to SARS-CoV-2 after vaccination was assessed using ELISA. Before and after vaccination, the levels of antiphospholipid, anti-nuclear, organ-specific and antihormonal autoantibodies were determined, peripheral blood lymphocytes were immunophenotyped to determine the main subpopulations (CD3, CD4, CD8, CD19, CD5, CD16, CD56), as well as the expression of activation markers of lymphocytes (HLA-DR, CD25, CD147) using monoclonal antibodies. The effectiveness and safety of the combined vector vaccine against COVID-19 were high. Specific IgG antibodies to SARS-CoV-2 were produced in 98.3% of vaccinated women, no serious adverse reactions were observed. After vaccination, there was an increase in the level of some autoantibodies within the reference ranges, only IgM antibodies to phosphatidylethanolamine (PE) and IgG antibodies to DNA increased above the reference values. However, this increase was transient. After vaccination, the following changes in the parameters of the immunogram were observed: an increase in the content of cells with CD3+CD25+, CD19+ phenotype in peripheral blood and a decrease in the content of cells with CD56+CD16+ phenotype within the reference ranges, a decrease in CD147+/CD3+. Weak correlations were noted between these changes in immunogram parameters and the levels of some autoantibodies. The specific antiviral immune response to vaccination did not correlate with the autoimmune response. Vaccination with "Gam-COVID-Vac” is effective and safe and does not lead to disorders in the immune system. The observed increase in the level of autoantibodies to PE and DNA is transient. Changes in the parameters of the immune status within the reference ranges may be due to vaccination and the development of a specific antiviral immune response. © 2022, SPb RAACI.

Probable pathways of SARS-CoV-2 to central nervous system

Various reported cases related to the COVID-19 pandemic since 2019 has shown that SARS-CoV-2 directly or indirectly affects the nervous system besides the upper respiratory tract (Whittaker et al. 2020). SARS-CoV-2 is a zoonotic strain of coronavirus with various structural proteins. It is reported that spike protein, which is one of its structural proteins, can bind to or interact with Neuropilin-1, CD147 (Basigin), KREMEN1, ASGR1 (Asialoglycoprotein Receptor), Furin, LRP1 (Lipoprotein Receptor-Related Protein 1) and Ephrin receptors as well as ACE-2 (Angiotensin Converting Enzyme-2) and TMPRSS2 (Transmembrane Serine Protease 2) receptors. The related studies suggest that these possible receptors in the target of SARS-CoV- 2 cooperate with ACE-2, hence make the central nervous system an open target for the virus (Zalpoor et al. 2022). The first possible route of SARS-CoV-2 is seen as the route from the olfactory epithelium to its bulb via the trigeminal nerve (CN V) and olfactory nerve (CN I) pathway. Additionally, the virus entering the bloodstream can reach the Blood Brain Barier, cross the barrier and spread to neurons through the oligodendrocyte in a process called “Trojen horse”. Lastly, another route considered focuses on the vagal nerves of the enteric system associated with the central nervous system (Guadarrama-Ortiz et al. 2020). This literature review focuses on possible entry routes of SARS-CoV-2 into the nervous system. In this context, a route has been established based on the receptors in the nervous system cells, which are reported to be the target of SARS-CoV-2, based on the studies.

Human interaction targets of SARS-COV-2 spike protein: A systematic review

Objectives: The development of effective targeted therapy and drug-design approaches against the SARS-CoV-2 is a universal health priority. Therefore, it is important to assess possible therapeutic strategies against SARS-CoV-2 via its most interaction targets. The present study aimed to perform a systematic review on clinical and experimental investigations regarding SARS-COV-2 interaction targets for human cell entry. Methods: A systematic search using relevant MeSH terms and keywords was performed in PubMed, Scopus, Embase, and Web of Science (ISI) databases up to July 2021. Two reviewers independently assessed the eligibility of the studies, extracted the data, and evaluated the methodological quality of the included studies. Additionally, a narrative synthesis was done as a qualitative method for data gathering and synthesis of each outcome measure. Results: A total of 5610 studies were identified, and 128 articles were included in the systematic review. Based on the results, spike antigen was the only interaction protein from SARS-CoV-2. However, the interaction proteins from humans varied including different spike receptors and several cleavage enzymes. The most common interactions of the spike protein of SARS-CoV-2 for cell entry were ACE2 (entry receptor) and TMPRSS2 (for spike priming). A lot of published studies have mainly focused on the ACE2 receptor followed by the TMPRSS family and furin. Based on the results, ACE2 polymorphisms as well as spike RBD mutations affected the SARS-CoV-2 binding affinity. Conclusion: The included studies shed more light on SARS-CoV-2 cellular entry mechanisms and detailed interactions, which could enhance the understanding of SARS-CoV-2 pathogenesis and the development of new and comprehensive therapeutic approaches.

Τargets and Therapeutic Agents against SARS-CoV-2

The recent coronavirus outbreak of SARS-CoV-2 has spread worldwide, causing serious socioeconomical disruption. Due to the urgency of the situation, various research strategies are ongoing, in order to evaluate the therapeutic efficacy of repurposed and experimental drugs, as there are neither prophylactic nor therapeutic treatments available. The present review provides a brief account of the COVID-19 disease and the reproductive cycle of SARS-CoV-2 with host proteins. Moreover, it apposes drugs/bioactive substances and their targets, that are being or may be used for the treatment of COVID 19. These include different therapeutic classes, such as ACE2 inhibitors, TMPRSS2 and CD147 inhibitors, antivirals, cardioprotective agents and anti inflammatory drugs. Therapeutic perspectives of the various vaccines and diagnostic tests that are being developed are also discussed.

CD147 expression and polymorphism as markers of cytomegalovirus infection in acute myeloid leukemia patients following allogeneic stem cell transplantation

CD147 (BSG, EMMPRIN) is a multifunctional immunoglobulin involved in pathogenesis of many diseases. It was shown to facilitate various viral infections, such as measles virus and SARS-CoV-2, and was reported to have a role in cytomegalovirus (CMV) infection. While mostly working as a membrane-bound protein, it can be released by cells in a soluble form that can be detected in serum. Our recent studies showed that CD147 polymorphism and serum level may be associated with risk and survival in acute myeloid leukemia (AML) patients. This prompted us to investigate CD147 serum levels and genotypes in AML patients with CMV infection after allogeneic stem cell transplantation (SCT). CD147 was measured using Quantikine ELISA Human EMMPRIN/ CD147 Immunoassay in serum of 16 AML patients undergoing SCT, of whom nine developed CMV infection, and 25 controls. Genotyping of CD147 variants was performed on 170 DNA samples, including 135 healthy individuals and 35 patients (18 with CMV infection) using Taqman assays. Serum CD147 levels were higher in patients with CMV infection than in those without detectable CMV infection (p = 0.026) and controls (p < 0.001). CD147 allele rs4919859C, a marker of risk and worse survival in AML, tended to be more common in patients with CMV infection than those without infection (p = 0.094). Furthermore, we built a logistic regression model incorporating the type of conditioning, sex of transplant donor and recipient, type of donor (related/ unrelated), donor and recipient serologic CMV status, and presence/absence of the rs4919859 C allele. The analysis confirmed allele rs4919859 C (p = 0.044) and recipient CMV status (p = 0.035) as independent markers of CMV infection. Our results suggest that higher serum CD147 levels and presence of the CD147 rs4919859C allele may be markers of CMV infection in AML patients undergoing SCT.

NEUROPILIN-1 MEDIATES SARS-CoV-2 INFECTION of ASTROCYTES PROMOTING NEURON DYSFUNCTION

Background: SARS-CoV-2 primarily infects the lung but may also damage other organs including the brain, heart, kidney, and intestine. Central nervous system (CNS) disorders include loss of smell and taste, headache, delirium, acute psychosis, seizures, and stroke. Pathological loss of gray matter occurs in SARS-CoV-2 infection but it is unclear whether this is due to direct viral infection, indirect effects associated with systemic inflammation, or both. Methods: We used iPSC-derived brain organoids and primary human astrocytes from cerebral cortex to study direct SARS-CoV-2 infection, as confirmed by Spike and Nucleocapsid immunostaining and RT-qPCR. siRNAs, blocking antibodies, and small molecule inhibitors were used to assess SARS-CoV-2 receptor candidates. Bulk RNA-seq, DNA methylation seq, and Nanostring GeoMx digital spatial profiling were utilized to identify virus-induced changes in host gene expression. Results: Astrocytes were robustly infected by SARS-CoV-2 in brain organoids while neurons and neuroprogenitor cells supported only low-level infection. Based on siRNA knockdowns, Neuropilin-1, not ACE2, functioned as the primary receptor for SARS-CoV-2 in astrocytes. The endolysosomal two-pore channel protein, TPC, also facilitated infection likely through its regulatory effects on endocytosis. Other alternative receptors, including the AXL tyrosine kinase, CD147, and dipeptidyl protease 4 (DPP4), did not function as SARS-CoV-2 receptors in astrocytes. SARS-CoV-2 infection dynamically induced type I, II, and III interferons, and genes involved in Toll-like receptor signaling, MDA5 and RIG-I sensing of double-stranded RNA, and production of inflammatory cytokines. Genes activating apoptosis were also increased. Down-regulated genes included those involved in water, ion and lipid transport, synaptic transmission, and formation of cell junctions. Epigenetic analyses revealed transcriptional changes related to DNA methylation states, particularly decreased DNA methylation in interferon-related genes. Long-term viral infection of brain organoids resulted in progressive neuronal degeneration and death. Conclusion: Our findings support a model where SARS-CoV-2 infection of astrocytes produces a panoply of changes in the expression of genes regulating innate immune signaling and inflammatory responses. Deregulation of these genes in astrocytes produces a microenvironment within the CNS that ultimately disrupts normal neuron function, promoting neuronal cell death and CNS deficits.

Red Blood Cells from COVID-19 Patients Show Evidence of Increased Oxidative Stress and Increased Lactate Influx

Red Blood Cells from COVID-19 Patients Show Evidence of Increased Oxidative Stress and Increased Lactate Influx Corona Disease 19 (COVID-19) is caused by SARS-CoV-2, a novel, highly infectious, single stranded RNA virus. In severe cases, excess oxidative stress produced by a ‘cytokine storm’ may generate excess reactive oxygen species (ROS) and lead to tissue damage in the lungs and elsewhere. As the potential role of RBCs in the pathophysiology of COVID-19 remains controversial (1), we investigated for evidence of increased oxidative stress and increased thrombotic tendency in RBCs from patients with COVID-19 infection. Following ethical approval and written informed consent, we used flow cytometry (BD FACSCanto II) to measure baseline RBC ROS following incubation with 2‘-7‘-dichlorofluorescein diacetate (DCF). RBC ROS were also measured following pre-incubation with hydrogen peroxide (H2O2) (2mM) +/- antioxidant N-acetyl cysteine (NAC) (0.6mM). We also measured RBC surface expression of adhesion molecules CD44, CD47 and CD242, as well as CD147. Results were expressed as mean +/- standard deviation (SD). RBC ROS were measured in 22 COVID-19 positive patients and in 10 age matched healthy controls. One patient died from respiratory failure, whilst only 3 others required ITU admission for continuous positive airway pressure (CPAP) or intubation. There was no statistical difference in mean basal RBC DCF mean fluorescence intensity (MFI) levels between COVID-19 positive patients and controls. However, mean increase in RBC DCF MFI following H2O2 incubation was significantly higher in the COVID-19 positive group (1105.7+/-336.3) compared to the control group (843.4+/-256.7)( p= 0.042). The increase in RBC DCF MFI in the COVID-19 positive group correlated with CRP (p=0.014) but not with D-dimer, serum ferritin or any complete blood count (CBC) parameters. Incubation of RBC with 0.6 mM NAC for 30 minutes prior to H2O2 exposure caused a mean reduction in DCF MFI of 26.7% in the COVID-19 positive group. RBC expression of CD44, CD47, CD242 and CD147 were measured In a separate cohort of COVID-19 positive patients (n=32), and in 22 age matched controls. There were no statistically significant differences in mean expression levels of CD44, CD47 and CD242 between the 2 groups. However, mean RBC CD147 MFI expression was higher in the COVID-19 group (1319.64+/-374.76) compared to controls (1061.59+/-253.33) (p=0.018). There was no significant correlation between RBC CD147 MFI and D-dimer, CRP, serum ferritin or any CBC parameters in the COVID-19 positive group. However, 21 of the 32 COVID-19 positive patients had blood lactate levels measured and there was a positive correlation between CD147 MFI expression and blood lactate (R=0.56, p=0.0077). Induction of oxidative stress by H2O2 resulted in a greater increase in ROS in RBCs from COVID-19 patients compared to controls and with correlation to CRP, despite the fact that there were very few patients with severe disease in the study. This suggests a role for oxidative stress in disease pathogenesis. Pre-incubation with NAC attenuated this increase in ROS, suggesting a possible role for antioxidants in therapy. Increased RBC cell surface expression of adhesion molecules CD44, CD47 and CD242 can facilitate RBC interaction with platelets and/or endothelial cells, potentially contributing to thrombosis. We found no increase in their expression in COVID-19 patients compared to controls although RBCs may contribute to thrombosis in COVID-19 infection by other means (1). CD147 is tightly associated with and enables proper expression of monocarboxylate transporter 1, the lactate transporter for RBCs. We found increased surface expression of CD147 on RBCs of COVID-19 patients, whilst CD147 expression showed a moderate correlation with serum lactate levels, suggesting that RBCs in COVID-19 infection may be acting as a lactate sink to protect against lactic acidosis. In summary, our study suggests that COVID-19 infection causes increased oxidative stress and increased lactate influx i RBCs. Further studies are warranted into the role of RBCs in COVID-19 infection. Reference: (1) Murphy P, Glavey S, Quinn J. Anemia and red blood cell abnormalities in COVID-19. Leuk Lymphoma 2021;62:1539 Disclosures: Quinn: Takeda: Honoraria. Glavey: Abbvie: Research Funding;Celgene and BMS company: Research Funding;Janssen: Honoraria, Research Funding;Amgen: Honoraria, Research Funding.

The SARS-CoV-2 Spike protein alters human cardiac pericyte function and interaction with endothelial cells through a non-infective mechanism involving activation of CD147 receptor signalling

Background: Human cardiac pericytes (PC) were proposed as the main cellular target for SARS-CoV-2 in the heart due to high transcriptional levels of the angiotensin-converting enzyme 2 (ACE2) receptor. Emerging reports indicate CD147/Basigin (BSG), highly expressed in endothelial cells (EC), is an alternative SARS-CoV-2 receptor. To date, the mechanism by which the virus infects and disrupts the heart vascular cells was not identified yet. Moreover, cleaved Spike (S) protein molecules could be released into the bloodstream from the leaking pulmonary epithelial-endothelial barrier in patients with severe COVID-19, opening to the possibility of non-infective diseases in organs distant from the primary site of infection. Purposes: (1) to confirm that human primary cardiac PC express ACE2 and CD147;(2) to verify if PC are permissible to SARS-CoV-2 infection;(3) to investigate if the recombinant SARS-CoV-2 S protein alone, without the other viral elements, can trigger molecular signalling and induce functional alterations in PC;(4) to explore which viral receptor is responsible for the observed events. Methods and results: Cardiac PC express both the ACE2 and CD147 receptors at mRNA and protein level. Incubation of PC for up to 5 days with SARS-CoV-2 expressing the green fluorescent protein (GFP) did not show any evidence of cell infection or viral replication. Next, we exposed the PC to the recombinant S protein (5.8 nM) and confirmed that the protein engaged with cellular receptors (western blot analysis of S protein in treated and control PC). Incubation with the S protein increased PC migration (wound closure assay, P<0.01 vs ctrl) and reduced the formation of tubular structures between PC and EC in a Matrigel assay (P<0.01 vs ctrl). Moreover, the S protein promoted the production of pro-inflammatory factors typical of the cytokine storm in PC (ELISA measurement of MCP1, IL-6, IL-1β, TNFα, P<0.05 vs ctrl), and induced the secretion of proapoptotic factors responsible for EC death (Caspase 3/7 assay, P<0.05 vs ctrl). Signalling studies revealed that the S protein triggers the phosphorylation/ activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) through the CD147 receptor, but not ACE2, in cardiac PC. The neutralization of CD147, using a blocking antibody, prevented ERK1/2 activation in PC, and was reflected into a partial rescue of the cell functional behaviour (migration and pro-angiogenic capacity). In contrast, blockage of CD147 failed to prevent the pro-inflammatory response in PC. Conclusions: We propose the novel hypothesis that COVID-19 associated heart's microvascular dysfunction is prompted by circulating S protein molecules rather than by the direct coronavirus infection of PC. Besides, we propose CD147, and not ACE2, as the leading receptor mediating S protein signalling in cardiac PC.