Peculiarities of the T Cell Immune Response in COVID-19

Comprehensive Risk Assessment of Infection Induced by SARS-CoV-2

The pandemic COVID-19 (coronavirus disease 2019) is caused by the severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), which devastated the global economy and healthcare system. The infection caused an unforeseen rise in COVID-19 patients and increased the mortality rate globally. This study gives an overall idea about host-pathogen interaction, immune responses to COVID-19, recovery status of infection, targeted organs and complications associated, and comparison of post-infection immunity in convalescent subjects and non-infected individuals. The emergence of the variants and episodes of COVID-19 infections made the situation worsen. The timely introduction of vaccines and precautionary measures helped control the infection's severity. Later, the population that recovered from COVID-19 grew significantly. However, understanding the impact of healthcare issues resulting after infection is paramount for improving an individual's health status. It is now recognised that COVID-19 infection affects multiple organs and exhibits a broad range of clinical manifestations. So, post COVID-19 infection creates a high risk in individuals with already prevailing health complications. The identification of post-COVID-19-related health issues and their appropriate management is of greater importance to improving patient's quality of life. The persistence, sequelae and other medical complications that normally last from weeks to months after the recovery of the initial infection are involved with COVID-19. A multi-disciplinary approach is necessary for the development of preventive measures, techniques for rehabilitation and strategies for clinical management when it comes to long-term care.

CD68-Negative Histiocytoses with Cardiac Involvement, Associated with COVID-19

Histiocytoses are rare diseases characterised by infiltration of affected organs by myeloid cells with a monocyte or dendritic cell phenotype. Symptoms can range from self-resolving localised forms to multisystemic lesions requiring specific treatment. To demonstrate extremely rare cases of CD68-negative cardiac histiocytosis with expression of SARS-CoV-2 antigen in infiltrate cells. We demonstrated a case of Erdheim-Chester disease in a 67-year-old man with pericardial involvement and positive dynamics with vemurafenib treatment, an autopsy case of xanthogranulomatous myopericarditis in a 63-year-old man, surgical material of xanthogranulomatous constrictive pericarditis in a 57-year-old man, and an autopsy case of xanthogranulomatosis in a 1-month-old girl. In all cases, xanthogranuloma cells expressed CD163, many of them spike protein SARS-CoV-2, while CD68 expression was detected only in single cells. In this article, we demonstrated four cases of extremely rare CD68-negative cardiac xanthogranulomatosis in three adults and one child with expression of the spike protein SARS-CoV-2 in M2 macrophages. This potential indirect association between COVID-19 and the development of histiocytosis in these patients warrants further investigation. To substantiate this hypothesis, more extensive research is needed.

Anti-virus activity and mechanisms of natural polysaccharides from medicinal herbs

There has been a sudden increase in viral diseases, such as coronavirus disease 2019 (COVID-19), causing significant harm to human and animal well-being, as well as economic development. Medicinal herbs, with a history of thousands of years in clinical use, contain versatile polysaccharides as one of their primary compounds. This review offers an overview of the antiviral effects of polysaccharides from medicinal herbs on viruses in humans, poultry, swine and aquaculture in recent years. The mechanism of these antiviral polysaccharides, involved in hindering various stages of the viral life cycle thereby blocking virus infection, is summarized. The review also explores other underlying mechanisms of antiviral effects, such as enhancing the immune response, regulating inflammatory reactions, balancing gut flora, reducing oxidative stress, and suppressing apoptosis through various corresponding signaling pathways. The structure-function relationships discussed in this article also aid in understanding the antiviral mechanism of natural polysaccharides, indicating the need for more in-depth research and analysis. Natural polysaccharides from medicinal herbs have emerged as valuable resources in the fight against viral infections, exhibiting high effectiveness. This review emphasizes the promising role of polysaccharides from medicinal herbs as potential candidates for blocking viral infections in humans and animals.

Vitamin D Metabolism Parameters and Cytokine Profile in COVID-19 Patients with Bolus Cholecalciferol Supplementation

Recent studies have demonstrated the relationship between vitamin D deficiency, infection severity and mortality from COVID-19. This study aimed to analyze the vitamin D metabolites and cytokine expression levels of COVID-19 patients who were hospitalized with bolus cholecalciferol supplementation.

MATERIALS AND METHODS

This study represents the next stage of the open-label randomized pilot conducted by the Almazov National Medical Research Centre. A total of 44 hospitalized patients, comparable in demographic, clinical, laboratory and instrumental baseline characteristics, with moderate/severe COVID-19 were included. All patients had similar doses of concomitant corticosteroid therapy. Twenty-two patients received 50,000 IU cholecalciferol on the first and eighth days of hospitalization. The serum 25(OH)D, 1,25(OH)2D and 28 plasma cytokines were estimated for each group initially and on the ninth day of hospitalization.

RESULTS

Initially, there were no differences in the 1,25(OH)2D and cytokine levels in patients with vitamin D deficiency and normal 25(OH)D. Bolus cholecalciferol therapy at a total dose of 100,000 IU led to an increase in 25(OH)D levels in hospitalized patients with COVID-19, while the levels of the active metabolite (1,25(OH)2D) did not show significant differences between the groups or in its increased level over time, regardless of cholecalciferol supplementation. Furthermore, cholecalciferol supplementation at a total dose of 100,000 IU did not affect the majority of the cytokines estimated on the ninth day of hospitalization, except for the pro-inflammatory marker IL-1b, the concentration of which was lower in the group of patients without vitamin D supplementation.

CONCLUSIONS

The 25(OH)D level was positively associated with an anti-inflammatory immune response, but cholecalciferol supplementation at a total dose of 100,000 IU did not affect the active-form vitamin D or cytokine expression levels. This fact may be explained by the impact of corticosteroid therapy, and it requires further investigation in a post-COVID-19 context.

Are Endomyocardial Ventricular Biopsies Useful for Assessing Myocardial Fibrosis?

Myocardial fibrosis is an important factor in the progression of cardiovascular diseases. However, there is still no universal lifetime method of myocardial fibrosis assessment that has a high prognostic significance. The aim of the study was to determine the significance of ventricular endomyocardial biopsies for the assessment of myocardial fibrosis and to identify the severity of myocardial fibrosis in different cardiovascular diseases. Material and Methods: Endomyocardial biopsies (EMBs) of 20 patients with chronic lymphocytic myocarditis (CM), endomyocardial fragments obtained during septal reduction of 21 patients with hypertrophic cardiomyopathy (HCM), and 36 patients with a long history of hypertensive and ischemic heart disease (HHD + IHD) were included in the study. The control group was formed from EMBs taken on 12-14 days after heart transplantation (n = 28). Also, for one patient without clinical and morphological data for cardiovascular pathology, postmortem myocardial fragments were taken from typical EMB and septal reduction sites. The relative area of fibrosis was calculated as the ratio of the total area of collagen fibers to the area of the whole biopsy. Endocardium and subendocardial fibrosis were not included in the total biopsy area. Results: The relative fibrosis area in the EMBs in the CM patient group was 5.6 [3.3; 12.6]%, 11.1 [6.6; 15.9]% in the HHD + IHD patient group, 13.4 [8.8; 16.7]% in the HCM patient group, and 2.7 [1.5; 4.6]% in the control group. When comparing the fibrosis area of the CM patients in repeat EMBs, it was found that the fibrosis area in the first EMBs was 7.6 [4.8; 12.0]%, and in repeat EMBs, it was 5.3 [3.2; 7.6]%. No statistically significant differences were found between the primary and repeat EMBs (p = 0.15). In ROC analysis, the area of fibrosis in the myocardium of 1.1% (or lower than one) was found to be highly specific for the control group of patients compared to the study patients. Conclusions: EMB in the assessment of myocardial fibrosis has a questionable role because of the heterogeneity of fibrotic changes in the myocardium.

Innovations and Challenges in the Development of COVID-19 Vaccines for a Safer Tomorrow

Vaccination, a historically effective public health intervention, has shielded millions from various diseases. Lessons from severe acute respiratory syndrome coronavirus (SARS-CoV) have improved COVID-19 vaccine development. Despite mRNA vaccines' efficacy, emerging variants pose challenges, exhibiting increased transmissibility, infectivity, and severity. Developing COVID-19 vaccines has faced hurdles due to urgency, limited virus understanding, and the need for safe solutions. Genetic variability necessitates continuous vaccine adjustments and production challenges demand scaling up manufacturing with stringent quality control. This review explores SARS-CoV-2's evolution, upcoming mutations that challenge vaccines, and strategies such as structure-based, T cell-based, respiratory mucosal-based, and nanotechnology approaches for vaccine development. This review insight provides a roadmap for navigating virus evolution and improving vaccine development.

Mesenchymal stem cells and their derived exosomes for the treatment of COVID-19

Coronavirus disease 2019 (COVID-19) is an acute respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 infection typically presents with fever and respiratory symptoms, which can progress to severe respiratory distress syndrome and multiple organ failure. In severe cases, these complications may even lead to death. One of the causes of COVID-19 deaths is the cytokine storm caused by an overactive immune response. Therefore, suppressing the overactive immune response may be an effective strategy for treating COVID-19. Mesenchymal stem cells (MSCs) and their derived exosomes (MSCs-Exo) have potent homing abilities, immunomodulatory functions, regenerative repair, and antifibrotic effects, promising an effective tool in treating COVID-19. In this paper, we review the main mechanisms and potential roles of MSCs and MSCs-Exo in treating COVID-19. We also summarize relevant recent clinical trials, including the source of cells, the dosage and the efficacy, and the clinical value and problems in this field, providing more theoretical references for the clinical use of MSCs and MSCs-Exo in the treatment of COVID-19.

Sarcoidosis-related autoimmune inflammation in COVID-19 convalescent patients

Currently, there are a large number of reports about the development of autoimmune conditions after COVID-19. Also, there have been cases of sarcoid-like granulomas in convalescents as a part of the post-COVID-19 syndrome. Since one of the etiological theories of sarcoidosis considers it to be an autoimmune disease, we decided to study changes in the adaptive humoral immune response in sarcoidosis and SARS-CoV-2 infection and to find out whether COVID-19 can provoke the development of sarcoidosis. This review discusses histological changes in lymphoid organs in sarcoidosis and COVID-19, changes in B cell subpopulations, T-follicular helper cells (Tfh), and T-follicular regulatory cells (Tfr), and analyzes various autoantibodies detected in these pathologies. Based on the data studied, we concluded that SARS-CoV-2 infection may cause the development of autoimmune pathologies, in particular contributing to the onset of sarcoidosis in convalescents.

High Risk of Heart Tumors after COVID-19

An emergence of evidence suggests that severe COVID-19 is associated with an increased risk of developing breast and gastrointestinal cancers. The aim of this research was to assess the risk of heart tumors development in patients who have had COVID-19.

METHODS

A comparative analysis of 173 heart tumors was conducted between 2016 and 2023. Immunohistochemical examination with antibodies against spike SARS-CoV-2 was performed on 21 heart tumors: 10 myxomas operated before 2020 (the control group), four cardiac myxomas, one proliferating myxoma, three papillary fibroelastomas, two myxofibrosarcomas, one chondrosarcoma resected in 2022-2023. Immunohistochemical analysis with antibodies against CD34 and CD68 was also conducted on the same 11 Post-COVID period heart tumors. Immunofluorescent examination with a cocktail of antibodies against spike SARS-CoV-2/CD34 and spike SARS-CoV-2/CD68 was performed in 2 cases out of 11 (proliferating myxoma and classic myxoma).

RESULTS

A 1.5-fold increase in the number of heart tumors by 2023 was observed, with a statistically significant increase in the number of myxomas. There was no correlation with vaccination, and no significant differences were found between patients from 2016-2019 and 2021-2023 in terms of gender, age, and cardiac rhythm dis-orders. Morphological examination revealed the expression of spike SARS-CoV-2 in tumor cells, endothelial cells, and macrophages in 10 out of 11 heart tumors.

CONCLUSION

The detection of SARS-CoV-2 persistence in endothelium and macrophages as well as in tumor cells of benign and malignant cardiac neoplasms, the increase in the number of these tumors, especially cardiac myxomas, after the pandemic by 2023 may indicate a trend toward an increased risk of cardiac neoplasms in COVID-19 patients, which re-quires further research on this issue and a search for new evidence.

Initial immune response after exposure to Mycobacterium tuberculosis or to SARS-COV-2: similarities and differences

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) and Coronavirus disease-2019 (COVID-19), whose etiologic agent is severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), are currently the two deadliest infectious diseases in humans, which together have caused about more than 11 million deaths worldwide in the past 3 years. TB and COVID-19 share several aspects including the droplet- and aerosol-borne transmissibility, the lungs as primary target, some symptoms, and diagnostic tools. However, these two infectious diseases differ in other aspects as their incubation period, immune cells involved, persistence and the immunopathological response. In this review, we highlight the similarities and differences between TB and COVID-19 focusing on the innate and adaptive immune response induced after the exposure to Mtb and SARS-CoV-2 and the pathological pathways linking the two infections. Moreover, we provide a brief overview of the immune response in case of TB-COVID-19 co-infection highlighting the similarities and differences of each individual infection. A comprehensive understanding of the immune response involved in TB and COVID-19 is of utmost importance for the design of effective therapeutic strategies and vaccines for both diseases.

Morphological Changes in the Myocardium of Patients with Post-Acute Coronavirus Syndrome: A Study of Endomyocardial Biopsies

The clinical manifestation study of post-acute sequelae of SARS-CoV-2 infection (PASC) has shown a lack of knowledge regarding its morphology and pathogenesis. The aim of this research was to investigate morphological manifestations of PASC in the myocardium.

MATERIALS AND METHODS

The study included 38 patients requiring endomyocardial biopsy (EMB) during the post-acute phase of coronavirus infection and a control group including patients requiring EMB prior to the SARS-CoV-2 pandemic. The patients' clinical and laboratory data were analyzed. Histological examination and immunohistochemistry (IHC) of the myocardial tissue was conducted with antibodies to CD3, CD68, HLA-DR, MHC1, C1q, VP1 enteroviruses, spike protein SARS-CoV-2, Ang1, von Willebrand factor (VWF), and VEGF. The morphometric analysis included counting the mean number of inflammatory infiltrate cells per mm2 and evaluating the expression of SARS-CoV-2 spike protein, HLA-DR, MHC1, C1q, Ang1, VWF, and VEGF using a scoring system. If the expression of SARS-CoV-2 spike protein was >3 points, an additional IHC test with antibodies to ACE2, CD16 as well as RT-PCR testing of the myocardial tissue were performed. For two patients, immunofluorescence tests of the myocardial tissue were performed using antibody cocktails to SARS-CoV-2 spike protein/CD16, SARS-CoV-2 spike protein/CD68, CD80/CD163. The statistical data analysis was carried out using the Python programming language and libraries such as NumPy, SciPy, Pandas, and Matplotlib.

RESULTS

The study demonstrated a significant increase in the number of CD68+ macrophages in the myocardium of PASC patients compared to patients who did not have a history of COVID-19 (p = 0.014 and p = 0.007 for patients with and without myocarditis, respectively), predominantly due to M2 macrophages. An increase in the number of CD68+ macrophages was more frequently observed in patients with shorter intervals between the most recent positive SARS-CoV-2 PCR test and the time of performing the EMB (r = -0.33 and r = -0.61 for patients with and without myocarditis, respectively). The expression scores of Ang1, VEGF, VWF, and C1q in PASC patients did not significantly differ from those in EMB samples taken before 2019.

CONCLUSION

The myocardium of PASC patients demonstrated a significant increase in the number of CD68+ macrophages and a decrease in the expression of markers associated with angiopathy. No evidence of coronavirus-associated myocarditis was observed in any PASC patient.

SARS-CoV-2 Antibody Responses in Pediatric Patients: A Bibliometric Analysis

The characteristics, dynamics and mechanisms/determinants of the immune response to SARS-CoV-2 infection are not fully understood. We performed a bibliometric review of studies that have assessed SARS-CoV-2 antibody responses in the pediatric population using Web of Science online databases, VOSviewer and Bibliometrix tools. The analysis was conducted on 84 publications, from 310 institutions located in 29 countries and published in 57 journals. The results showed the collaboration of scientists and organizations, international research interactions and summarized the findings on (i) the measured titers of antibodies (total antibody and/or individual antibody classes IgG, IgM, IgA) against different antigens (C-terminal region of N (N CT), full-length N protein (N FL), RBD, RBD Alpha, RBD Beta, RBD Gamma, RBD Delta, spike (S), S1, S2) in the case of different clinical forms of the disease; and (ii) the correlations between SARS-CoV-2 antibodies and cytokines, chemokines, neutrophils, C-reactive protein, ferritin, and the erythrocyte sedimentation rate. The presented study offers insights regarding research directions to be explored in the studied field and may provide a starting point for future research.

Regulatory T Cells (Tregs) and COVID-19: Unveiling the Mechanisms, and Therapeutic Potentialities with a Special Focus on Long COVID

The COVID-19 pandemic has caused havoc all around the world. The causative agent of COVID-19 is the novel form of the coronavirus (CoV) named SARS-CoV-2, which results in immune system disruption, increased inflammation, and acute respiratory distress syndrome (ARDS). T cells have been important components of the immune system, which decide the fate of the COVID-19 disease. Recent studies have reported an important subset of T cells known as regulatory T cells (Tregs), which possess immunosuppressive and immunoregulatory properties and play a crucial role in the prognosis of COVID-19 disease. Recent studies have shown that COVID-19 patients have considerably fewer Tregs than the general population. Such a decrement may have an impact on COVID-19 patients in a number of ways, including diminishing the effect of inflammatory inhibition, creating an inequality in the Treg/Th17 percentage, and raising the chance of respiratory failure. Having fewer Tregs may enhance the likelihood of long COVID development in addition to contributing to the disease's poor prognosis. Additionally, tissue-resident Tregs provide tissue repair in addition to immunosuppressive and immunoregulatory activities, which may aid in the recovery of COVID-19 patients. The severity of the illness is also linked to abnormalities in the Tregs' phenotype, such as reduced expression of FoxP3 and other immunosuppressive cytokines, including IL-10 and TGF-beta. Hence, in this review, we summarize the immunosuppressive mechanisms and their possible roles in the prognosis of COVID-19 disease. Furthermore, the perturbations in Tregs have been associated with disease severity. The roles of Tregs are also explained in the long COVID. This review also discusses the potential therapeutic roles of Tregs in the management of patients with COVID-19.

Cell-mediated and humoral immunity during COVID-19 in the Republic of Crimea

The COVID-19 (coronavirus disease 2019) pandemic has spurred the development of highly effective quantitative methods for assessing the adaptive immune response to the SARS-CoV-2 (severe acute respiratory syndrome-related coronavirus 2) virus. In order to assess the humoral component of the immune response, various methods for detecting immunoglobulins A, M, G are widely used. ELISPOT seems to be the most accessible and effective method to assess the level of T cells that specifically respond to the SARS-CoV-2 virus antigens.

The aim. To assess cell-mediated and humoral immunity in COVID-19 in residents of the Republic of Crimea.

Methods. The study was performed on 24 volunteers: the presence of coronavirus antibodies was determined by ELISA method, and the presence of contact with coronavirus proteins – by the ELISPOT “TigraTest®  SARS-CoV-2” method (Generium, Russia). For retrospective study of  humoral immunity in the population, we assessed 10 000 ELISA tests (ECOlab IgM and IgG, Russia) performed in our laboratory for the period from July 2020 to January 2022.

Results. The results show the effectiveness of using the ELISPOT method to detect latent forms of coronavirus infection. It is important to note that there is statistically significant relationship between the timing of the disease and the number of spots in  both antigen panels. After vaccination against SARS-CoV-2, cell-mediated immunity lasts up to 6 months or more.

Conclusions. As a result of the study, it was found that during 2021, the level of  immunization of the population of the Republic of Crimea against COVID-19 has significantly increased; the proportion of residents who have positive IgG test has increased from 27 % to 87 %. The results of ELISPOT studies using a set of reagents for in vitro detection of blood T-lymphocytes that specifically respond to SARS-COV-2 virus antigens (“TigraTest® SARS-CoV-2”) showed that this method is more sensitive than ELISA in detecting latent diseases. 

T-Cell Immunity in COVID-19-Recovered Individuals and Individuals Vaccinated with the Combined Vector Vaccine Gam-COVID-Vac

The COVID-19 pandemic has required extensive research on the new coronavirus SARS-CoV-2 and the creation of new highly effective vaccines. The presence of T-cells in the body that respond to virus antigens suggests adequate antiviral immunity. We investigated T-cell immunity in individuals who recovered from mild and moderate COVID-19 and in individuals vaccinated with the Gam-COVID-Vac combined vector vaccine. The ELISPOT method was used to determine the number of T-cells responding with IFN-γ synthesis to stimulation by peptides containing epitopes of the S-protein or N-, M-, ORF3, and ORF7 proteins, using peripheral blood mononuclear cells (PBMCs). At the same time, the multiplex method was used to determine the accumulation of IFN-γ and other cytokines in the culture medium. According to the data obtained, the proportion of positive conclusions about the T-cell immune response to SARS-CoV-2 antigens in control, recovered, and vaccinated individuals was 12%, 70%, and 52%, respectively. At the same time, more than half of the vaccinated individuals with a T-cell response were sensitized to the antigens of N-, M-, ORF3, and ORF7 proteins not produced by Gam-COVID-Vac, indicating a high likelihood of asymptomatic SARS-CoV-2 infection. Increased IFN-γ release by single sensitized T-cells in response to specific stimulation in recovered and vaccinated individuals did not result in the accumulation of this and other cytokines in the culture medium. These findings suggest a balance between cytokine production and utilization by immunocompetent cells as a prerequisite for providing a controlled cytokine signal and avoiding a "cytokine storm".

COVID-19 Heart Lesions in Children: Clinical, Diagnostic and Immunological Changes

In the beginning of COVID-19, the proportion of confirmed cases in the pediatric population was relatively small and there was an opinion that children often had a mild or asymptomatic course of infection. Our understanding of the immune response, diagnosis and treatment of COVID-19 is highly oriented towards the adult population. At the same time, despite the fact that COVID-19 in children usually occurs in a mild form, there is an incomplete understanding of the course as an acute infection and its subsequent manifestations such as Long-COVID-19 or Post-COVID-19, PASC in the pediatric population, correlations with comorbidities and immunological changes. In mild COVID-19 in childhood, some authors explain the absence of population decreasing T and B lymphocytes. Regardless of the patient's condition, they can have the second phase, related to the exacerbation of inflammation in the heart tissue even if the viral infection was completely eliminated-post infectious myocarditis. Mechanism of myocardial dysfunction development in MIS-C are not fully understood. It is known that various immunocompetent cells, including both resident inflammatory cells of peripheral tissues (for example macrophages, dendritic cells, resident memory T-lymphocytes and so on) and also circulating in the peripheral blood immune cells play an important role in the immunopathogenesis of myocarditis. It is expected that hyperproduction of interferons and the enhanced cytokine response of T cells 1 and 2 types contribute to dysfunction of the myocardium. However, the role of Th1 in the pathogenesis of myocarditis remains highly controversial. At the same time, the clinical manifestations and mechanisms of damage, including the heart, both against the background and after COVID-19, in children differ from adults. Further studies are needed to evaluate whether transient or persistent cardiac complications are associated with long-term adverse cardiac events.

Updated Insights into the T Cell-Mediated Immune Response against SARS-CoV-2: A Step towards Efficient and Reliable Vaccines

The emergence of novel variants of SARS-CoV-2 and their abilities to evade the immune response elicited through presently available vaccination makes it essential to recognize the mechanisms through which SARS-CoV-2 interacts with the human immune response. It is essential not only to comprehend the infection mechanism of SARS-CoV-2 but also for the generation of effective and reliable vaccines against COVID-19. The effectiveness of the vaccine is supported by the adaptive immune response, which mainly consists of B and T cells, which play a critical role in deciding the prognosis of the COVID-19 disease. T cells are essential for reducing the viral load and containing the infection. A plethora of viral proteins can be recognized by T cells and provide a broad range of protection, especially amid the emergence of novel variants of SARS-CoV-2. However, the hyperactivation of the effector T cells and reduced number of lymphocytes have been found to be the key characteristics of the severe disease. Notably, excessive T cell activation may cause acute respiratory distress syndrome (ARDS) by producing unwarranted and excessive amounts of cytokines and chemokines. Nevertheless, it is still unknown how T-cell-mediated immune responses function in determining the prognosis of SARS-CoV-2 infection. Additionally, it is unknown how the functional perturbations in the T cells lead to the severe form of the disease and to reduced protection not only against SARS-CoV-2 but many other viral infections. Hence, an updated review has been developed to understand the involvement of T cells in the infection mechanism, which in turn determines the prognosis of the disease. Importantly, we have also focused on the T cells' exhaustion under certain conditions and how these functional perturbations can be modulated for an effective immune response against SARS-CoV-2. Additionally, a range of therapeutic strategies has been discussed that can elevate the T cell-mediated immune response either directly or indirectly.

Cardiac Involvement in Children Affected by COVID-19: Clinical Features and Diagnosis

COVID-19 (Coronavirus disease 2019) in children is usually mild. However, multiple organ disorders associated with SARS-CoV-2 (severe acute respiratory syndrome-related coronavirus 2) have been detected with poor respiratory symptoms. Cardiac changes are noted in 17% to 75% of cases, which are associated with diagnostic difficulties in high-risk groups for the development of complications that are associated with myocardial damage by the SARS-CoV-2 virus. The objective of this review is to identify the most significant symptoms of cardiac involvement affected by COVID-19, which require in-depth examination. The authors analyzed publications from December 2019 to the October 2022, which were published in accessible local and international databases. According to the analysis data, the main sign of myocardial involvement was increasing as cardiomarkers in the patient's blood, in particular troponin I or troponin T. Many authors noted that the increased level of CRP (C-reactive protein) and NT-proBNP, which are accompanied by changes in the ECG (electrocardiogram) and EchoCG (echocardiography), as a rule, were nonspecific. However, the identified cardiac functional dysfunctions affected by SARS-CoV-2, required an cardiac MRI. The lack of timely diagnosis of myocardial involvements, especially in children at high risk for the development of complications associated with SARS-CoV-2 myocardial injury, can lead to death. The direct damage of the structural elements of myocardial blood vessels in patients with severe hypoxic changes resulted from respiratory failure caused by SARS-CoV-2 lung damage, with the development of severe acute diffuse alveolar damage and cell-mediated immune response and myocardial involvement affected by SARS-CoV-2 damage. In this article, the authors introduce a clinical case of a child who dead from inflammatory myocardities with COVID-19 in a background of congenital heart disease and T-cell immunodeficiency.

ELISPOT assay of the SARS-CoV-2 specific T cells immune response

The COVID-19 pandemic has stimulated interest in the development of biotechnology, as well as in the search for new solutions in the diagnostics of immune processes. The response of immunoglobulins A, M and G had a significant role in the assessment of virus-specific immune responses. Later, it was understood that for a comprehensive assessment of adaptive immunity processes, it is reasonable to study its cellular component. One of the most affordable methods for assessing T cell immunity, which has proven itself in the diagnosis of other infectious diseases, such as latent tuberculosis infection, is IGRA ELISPOT.The aim of the study. To determine SARS-СoV-2 specific immune response of T lymphocytes in vitro in the peripheral blood of volunteers from various groups using IGRA ELISPOT method. We evaluated the applicability of the method to assess T cell immune response to infection and vaccination. In addition, we determined the duration of the maintenance period of the SARS-CoV-2 specific T cells immune response induced by vaccination.Materials and methods. The study was carried out on venous blood samples of volunteers from three groups: 1) hospital patients with COVID-19; 2) COVID-19 convalescents; 3) vaccinated against COVID-19. The T cell immune response was assessed using the TigraTest® SARS-CoV-2 test system, which determines in vitro the number of T cells secreting interferon-gamma in response to stimulation with SARS-СoV-2 peptides in two antigens panels: 1) peptides of the spike protein (S); 2) peptides of N, M, Orf3a and Orf7a proteins.Conclusion. The IGRA ELISPOT assay is a specific and sensitive tool in the assessment of T cell immunity to the SARS-CoV-2 virus. The method makes it possible to assess SARS-CoV-2 specific T cell responses induced both by natural encounter with the pathogen and by vaccination. It is advisable to use the method in routine practice for comprehensive assessment of immunity to SARS-CoV-2.

Comparison of the Immune Response in Vaccinated People Positive and Negative to SARS-CoV-2 Employing FTIR Spectroscopy

Various immunopathological events characterize the systemic acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Moreover, it has been reported that coronavirus disease 2019 (COVID-19) vaccination and infection by SARS-CoV-2 induce humoral immunity mediated by B-cell-derived antibodies and cellular immunity mediated by T cells and memory B cells. Immunoglobulins, cytokines, and chemokines play an important role in shaping immunity in response to infection and vaccination. Furthermore, different vaccines have been developed to prevent COVID-19. Therefore, this research aimed to analyze and compare Fourier-transform infrared (FTIR) spectra of vaccinated people with a positive (V-COVID-19 group) or negative (V-Healthy group) real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) test, evaluating the immunoglobulin and cytokine content as an immunological response through FTIR spectroscopy. Most individuals that integrated the V-Healthy group (88.1%) were asymptomatic; on the contrary, only 28% of the V-COVID-19 group was asymptomatic. Likewise, 68% of the V-COVID-19 group had at least one coexisting illness. Regarding the immunological response analyzed through FTIR spectroscopy, the V-COVID-19 group showed a greater immunoglobulins G, A, and M (IgG, IgA, and IgM) content, as well as the analyzed cytokines interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-ɑ), and interleukins 1β, 6, and 10 (IL-1β, IL-6, and IL-10). Therefore, we can state that it was possible to detect biochemical changes through FTIR spectroscopy associated with COVID-19 immune response in vaccinated people.

COVID-19 Vaccines: An Updated Overview of Different Platforms

Vaccination has been identified as a critical method of disease control in the context of the current COVID-19 pandemic. The goal of this review is to update information on vaccine development and to identify areas of concern that require further research. We reviewed the literature on the development of COVID-19 vaccines, their efficacy, and use in special populations, as well as current vaccination strategies. To date, 170 vaccines are in clinical development, with 41 being already approved for use in various countries. The majority of vaccines approved for human use are vector-, subunit-, DNA-, or mRNA-based vaccines, or inactivated viruses. Because of the ongoing mutation of the SARS-CoV-2 virus, well-studied vector vaccines are losing relevance due to the ability of new virus strains to bypass neutralizing antibodies. Simultaneously, PS-based vaccines are becoming more popular. There is mounting evidence that the immunogenicity of COVID-19 vaccines is linked to their clinical efficacy. This has resulted in a shift in vaccination strategies, as well as the use of booster doses and revaccination. Furthermore, vaccination restrictions for children, pregnant women, the elderly, and people with chronic immunosuppressive diseases have been lifted, allowing more people to be vaccinated. New data on vaccine safety, including the incidence of serious adverse events, have been collected. Despite significant advances in the development of and research on COVID-19 vaccines, many questions remain that require further investigation.

Generalized Modules for Membrane Antigens (GMMA), an outer membrane vesicle-based vaccine platform, for efficient viral antigen delivery

Vaccine platforms enable fast development, testing, and manufacture of more affordable vaccines. Here, we evaluated Generalized Modules for Membrane Antigens (GMMA), outer membrane vesicles (OMVs) generated by genetically modified Gram-negative bacteria, as a vaccine platform for viral pathogens. Influenza A virus hemagglutinin (HA), either physically mixed with GMMA (HA+STmGMMA mix), or covalently linked to GMMA surface (HA-STmGMMA conjugate), significantly increased antigen-specific humoral and cellular responses, with HA-STmGMMA conjugate inducing further enhancement than HA+STmGMMA mix. HA-STmGMMA conjugate protected mice from lethal challenge. The versatility for this platform was confirmed by conjugation of rabies glycoprotein (RABVG) onto GMMA through the same method. RABVG+STmGMMA mix and RABVG-STmGMMA conjugate exhibited similar humoral and cellular response patterns and protection efficacy as the HA formulations, indicating relatively consistent responses for different vaccines based on the GMMA platform. Comparing to soluble protein, GMMA was more efficiently taken up in vivo and exhibited a B-cell preferential uptake in the draining lymph nodes (LNs). Together, GMMA enhances immunity against viral antigens, and the platform works well with different antigens while retaining similar immunomodulatory patterns. The findings of our study imply the great potential of GMMA-based vaccine platform also against viral infectious diseases.

Recovering or Persisting: The Immunopathological Features of SARS-CoV-2 Infection in Children

Background. The profile of cellular immunological responses of children across the spectrum of COVID-19, ranging from acute SARS-CoV-2 infection to full recovery or Long COVID, has not yet been fully investigated. Methods. We examined and compared cytokines in sera and cell subsets in peripheral blood mononuclear cells (B and regulatory T lymphocytes) collected from four distinct groups of children, distributed as follows: younger than 18 years of age with either acute SARS-CoV-2 infection (n = 49); fully recovered from COVID-19 (n = 32); with persistent symptoms (Long COVID, n = 51); and healthy controls (n = 9). Results. In the later stages after SARS-CoV-2 infection, the cohorts of children, both with recovered and persistent symptoms, showed skewed T and B subsets, with remarkable differences when compared with children at the onset of the infection and with controls. The frequencies of IgD+CD27− naïve B cells, IgD+IgM+ and CD27−IgM+CD38dim B cells were higher in children with recent infection than in those with an older history of disease (p < 0.0001 for all); similarly, the total and natural Tregs compartments were more represented in children at onset when compared with Long COVID (p < 0.0001 and p = 0.0005, respectively). Despite the heterogeneity, partially due to age, sex and infection incidence, the susceptibility of certain children to develop persistent symptoms after infection appeared to be associated with the imbalance of the adaptive immune response. Following up and comparing recovered versus Long COVID patients, we analyzed the role of circulating naïve and switched B and regulatory T lymphocytes in counteracting the evolution of the symptomatology emerged, finding an interesting correlation between the amount and ability to reconstitute the natural Tregs component with the persistence of symptoms (linear regression, p = 0.0026). Conclusions. In this study, we suggest that children affected by Long COVID may have a compromised ability to switch from the innate to the adaptive immune response, as supported by our data showing a contraction of naïve and switched B cell compartment and an unstable balance of regulatory T lymphocytes occurring in these children. However, further prospective immunological studies are needed to better clarify which factors (epigenetic, diet, environment, etc.) are involved in the impairment of the immunological mechanisms in the Long COVID patients.

Human Identical Sequences, hyaluronan, and hymecromone ─ the new mechanism and management of COVID-19

COVID-19 caused by SARS-CoV-2 has created formidable damage to public health and market economy. Currently, SARS-CoV-2 variants has exacerbated the transmission from person-to-person. Even after a great deal of investigation on COVID-19, SARS-CoV-2 is still rampaging globally, emphasizing the urgent need to reformulate effective prevention and treatment strategies. Here, we review the latest research progress of COVID-19 and provide distinct perspectives on the mechanism and management of COVID-19. Specially, we highlight the significance of Human Identical Sequences (HIS), hyaluronan, and hymecromone ("Three-H") for the understanding and intervention of COVID-19. Firstly, HIS activate inflammation-related genes to influence COVID-19 progress through NamiRNA-Enhancer network. Accumulation of hyaluronan induced by HIS-mediated HAS2 upregulation is a substantial basis for clinical manifestations of COVID-19, especially in lymphocytopenia and pulmonary ground-glass opacity. Secondly, detection of plasma hyaluronan can be effective for evaluating the progression and severity of COVID-19. Thirdly, spike glycoprotein of SARS-CoV-2 may bind to hyaluronan and further serve as an allergen to stimulate allergic reaction, causing sudden adverse effects after vaccination or the aggravation of COVID-19. Finally, antisense oligonucleotides of HIS or inhibitors of hyaluronan synthesis (hymecromone) or antiallergic agents could be promising therapeutic agents for COVID-19. Collectively, Three-H could hold the key to understand the pathogenic mechanism and create effective therapeutic strategies for COVID-19.

Dynamics of Neutralizing Antibody and T-Cell Responses to SARS-CoV-2 and Variants of Concern after Primary Immunization with CoronaVac and Booster with BNT162b2 or ChAdOx1 in Health Care Workers

Inactivated SARS-CoV-2 vaccine (CoronaVac) is commonly used in national immunization programs. However, the immune response significantly declines within a few months. Our study assessed the immune response against SARS-CoV-2 after receiving booster shots of BNT162b2 or ChAdOx1 among health care workers who previously received CoronaVac as their primary immunization. Fifty-six participants who received ChAdOx1 and forty-two participants who received BNT162b2 were enrolled into this study, which evaluated immune responses, including anti-SARS-CoV-2 spike total antibodies (Elecsys®), surrogated viral neutralization test (sVNT) to ancestral strain (cPass™; GenScript), five variants of concern (Alpha, Beta, Gamma, Delta, and Omicron) (Luminex; multiplex sVNT) and the ELISpot with spike (S1 and S2) peptide pool against the ancestral SARS-CoV-2 strain. The samples were analyzed at baseline, 4, and 12 weeks after primary immunization, as well as 4 and 12 weeks after receiving the booster. This study showed a significant increase in anti-SARS-CoV-2 spike total antibodies, sVNT, and T-cell immune response after the booster, including against the Omicron variant. Immune responses rapidly decreased in the booster group at 12 weeks after booster but were still higher than post-primary vaccination. A fourth dose or a second booster should be recommended, particularly in health care workers.

Calcium, Magnesium, and Zinc Supplementation during Pregnancy: The Additive Value of Micronutrients on Maternal Immune Response after SARS-CoV-2 Infection

Magnesium may contribute to the immune response during and after SARS-CoV-2 infection by acting as a cofactor for immunoglobulin production and other processes required for T and B cell activity. Considering magnesium as a recommended dietary supplement during pregnancy and the possible role of magnesium deficiency in COVID-19 and its complications, the current study sought to determine the effect of magnesium and magnesium-containing nutritional supplements on the immune response following SARS-CoV-2 infection in pregnant women, as well as to observe differences in pregnancy outcomes based on the supplements taken during pregnancy. The study followed a cross-sectional design, where patients with a history of SARS-CoV-2 infection during their pregnancy were surveyed for their preferences in nutritional supplementation and their profile compared with existing records from the institutional database. A cohort of 448 pregnant women with COVID-19 during 22 months of the pandemic was assembled, out of which 13.6% took a magnesium-only supplement, and 16.5% supplemented their diet with a combination of calcium, magnesium, and zinc. Around 60% of patients in the no-supplementation group had the SARS-CoV-2 anti-RBD lower than 500 U/mL, compared with 50% in those who took magnesium-based supplements. A quantity of magnesium >450 mg in the taken supplements determined higher levels of antibody titers after COVID-19. Low magnesium dosage (<450 mg) was an independent risk factor for a weak immune response (OR-1.25, p-value = 0.003). The observed findings suggest supplementing the nutritional intake of pregnant women with magnesium-based supplements to determine higher levels of SARS-CoV-2 anti-RBD antibodies, although causality remains unclear.