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A hepatitis B virus (HBV) infection can progress to chronic hepatitis, leading to liver fibrosis, cirrhosis, and hepatocellular carcinoma. CX3CL1/Fractalkine plays a crucial role in recruiting immune cells that are responsible for protecting against HBV infection. The aim of this study was to measure CX3CL1/Fractalkine concentrations in the blood plasma of individuals infected with HBV and to evaluate the role of this chemokine in the development of liver tissue fibrosis. Our study included patients infected with HBV, patients infected with HCV, autoimmune hepatitis, and healthy donors. We analyzed the CX3CL1/Fractalkine concentrations in blood plasma using the xMAP technology. Our results showed that HBV-infected patients had lower concentrations of CX3CL1/Fractalkine. Furthermore, in HBV-infected patients with severe fibrosis/cirrhosis, we observed significantly lower concentrations of CX3CL1/Fractalkine compared to those with no/mild fibrosis. Our study revealed that CX3CL1/Fractalkine concentrations are significantly associated with the stage of fibrosis in HBV infection. We demonstrated that lowered CX3CL1/Fractalkine concentrations might have prognostic value for predicting fibrosis development in liver tissue. Our findings suggest that decreased concentrations of CX3CL1/Fractalkine are associated with an increased risk of progressive liver fibrosis, indicating the potential of this chemokine as a prognostic biomarker for the development of liver fibrosis.

Hepatitis B is an infectious disease resulting from infection with the hepatitis B virus. Chronic hepatitis B (CHB) is characterized by prolonged inflammation in the liver, the development of fibrosis, liver cirrhosis and hepatocellular carcinoma. Factors of the immune system play a critical role in the pathogenesis of CHB. Thanks to chemokines, immune cells migrate to the site of inflammation to implement their effector functions. The CX3CL1/Fractalkine chemokine is the only member of the CX3C family of chemokines with unique structural and functional properties. Its receptor CX3CR1 is expressed mainly on the surface of cytotoxic effector lymphocytes such as NK cells, TNK and cytotoxic T lymphocytes. The purpose of our study was to analyze the content of CX3CL1/Fractalkine in the blood plasma of patients with CHB and the analysis of this chemokine with liver fibrosis. The concentration of CX3CL1/Fractalkine was determined in the blood plasma of patients with CHB using a multiplex assay based on xMAP technology. Blood plasma from patients with chronic viral hepatitis C (CHC) and autoimmune liver diseases (AILD) was used as a comparison group. The control group consisted of healthy individuals. For statistical analysis of data, nonparametric statistics methods were used: Kruskal–Wallis test, Spearman correlation coefficient ROC-analysis. It was shown a reduced level of CX3CL1/Fractalkine in patients with CHB compared with the control group (p = 0.0003) and with the comparison groups of CHC (p 0.0001) and AILD (p = 0.0005). A reduced concentration of CX3CL1/Fractalkine was shown in the blood plasma of CHB patients with initial fibrosis (p = 0.0092) and severe fibrosis/cirrhosis (p = 0.0009), while in patients with severe fibrosis/cirrhosis, a significantly reduced level of this chemokine was established compared with the initial degree of liver fibrosis (p = 0.0081). Correlation analysis revealed a highly significant inverse relationship between the severity of liver fibrosis and the content of CX3CL1/Fractalkine in the blood plasma of patients with CHB (Spearman r = –0.33; p = 0.02). Thus, the chemokine CX3CL1/Fractalkine is included in the immunopathogenesis of CHB; its reduced content is characteristic only of CHB and does not change in other chronic liver diseases. It is involved in the processes of liver fibrosis during infection with the hepatitis B virus. The concentration of the chemokine CX3CL1/Fractalkine depends on the stage of liver fibrosis in CHB, and a decrease in the level of CX3CL1/Fractalkine in the blood plasma can serve as a negative factor in the development of CHB.

According to the WHO data, the number of infected people exceeded 765.2 million people during the COVID-19 pandemic. The severity of patient’s condition is determined by immune system hyperactivation. Activation of T- and B-lymphocyte subsets plays a prominent role in the control of infectious process. A content of small circular DNA molecules — T-cell receptor excision circles (TREC — T-cell receptor excision circles) and B-cell (“kappa”) excision rings (KREC — Kappa-deleting recombination excision circles) — in the peripheral blood can be used as a marker of the functionally active T and B cells maturation. The purpose of this work is to quantify peripheral blood TREC and KREC level in patients with the new coronavirus infection COVID-19 of varying severity.Materials and methods.The material consisted of 1028 blood samples from patients with a confirmed diagnosis of COVID-19, as well as 717 blood samples from apparently healthy volunteers. The content of TREC and KREC DNA fragments in the total DNA fraction was assessed by quantitative Real-time PCR using the “TREC/KREC-AMP PS” test system (St. Petersburg Pasteur Institute, Russia). Blood cell phenotyping was carried out using flow cytometry.Results.TREC/KREC levels were significantly reduced in COVID-19 patients (p 0.0001 at 95% CI). A significant direct correlation was established between the levels of peripheral blood TREC molecules and level of CD45+CD3+CD19–T cells (r = 0.59, p 0.0001), as well as between KREC level and count of CD45+CD3–CD19+B cells (r = 0.66, p 0.0001). The level of TREC molecules in patients with severe vs. moderate infection was significantly reduced in patients aged 30–39 years old (p = 0.0404) and 40–49 years old (p = 0.0356). The negative correlation between severity of COVID-19 clinical manifestations and TREC level in the blood of patients in 30–49 year age group indicates about an opportunity of using this analyte as a diagnostic and prognostic laboratory marker of patient’s condition. A simple PCR analysis algorithm makes it relevant to use the described method for assessing a state of immunity in coronavirus patients in the context of systemic negative impact of the SARS-CoV-2 virus on human organism.

Cytokine storm is usually described as one of the main reasons behind COVID-associated mortality. Cytokines are essential protein molecules engaged in immune responses; they play a critical role in protection against infections. However, they also contribute to inflammatory reactions and tissue damage, becoming a double-edged sword in the context of COVID-19. Recent studies have suggested various cytokines and chemokines that play a crucial role in the immune response to SARS-CoV-2 infection. One such cytokine is interleukin 27 (IL-27), which has been found to be elevated in the blood plasma of patients with COVID-19. Within this study, we will explore the role of IL-27 in immune responses and analyze both the existing literature and our own prior research findings on this cytokine in the context of COVID-19. It affects a wide variety of immune cells. Regardless of the pathological process it is involved in, IL-27 is critical for upholding the necessary balance between tissue damage and cytotoxicity against infectious agents and/or tumors. In COVID-19, it is involved in multiple processes, including antiviral cytotoxicity via CD8+ cells, IgG subclass switching, and even the activation of Tregs.

Macrophage-derived chemokine (MDC/CCL22) is a chemokine of the C-C subfamily. It is involved in T-cellular maturation and migration. Our previous research shows that plasma CCL22/MDC tends to show a statistically significant depletion of concentrations in acute patients and convalescents when compared to healthy donors. In the current work, we investigate existing views on MDC/CCL22 dynamics in association with various pathologies, including respiratory diseases and, specifically, COVID-19. Additionally, we present our explanations for the observed decrease in MDC/CCL22 concentrations in COVID-19. The first hypothesis we provide implies that viral products bind to MDC/CCL22 and block its activity. Another explanation for this phenomenon is based on dendritic cells population and the inhibition of their function.

Background. Humoral immunity requires interaction between B cell and T follicular helper cells (Tfh) to produce effective immune response, but the data regarding a role of B cells and Tfh in SARS-CoV-2 defense are still sparse. Methods. Blood samples from patients with acute COVID-19 (n = 64), convalescents patients who had specific IgG to SARS-CoV-2 N-protein (n = 55), and healthy donors with no detectable antibodies to any SARS-CoV-2 proteins (HC, n = 44) were analyses by multicolor flow cytometry. Results. Patients with acute COVID-19 showed decreased levels of memory B cells subsets and increased proportion plasma cell precursors compared to HC and COVID-19 convalescent patients, whereas for the latter the elevated numbers of virgin naïve, Bm2′ and “Bm3+Bm4” was found if compared with HC. During acute COVID-19 CXCR3+CCR6− Tfh1-like cells were decreased and the levels of CXCR3−CCR6+ Tfh17-like were increased then in HC and convalescent patients. Finally, COVID-19 convalescent patients had increased levels of Tfh2-, Tfh17- and DP Tfh-like cells while comparing their amount with HC. Conclusions. Our data indicate that COVID-19 can impact the humoral immunity in the long-term.

Purpose: The aim of this research is to develop an accurate and interpretable aggregated score not only for hospitalization outcome prediction (death/discharge) but also for the daily assessment of the COVID-19 patient's condition.Patients and Methods: In this single-center cohort study, real-world data collected within the first two waves of the COVID-19 pandemic was used (27.04.2020–03.08.2020 and 01.11.2020–19.01.2021, respectively). The first wave data (1,349 cases) was used as a training set for the score development, while the second wave data (1,453 cases) was used as a validation set. No overlapping cases were presented in the study. For all the available patients' features, we tested their association with an outcome. Significant features were taken for further analysis, and their partial sensitivity, specificity, and promptness were estimated. Sensitivity and specificity were further combined into a feature informativeness index. The developed score was derived as a weighted sum of nine features that showed the best trade-off between informativeness and promptness.Results: Based on the training cohort (median age ± median absolute deviation 58 ± 13.3, females 55.7%), the following resulting score was derived: APTT (4 points), CRP (3 points), D-dimer (4 points), glucose (4 points), hemoglobin (3 points), lymphocytes (3 points), total protein (6 points), urea (5 points), and WBC (4 points). Internal and temporal validation based on the second wave cohort (age 60 ± 14.8, females 51.8%) showed that a sensitivity and a specificity over 90% may be achieved with an expected prediction range of more than 7 days. Moreover, we demonstrated high robustness of the score to the varying peculiarities of the pandemic.Conclusions: An extensive application of the score during the pandemic showed its potential for optimization of patient management as well as improvement of medical staff attentiveness in a high workload stress. The transparent structure of the score, as well as tractable cutoff bounds, simplified its implementation into clinical practice. High cumulative informativeness of the nine score components suggests that these are the indicators that need to be monitored regularly during the follow-up of a patient with COVID-19.

This study is a successor of our previous work concerning changes in the chemokine profile in infection that are associated with different SARS-CoV-2 genetic variants. The goal of our study was to take into account both the virus and the host immune system by assessing concentrations of cytokines in patients infected with different SARS-CoV-2 variants (ancestral Wuhan strain, Alpha, Delta and Omicron). Our study was performed on 340 biological samples taken from COVID-19 patients and healthy donors in the timespan between May 2020 and April 2022. We performed genotyping of the virus in nasopharyngeal swabs, which was followed by assessment of cytokines’ concentration in blood plasma. We noted that out of nearly 30 cytokines, only four showed stable elevation independently of the variant (IL-6, IL-10, IL-18 and IL-27), and we believe them to be ‘constant’ markers for COVID-19 infection. Cytokines that were studied as potential biomarkers lose their diagnostic value as the virus evolves, and the specter of potential targets for predictive models is narrowing. So far, only four cytokines (IL-6, IL-10, IL-18, and IL-27) showed a consistent rise in concentrations independently of the genetic variant of the virus. Although we believe our findings to be of scientific interest, we still consider them inconclusive; further investigation and comparison of immune responses to different variants of SARS-CoV-2 is required.

Background. The adaptive antiviral immune response requires interaction between CD8+ T cells, dendritic cells, and Th1 cells for controlling SARS-CoV-2 infection, but the data regarding the role of CD8+ T cells in the acute phase of COVID-19 and post-COVID-19 syndrome are still limited. Methods.. Peripheral blood samples collected from patients with acute COVID-19 (n = 71), convalescent subjects bearing serum SARS-CoV-2 N-protein-specific IgG antibodies (n = 51), and healthy volunteers with no detectable antibodies to any SARS-CoV-2 proteins (HC, n = 46) were analyzed using 10-color flow cytometry. Results. Patients with acute COVID-19 vs. HC and COVID-19 convalescents showed decreased absolute numbers of CD8+ T cells, whereas the frequency of CM and TEMRA CD8+ T cells in acute COVID-19 vs. HC was elevated. COVID-19 convalescents vs. HC had increased naïve and CM cells, whereas TEMRA cells were decreased compared to HC. Cell-surface CD57 was highly expressed by the majority of CD8+ T cells subsets during acute COVID-19, but convalescents had increased CD57 on ‘naïve’, CM, EM4, and pE1 2–3 months post-symptom onset. CXCR5 expression was altered in acute and convalescent COVID-19 subjects, whereas the frequencies of CXCR3+ and CCR4+ cells were decreased in both patient groups vs. HC. COVID-19 convalescents had increased CCR6-expressing CD8+ T cells. Moreover, CXCR3+CCR6- Tc1 cells were decreased in patients with acute COVID-19 and COVID-19 convalescents, whereas Tc2 and Tc17 levels were increased compared to HC. Finally, IL-27 negatively correlated with the CCR6+ cells in acute COVID-19 patients. Conclusions. We described an abnormal CD8+ T cell profile in COVID-19 convalescents, which resulted in lower frequencies of effector subsets (TEMRA and Tc1), higher senescent state (upregulated CD57 on ‘naïve’ and memory cells), and higher frequencies of CD8+ T cell subsets expressing lung tissue and mucosal tissue homing molecules (Tc2, Tc17, and Tc17.1). Thus, our data indicate that COVID-19 can impact the long-term CD8+ T cell immune response.

Background. Infection caused by SARS-CoV-2 mostly affects the upper and lower respiratory tracts and causes symptoms ranging from the common cold to pneumonia with acute respiratory distress syndrome. Chemokines are deeply involved in the chemoattraction, proliferation, and activation of immune cells within inflammation. It is crucial to consider that mutations within the virion can potentially affect the clinical course of SARS-CoV-2 infection because disease severity and manifestation vary depending on the genetic variant. Our objective was to measure and assess the different concentrations of chemokines involved in COVID-19 caused by different variants of the virus. Methods. We used the blood plasma of patients infected with different variants of SARS-CoV-2, i.e., the ancestral Wuhan strain and the Alpha, Delta, and Omicron variants. We measured the concentrations of 11 chemokines in the samples: CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, CCL7/MCP-3, CCL11/Eotaxin, CCL22/MDC, CXCL1/GROα, CXCL8/IL-8, CXCL9/MIG, CXCL10/IP-10, and CX3CL1/Fractalkine. Results. We noted a statistically significant elevation in the concentrations of CCL2/MCP-1, CXCL8/IL-8, and CXCL1/IP-10 independently of the variant, and a drop in the CCL22/MDC concentrations. Conclusions. The chemokine concentrations varied significantly depending on the viral variant, leading us to infer that mutations in viral proteins play a role in the cellular and molecular mechanisms of immune responses.

IgG is the most prominent marker of post-COVID-19 immunity. Not only does this subtype mark the late stages of infection, but it also stays in the body for a timespan of at least 6 months. However, different IgG subclasses have different properties, and their roles in specific anti-COVID-19 responses have yet to be determined. We assessed the concentrations of IgG1, IgG2, IgG3, and IgG4 against different SARS-CoV-2 antigens (N protein, S protein RBD) using a specifically designed method and samples from 348 COVID-19 patients. We noted a statistically significant association between severity of COVID-19 infection and IgG concentrations (both total and subclasses). When assessing anti-N protein and anti-RBD IgG subclasses, we noted the importance of IgG3 as a subclass. Since it is often associated with early antiviral response, we presumed that the IgG3 subclass is the first high-affinity IgG antibody to be produced during COVID-19 infection.

Chronic hepatitis C (CHC) represents a significant public health concern. In the majority of cases, the infection progresses to a chronic form, which is characterised by the development of fibrosis and cirrhosis of the liver. A plethora of cytokines and chemokines are generated as a consequence of inflammatory processes within the liver. These can exert a dual effect, both protective and damaging, particularly in relation to the death of hepatocytes and the progression of liver fibrosis. Furthermore, a number of growth factors have been identified as playing a role in the pathogenesis of CHC. The objective of the study was a comprehensive evaluation of a wide range of cytokines, chemokines and growth factors in the blood plasma of patients with CHC at varying stages of liver fibrosis. The study cohort comprised 63 patients diagnosed with CHC, who were divided into three groups according to the stage of liver fibrosis. The control group comprised healthy individuals (n=32). Concentrations of the following cytokines were determined in plasma: Interleukins and some cytokines (IL-1α, IL-1β, IL-1RA, IL-2, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-12 (p40), IL-12 (p70), IL-13, IL-15, IL-17A, IL-17-E/IL-25, IL-17F, IL-18, IL-27, IFNα, IFNγ, TNFα, TNFβ); chemokines (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, CCL7/MCP-3, CCL11/Eotaxin, CCL22/MDC, CXCL1/GROα, CXCL8/IL-8, CXCL9/MIG, CXCL10/IP-10, CX3CL1/Fractalkine) and growth factors (EGF, FGF-2, Flt-3L, G-CSF, M-CSF, PDGF-AA, PDGF-AB/BB, TGFα, VEGF-A) by multiplex analysis based on xMAP technology. Nonparametric statistics methods were used for statistical analysis. As a result of the study, increased concentrations of cytokines IL-12 (p40), IL-15, IL-17E/IL-25, IL-27, IFNγ, TNFα, chemokines CXCL9/MIG and CXCL-10/IP-10 and growth factors FGF-2 and M-CSF were found at all stages of liver fibrosis. Elevated concentrations of cytokines IL-1α, IL-1β, IL-2, IL-6, IL-9, IL-10, IL-17F, IFNα, TNFβ, chemokines CCL2/MCP-1, CCL11/Eotaxin, CCL22/MDC and growth factors G-CSF, TGFα, Flt-3L were found in severe liver fibrosis/cirrhosis. Correlation analysis revealed a relationship of high significance between the severity of liver fibrosis and the content of cytokines IL-6, IFNγ, TNFα, IL-7, chemokines CCL2/MCP-1, CCL11/Eotaxin, CXCL9/MIG, CXCL10/IP-10, CXCL1/GROα, growth factors TGFα, PDGF-AA, PDGF-AB/BB. Thus, a certain profile of cytokines characteristic for CHC was revealed, cytokines, chemokines and growth factors significant for liver fibrosis in CHC were found.