Restoration of dendritic cell homeostasis and Type I/Type III interferon levels in convalescent COVID-19 individuals

Evaluation of Dendritic Cell Subpopulations Frequency in COVID-19 Patients and their Correlation with Disease Severity

Background

COVID-19 (2019) clearly demonstrates an imbalanced immune response. Variations in the function and subtypes of dendritic cells (DCs) may have effects on immune responses in COVID-19 patients and contribute to immunopathology.

Objective

To assess the phenotype and frequency of Plasmacytoid dendritic cells (pDCs), Conventional DCs (cDCs), and double-positive DCs in COVID-19 patients admitted to the ICU and non-ICU compared to the healthy control group.

Methods

The study included 10 healthy individuals and 25 COVID-19 patients. In the second week of their illness, Peripheral blood mononuclear cells (PBMCs) were isolated from the patients and labeled with targeted antibodies for HLA-DR, CD123, and CD11c. The samples were then analyzed using flow cytometry. The COVID-19 patients were divided into two ICU and non-ICU groups and were closely monitored throughout the study.

Results

In comparison to healthy controls, COVID-19 patients exhibited a significantly lower pDCs ratio (P=0.04). Patients were categorized into two groups: (A) the ICU group (n=11; 44%) and (B) the non-ICU group (n=14; 56%). The frequency of pDC was significantly lower in ICU patients than in non-ICU patients (P<0.01). Although not statistically significant, ICU patients had a lower frequency of cDCs and double positive DCs compared to non-ICU patients. Additionally, a significant association between the age of COVID-19 patients and cDC levels was observed (p=0.049).

Conclusion

SARS-CoV-2 can evade attacks from the immune response by reducing the number of DCs and suppressing their function of DCs, ultimately resulting in weakened development of both innate and adaptive immunity.

Anti-interferon armamentarium of human coronaviruses

Cellular innate immune pathways are formidable barriers against viral invasion, creating an environment unfavorable for virus replication. Interferons (IFNs) play a crucial role in driving and regulating these cell-intrinsic innate antiviral mechanisms through the action of interferon-stimulated genes (ISGs). The host IFN response obstructs viral replication at every stage, prompting viruses to evolve various strategies to counteract or evade this response. Understanding the interplay between viral proteins and cell-intrinsic IFN-mediated immune mechanisms is essential for developing antiviral and anti-inflammatory strategies. Human coronaviruses (HCoVs), including SARS-CoV-2, MERS-CoV, SARS-CoV, and seasonal coronaviruses, encode a range of proteins that, through shared and distinct mechanisms, inhibit IFN-mediated innate immune responses. Compounding the issue, a dysregulated early IFN response can lead to a hyper-inflammatory immune reaction later in the infection, resulting in severe disease. This review provides a brief overview of HCoV replication and a detailed account of its interaction with host cellular innate immune pathways regulated by IFN.

Elucidating systemic immune responses to acute and convalescent SARS-CoV-2 infection in children and elderly individuals

BACKGROUND

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), a causative pathogen of the COVID-19 pandemic, affects all age groups. However, various studies have shown that COVID-19 presentation and severity vary considerably with age. We, therefore, wanted to examine the differences between the immune responses of children with COVID-19 and elderly COVID-19 individuals.

METHODS

We analyzed cytokines, chemokines, growth factors, and acute phase proteins in acute and convalescent COVID-19 children and the elderly with acute and convalescent COVID-19.

RESULTS

We show that most of the pro-inflammatory cytokines (interferon [IFN]γ, interleukin [IL]-2, tumor necrosis factor-α [TNFα], IL-1α, IFNα, IFNβ, IL-6, IL-12, IL-3, IL-7, IL-1Ra, IL-13, and IL-10), chemokines (CCL4, CCL11, CCL19, CXCL1, CXCL2, CXCL8, and CXL10), growth factors (vascular endothelial growth factor and CD40L) and acute phase proteins (C-reactive protein, serum amyloid P, and haptoglobin) were decreased in children with acute COVID 19 as compared with elderly individuals. In contrast, children with acute COVID-19 exhibited elevated levels of cytokines- IL-1β, IL-33, IL-4, IL-5, and IL-25, growth factors-fibroblast growth factor-2, platelet- derived growth factors-BB, and transforming growth factorα as compared with elderly individuals. Similar, differences were manifest in children and elderly with convalescent COVID-19.

CONCLUSION

Thus, COVID-19 children are characterized by distinct cytokine/chemokine/growth factor/acute phase protein markers that are markedly different from elderly COVID-19 individuals.

Tolerogenic dendritic cells in radiation-induced lung injury

Radiation-induced lung injury is a common complication associated with radiotherapy. It is characterized by early-stage radiation pneumonia and subsequent radiation pulmonary fibrosis. However, there is currently a lack of effective therapeutic strategies for radiation-induced lung injury. Recent studies have shown that tolerogenic dendritic cells interact with regulatory T cells and/or regulatory B cells to stimulate the production of immunosuppressive molecules, control inflammation, and prevent overimmunity. This highlights a potential new therapeutic activity of tolerogenic dendritic cells in managing radiation-induced lung injury. In this review, we aim to provide a comprehensive overview of tolerogenic dendritic cells in the context of radiation-induced lung injury, which will be valuable for researchers in this field.

Characterization of IL-10 Family of Cytokines in Acute and Convalescent COVID-19 Individuals

Cytokines are major players in orchestrating inflammation, disease pathogenesis, and severity during COVID-19. Members of the interleukin (IL)-10 family of cytokines play important roles in regulating immune responses to various inflammatory and infectious diseases. However, the role of the IL-10 family of cytokines in COVID-19 remains elusive. Hence, we determined the plasma levels of the IL-10 family of cytokines (IL-10, IL-19, IL-20, IL-22, and IL-24) in 7 groups of COVID-19 individuals, based on days since real-time reverse transcriptase-polymerase chain reaction confirmation of SARS-CoV-2 infection. Our data show that the levels of IL-10, IL-19, IL-20, IL-22, and IL-24 cytokines decreased from days 15-30 to days 61-90 and plateaued thereafter. Severe COVID-19 patients exhibit increased plasma levels of IL-10, IL-19, IL-20, IL-22, and IL-24 compared to mild patients. Thus, our study provides evidence of alterations in the plasma levels of the IL-10 family of cytokines in convalescent COVID-19 individuals.

IRF7: role and regulation in immunity and autoimmunity

Interferon regulatory factor (IRF) 7 was originally identified as master transcriptional factor that produced IFN-I and regulated innate immune response, subsequent studies have revealed that IRF7 performs a multifaceted and versatile functions in multiple biological processes. In this review, we provide a comprehensive overview on the current knowledge of the role of IRF7 in immunity and autoimmunity. We focus on the latest regulatory mechanisms of IRF7 in IFN-I, including signaling pathways, transcription, translation, and post-translational levels, the dimerization and nuclear translocation, and the role of IRF7 in IFN-III and COVID-19. In addition to antiviral immunity, we also discuss the role and mechanism of IRF7 in autoimmunity, and the further research will expand our understanding of IRF7.

Novel evidence of Thymosin α1 immunomodulatory properties in SARS-CoV-2 infection: Effect on innate inflammatory response in a peripheral blood mononuclear cell-based in vitro model

The peculiar property of Thymosin alpha 1 (Tα1) to act as master regulator of immune homeostasis has been successfully defined in different physiological and pathological contexts ranging from cancer to infection. Interestingly, recent papers also demonstrated its mitigating effect on the "cytokine storm" as well as on the T-cell exhaustion/activation in SARS-CoV-2 infected individuals. Nevertheless, in spite of the increasing knowledge on Tα1-induced effects on T cell response confirming the distinctive features of this multifaceted peptide, little is known on its effects on innate immunity during SARS-CoV-2 infection. Here, we interrogated peripheral blood mononuclear cell (PBMC) cultures stimulated with SARS-CoV-2 to disclose Tα1 properties on the main cell players of early response to infection, namely monocytes and myeloid dendritic cells (mDC). Moving from ex vivo data showing an enhancement in the frequency of inflammatory monocytes and activated mDC in COVID-19 patients, a PBMC-based experimental setting reproduced in vitro a similar profile with an increased percentage of CD16⁺ inflammatory monocytes and mDC expressing CD86 and HLA-DR activation markers in response to SARS-CoV-2 stimulation. Interestingly, the treatment of SARS-CoV-2-stimulated PBMC with Tα1 dampened the inflammatory/activation status of both monocytes and mDC by reducing the release of pro-inflammatory mediators, including TNF-α, IL-6 and IL-8, while promoting the production of the anti-inflammatory cytokine IL-10. This study further clarifies the working hypothesis on Tα1 mitigating action on COVID-19 inflammatory condition. Moreover, these evidence shed light on inflammatory pathways and cell types involved in acute SARS-CoV-2 infection and likely targetable by newly immune-regulating therapeutic approaches.

Immune responses in mildly versus critically ill COVID-19 patients

The current coronavirus pandemic (COVID-19), caused by SARS-CoV-2, has had devastating effects on the global health and economic system. The cellular and molecular mediators of both the innate and adaptive immune systems are critical in controlling SARS-CoV-2 infections. However, dysregulated inflammatory responses and imbalanced adaptive immunity may contribute to tissue destruction and pathogenesis of the disease. Important mechanisms in severe forms of COVID-19 include overproduction of inflammatory cytokines, impairment of type I IFN response, overactivation of neutrophils and macrophages, decreased frequencies of DC cells, NK cells and ILCs, complement activation, lymphopenia, Th1 and Treg hypoactivation, Th2 and Th17 hyperactivation, as well as decreased clonal diversity and dysregulated B lymphocyte function. Given the relationship between disease severity and an imbalanced immune system, scientists have been led to manipulate the immune system as a therapeutic approach. For example, anti-cytokine, cell, and IVIG therapies have received attention in the treatment of severe COVID-19. In this review, the role of immunity in the development and progression of COVID-19 is discussed, focusing on molecular and cellular aspects of the immune system in mild vs. severe forms of the disease. Moreover, some immune- based therapeutic approaches to COVID-19 are being investigated. Understanding key processes involved in the disease progression is critical in developing therapeutic agents and optimizing related strategies.