ABSTRACT
Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2-4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells - basophiles and eosinophils - were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased "regulatory" Tfh1 cell and increased "pro-inflammatory" Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of "naive" and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24- plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.Copyright © 2022 Saint Petersburg Pasteur Institute. All rights reserved.
ABSTRACT
Current review presents a brief overview of the immune system dysregulation during acute COVID-19 and illustrates the main alterations in peripheral blood CD4+ T-cell (Th) subsets as well as related target cells. Effects of dendritic cell dysfunction induced by SARS-CoV-2 exhibited decreased expression of cell-surface HLA-DR, CCR7 as well as co-stimulatory molecules CD80 and CD86, suggesting reduced antigen presentation, migratory and activation capacities of peripheral blood dendritic cells. SARS-CoV-2-specific Th cells could be detected as early as days 2–4 post-symptom onset, whereas the prolonged lack of SARS-CoV-2-specific Th cells was associated with severe and/or poor COVID-19 outcome. Firstly, in acute COVID-19 the frequency of Th1 cell was comparable with control levels, but several studies have reported about upregulated inhibitory immune checkpoint receptors and exhaustion-associated molecules (TIM3, PD-1, BTLA, TIGIT etc.) on circulating CD8+ T-cells and NK-cells, whereas the macrophage count was increased in bronchoalveolar lavage (BAL) samples. Next, type 2 immune responses are mediated mainly by Th2 cells, and several studies have revealed a skewing towards dominance of Th2 cell subset in peripheral blood samples from patients with acute COVID-19. Furthermore, the decrease of circulating main Th2 target cells — basophiles and eosinophils — were associated with severe COVID-19, whereas the lung tissue was enriched with mast cells and relevant mediators released during degranulation. Moreover, the frequency of peripheral blood Th17 cells was closely linked to COVID-19 severity, so that low level of Th17 cells was observed in patients with severe COVID-19, but in BAL the relative number of Th17 cells as well as the concentrations of relevant effector cytokines were dramatically increased. It was shown that severe COVID-19 patients vs. healthy control had higher relative numbers of neutrophils if compared, and the majority of patients with COVID-19 had increased frequency and absolute number of immature neutrophils with altered ROS production. Finally, the frequency of Tfh cells was decreased during acute COVID-19 infection. Elevated count of activated Tfh were found as well as the alterations in Tfh cell subsets characterized by decreased "regulatory” Tfh1 cell and increased "pro-inflammatory” Tfh2 as well as Tfh17 cell subsets were revealed. Descriptions of peripheral blood B cells during an acute SARS-CoV-2 infection werev reported as relative B cell lymphopenia with decreased frequency of "naïve” and memory B cell subsets, as well as increased level of CD27hiCD38hiCD24– plasma cell precursors and atypical CD21low B cells. Thus, the emerging evidence suggests that functional alterations occur in all Th cell subsets being linked with loss-of-functions of main Th cell subsets target cells. Furthermore, recovered individuals could suffer from long-term immune dysregulation and other persistent symptoms lasting for many months even after SARS-CoV-2 elimination, a condition referred to as post-acute COVID-19 syndrome.
ABSTRACT
Background & Aim: Due to its immunomodulatory potential, therapy based on the transfer of regulatory T cells (Tregs) has acquired great interest in the treatment of diseases in which it is necessary to restore immune homeostasis. Until now, autologous Treg cell therapy has proven to be safe, but the employment of blood as the source of Treg presents several limitations in terms of Treg recovery and the quality of the employed Tregs. Our group has developed a new technology to produce massive amounts of GMP Treg derived from the pediatric thymic tissue discarded in pediatric cardiac surgeries (thyTreg) that could overcome the main obstacles. Indeed, we are employing thyTreg cells with success in a clinical trial as autologous cell therapy in transplanted children. Given the large amounts of thyTreg that can be obtained from a single thymus, the main objective of this work is to evaluate the immunogenicity of thyTreg and confirm that its immature phenotype makes possible the allogeneic use of this cellular therapy in order to treat a range of immune diseases and patients. Methods, Results & Conclusion: The thyTreg obtained in the laboratory using the protocol developed by our group exhibit high viability (>90%) and high purity (>80%) in terms of CD25+FoxP3+ expression. ThyTreg have been observed to express low levels of immunogenicity markers (CD40L, CD80, CD86) by flow cytometry. Moreover, in vitro models of thyTreg co-culture with allogeneic peripheral blood mononuclear cells (PBMC) from healthy donors have been performed to i) determine if thyTreg generate an immunogenic response on PBMC, and ii) evaluate the capacity of thyTreg to suppress the proliferation of allogeneic PBMC. Even that the HLA disparity in the allogeneic cocultures between thyTreg and PBMC was high (13 of the 21 typed pairs had HLA <4/12 concordance), thyTreg did not induce the expression of activation markers (CD25, CD69) nor the proliferation or the production of pro-inflammatory cytokines (IFN-g) by allogeneic PBMCs. Moreover, thyTreg greatly inhibit the proliferation of allogeneic CD4 and CD8 T cells, reaching levels of around 70% inhibition of proliferation at a 1: 1 ratio. The results suggest that allogenic thyTreg are not immunogenic and are capable of exerting their suppressive function in an allogeneic context, indicating their possible off-the-shelf use as a treatment for transplant rejection, graft-versus- host disease, autoimmune diseases or the cytokine release syndrome characteristic of severe COVID-19 patients.
ABSTRACT
Rationale: Despite the availability of pharmacologic therapies, idiopathic pulmonary fibrosis (IPF) is still a clinical challenge with several unmet needs. Robust evidence supports monocytes as cellular biomarkers of progression in IPF. Yet, their precise role and whether specific subtypes might predict progression and drive disease is unknown. We reported, for the first time, that myeloidderived suppressor cells (MDSC), immature precursors of monocytes, are increased in numbers, functionally active in IPF. Monocytic MDSC is the predominant subtype in IPF, and yet, functional characterization and immune modulation properties have not been explored. Methods and Results: characterization of circulating myeloid populations in IPF by multicolor FACS confirmed the abundance of MDSC (Lin-, HLA-DRlo, CD33+, CD14+, S100A+, CD28L1+ and ICOSL+) in IPF (n=78) and fILD (n=83), also abundant in whole blood scRNA seq of severe Covid-19 patients that progressed into fibrosis, and not in mild Covid-19. Then, we prospectively followed 83 fILD patients (45% IPF, 55% non-IPF -EAA, CTD-ILD, NSIP-) over 1 year and immunophenotyped them every 3 months. Cross-sectional analysis showed that patients with a higher number circulating MDSC, had a higher GAP index (7-8) (p<0,001). Longitudinal follow-up showed that patients with constant higher circulating MDSC had lower transplant-free survival (p=0.0058). Primary isolated MDSC when co-cultured with autologous T cells induced CD8+ T cell exhaustion (PD1hi, Lag3hi, Tim3hi, TNFalpha lo, INFglo), and downregulation of co-stimulatory T cell signaling (CD28, ICOS, ITK, and LCK), preliminary data support the induction of de-novo FoxP3 Treg formation, creating a suppressive and immunosenescent microenvironment in IPF. FACS analysis of explanted lungs demonstrated the increase of tissue-resident MDSC in fibrosis (HP, NSIP, IPF) compared with donor lungs, as well as in bleomycin-induced fibrosis compared to PBS. Conclusion: Taking together, a high number of circulating MDSC reflects worse lung function and higher GAP index in cross-sectional analysis, and associates with lower transplant-free survival longitudinally. The role that immature and mature monocytes play during promotion of a suppressive microenvironment in IPF is an unexplored area that may lead to a paradigm shift in our understanding of the sequelae of exhaustion and immunosenescence, contributing to the identification of novel targets useful for therapeutic myeloid selection in IPF.
ABSTRACT
Background. The initial response of immune cells against respiratory viruses often determines the severity and duration of disease. The early trajectory of the immune response during infection with SARS-CoV-2 remains poorly understood. Dysregulation of innate immune factors that facilitate viral clearance and the adaptive response, such as type I interferons, have been implicated in severe COVID-19. However, collection of biological samples during the first seven days post-symptom onset has posed a logistical challenge, limiting our knowledge surrounding the immune responses that drive protection versus immunopathology. Methods. From March 2020, Military Health System beneficiaries presenting with a positive SARS-CoV-2 test, a COVID-19 like illness, or a high-risk SARS-CoV-2 exposure at nine military medical treatment facilities across the United States were eligible for enrollment in our longitudinal cohort study, which included collection of respiratory sample, sera, plasma, and peripheral blood mononuclear cells (PBMCs). Twenty-five SARS-CoV-2 infected study participants provided samples with in the first seven days of symptom onset, fifteen of whom were hospitalized with COVID-19. We employed multiparameter spectral flow cytometry to comprehensively analyze the early trajectory of the innate and adaptive immune responses. Results. We discovered that early activation of critical antigen presenting cell subsets was impaired upon comparing inpatients with outpatients, correlating with decreased antigen-experienced T cell responses. Specifically, we noted reduced expression of key costimulatory molecules, CD80 and CD86, on conventional dendritic cells that are required for viral antigen-specific T cell priming. Reduction in CD38, a marker of activation was also observed on inpatient dendritic cell subsets. Conclusion. Reduced antigen presenting cell activation and expression of ligands that facilitate T cell engagement may impede the efficient clearance of SARS-CoV-2, coinciding with more severe disease in our cohort. Further analysis of the functional activation of early innate immune responses triggered by SARS-CoV-2 may unveil new immune biomarkers and therapeutic targets to predict and prevent severe disease associated with inadequate T cell immunity.
ABSTRACT
The introduction of post-transplant cyclophosphamide (PTCy) has circumvented the need for T-cell depletion following haploidentical stem cell transplantation (SCT). By expanding the donor pool for patients from certain ethnic minorities, this has addressed to some degree an important health care disparity issue in SCT. However, a recent registry study showed increased incidence GvHD and inferior outcomes in patients receiving haploidentical SCT with PTCy, tacrolimus and mycophenolate mofetil for GvHD prevention as opposed to matched unrelated donor SCT with PTCy-based GvHD prevention. Seeking to improve the results of GvHD prevention in the setting of haploidentical SCT, we examined a combination of PTCy, abatacept and a short course of tacrolimus (CAST). Abatacept is a recombinant soluble fusion protein composed of the extracellular domain of cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) fused to the Fc region of IgG1. Abatacept blocks CD28-CD80I86 axis and prevents T-cell co-stimulation. In early studies, abatacept has shown promising results when added to methotrexate and tacrolimus in matched and mismatched donor SCT. We initiated a phase Ib-II clinical trial for patients with hematological malignancies undergoing haploidentical SCT. Patients received G-CSF mobilized peripheral blood grafts from related haploidentical donors. GvHD prevention consisted of PTCy 50mg/kg IV on day +3 and +4 with forced hydration, abatacept 10mg/kg IV on day +5, +14 and +28 and tacrolimus. Tacrolimus was started on day +5 at 0.02mg/kg/day by continuous IV and adjusted thereafter to maintain a trough level of 5-12ng/mL. Tacrolimus taper was planned to begin on day +60 and complete by day +90 in the absence of GvHD. All patients received standard supportive care including levofloxacin until neutrophil engraftment, posaconazole until day +75, acyclovir for 1 year and, if CMV positive by serology, letermovir until day +100. Pneumocystis Jiroveci prophylaxis was started after neutrophil engraftment and continued until 6 months post-transplant. G-CSF was administered routinely until neutrophil engraftment. Since September 2020, 19 patients were enrolled. Three patients are too early in their post-transplant course and were excluded from this analysis. Patients' characteristics are summarized in the table. All but 2 patients received cryopreserved products. Median times to ANC and platelet engraftment were 18.5 days (14-30) and 28.5 (16-61). All 16 patients achieved full whole blood donor chimerism by day +30. There was no secondary graft failure. With a median follow-up was 149.5 days (41-308) with 10 patients having >120 days and 8 >180 days of follow-up, 4 patients developed skin acute GvHD (all grade I). No patient developed grade II-IV acute GvHD. Two patients developed skin chronic GvHD (limited, both moderate). Both cases were diagnosed following COVID-19 vaccination. Fifteen patients completed tacrolimus taper by day +90. Two patients received systemic steroids, one for treatment of cGvHD. The remaining patients required no further immunosuppressive therapy beyond day +90. CMV activation rate was 25%. One patient had EBV reactivation and required preemptive therapy with 2 weekly rituximab doses. There were no cases of adenovirus, HHV-6 virus or BK virus reactivation. Four patients developed renal insufficiency (3 in the setting of acute sepsis and 1 with thrombotic microangiopathy, which resolved after tapering off tacrolimus. One patient with adult T-cell leukemia/lymphoma relapsed and died. All other patients are alive and well. In summary, our preliminary results suggest that CAST with shortened course of tacrolimus is feasible and seems to offer very promising outcomes with low rates of acute GvHD. The study is accruing actively and the results of a larger cohort with longer follow-up will be presented at the meeting. If confirmed, by improving the outcomes of haploidentical SCT, this regimen may further address a health care disparity issue, offering almost every patient in need of allogeneic SCT an alternative donor op ion with equal outcomes. [Formula presented] Disclosures: Al-Homsi: Daichii Sanyko: Consultancy;Celyad: Other: Advisory Board. Abdul-Hay: Abbvie: Consultancy;Servier: Other: Advisory Board, Speakers Bureau;Jazz: Other: Advisory Board, Speakers Bureau;Takeda: Speakers Bureau;Amgen: Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Abatacept - off label use as GvHD prevention Cyclophosphamide - off label use as GvHD prevention