Tyrosine kinase 2 modulates splenic B cells through type I IFN and TLR7 signaling

Tyrosine kinase 2 (TYK2) is involved in type I interferon (IFN-I) signaling through IFN receptor 1 (IFNAR1). This signaling pathway is crucial in the early antiviral response and remains incompletely understood on B cells. Therefore, to understand the role of TYK2 in B cells, we studied these cells under homeostatic conditions and following in vitro activation using Tyk2-deficient (Tyk2-/-) mice. Splenic B cell subpopulations were altered in Tyk2-/- compared to wild type (WT) mice. Marginal zone (MZ) cells were decreased and aged B cells (ABC) were increased, whereas follicular (FO) cells remained unchanged. Likewise, there was an imbalance in transitional B cells in juvenile Tyk2-/- mice. RNA sequencing analysis of adult MZ and FO cells isolated from Tyk2-/- and WT mice in homeostasis revealed altered expression of IFN-I and Toll-like receptor 7 (TLR7) signaling pathway genes. Flow cytometry assays corroborated a lower expression of TLR7 in MZ B cells from Tyk2-/- mice. Splenic B cell cultures showed reduced proliferation and differentiation responses after activation with TLR7 ligands in Tyk2-/- compared to WT mice, with a similar response to lipopolysaccharide (LPS) or anti-CD40 + IL-4. IgM, IgG, IL-10 and IL-6 secretion was also decreased in Tyk2-/- B cell cultures. This reduced response of the TLR7 pathway in Tyk2-/- mice was partially restored by IFNα addition. In conclusion, there is a crosstalk between TYK2 and TLR7 mediated by an IFN-I feedback loop, which contributes to the establishment of MZ B cells and to B cell proliferation and differentiation.

T regulatory lymphocytes specific for SARS-CoV-2 display increased functional plasticity

The study of phenotypic and functional characteristics of immune cells involved in host response to SARS-CoV-2 is relevant for understanding COVID-19 pathogenesis and individual differences in disease progression. We have analyzed chemokine receptor expression in SARS-CoV-2-specific CD4+ T lymphocytes from vaccinated donors, and have found an increase of CCR9+ and CCR6+ cells. CCR9+ specific CD4+ cells are enriched in T regulatory (Treg) lymphocytes. These cells specifically show heterogeneous regulatory activity, associated with different profiles of CCR9/CCR6 expression, individual differences in IL-10 and IL-17 production, and variable FoxP3 and Notch4 expression. A higher heterogeneity in FoxP3 is selectively observed in convalescent individuals within vaccinated population. Accordingly, SARS-CoV-2-specific CD4+ lymphocytes from COVID-19 patients are also enriched in CCR9+ and CCR6+ cells. CCR6+ specific Treg lymphocytes are mainly increased in critically ill individuals, indicating a preferential role for these cells in lung injury pathogenesis. We provide experimental evidence for a SARS-CoV-2-specific Treg population with increased plasticity, which may contribute to the differential pathogenic response against SARS-CoV-2 among individuals, and underlie the development of autoimmune conditions following SARS-CoV-2 infection.

KLRG1 expression on natural killer cells is associated with HIV persistence, and its targeting promotes the reduction of the viral reservoir

Human immunodeficiency virus (HIV) infection induces immunological dysfunction, which limits the elimination of HIV-infected cells during treated infection. Identifying and targeting dysfunctional immune cells might help accelerate the purging of the persistent viral reservoir. Here, we show that chronic HIV infection increases natural killer (NK) cell populations expressing the negative immune regulator KLRG1, both in peripheral blood and lymph nodes. Antiretroviral treatment (ART) does not reestablish these functionally impaired NK populations, and the expression of KLRG1 correlates with active HIV transcription. Targeting KLRG1 with specific antibodies significantly restores the capacity of NK cells to kill HIV-infected cells, reactivates latent HIV present in CD4+ T cells co-expressing KLRG1, and reduces the intact HIV genomes in samples from ART-treated individuals. Our data support the potential use of immunotherapy against the KLRG1 receptor to impact the viral reservoir during HIV persistence.

Extracellular vesicles from Listeria monocytogenes-infected dendritic cells alert the innate immune response

Communication through cell-cell contacts and extracellular vesicles (EVs) enables immune cells to coordinate their responses against diverse types of pathogens. The function exerted by EVs in this context depends on the proteins and nucleic acids loaded into EVs, which elicit specific responses involved in the resolution of infection. Several mechanisms control protein and nucleic acid loading into EVs; in this regard, acetylation has been described as a mechanism of cellular retention during protein sorting to exosomes. HDAC6 is a deacetylase involved in the control of cytoskeleton trafficking, organelle polarity and cell migration, defense against Listeria monocytogenes (Lm) infection and other immune related functions. Here, we show that the protein content of dendritic cells (DCs) and their secreted EVs (DEVs) vary during Lm infection, is enriched in proteins related to antiviral functions compared to non-infected cells and depends on HDAC6 expression. Analyses of the post-translational modifications revealed an alteration of the acetylation and ubiquitination profiles upon Lm infection both in DC lysates and DEVs. Functionally, EVs derived from infected DCs upregulate anti-pathogenic genes (e.g. inflammatory cytokines) in recipient immature DCs, which translated into protection from subsequent infection with vaccinia virus. Interestingly, absence of Listeriolysin O in Lm prevents DEVs from inducing this anti-viral state. In summary, these data underscore a new mechanism of communication between bacteria-infected DC during infection as they alert neighboring, uninfected DCs to promote antiviral responses.

Development of an Effective Immune Response in Adults With Down Syndrome After Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Vaccination

BACKGROUND

Immune dysregulation in individuals with Down syndrome (DS) leads to an increased risk for hospitalization and death due to coronavirus disease 2019 (COVID-19) and may impair the generation of protective immunity after vaccine administration.

METHODS

The cellular and humoral responses of 55 individuals with DS who received a complete SARS-CoV-2 vaccination regime at 1 to 3 (visit [V 1]) and 6 (V2) months were characterized.

RESULTS

SARS-CoV-2-reactive CD4+ and CD8+ T lymphocytes with a predominant Th1 phenotype were observed at V1 and increased at V2. Likewise, an increase in SARS-CoV-2-specific circulating Tfh (cTfh) cells and CD8+ CXCR5+ PD-1hi lymphocytes was already observed at V1 after vaccine administration. Specific immunoglobulin G (IgG) antibodies against SARS-CoV-2 S protein were detected in 96% and 98% of subjects at V1 and V2, respectively, although IgG titers decreased significantly between both time points.

CONCLUSIONS

Our findings show that DS individuals develop an effective immune response to usual regimes of SARS-CoV-2 vaccination.

Antiretroviral therapy duration and immunometabolic state determine efficacy of ex vivo dendritic cell-based treatment restoring functional HIV-specific CD8+ T cells in people living with HIV

Background

Dysfunction of CD8⁺ T cells in people living with HIV-1 (PLWH) receiving anti-retroviral therapy (ART) has restricted the efficacy of dendritic cell (DC)-based immunotherapies against HIV-1. Heterogeneous immune exhaustion and metabolic states of CD8⁺ T cells might differentially associate with dysfunction. However, specific parameters associated to functional restoration of CD8⁺ T cells after DC treatment have not been investigated.

Methods

We studied association of restoration of functional HIV-1-specific CD8⁺ T cell responses after stimulation with Gag-adjuvant-primed DC with ART duration, exhaustion, metabolic and memory cell subsets profiles.

Findings

HIV-1-specific CD8⁺ T cell responses from a larger proportion of PLWH on long-term ART (more than 10 years; LT-ARTp) improved polyfunctionality and capacity to eliminate autologous p24⁺ infected CD4⁺ T cells in vitro. In contrast, functional improvement of CD8⁺ T cells from PLWH on short-term ART (less than a decade; ST-ARTp) after DC treatment was limited. This was associated with lower frequencies of central memory CD8⁺ T cells, increased co-expression of PD1 and TIGIT and reduced mitochondrial respiration and glycolysis induction upon TCR activation. In contrast, CD8⁺ T cells from LT-ARTp showed increased frequencies of TIM3⁺ PD1⁻ cells and preserved induction of glycolysis. Treatment of dysfunctional CD8⁺ T cells from ST-ARTp with combined anti-PD1 and anti-TIGIT antibodies plus a glycolysis promoting drug restored their ability to eliminate infected CD4⁺ T cells.

Interpretation

Together, our study identifies specific immunometabolic parameters for different PLWH subgroups potentially useful for future personalized DC-based HIV-1 vaccines.

Funding

NIH (R21AI140930), MINECO/FEDER RETOS (RTI2018-097485-A-I00) and CIBERINF grants.

A Differential Signature of Circulating miRNAs and Cytokines Between COVID-19 and Community-Acquired Pneumonia Uncovers Novel Physiopathological Mechanisms of COVID-19

Coronavirus Disease 2019 (COVID-19) pneumonia is a life-threatening infectious disease, especially for elderly patients with multiple comorbidities. Despite enormous efforts to understand its underlying etiopathogenic mechanisms, most of them remain elusive. In this study, we compared differential plasma miRNAs and cytokines profiles between COVID-19 and other community-acquired pneumonias (CAP). A first screening and subsequent validation assays in an independent cohort of patients revealed a signature of 15 dysregulated miRNAs between COVID-19 and CAP patients. Additionally, multivariate analysis displayed a combination of 4 miRNAs (miR-106b-5p, miR-221-3p, miR-25-3p and miR-30a-5p) that significantly discriminated between both pathologies. Search for targets of these miRNAs, combined with plasma protein measurements, identified a differential cytokine signature between COVID-19 and CAP that included EGFR, CXCL12 and IL-10. Significant differences were also detected in plasma levels of CXCL12, IL-17, TIMP-2 and IL-21R between mild and severe COVID-19 patients. These findings provide new insights into the etiopathological mechanisms underlying COVID-19.

CD4+ T Cell Immune Specificity Changes After Vaccination in Healthy And COVID-19 Convalescent Subjects

The immune response promoted by SARS-CoV-2 vaccination is relevant to develop novel vaccines and optimized prevention strategies. We analyzed the adaptive immunity in healthy donors (HD) and convalescent individuals (CD), before and after administering BNT162b2 vaccine. Our results revealed specific changes in CD4+ T cell reactivity profile in vaccinated HD and CD, with an increase in S1 and S2 positive individuals, proportionally higher for S2. On the contrary, NCAP reactivity observed in HD and CD patients was no longer detectable after vaccination. Despite the substantial antibody response in CD, MPro-derived peptides did not elicit CD4+ lymphocyte activation in our assay in either condition. HD presented an increment in anti-S and anti-RBD IgG after first dose vaccination, which increased after the second vaccination. Conversely, anti-S and anti-RBD IgG and IgA titers increased in already positive CD after first dose administration, remaining stable after second dose inoculation. Interestingly, we found a strong significant correlation between S1-induced CD4+ response and anti-S IgA pre-vaccination, which was lost after vaccine administration.

Poly I:C and STING agonist-primed DC increase lymphoid tissue polyfunctional HIV-1-specific CD8+ T cells and limit CD4+ T cell loss in BLT mice

Effective function of CD8⁺ T cells and enhanced innate activation of dendritic cells (DC) in response to HIV-1 is linked to protective antiviral immunity in controllers. Manipulation of DC targeting the master regulator TANK-binding Kinase 1 (TBK1) might be useful to acquire controller-like properties. Here, we evaluated the impact of the combination of 2´3´-c´diAM(PS)2 and Poly I:C as potential adjuvants capable of potentiating DC´s abilities to induce polyfunctional HIV-1 specific CD8⁺ T cell responses in vitro and in vivo using a humanized BLT mouse model. Adjuvant combination enhanced TBK-1 phosphorylation and IL-12 and IFNβ expression on DC and increased their ability to activate polyfunctional HIV-1-specific CD8⁺ T cells in vitro. Moreover, higher proportions of hBLT mice vaccinated with ADJ-DC exhibited less severe CD4⁺ T cell depletion following HIV-1 infection compared to control groups. This was associated with infiltration of CD8⁺ T cells in the white pulp from the spleen, reduced spread of infected p24⁺ cells to lymph node and with preserved abilities of CD8⁺ T cells from the spleen and blood of vaccinated animals to induce specific polyfunctional responses upon antigen stimulation. Therefore, priming of DC with Poly I:C and STING agonists might be useful for future HIV-1 vaccine studies. This article is protected by copyright. All rights reserved.

Deregulated cellular circuits driving immunoglobulins and complement consumption associate with the severity of COVID-19 patients

SARS‐CoV‐2 infection causes an abrupt response by the host immune system, which is largely responsible for the outcome of COVID‐19. We investigated whether the specific immune responses in the peripheral blood of 276 patients were associated with the severity and progression of COVID‐19. At admission, dramatic lymphopenia of T, B, and NK cells is associated with severity. Conversely, the proportion of B cells, plasmablasts, circulating follicular helper T cells (cTfh) and CD56^–CD16⁺ NK‐cells increased. Regarding humoral immunity, levels of IgM, IgA, and IgG were unaffected, but when degrees of severity were considered, IgG was lower in severe patients. Compared to healthy donors, complement C3 and C4 protein levels were higher in mild and moderate, but not in severe patients, while the activation peptide of C5 (C5a) increased from the admission in every patient, regardless of their severity. Moreover, total IgG, the IgG1 and IgG3 isotypes, and C4 decreased from day 0 to day 10 in patients who were hospitalized for more than two weeks, but not in patients who were discharged earlier. Our study provides important clues to understand the immune response observed in COVID‐19 patients, associating severity with an imbalanced humoral response, and identifying new targets for therapeutic intervention.

COVID-19 severity associates with pulmonary redistribution of CD1c+ DCs and inflammatory transitional and nonclassical monocytes

SARS-CoV-2 is responsible for the development of coronavirus disease 2019 (COVID-19) in infected individuals, who can either exhibit mild symptoms or progress toward a life-threatening acute respiratory distress syndrome (ARDS). Exacerbated inflammation and dysregulated immune responses involving T and myeloid cells occur in COVID-19 patients with severe clinical progression. However, the differential contribution of specific subsets of dendritic cells and monocytes to ARDS is still poorly understood. In addition, the role of CD8+ T cells present in the lung of COVID-19 patients and relevant for viral control has not been characterized. Here, we have studied the frequencies and activation profiles of dendritic cells and monocytes present in the blood and lung of COVID-19 patients with different clinical severity in comparison with healthy individuals. Furthermore, these subpopulations and their association with antiviral effector CD8+ T cell subsets were also characterized in lung infiltrates from critical COVID-19 patients. Our results indicate that inflammatory transitional and nonclassical monocytes and CD1c+ conventional dendritic cells preferentially migrate from blood to lungs in patients with severe COVID-19. Thus, this study increases the knowledge of specific myeloid subsets involved in the pathogenesis of COVID-19 disease and could be useful for the design of therapeutic strategies for fighting SARS-CoV-2 infection.

IL-6 serum levels predict severity and response to tocilizumab in COVID-19: An observational study

BACKGROUND

Patients with coronavirus disaese 2019 (COVID-19) can develop a cytokine release syndrome that eventually leads to acute respiratory distress syndrome requiring invasive mechanical ventilation (IMV). Because IL-6 is a relevant cytokine in acute respiratory distress syndrome, the blockade of its receptor with tocilizumab (TCZ) could reduce mortality and/or morbidity in severe COVID-19.

OBJECTIVE

We sought to determine whether baseline IL-6 serum levels can predict the need for IMV and the response to TCZ.

METHODS

A retrospective observational study was performed in hospitalized patients diagnosed with COVID-19. Clinical information and laboratory findings, including IL-6 levels, were collected approximately 3 and 9 days after admission to be matched with preadministration and postadministration of TCZ. Multivariable logistic and linear regressions and survival analysis were performed depending on outcomes: need for IMV, evolution of arterial oxygen tension/fraction of inspired oxygen ratio, or mortality.

RESULTS

One hundred forty-six patients were studied, predominantly males (66%); median age was 63 years. Forty-four patients (30%) required IMV, and 58 patients (40%) received treatment with TCZ. IL-6 levels greater than 30 pg/mL was the best predictor for IMV (odds ratio, 7.1; P < .001). Early administration of TCZ was associated with improvement in oxygenation (arterial oxygen tension/fraction of inspired oxygen ratio) in patients with high IL-6 (P = .048). Patients with high IL-6 not treated with TCZ showed high mortality (hazard ratio, 4.6; P = .003), as well as those with low IL-6 treated with TCZ (hazard ratio, 3.6; P = .016). No relevant serious adverse events were observed in TCZ-treated patients.

CONCLUSIONS

Baseline IL-6 greater than 30 pg/mL predicts IMV requirement in patients with COVID-19 and contributes to establish an adequate indication for TCZ administration.

Spatially restricted JAG1-Notch signaling in human thymus provides suitable DC developmental niches

Martín-Gayo et al. report that human early thymic progenitors can undergo a GATA2-dependent myeloid developmental program leading to resident dendritic cells (DCs) upon JAG1-Notch activation. The identification of JAG1⁺ DC-permissive intrathymic niches validates the human thymus as a DC-poietic organ.

A key unsolved question regarding the developmental origin of conventional and plasmacytoid dendritic cells (cDCs and pDCs, respectively) resident in the steady-state thymus is whether early thymic progenitors (ETPs) could escape T cell fate constraints imposed normally by a Notch-inductive microenvironment and undergo DC development. By modeling DC generation in bulk and clonal cultures, we show here that Jagged1 (JAG1)-mediated Notch signaling allows human ETPs to undertake a myeloid transcriptional program, resulting in GATA2-dependent generation of CD34⁺ CD123⁺ progenitors with restricted pDC, cDC, and monocyte potential, whereas Delta-like1 signaling down-regulates GATA2 and impairs myeloid development. Progressive commitment to the DC lineage also occurs intrathymically, as myeloid-primed CD123⁺ monocyte/DC and common DC progenitors, equivalent to those previously identified in the bone marrow, are resident in the normal human thymus. The identification of a discrete JAG1⁺ thymic medullary niche enriched for DC-lineage cells expressing Notch receptors further validates the human thymus as a DC-poietic organ, which provides selective microenvironments permissive for DC development.

Intravenous immunoglobulin promotes antitumor responses by modulating macrophage polarization

Intravenous Igs (IVIg) therapy is widely used as an immunomodulatory strategy in inflammatory pathologies and is suggested to promote cancer regression. Because progression of tumors depends on their ability to redirect the polarization state of tumor-associated macrophages (from M1/immunogenic/proinflammatory to M2/anti-inflammatory), we have evaluated whether IVIg limits tumor progression and dissemination through modulation of macrophage polarization. In vitro, IVIg inhibited proinflammatory cytokine production from M1 macrophages and induced a M2-to-M1 polarization switch on human and murine M2 macrophages. In vivo, IVIg modified the polarization of tumor-associated myeloid cells in a Fcεr1γ chain-dependent manner, modulated cytokine blood levels in tumor-bearing animals, and impaired tumor progression via FcγRIII (CD16), FcγRIV, and FcRγ engagement, the latter two effects being macrophage mediated. Therefore, IVIg immunomodulatory activity is dependent on the polarization state of the responding macrophages, and its ability to trigger a M2-to-M1 macrophage polarization switch might be therapeutically useful in cancer, in which proinflammatory or immunogenic functions should be promoted.

The novel RUNX3/p33 isoform is induced upon monocyte-derived dendritic cell maturation and downregulates IL-8 expression

RUNX proteins are heterodimeric factors that play crucial roles during development and differentiation of cells of the immune system. The RUNX3 transcription factor controls lineage decisions during thymopoiesis and T-cell differentiation, and modulates myeloid cell effector functions. We now report the characterization of the human RUNX3/p33 isoform, generated by splicing out a Runt DNA-binding domain-encoding exon, and whose transcriptional activities differ from those of the prototypic RUNX3/p44 molecule. Unlike RUNX3/p44, RUNX3/p33 is induced upon maturation of monocyte-derived dendritic cells (MDDC), and is unable to transactivate the regulatory regions of the CD11a, CD11c and CD49e integrin genes. Overexpression of RUNX3/p33 in myeloid cell lines led to diminished expression of genes involved in inflammatory responses. Moreover, overexpression of RUNX3/p33 down-modulated the basal level of IL-8 production from immature monocyte-derived dendritic cells (MDDC). Besides, siRNA-mediated knock-down of RUNX3 led to diminished levels of IL-8 RNA in immature MDDC, and modulated the neutrophil-recruiting capacity of myeloid cell line supernatants. Since IL-8 promotes neutrophil chemotaxis and degranulation during inflammatory responses, and exerts mitogenic and angiogenic actions within tumor microenvironment, our results imply that myeloid RUNX3 expression regulates the recruitment of leukocytes towards inflammatory foci and might also contribute to human cancer progression.

CSL-MAML-dependent Notch1 signaling controls T lineage-specific IL-7R{alpha} gene expression in early human thymopoiesis and leukemia

Notch1 activation is essential for T-lineage specification of lymphomyeloid progenitors seeding the thymus. Progression along the T cell lineage further requires cooperative signaling provided by the interleukin 7 receptor (IL-7R), but the molecular mechanisms responsible for the dynamic and lineage-specific regulation of IL-7R during thymopoiesis are unknown. We show that active Notch1 binds to a conserved CSL-binding site in the human IL7R gene promoter and critically regulates IL7R transcription and IL-7R α chain (IL-7Rα) expression via the CSL–MAML complex. Defective Notch1 signaling selectively impaired IL-7Rα expression in T-lineage cells, but not B-lineage cells, and resulted in a compromised expansion of early human developing thymocytes, which was rescued upon ectopic IL-7Rα expression. The pathological implications of these findings are demonstrated by the regulation of IL-7Rα expression downstream of Notch1 in T cell leukemias. Thus, Notch1 controls early T cell development, in part by regulating the stage- and lineage-specific expression of IL-7Rα.