Frequency Of Plasmacytoid Dendritic Cells Research Articles

7820 Immune system adaptation during gender-affirming testosterone treatment

Abstract Disclosure: T. Lakshmikanth: None. C. Consiglio: None. F. Sardh: None. R. Forlin: None. J. Wang: None. Z. Tan: None. H. Barencilla: None. L. Rodriguez: None. J. Sugrue: None. P. Noori: None. M. Ivanchenko: None. L. Piñero Páez: None. L. Gonzalez: None. C. Habimana Mugabo: None. A. Johnsson: None. H. Ryberg: None. Å. Hallgren: None. C. Pou: None. Y. Chen: None. J. Mikeš: None. A. James: None. P.M. Dahlqvist: None. J. Wahlberg Hughes: None. A. Hagelin: None. M. Holmberg: None. M. Degerblad: None. M. Isaksson: None. D. Duffy: None. O. Kampe: None. N. Landegren: None. P. Brodin: None. Immune system adaptation during gender-affirming testosterone treatment Infectious, inflammatory and autoimmune conditions present differently in males and females. Following SARS-CoV-2 infection, male sex is associated with increased risk of death, while female sex is associated with increased risk of the postinfectious disorder, long COVID. Similar trends are seen in other infections. Female immune responses to vaccines are typically stronger, and adverse reactions are more frequent, like most autoimmune diseases. Immunological sex-differences stem from genetic, hormonal and behavioural factors but their relative importance is poorly understood. To understand the consequences of changing sex-hormones in vivo, we performed longitudinal, systems-level analyses in 22 adults, assigned female at birth, and undergoing gender-affirming testosterone treatment (trans-men). We find that sex hormones modulate a cross-regulation axis of type-I interferon (IFN-I) and TNFα in humans. This is mediated by a reduced frequency of plasmacytoid dendritic cells (pDC), and functional attenuation of IFN-I responses in both pDCs and monocytes. Conversely, testosterone potentiates monocyte responses to lipopolysaccharide (LPS) leading to increased TNFα, IL-6 and IL-15 production and downstream epigenetic opening of NFκB regulated genes and potentiation of IFNγ responses, primarily by NK cells. IFNγ in turn feeds back onto monocytes leading to upregulation of SLAMF7 and further enhanced TNFα responses by myeloid cells. These results are corroborated by sex-divergent responses in multiple public datasets and collectively illustrate the dynamic recalibration of human immune systems by sex hormones with implications for individuals undergoing gender-affirming hormone therapy, but also better understanding of divergent responses to infection, vaccines and self-antigens in cisgender individuals. Presentation: 6/2/2024

7820 Immune system adaptation during gender-affirming testosterone treatment

Abstract Disclosure: T. Lakshmikanth: None. C. Consiglio: None. F. Sardh: None. R. Forlin: None. J. Wang: None. Z. Tan: None. H. Barencilla: None. L. Rodriguez: None. J. Sugrue: None. P. Noori: None. M. Ivanchenko: None. L. Piñero Páez: None. L. Gonzalez: None. C. Habimana Mugabo: None. A. Johnsson: None. H. Ryberg: None. Å. Hallgren: None. C. Pou: None. Y. Chen: None. J. Mikeš: None. A. James: None. P.M. Dahlqvist: None. J. Wahlberg Hughes: None. A. Hagelin: None. M. Holmberg: None. M. Degerblad: None. M. Isaksson: None. D. Duffy: None. O. Kampe: None. N. Landegren: None. P. Brodin: None. Infectious, inflammatory and autoimmune conditions present differently in males and females. Following SARS-CoV-2 infection, male sex is associated with increased risk of death, while female sex is associated with increased risk of the postinfectious disorder, long COVID. Similar trends are seen in other infections. Female immune responses to vaccines are typically stronger, and adverse reactions are more frequent, like most autoimmune diseases. Immunological sex-differences stem from genetic, hormonal and behavioural factors but their relative importance is poorly understood. To understand the consequences of changing sex-hormones in vivo, we performed longitudinal, systems-level analyses in 22 adults, assigned female at birth, and undergoing gender-affirming testosterone treatment (trans-men). We find that sex hormones modulate a cross-regulation axis of type-I interferon (IFN-I) and TNFα in humans. This is mediated by a reduced frequency of plasmacytoid dendritic cells (pDC), and functional attenuation of IFN-I responses in both pDCs and monocytes. Conversely, testosterone potentiates monocyte responses to lipopolysaccharide (LPS) leading to increased TNFα, IL-6 and IL-15 production and downstream epigenetic opening of NFκB regulated genes and potentiation of IFNγ responses, primarily by NK cells. IFNγ in turn feeds back onto monocytes leading to upregulation of SLAMF7 and further enhanced TNFα responses by myeloid cells. These results are corroborated by sex-divergent responses in multiple public datasets and collectively illustrate the dynamic recalibration of human immune systems by sex hormones with implications for individuals undergoing gender-affirming hormone therapy, but also better understanding of divergent responses to infection, vaccines and self-antigens in cisgender individuals. Presentation: 6/2/2024

Controlled human hookworm infection remodels plasmacytoid dendritic cells and regulatory T cells towards profiles seen in natural infections in endemic areas

Hookworm infection remains a significant public health concern, particularly in low- and middle-income countries, where mass drug administration has not stopped reinfection. Developing a vaccine is crucial to complement current control measures, which necessitates a thorough understanding of host immune responses. By leveraging controlled human infection models and high-dimensional immunophenotyping, here we investigated the immune remodeling following infection with 50 Necator americanus L3 hookworm larvae in four naïve volunteers over two years of follow-up and compared the profiles with naturally infected populations in endemic areas. Increased plasmacytoid dendritic cell frequency and diminished responsiveness to Toll-like receptor 7/8 ligand were observed in both controlled and natural infection settings. Despite the increased CD45RA+ regulatory T cell (Tregs) frequencies in both settings, markers of Tregs function, including inducible T-cell costimulatory (ICOS), tumor necrosis factor receptor 2 (TNFR2), and latency-associated peptide (LAP), as well as in vitro Tregs suppressive capacity were higher in natural infections. Taken together, this study provides unique insights into the immunological trajectories following a first-in-life hookworm infection compared to natural infections.

Peripheral T-cell responses of EphB2- and EphB3-deficient mice in a model of collagen-induced arthritis

Both EphB2- and EphB3-deficient mice exhibit profound histological alterations in the thymic epithelial network but few changes in T-cell differentiation, suggesting that this organization would be sufficient to produce functional T lymphocytes. Also, other antigen-presenting cells involved in immunological education could substitute the thymic epithelium. Accordingly, we found an increased frequency of plasmacytoid dendritic cells but not of conventional dendritic cells, medullary fibroblasts or intrathymic B lymphocytes. In addition, there are no lymphoid infiltrates in the organs of mutant mice nor do they contain circulating autoantibodies. Furthermore, attempts to induce arthritic lesions after chicken type II collagen administration fail totally in EphB2-deficient mice whereas all WT and half of the immunized EphB3−/− mice develop a typical collagen-induced arthritis. Our results point out that Th17 cells, IL4-producing Th2 cells and regulatory T cells are key for the induction of disease, but mutant mice appear to have deficits in T cell activation or cell migration properties. EphB2−/− T cells show reduced in vitro proliferative responses to anti-CD3/anti-CD28 antibodies, produce low levels of anti-type II collagen antibodies, and exhibit low proportions of T follicular helper cells. On the contrary, EphB3−/− lymph node cells respond accurately to the different immune stimuli although in lower levels than WT cells but show a significantly reduced migration in in vitro transwell assays, suggesting that no sufficient type II collagen-dependent activated lymphoid cells reached the joints, resulting in reduced arthritic lesions.

Menstrual blood-derived mesenchymal stromal cells efficiently ameliorate experimental autoimmune encephalomyelitis by inhibiting T cell activation in mice

BackgroundImmunosuppressive properties grant mesenchymal stromal cells (MSCs) promising potential for treating autoimmune diseases. As autologous MSCs suffer from limited availability, the readily available allogeneic MSCs isolated from menstrual blood (MB-MSCs) donated by young, healthy individuals offer great potential. Here, we evaluate the therapeutic potential of MB-MSCs as ready-to-use allo-MSCs in multiple sclerosis, an autoimmune disease developed by the activation of myelin sheath-reactive Th1 and Th17 cells, by application in its animal model experimental autoimmune encephalomyelitis (EAE).MethodsWe assessed the therapeutic effect of MB-MSCs transplanted via either intravenous (i.v.) or intraperitoneal (i.p.) route in EAE in comparison with umbilical cord-derived MSCs (UC-MSCs). We used histology to assess myelin sheath integrity and infiltrated immune cells in CNS and flow cytometry to evaluate EAE-associated inflammatory T cells and antigen-presenting cells in lymphoid organs.ResultsWe observed disease-ameliorating effects of MB-MSCs when transplanted at various stages of EAE (day − 1, 6, 10, and 19), via either i.v. or i.p. route, with a potency comparable to UC-MSCs. We observed reduced Th1 and Th17 cell responses in mice that had received MB-MSCs via either i.v. or i.p. injection. The repressed Th1 and Th17 cell responses were associated with a reduced frequency of plasmacytoid dendritic cells (pDCs) and a suppressed co-stimulatory capacity of pDCs, cDCs, and B cells.ConclusionsOur data demonstrate that the readily available MB-MSCs significantly reduced the disease severity of EAE upon transplantation. Thus, they have the potential to be developed as ready-to-use allo-MSCs in MS-related inflammation.Graphical abstract

Transcriptomic landscape of circulating mononuclear phagocytes in Langerhans cell histiocytosis at the single-cell level

AbstractLangerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm caused by aberrant activation of the mitogen-activated protein kinase (MAPK) pathway. Circulating myeloid cells from patients often carry disease-associated mutations and can be differentiated into langerinhigh LCH-like cells in vitro, but their detailed immune-phenotypic and molecular profiles are lacking and could shed key insights into disease biology. Here we recruited 217 pediatric LCH patients and took blood and tissue samples for BRAFV600E analysis. Immune-phenotyping of the circulating Lin−HLA-DR+ immune population in 49 of these patients revealed that decreased frequency of plasmacytoid dendritic cells was significantly linked to disease severity. By single-cell RNA sequencing of samples from 14 patients, we identified key changes in expression of RAS-MAPK-extracellular signal-regulated kinase (ERK) signaling-related genes and transcription factors in distinct members of the mononuclear phagocyte system in the presence of BRAFV600E. Moreover, treatment of patients with the BRAF inhibitor dabrafenib resulted in MAPK cascade inhibition, inflammation prevention, and regulation of cellular metabolism within mononuclear phagocytes. Finally, we also observed elevated expression of RAS-MAPK-ERK signaling-related genes in a CD207+CD1a+ cell subcluster in skin. Taken together, our data extend the molecular understanding of LCH biology at single-cell resolution, which might contribute to improvement of clinical diagnostics and therapeutics, and aid in the development of personalized medicine approaches.

Distribution of Myeloid and Plasmacytoid Dendritic Cell Subpopulations in Peripheral Blood of Hyperprolactinemic Women

Dendritic cells (DCs) play key roles in regulating the immune response using the specialized function of processing and presenting antigens. Prolactin (PRL), a hormone produced by the pituitary gland, participates in DC maturation and function. The present study was aimed to determine the frequencies of peripheral blood DC subpopulations of myeloid DC (MDC) and plasmacytoid DC (PDC) in hyperprolactinemic (HPRL) women compared to normal healthy volunteers. This study was conducted on 70 women, including 35 HPRL patients and 35 matched healthy controls, whose PRL serum levels were in the normal range (lower than 25 ng/mL). Serum thyroid-stimulating hormone (TSH) levels were measured in both groups as an indicator of normal thyroid function. The electrochemiluminescence immunoassay method was applied to measure the serum levels of TSH and PRL. The frequencies of MDC and PDC in the peripheral blood samples of both groups were determined by flow cytometry. The mean serum PRL levels in the HPRL patients and healthy individuals were 46.41±21.96 and 13.75±11.19, respectively (p<0.0001); however TSH levels in both groups were similar and within the normal range (0.4-4.5 mIU/mL) (p=0.2). The frequencies of both MDC and PDC subpopulations in the peripheral blood of HPRL patients were significantly lower than they were in the healthy controls. However, the ratio of MDCs/PDCs in HPRL patients was not significantly different between the two groups (p=0.8). Our study revealed that an increased level of serum PRL may lead to a reduction in the number of MDC and PDC subpopulations. These results could help clarify the complex relationship between the immune system and the neuroendocrine axis and may be of potential use in understanding the pathogenesis of endocrine and immune disorders.

Dendritic cell responses to Plasmodium falciparum in a malaria-endemic setting

BackgroundPlasmodium falciparum causes the majority of malaria cases worldwide and children in sub-Saharan Africa are the most vulnerable group affected. Non-sterile clinical immunity that protects from symptoms develops slowly and is relatively short-lived. Moreover, current malaria vaccine candidates fail to induce durable high-level protection in endemic settings, possibly due to the immunomodulatory effects of the malaria parasite itself. Because dendritic cells play a crucial role in initiating immune responses, the aim of this study was to better understand the impact of cumulative malaria exposure as well as concurrent P. falciparum infection on dendritic cell phenotype and function.MethodsIn this cross-sectional study, the phenotype and function of dendritic cells freshly isolated from peripheral blood samples of Malian adults with a lifelong history of malaria exposure who were either uninfected (n = 27) or asymptomatically infected with P. falciparum (n = 8) was assessed. Additionally, plasma cytokine and chemokine levels were measured in these adults and in Malian children (n = 19) with acute symptomatic malaria.ResultsWith the exception of lower plasmacytoid dendritic cell frequencies in asymptomatically infected Malian adults, peripheral blood dendritic cell subset frequencies and HLA-DR surface expression did not differ by infection status. Peripheral blood myeloid dendritic cells of uninfected Malian adults responded to in vitro stimulation with P. falciparum blood-stage parasites by up-regulating the costimulatory molecules HLA-DR, CD80, CD86 and CD40 and secreting IL-10, CXCL9 and CXCL10. In contrast, myeloid dendritic cells of asymptomatically infected Malian adults exhibited no significant responses above the uninfected red blood cell control. IL-10 and CXCL9 plasma levels were elevated in both asymptomatic adults and children with acute malaria.ConclusionsThe findings of this study indicate that myeloid dendritic cells of uninfected adults with a lifelong history of malaria exposure are able to up-regulate co-stimulatory molecules and produce cytokines. Whether mDCs of malaria-exposed individuals are efficient antigen-presenting cells capable of mounting an appropriate immune response remains to be determined. The data also highlights IL-10 and CXCL9 as important factors in both asymptomatic and acute malaria and add to the understanding of asymptomatic P. falciparum infections in malaria-endemic areas.

Plasmacytoid Dendritic Cell Infiltration in Acute Myeloid Leukemia.

IntroductionIncreasing evidence has demonstrated that plasmacytoid dendritic cells (PDCs) in the tumor microenvironment (TME) play an important role in tumorigenesis and progression. PDC infiltration has been found in certain malignancies such as classic Hodgkin’s lymphoma and chronic myelomonocytic leukemia. Our previous work reported that PDC infiltration could occur in acute myeloid leukemia (AML), but the clinical significance of PDC in AML has not been thoroughly investigated.Patients and MethodsHere, we evaluated the clinical significance of PDC to AML transition in a leukemia microenvironment. The frequency of PDCs in 80 acute myelomonocytic leukemia (AML-M4) and 83 acute monocytic leukemia (AML-M5) patients was determined by flow cytometry.ResultsWe found 62 cases with PDC infiltration. These patients showed higher numbers of bone marrow blasts, higher mean Hb concentration, and required more cycles of chemotherapy before achieving complete remission (CR), but had lower white blood cell and platelet counts compared to patients without PDC infiltration. Drug sensitivity analysis showed that patients with PDC infiltration had lower sensitivity to standard chemotherapy regimens. Kaplan–Meier survival curves demonstrated that patients with PDC infiltration had a shorter overall survival (OS) time and progression-free survival time.DiscussionThese results suggested that PDC infiltration can be used for risk stratification of AML-M4/M5, and PDCs may transdifferentiate into leukemia in an AML microenvironment.

Effective control of early Zika virus replication by Dengue immunity is associated to the length of time between the 2 infections but not mediated by antibodies.

Little is known about the contribution of virus-specific and cross-reacting antibodies (Abs) or the cellular immune response generated by a primary dengue (DENV) infection on the course of a secondary zika (ZIKV) infection in vivo. Here we show that the length of time between DENV/ZIKV infections has a qualitative impact on controlling early ZIKV replication. Depletion of DENV2-specific Abs in sera confirmed that those type-specific Abs do not contribute to ZIKV control. We show that the magnitude and durability of the neutralizing antibodies (nAbs) induced by a secondary ZIKV infection is modest compared to the response induced after a secondary heterologous DENV infection. Our in vivo results are showing a complex interplay between the cellular and innate immune responses characterized by a high frequency of plasmacytoid dendritic cells (pDC) correlating with an increase in the frequency of DENV antigen specific T cells and a significant control of ZIKV replication which is time dependent. Taken together, our results suggest that early after ZIKV infection other mechanisms such as the innate and cellular immune responses may play a predominant role in controlling ZIKV replication. Regardless of the time elapsed between infections there was no evidence of in vivo antibody-dependent enhancement (ADE) of ZIKV by DENV immunity. These findings have pivotal implications while interpreting ZIKV pathogenesis in flavivirus-experimented populations, diagnostic results interpretation and vaccine designs and schedules among others.

Mass cytometry reveals cellular fingerprint associated with IgE+\u2009peanut tolerance and allergy in early life

IgE-mediated peanut allergic is common, often serious, and usually lifelong. Not all individuals who produce peanut-specific IgE will react upon consumption of peanut and can eat the food without adverse reactions, known as sensitized tolerance. Here, we employ high-dimensional mass cytometry to define the circulating immune cell signatures associated with sensitized tolerance and clinical allergy to peanut in the first year of life. Key features of clinical peanut allergic are increased frequency of activated B cells (CD19hiHLADRhi), overproduction of TNFα and increased frequency of peanut-specific memory CD4 T cells. Infants with sensitized tolerance display reduced frequency but hyper-responsive naive CD4 T cells and an increased frequency of plasmacytoid dendritic cells. This work demonstrates the utility and power of high-dimensional mass cytometry analysis to interrogate the cellular interactions that are associated with allergic sensitization and clinical food allergy in the first year of life.

Cytometry by time of flight identifies distinct signatures in patients with systemic sclerosis, systemic lupus erythematosus and Sjögrens syndrome.

Systemic sclerosis (SSc), systemic lupus erythematosus (SLE) and primary Sjögrens syndrome (pSS) are clinically distinct systemic autoimmune diseases (SADs) that share molecular pathways. We quantified the frequency of circulating immune-cells in 169 patients with these SADs and 44 healty controls (HC) using mass-cytometry and assessed the diagnostic value of these results. Alterations in the frequency of immune-cell subsets were present in all SADs compared to HC. Most alterations, including a decrease of CD56hi NK-cells in SSc and IgM+ Bcells in pSS, were disease specific; only a reduced frequency of plasmacytoid dendritic cells was common between all SADs Strikingly, hierarchical clustering of SSc patients identified 4 clusters associated with different clinical phenotypes, and 9 of the 12 cell subset-alterations in SSc were also present during the preclinical-phase of the disease. Additionally, we found a strong association between the use of prednisone and alterations in B-cell subsets. Although differences in immune-cell frequencies between these SADs are apparent, the discriminative value thereof is too low for diagnostic purposes. Within each disease, mass cytometry analyses revealed distinct patterns between endophenotypes. Given the lack of tools enabling early diagnosis of SSc, our results justify further research into the value of cellular phenotyping as a diagnostic aid.

Altered Peripheral Blood Leucocyte Phenotype and Responses in Healthy Individuals with Homozygous Deletion of FHR1 and FHR3 Genes.

A homozygous 83-kb deletion encompassing the genes for complement factor-H-related proteins 1 and 3 (FHR 1, FHR3) is known as a risk factor for some immune inflammatory disorders. However, the functional relevance of this FHR1/3 deletion is relatively unexplored. Globally, healthy populations of all ethnic groups tested show an 8-10% prevalence of homozygosity for this deletion polymorphism. We have begun to compare the peripheral leucocyte phenotype and functionality between FHR1/3-/- and FHR1/3+/+ healthy adult individuals. We report that the two groups show significant differences in their peripheral blood innate leucocyte subset composition, although the adaptive immune subsets are similar between them. Specifically, FHR1/3-/- individuals show higher frequencies of patrolling monocytes and lower frequencies of classical monocytes than FHR1/3+/+ individuals. Similarly, FHR1/3-/- individuals show higher frequencies of plasmacytoid dendritic cells (pDCs) and lower frequencies of myeloid DCs (mDCs) than FHR1/3+/+ individuals. Notably, classical monocytes specifically showed cell-surface-associated factor H (FH), and cells from the FHR1/3-/- group had somewhat higher surface-associated FH levels than those from FHR1/3+/+ individuals. FHR1/3-/- monocytes also showed elevated secretion of TNF-α, IL-1β, and IL-10 in response to TLR7/8 or TLR4 ligands. Similarly, FHR1/3-/- mDCs and pDCs showed modest but evident hyper-responsiveness to TLR ligands. Our findings, that the FHR1/3-/- genotype is associated with significant alterations of both the relative prominence and the functioning of monocyte and DC subsets, may be relevant in understanding the mechanism underlying the association of the genotype with immune inflammatory disorders.

Escherichia coli Nissle 1917 protects gnotobiotic pigs against human rotavirus by modulating pDC and NK-cell responses.

Lactobacillus rhamnosus GG (LGG), a gram-positive lactic acid bacterium, is one of the most widely used probiotics; while fewer gram-negative probiotics including Escherichia coli Nissle 1917 (EcN) are characterized. A mechanistic understanding of their individual and interactive effects on human rotavirus (HRV) and immunity is lacking. In this study, noncolonized, EcN-, LGG-, and EcN + LGG-colonized neonatal gnotobiotic (Gn) pigs were challenged with HRV. EcN colonization is associated with a greater protection against HRV, and induces the highest frequencies of plasmacytoid dendritic cells (pDCs), significantly increased NK-cell function and decreased frequencies of apoptotic and TLR4+ mononuclear cells (MNCs). Consistent with the highest NK-cell activity, splenic CD172+ MNCs (DC enriched fraction) of EcN-colonized pigs produced the highest levels of IL-12 in vitro. LGG colonization has little effect on the above parameters, which are intermediate in EcN + LGG-colonized pigs, suggesting that probiotics modulate each other's effects. Additionally, in vitro EcN-treated splenic or intestinal MNCs produce higher levels of innate, immunoregulatory and immunostimulatory cytokines, IFN-α, IL-12, and IL-10, compared to MNCs of pigs treated with LGG. These results indicate that the EcN-mediated greater protection against HRV is associated with potent stimulation of the innate immune system and activation of the DC-IL-12-NK immune axis.

PTPN22 Variant R620W Is Associated With Reduced Toll-like Receptor 7-Induced Type I Interferon in Systemic Lupus Erythematosus.

Protein tyrosine phosphatase nonreceptor type 22 (PTPN22) is associated with an increased risk of systemic lupus erythematosus (SLE). PTPN22 encodes Lyp, and a disease-associated coding variant bears an R620W substitution (LypW). LypW carriage is associated with impaired production of type I interferon (IFN) by myeloid cells following Toll-like receptor (TLR) engagement. The aim of this study was to investigate the effects of LypW carriage on TLR signaling in patients with SLE. Plasma IFNα concentrations and whole-blood IFN gene scores were compared in SLE patients who were LypW carriers and those who were noncarriers. TLR-7 agonist R848-stimulated IFNα and tumor necrosis factor levels, IFN-dependent gene expression, and STAT-1 activation were determined in peripheral blood mononuclear cells (PBMCs) and/or plasmacytoid dendritic cells (PDCs) obtained from these patients. The effect of LypW expression on the systemic type I IFN response to R848 stimulation in vivo was assessed in transgenic mice. Plasma IFNα levels and whole-blood IFN gene signatures were comparable in SLE patients who were LypW carriers and those who were noncarriers. However, PBMCs from LypW carriers produced less IFNα and showed reduced IFN-dependent gene up-regulation and STAT-1 activation after R848 stimulation. The frequency of PDCs producing IFNα2 and the per-cell IFNα2 levels were significantly reduced in LypW carriers. LypW-transgenic mice displayed reduced TLR-7-induced circulating type I IFN responses. PDCs from SLE patients carrying the disease-associated PTPN22 variant LypW showed a reduced capacity for TLR-7 agonist-induced type I IFN production, even though LypW carriers displayed systemic type I IFN activation comparable with that observed in noncarriers. LypW carriage identifies SLE patients who may harbor defects in TLR- and PDC-dependent host defense or antiinflammatory functions.

Intrabronchial infection of rhesus macaques with simian varicella virus results in a robust immune response in the lungs.

Varicella-zoster virus (VZV) is the etiological agent of varicella (chickenpox) and herpes zoster (shingles). Primary VZV infection is believed to occur via the inhalation of virus either in respiratory droplets or from shedding varicella lesions or by direct contact with infectious vesicular fluid. However, the ensuing immune response in the lungs remains incompletely understood. We have shown that intrabronchial inoculation of rhesus macaques with simian varicella virus (SVV), a homolog of VZV, recapitulates the hallmarks of acute and latent VZV infection in humans. In this study, we performed an in-depth analysis of the host immune response to acute SVV infection in the lungs and peripheral blood. We report that acute SVV infection results in a robust innate immune response in the lungs, characterized by the production of inflammatory cytokines, chemokines, and growth factors as well as an increased frequency of plasmacytoid dendritic cells (DCs) that corresponded with alpha interferon (IFN-α) production and a rapid decrease in viral loads in the lungs. This is followed by T and B cell proliferation, antibody production, T cell differentiation, and cytokine production, which correlate with the complete cessation of viral replication. Although terminally differentiated CD8 T cells became the predominant T cell population in bronchoalveolar lavage cells, a higher percentage of CD4 T cells were SVV specific, which suggests a critical role for these cells in the resolution of primary SVV infection in the lungs. Given the homology between SVV and VZV, our data provide insight into the immune response to VZV within the lung. Although primary VZV infection occurs primarily via the respiratory route, the host response in the lungs and its contribution to the cessation of viral replication and establishment of latency remain poorly understood. The difficulty in accessing lung tissue and washes from individuals infected with VZV has hampered efforts to address this knowledge gap. SVV infection of rhesus macaques is an important model of VZV infection of humans; therefore, we utilized this animal model to gain a comprehensive view of the kinetics of the immune response to SVV in the lung and its relationship to the resolution of acute infection in respiratory tissues. These data not only advance our understanding of host immunity to VZV, a critical step in developing new vaccines, but also provide additional insight into immunity to respiratory pathogens.

GCN2 kinase plays an important role triggering the remission phase of experimental autoimmune encephalomyelitis (EAE) in mice

Experimental autoimmune encephalomyelitis (EAE) has been widely employed as a model to study multiple sclerosis (MS) and indeed has allowed some important advances in our comprehension of MS pathogenesis. Several pieces of evidence suggest that infiltrating Th1 and Th17 lymphocytes are important players leading to CNS demyelination and lesion during the peak of murine EAE. Subsequently, effector T cell responses rapidly decline and the recovery phase of the disease strongly correlates with the expression of anti-inflammatory cytokines and the enrichment of Foxp3+ regulatory T (Treg) cells within the target organ. However, the mechanisms leading to the increased presence of Treg cells and to the remission phase of the disease are still poorly understood. Recent researches demonstrated that chemically induced amino-acid starvation response might suppress CNS immune activity. Here we verified an important participation of the general control nonrepressible 2 (GCN2), a key regulator kinase of the amino-acid starvation response, in the development of the remission phase of EAE in C57BL/6 mice. By immunizing wild type C57BL/6 (WT) and GCN2 knock-out mice (GCN2 KO) with myelin oligodendrocyte glycoprotein peptide (MOG35-55), it was noticed that GCN2 KO mice did not develop the remission phase of the disease and this was associated with higher levels of CNS inflammation and increased presence of effector T cells (Th1/Th17). These animals also showed lower frequency of Treg cells within the CNS as compared to WT animals. Higher expression of indoleamine 2,3-dioxygenase (IDO) and higher frequency of plasmacytoid dendritic cells (pDCs) were found at the peak of the disease in the CNS of WT animals. Our results suggest that the GCN2 kinase-dependent sensing of IDO activity represents an important trigger to the EAE remission phase. The IDO-mediated immunoregulatory events may include the arresting of effector T cell responses and the differentiation/expansion of Treg cells within the target organ.

Hepatitis C virus alternate reading frame protein decreases interferon-α secretion in peripheral blood mononuclear cells

The hepatitis C virus (HCV) alternate reading frame protein (ARFP or F protein) of the HCV 1b genotype is a double-frameshift product of the HCV core protein (Core). The discovery of HCV F protein challenges various biological functions attributed to Core. However, the specific characteristics of the host cellular immune response to F protein during HCV infection have yet to be fully elucidated. Therefore, the present study investigated the cytokine response to HCV Core or F protein in peripheral blood mononuclear cells (PBMCs) and plasmacytoid dendritic cells (PDCs) from patients with chronic HCV and healthy donors in vitro. The results demonstrated that the levels of interferon (IFN)-α, analyzed by an enzyme-linked immunosorbent assay, secreted by PBMCs in patients positive for the anti-F protein antibody, were lower than those of patients negative for the anti-F protein antibody. Moreover, the frequency of PDCs in patients negative for the anti-F protein antibody, were higher than in the group positive for the anti-F protein antibody. Furthermore, HCV F protein and Core not only inhibited specific unmethylated CpG oligonucleotide sequences of type A (CpG‑A)-induced IFN-α production by PBMCs and PDCs, but also upregulated the production of interleukin (IL)-10 by PBMCs in patients with chronic HCV and healthy controls. Notably, following neutralization of IL-10 in the media and in vitro Core or F protein stimulation, levels of IFN-α were increased. Moreover, the results revealed that the roles of F protein and Core were similar with regard to the induction of apoptosis of PDCs in patients with chronic HCV. These findings suggest that F protein may inhibit PBMC IFN-α secretion by regulating the production of IL-10, and may contribute to an increase in the rates of apoptosis in PDCs. In conclusion, the results have revealed a potential involvement of F protein in the mechanisms of chronic hepatitis C.

Short-term HIV-1 treatment interruption is associated with dysregulated TLR-stimuli responsiveness

Viremia during human immunodeficiency virus type-1 (HIV-1) infection results in progressive impairment of several components of the immune system. Here a unique model of repeated treatment interruptions (TIs) was used with the aim to reveal the effect of controlled short-term viremia on innate stimuli responsiveness and circulating dendritic cells (DCs). Sequential peripheral blood samples from HIV-1-infected patients on combination antiretroviral therapy, subjected to repeated TI cycles as part of a therapeutic DNA vaccination study, were analyzed. In vitro responsiveness of peripheral blood mononuclear cells to toll-like receptor (TLR) stimuli was analyzed by cytokine secretion, and frequencies of plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) were monitored by flow cytometry. These parameters were found not to be significantly different between the vaccinated and placebo groups. Instead, independent of vaccination altered in vitro TLR responsiveness was observed in parallel with TI cycles. TLR7/8-triggered secretion of IL-12 and IFN-α, as well as TLR9-triggered secretion of IL-12, was hyperactivated. In contrast, expression of IFN-α after TLR9 stimulation decreased during the initial cycle of TI. Reduced frequencies of pDCs and mDCs, compared with baseline, were noted before and during the second TI, respectively. Furthermore, spontaneous ex vivo release of IL-12 from PBMC was noted during cycles of TI. In conclusion, these results suggest that consequences of short-term TI include dysregulated TLR responses and fluctuations in the frequencies of circulating DCs. Knowledge of these immunological factors may influence the continuation of stringent treatment schedules during HIV infections.

Myeloid dendritic cells frequencies are increased in children with autism spectrum disorder and associated with amygdala volume and repetitive behaviors.

The pathophysiology of autism spectrum disorder (ASD) is not yet known; however, studies suggest that dysfunction of the immune system affects many children with ASD. Increasing evidence points to dysfunction of the innate immune system including activation of microglia and perivascular macrophages, increases in inflammatory cytokines/chemokines in brain tissue and CSF, and abnormal peripheral monocyte cell function. Dendritic cells are major players in innate immunity and have important functions in the phagocytosis of pathogens or debris, antigen presentation, activation of naïve T cells, induction of tolerance and cytokine/chemokine production. In this study, we assessed circulating frequencies of myeloid dendritic cells (defined as Lin-1(-)BDCA1(+)CD11c(+) and Lin-1(-)BDCA3(+)CD123(-)) and plasmacytoid dendritic cells (Lin-1(-)BDCA2(+)CD123(+) or Lin-1(-)BDCA4(+) CD11c(-)) in 57 children with ASD, and 29 typically developing controls of the same age, all of who were enrolled as part of the Autism Phenome Project (APP). The frequencies of dendritic cells and associations with behavioral assessment and MRI measurements of amygdala volume were compared in the same participants. The frequencies of myeloid dendritic cells were significantly increased in children with ASD compared to typically developing controls (p<0.03). Elevated frequencies of myeloid dendritic cells were positively associated with abnormal right and left amygdala enlargement, severity of gastrointestinal symptoms and increased repetitive behaviors. The frequencies of plasmacytoid dendritic cells were also associated with amygdala volumes as well as developmental regression in children with ASD. Dendritic cells play key roles in modulating immune responses and differences in frequencies or functions of these cells may result in immune dysfunction in children with ASD. These data further implicate innate immune cells in the complex pathophysiology of ASD.