Reduced Expression of HLA-DR on Monocytes During Severe Respiratory Syncytial Virus Infections

Characterizing the Immature Immunophenotype of Sickle Cell Disease Monocytes

Sickle cell disease (SCD) is marked by episodic vaso-occlusive crisis (VOC). Recurrent VOC creates a pro-inflammatory state that induces phenotypic alterations in innate immune cells. Monocytes are of particular interest to VOC pathophysiology because they are especially malleable to inflammatory signaling. Indeed, inflammatory disease states such as chronic obstructive pulmonary disease (COPD), obesity and atherosclerosis are known to influence monocyte development and alter monocyte subpopulations. In this study, we describe SCD monocyte subsets by performing immunophenotypic flow cytometric, enzymatic, and morphologic analysis on peripheral blood. Herein, we add to the growing body of evidence suggesting aberrant monocyte populations underpin VOC pathophysiology. We found that SCD monocytes possess an immature phenotype as demonstrated by 1) decreased CD4 positivity (p < .01), 2) low α-naphthyl butyrate esterase (ANBE) expression, and 3) naïve morphologic features. We additionally found an increase in CD14+CD16-CD4- monocytes (p < .01), a subset associated with the impaired immune response of post-trauma patients. Interestingly, we also found a large proportion of CD14+CD4-HLA-DR- monocytes which, under normal circumstances, are exclusively found in neonates (p < .01). Finally, we report an increase in nonclassical monocytes (CD14dimCD16+), a subset recently shown to have a critical role in prevention and recovery from VOC.

Immunomodulatory activity of heat-killed Lacticaseibacillus paracaseiMCC1849 based on the activation of plasmacytoid dendritic cells in the peripheral blood of healthy adults

Probiotics are widely used in food for their health benefits to the host. Inactivated probiotics also reportedly improve the intestinal environment and immune regulation. Our previous studies showed that heat-killed Lacticaseibacillus paracasei MCC1849 (hk-MCC1849) effectively induced IL-12 production in mouse spleen cells and significantly reduced cold symptoms in clinical trial subjects. To further elucidate the mechanism of host immune regulation by hk-MCC1849, human peripheral blood mononuclear cells (PBMCs) were cocultured with hk-MCC1849. The Toll-like receptor 9 ligands CpG-ODN 2216 and hk-MCC1849 and the heat-killed Lacticaseibacillus rhamnosus ATCC53103 were used as positive and negative controls, respectively. The results showed that, compared with the control, hk-MCC1849 significantly increased the expression of the plasmacytoid dendritic cell (pDC) marker CD86 (p < .0001) and the pDC marker HLA-DR (p < .001) in PBMCs. The expression levels of the IL-12p40, IFNα, IFNα1, IFNγ, and ISG15 genes were significantly increased after coculture with hk-MCC1849 (p < .05, p < .05, p < .05, p < .05, and p < .05, respectively, vs. control). Furthermore, to confirm whether hk-MCC1849 directly interacted with pDCs, DCs were enriched with PBMCs following 24 h of coculture with hk-MCC1849. Phagocytosis of fluorescently labeled hk-MCC1849 by pDCs was observed, and there were significant increases in CD86 (p < .05) and HLA-DR (p < .0001) expression in pDCs. These results suggest that hk-MCC1849 exerts a potential immunomodulatory effect on the host through the activation of peripheral pDCs.

Evaluation the frequencies of HLA alleles in moderate and severe COVID-19 patients in Iran: A molecular HLA typing study

Background

Severe acute respiratory syndrome coronavirus 2 was first reported in December 2019 and it has spread globally ever since. The HLA system is crucial in directing anti-viral immunity and recent studies are investigating the possible involvement of the HLA genes on the severity of immune inflammation in different phases of COVID-19.

Methods

In this cross-sectional study, peripheral blood-extracted genomic DNAs of 109 COVID-19 patients and 70 healthy controls were genotyped for different alleles of HLA-A, HLA-B, and HLA-DRB1 loci using sequence-specific primer PCR method.

Results

The results indicated that frequencies of HLA-DRB1*11:01 and HLA-DRB1*04:03 were significantly higher in severe patients rather than moderates (p: <0.001 and 0.004, respectively). Also, it was observed that HLA-DRB1*04:01 was more frequent in moderate patients and healthy controls (p:0.002). In addition, HLA-B*07:35, and HLA-DRB1*07:01 showed higher frequencies in patients compared with controls (p: 0.031 and 0.003 respectively). Inversely, due to the higher frequencies of HLA-B*51:01 (p:0.027), HLA-DRB1*11:05 (p:0.003), HLA-DRB1*13:05 (p:0.022), and HLA-DRB1*14:01 (p:0.006) in healthy individuals rather than patients, they may be associated with COVID-19 resistance.

Conclusion

The results show that, based on the population differences, the type of alleles related to the severity of COVID-19 is different, which should be clarified by designing large-scale studies in order to develop HLA-based treatments and vaccines.

Airway and Blood Monocyte Transcriptomic Profiling Reveals an Antiviral Phenotype in Infants With Severe Respiratory Syncytial Virus Infection

BACKGROUND

Respiratory syncytial virus (RSV) infection is the primary cause of lower respiratory tract infections in children <5 years of age. Monocytes, especially in the respiratory tract, are suggested to contribute to RSV pathology, but their role is incompletely understood. With transcriptomic profiling of blood and airway monocytes, we describe the role of monocytes in severe RSV infection.

METHODS

Tracheobronchial aspirates and blood samples were collected from control patients (n = 9) and those infected with RSV (n = 14) who were admitted to the pediatric intensive care unit. Monocytes (CD14+) were sorted and analyzed by RNA sequencing for transcriptomic profiling.

RESULTS

Peripheral blood and airway monocytes of patients with RSV demonstrated increased expression of antiviral and interferon-responsive genes as compared with controls. Cytokine signaling showed a shared response between blood and airway monocytes while displaying responses that were more pronounced according to the tissue of origin. Airway monocytes upregulated additional genes related to migration and inflammation.

CONCLUSIONS

We found that the RSV-induced interferon response extends from the airways to the peripheral blood. Moreover, RSV induces a migration-promoting transcriptional program in monocytes. Unraveling the monocytic response and its role in the immune response to RSV infection could help the development of therapeutics to prevent severe disease.

The implication of infection with respiratory syncytial virus in pediatric recurrent wheezing and asthma: knowledge expanded post-COVID-19 era

BACKGROUND

Respiratory syncytial virus (RSV) infection has been identified to serve as the primary cause of acute lower respiratory infectious diseases in children under the age of one and a significant risk factor for the emergence and development of pediatric recurrent wheezing and asthma, though the exact mechanism is still unknown.

METHODS AND RESULTS

In this study, we discuss the key routes that lead to recurrent wheezing and bronchial asthma following RSV infection. It is interesting to note that following the coronavirus disease 2019 (COVID-19) epidemic, the prevalence of RSV changes significantly. This presents us with a rare opportunity to better understand the associated mechanism for RSV infection, its effects on the respiratory system, and the immunological response to RSV following the COVID-19 epidemic. To better understand the associated mechanisms in the occurrence and progression of pediatric asthma, we thoroughly described how the RSV infection directly destroys the physical barrier of airway epithelial tissue, promotes inflammatory responses, enhances airway hyper-responsiveness, and ultimately causes the airway remodeling. More critically, extensive discussion was also conducted regarding the potential impact of RSV infection on host pulmonary immune response.

CONCLUSION

In conclusion, this study offers a comprehensive perspective to better understand how the RSV infection interacts in the control of the host's pulmonary immune system, causing recurrent wheezing and the development of asthma, and it sheds fresh light on potential avenues for pharmaceutical therapy in the future.

The Potential Immunomodulatory Effect of Bifidobacterium longum subsp. longum BB536 on Healthy Adults through Plasmacytoid Dendritic Cell Activation in the Peripheral Blood

The interaction between the gut microbiota and the host can influence the host's immune system. Bifidobacterium, a commensal genus of gut bacteria, seems to have positive effects on host health. Our previous clinical research showed that B. longum subsp. longum BB536 enhanced innate and adaptive immune responses in elderly individuals with a lower grade of immunity, but the immunomodulatory mechanism is still unclear. In this study, dendritic cell (DC) surface markers in peripheral blood mononuclear cells isolated from healthy individuals were evaluated through coculture with heat-killed BB536. DC markers, innate immune activity and cytokine levels in plasma were also evaluated by a randomized, double-blind, placebo-controlled, parallel-group study (UMIN000045564) with 4 weeks of continuous live BB536 intake. BB536 significantly increased the expression of CD86 and HLA-DR on plasmacytoid DCs (pDCs) in vitro. Compared to placebo (n = 48), a significant increase in the expression of CD86 on peripheral pDCs was detected at week 4 of live BB536 intake (n = 49; 1 × 1010 CFU/day). Furthermore, coculture with hk-BB536 significantly increased the IFNγ expression level and demonstrated trends of increased IFNα1 and IFNβ expression. These findings suggest that consumption of BB536 has potential immunomodulatory effects on healthy individuals through the activation of peripheral pDCs.

Host Responses to Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) infections are a constant public health problem, especially in infants and older adults. Virtually all children will have been infected with RSV by the age of two, and reinfections are common throughout life. Since antigenic variation, which is frequently observed among other respiratory viruses such as SARS-CoV-2 or influenza viruses, can only be observed for RSV to a limited extent, reinfections may result from short-term or incomplete immunity. After decades of research, two RSV vaccines were approved to prevent lower respiratory tract infections in older adults. Recently, the FDA approved a vaccine for active vaccination of pregnant women to prevent severe RSV disease in infants during their first RSV season. This review focuses on the host response to RSV infections mediated by epithelial cells as the first physical barrier, followed by responses of the innate and adaptive immune systems. We address possible RSV-mediated immunomodulatory and pathogenic mechanisms during infections and discuss the current vaccine candidates and alternative treatment options.

Macrophages Orchestrate Airway Inflammation, Remodeling, and Resolution in Asthma

Asthma is a heterogenous chronic inflammatory lung disease with endotypes that manifest different immune system profiles, severity, and responses to current therapies. Regardless of endotype, asthma features increased immune cell infiltration, inflammatory cytokine release, and airway remodeling. Lung macrophages are also heterogenous in that there are separate subsets and, depending on the environment, different effector functions. Lung macrophages are important in recruitment of immune cells such as eosinophils, neutrophils, and monocytes that enhance allergic inflammation and initiate T helper cell responses. Persistent lung remodeling including mucus hypersecretion, increased airway smooth muscle mass, and airway fibrosis contributes to progressive lung function decline that is insensitive to current asthma treatments. Macrophages secrete inflammatory mediators that induce airway inflammation and remodeling. Additionally, lung macrophages are instrumental in protecting against pathogens and play a critical role in resolution of inflammation and return to homeostasis. This review summarizes current literature detailing the roles and existing knowledge gaps for macrophages as key inflammatory orchestrators in asthma pathogenesis. We also raise the idea that modulating inflammatory responses in lung macrophages is important for alleviating asthma.

Mucosal Immune Responses to Respiratory Syncytial Virus

Despite over half a century of research, respiratory syncytial virus (RSV)-induced bronchiolitis remains a major cause of hospitalisation in infancy, while vaccines and specific therapies still await development. Our understanding of mucosal immune responses to RSV continues to evolve, but recent studies again highlight the role of Type-2 immune responses in RSV disease and hint at the possibility that it dampens Type-1 antiviral immunity. Other immunoregulatory pathways implicated in RSV disease highlight the importance of focussing on localised mucosal responses in the respiratory mucosa, as befits a virus that is essentially confined to the ciliated respiratory epithelium. In this review, we discuss studies of mucosal immune cell infiltration and production of inflammatory mediators in RSV bronchiolitis and relate these studies to observations from peripheral blood. We also discuss the advantages and limitations of studying the nasal mucosa in a disease that is most severe in the lower airway. A fresh focus on studies of RSV pathogenesis in the airway mucosa is set to revolutionise our understanding of this common and important infection.

The Micro-Immunotherapy Medicine 2LEID Exhibits an Immunostimulant Effect by Boosting Both Innate and Adaptive Immune Responses

This study aimed at evaluating the effects of the micro-immunotherapy medicine (MIM) 2LEID, both in vitro and in vivo, on several components of the innate and adaptive immune system. MIM increased the phagocytic activity of macrophages, and it augmented the expression of the activation markers CD69 and HLA-DR in NK cells and monocytes/macrophages, respectively. The effect of MIM was evaluated in a model of respiratory infection induced by influenza A virus administration to immunocompetent mice in which it was able to improve neutrophil recruitment within the lungs (p = 0.1051) and slightly increased the circulating levels of IgM (p = 0.1655). Furthermore, MIM stimulated the proliferation of CD3-primed T lymphocytes and decreased the secretion of the immunosuppressive cytokine IL-10 in CD14⁺-derived macrophages. Human umbilical vein endothelial cells were finally used to explore the effect of MIM on endothelial cells, in which it slightly increased the expression of immune-related markers such as HLA-I, CD137L, GITRL, PD-L1 and ICAM-1. In conclusion, the present study suggests that MIM might be a promising nonspecific (without antigen specificity) immunostimulant drug in preventing and early treating respiratory infections, but not only exclusively, as it would gently support several facets of the immune system and host defenses.

Immune profiles provide insights into respiratory syncytial virus disease severity in young children

Respiratory syncytial virus (RSV) is associated with major morbidity in infants, although most cases result in mild disease. The pathogenesis of the disease is incompletely understood, especially the determining factors of disease severity. A better characterization of these factors may help with development of RSV vaccines and antivirals. Hence, identification of a "safe and protective" immunoprofile induced by natural RSV infection could be used as a as a surrogate of ideal vaccine-elicited responses in future clinical trials. In this study, we integrated blood transcriptional and cell immune profiling, RSV loads, and clinical data to identify factors associated with a mild disease phenotype in a cohort of 190 children <2 years of age. Children with mild disease (outpatients) showed higher RSV loads, greater induction of interferon (IFN) and plasma cell genes, and decreased expression of inflammation and neutrophil genes versus children with severe disease (inpatients). Additionally, only infants with severe disease had increased numbers of HLA-DR^low monocytes, not present in outpatients. Multivariable analyses confirmed that IFN overexpression was associated with decreased odds of hospitalization, whereas increased numbers of HLA-DR^low monocytes were associated with increased risk of hospitalization. These findings suggest that robust innate immune responses are associated with mild RSV infection in infants.

Severe respiratory syncytial virus disease in preterm infants: a case of innate immaturity

Respiratory syncytial virus (RSV) is the most common viral pathogen associated with acute lower respiratory tract infection (LRTI) in children under 5 years of age. Severe RSV disease is associated with the development of chronic respiratory complications such as recurrent wheezing and asthma. A common risk factor for developing severe RSV disease is premature gestation and this is largely due to an immature innate immune system. This increases susceptibility to RSV since the innate immune system is less able to protect against pathogens at a time when adaptive immunity has not fully developed. This review focuses on comparing different aspects of innate immunity between preterm and term infants to better understand why preterm infants are more susceptible to severe RSV disease. Identifying early life innate immune biomarkers associated with the development of severe RSV disease, and understanding how these compare between preterm and term infants, remains a critically important question that would aid the development of interventions to reduce the burden of disease in this vulnerable population.

Quantitative and qualitative alterations of circulating myeloid cells and plasmacytoid DC in SARS-CoV-2 infection

SARS-CoV-2 is responsible for a new infectious disease (COVID-19) in which individuals can either remain asymptomatic or progress from mild to severe clinical conditions including acute respiratory distress syndrome and multiple organ failure. The immune mechanisms that potentially orchestrate the pathology in SARS-CoV-2 infection are complex and only partially understood. There is still paucity of data on the features of myeloid cells involved in this viral infection. For this reason, we investigated the different activation status profiles and the subset distribution of myeloid cells and their correlation with disease progression in 40 COVID-19 patients at different stages of disease. COVID-19 patients showed a decrease in the absolute number of plasmacytoid and myeloid dendritic cells, different subset distribution of monocytes and different activation patterns of both monocytes and neutrophils, coupled to a significant reduction of HLA-DR monocyte levels. We found that some of these alterations are typical of all COVID-19 patients, while some others vary at different stages of the disease and correlate with biochemical parameters of inflammation. Collectively, these data suggest that not only the lymphoid, but also the myeloid compartment, is severely affected by SARS-CoV-2 infection.

Elevated monocytic myeloid-derived suppressor cells positively correlate with infection frequency in children with RRTIs

In children with recurrent respiratory tract infections (RRTIs), the percentages and numbers of monocytic myeloid-derived suppressor cells (MDSCs) were elevated. The elevated MDSCs positively correlate with respiratory tract infection frequency in RRTIs children. The elevated MDSCs can inhibit CD8+ T-cells proliferation in RRTIs children.

Monocyte subsets study in children with Mycoplasma pneumoniae pneumonia

The aim of this study was to evaluate the changes in the three subsets of monocyte (classical, intermediate, and non-classical) and the expression of human leukocyte antigen-DR (HLA-DR) on monocyte subsets during MP pneumonia in children. Monocyte subsets were analyzed in the peripheral blood of healthy volunteers and MP pneumonia patients at the stages of admission and remission after clinical therapy. They were defined as classical (CD14⁺CD16^-), intermediate (CD14^brightCD16⁺), and non-classical (CD14^dimCD16⁺) using flow cytometry. Furthermore, three subsets of monocyte were analyzed for the expression of HLA-DR. Patients with MP pneumonia at admission had a higher proportion of intermediate and non-classical monocytes than healthy subjects (all P < 0.05). The proportion of intermediate subset and non-classical subset was lower in MP pneumonia patients at remission than at admission (all P < 0.05). In comparison with the other monocyte subsets, intermediate subset showed a significantly higher percentage of HLA-DR in MP pneumonia patients at admission (P < 0.05). Further analysis revealed that the expression of HLA-DR on intermediate subset was lower in severe patients than in non-severe patients (P < 0.05).Our data has shown for the first time that MP pneumonia is associated with the increased proportion of non-classical and intermediate monocytes, indicating the involvement of monocyte-related mechanisms in the pathogenesis of this disease. Additionally, the decreased expression of HLA-DR on CD14^brightCD16⁺ subset may be a potential indicator of the severity of MP pneumonia.

Immune biomarkers predicting bronchiolitis disease severity: A systematic review

Bronchiolitis is one of the leading causes of hospitalisation in infancy, with highly variable clinical presentations ranging from mild disease safely managed at home to severe disease requiring invasive respiratory support. Identifying immune biomarkers that can predict and stratify this variable disease severity has important implications for clinical prognostication/disposition. A systematic literature search of the databases Embase, PubMed, ScienceDirect, Web of Science, and Wiley Online Library was performed. English language studies that assessed the association between an immune biomarker and bronchiolitis disease severity among children aged less than 24 months were included. 252 distinct biomarkers were identified across 90 studies. A substantial degree of heterogeneity was observed in the bronchiolitis definitions, measures of disease severity, and study designs. 99 biomarkers showed some significant association with disease severity, but only 18 were significant in multiple studies. However, all of these candidate biomarkers had comparable studies that reported conflicting results. Conclusion: The heterogeneity among included studies and the lack of a consistently significant biomarker highlight the need for consensus on bronchiolitis definitions and severity measures, as well as further studies assessing their clinical utility both in isolation and in combination.

Cell surface antigens of neonatal monocytes are selectively impaired in basal expression, but hyperresponsive to lipopolysaccharide and zymosan

Toll-like receptors (TLRs) are important components of the innate immune system, but how neonatal TLR-mediated immune responses differ from those of adults is unknown. We aimed to clarify the TLR-mediated expression profiles of cell surface antigens related to antigen presentation in neonates. CD14-positive monocytes were isolated from human cord blood and adult peripheral blood and then stimulated with lipopolysaccharide (LPS; TLR4 agonist) or zymosan (TLR2/6 agonist) or left unstimulated. Expression levels of the surface antigens major histocompatibility (MHC)-class II, CD80, CD86, CD11b, CD11c, CD14, and CD16 were then evaluated by flow cytometry. Cord blood CD14⁺CD16^high monocytes (CBM) showed significantly lower basal levels of MHC-class II, CD80, and CD11b than adult blood CD14⁺CD16^intermediate monocytes (ABM) (P < 0.01, P < 0.001, P < 0.001, respectively). LPS stimulation enhanced expression of MHC class II, CD80, and CD11b significantly more in CBM than in ABM (P < 0.001, P < 0.01, P < 0.01, respectively), resulting in levels that did not differ between CBM and ABM. Zymosan stimulation also enhanced expression of MHC class II, CD86, CD11b, and CD11c significantly more in CBM than in ABM (P < 0.001, P < 0.01, P < 0.001, P < 0.01, respectively), resulting in levels of CD86 and CD11c that did not differ in CBM and ABM. However, MHC class II, CD80, and CD11b remained significantly higher in ABM than in CBM (P < 0.05, P < 0.01, P < 0.05, respectively). These data indicate that CBM and ABM have distinct phenotypes and responses to stimulation.

Host Components Contributing to Respiratory Syncytial Virus Pathogenesis

Respiratory syncytial virus (RSV) is the most prevalent viral etiological agent of acute respiratory tract infection. Although RSV affects people of all ages, the disease is more severe in infants and causes significant morbidity and hospitalization in young children and in the elderly. Host factors, including an immature immune system in infants, low lymphocyte levels in patients under 5 years old, and low levels of RSV-specific neutralizing antibodies in the blood of adults over 65 years of age, can explain the high susceptibility to RSV infection in these populations. Other host factors that correlate with severe RSV disease include high concentrations of proinflammatory cytokines such as interleukins (IL)-6, IL-8, tumor necrosis factor (TNF)-α, and thymic stromal lymphopoitein (TSLP), which are produced in the respiratory tract of RSV-infected individuals, accompanied by a strong neutrophil response. In addition, data from studies of RSV infections in humans and in animal models revealed that this virus suppresses adaptive immune responses that could eliminate it from the respiratory tract. Here, we examine host factors that contribute to RSV pathogenesis based on an exhaustive review of in vitro infection in humans and in animal models to provide insights into the design of vaccines and therapeutic tools that could prevent diseases caused by RSV.

Airway Epithelial Derived Cytokines and Chemokines and Their Role in the Immune Response to Respiratory Syncytial Virus Infection

The airway epithelium is the primary target of respiratory syncytial virus infection. It is an important component of the antiviral immune response. It contributes to the recruitment and activation of innate immune cells from the periphery through the secretion of cytokines and chemokines. This paper provides a broad review of the cytokines and chemokines secreted from human airway epithelial cell models during respiratory syncytial virus (RSV) infection based on a comprehensive literature review. Epithelium-derived chemokines constitute most inflammatory mediators secreted from the epithelium during RSV infection. This suggests chemo-attraction of peripheral immune cells, such as monocytes, neutrophils, eosinophils, and natural killer cells as a key function of the epithelium. The reports of epithelium-derived cytokines are limited. Recent research has started to identify novel cytokines, the functions of which remain largely unknown in the wider context of the RSV immune response. It is argued that the correct choice of in vitro models used for investigations of epithelial immune functions during RSV infection could facilitate greater progress in this field.

Infant Immune Response to Respiratory Viral Infections

Of all respiratory viruses that affect infants, respiratory syncytial virus (RSV) and rhinovirus (RV) represent the leading pathogens causing acute disease (bronchiolitis) and are associated with the development of recurrent wheezing and asthma. The immune system in infants is still developing, and several factors contribute to their increased susceptibility to viral infections. These factors include differences in pathogen detection, weaker interferon responses, lack of immunologic memory toward the invading pathogen, and T-cell responses that are balanced to promote tolerance and restrain inflammation. These aspects are reviewed here with a focus on RSV and RV infections.

Blood monocyte profiles in COPD patients with PiMM and PiZZ α1-antitrypsin

Human blood monocytes are divided into populations based on the differential expression of CD14 and CD16 receptors: CD14 ⁺ CD16(classical), CD14 ⁺ CD16 ⁺ (intermediate), and CD14^-CD16⁺ (non-classical). Given their functional differences and their role in pathogenesis of chronic obstructive pulmonary disease (COPD), monocyte profiling is of clinical interest. Here we investigated blood monocyte subsets in clinically stable COPD patients with alpha1-antitrypsin (AAT) deficiency (PiZZ, n = 7) and with normal AAT variant (PiMM, n = 7). Peripheral whole blood was collected in sodium heparin tubes and incubated with LPS (from E. coli; 1 μg/ml) or placebo for 6 h at 37 °C, 5% CO2. To profile monocyte subsets we performed flow cytometry analysis based on HLA-DR and CD14/CD16 staining. HLA-DR + subsets of cells did not differ between PiZZ and PiMM COPD, and healthy controls (n = 7), used as a reference. Monocyte profiling, which express the CD14 and CD16, but not the HLA-DR (HLA-DR-) showed that intermediate monocytes subset was lowest in PiZZ group, and almost totally disappeared from blood treated with LPS. The non-classical subset was almost absent in PiZZ patients independently of LPS treatment. Recent studies demonstrate that non-classical monocytes exhibit a unique ability to protect the vascular endothelium under both homeostatic and inflammatory conditions whereas intermediate monocytes are recruited at a later stage of inflammation, and are associated with secretion of cytokines/chemokines and wound healing. Evident alterations in blood monocyte subsets together with a partial reduction of AAT levels, an important anti-inflammatory protein, can be key factors for the early manifestation of emphysema in some PiZZ AATD carriers.

Restoration of Peripheral Intermediate and Classical Monocytes Expressing HLA-DR in Patients With Lung Adenocarcinoma After Platinum-Based Chemotherapy

Lung adenocarcinoma represents one of the lung cancer subtypes with major prevalence. Accumulating evidence indicates that the immune system plays an important role in the evolution of the neoplastic process; additionally, several reports suggest that chemotherapy has an immunomodulatory effect. In order to identify the peripheral subpopulations of leukocytes that may change after chemotherapy, we evaluated several peripheral immune subpopulations of monocytes and lymphocytes by multicolor flow cytometry. In addition, we also measured cytokines and growth factors on plasma in order to evaluate the pro-inflammatory context in patients with lung adenocarcinoma after chemotherapy. We found that HLA-DR⁺ classical and intermediate monocytes were decreased in patients before chemotherapy, compared to controls. After chemotherapy, the relative percentage of those subpopulations was restored. In addition, interleukin 1β, interleukin 12, and interleukin 5 were increased after chemotherapy compared to prechemotherapy levels, while MIP-1β was decreased.

Siglec-1 inhibits RSV-induced interferon gamma production by adult T cells in contrast to newborn T cells

Interferon gamma (IFN‐γ) plays an important role in the antiviral immune response during respiratory syncytial virus (RSV) infections. Monocytes and T cells are recruited to the site of RSV infection, but it is unclear whether cell‐cell interactions between monocytes and T cells regulate IFN‐γ production. In this study, micro‐array data identified the upregulation of sialic acid‐binding immunoglobulin‐type lectin 1 (Siglec‐1) in human RSV‐infected infants. In vitro, RSV increased expression of Siglec‐1 on healthy newborn and adult monocytes. RSV‐induced Siglec‐1 on monocytes inhibited IFN‐γ production by adult CD4⁺ T cells. In contrast, IFN‐γ production by RSV in newborns was not affected by Siglec‐1. The ligand for Siglec‐1, CD43, is highly expressed on adult CD4⁺ T cells compared to newborns. Our data show that Siglec‐1 reduces IFN‐γ release by adult T cells possibly by binding to the highly expressed CD43. The Siglec‐1‐dependent inhibition of IFN‐γ in adults and the low expression of CD43 on newborn T cells provides a better understanding of the immune response against RSV in early life and adulthood.

Direct and Intestinal Epithelial Cell-Mediated Effects of TLR8 Triggering on Human Dendritic Cells, CD14+CD16+ Monocytes and γδ T Lymphocytes

Toll-like receptor (TLR)7/8 plays a crucial role in host recognition/response to viruses and its mucosal expression directly correlates with intestinal inflammation. The aim of this study was to investigate the role of TLR7/8 stimulation of intestinal epithelium in shaping the phenotype and functions of innate immunity cell subsets, and to define direct and/or epithelial cell-mediated mechanisms of the TLR7/8 agonist R848 immunomodulatory activity. We describe novel, TLR8-mediated, pro- and anti-inflammatory effects of R848 on ex vivo cultured human blood monocytes and γδ T lymphocytes, either induced by direct immune cell stimulation or mediated by intestinal epithelial cells (IEC). Apical stimulation with R848 led to its transport across normal polarized epithelial cell monolayer and resulted in the inhibition of monocyte differentiation toward immunostimulatory dendritic cells and Th1 type response. Furthermore, γδ T lymphocyte activation was promoted following direct exposure of these cells to the agonist. Conversely, a selective enrichment of the CD14⁺CD16⁺ monocyte subpopulation was observed, which required a CCL2-mediated inflammatory response of normal epithelial cells to R848. Of note, a TLR-mediated activation of control γδ T lymphocytes was promoted by inflamed intestinal epithelium from active Crohn's disease patients. This study unravels a novel regulatory mechanism linking the activation of the TLR8 pathway in IEC to the monocyte-mediated inflammatory response, and highlights the capacity of the TLR7/8 agonist R848 to directly enhance the activation of γδ T lymphocytes. Overall these results expand the range of cell targets and immune responses controlled by TLR8 triggering that may contribute to the antiviral response, to chronic inflammation, as well as to the adjuvant activity of TLR8 agonists, highlighting the role of intestinal epithelium microenvironment in shaping TLR agonist-induced responses.

Functional Impairment of Mononuclear Phagocyte System by the Human Respiratory Syncytial Virus

The mononuclear phagocyte system (MPS) comprises of monocytes, macrophages (MΦ), and dendritic cells (DCs). MPS is part of the first line of immune defense against a wide range of pathogens, including viruses, such as the human respiratory syncytial virus (hRSV). The hRSV is an enveloped virus that belongs to the Pneumoviridae family, Orthopneumovirus genus. This virus is the main etiological agent causing severe acute lower respiratory tract infection, especially in infants, children and the elderly. Human RSV can cause bronchiolitis and pneumonia and it has also been implicated in the development of recurrent wheezing and asthma. Monocytes, MΦ, and DCs significantly contribute to acute inflammation during hRSV-induced bronchiolitis and asthma exacerbation. Furthermore, these cells seem to be an important component for the association between hRSV and reactive airway disease. After hRSV infection, the first cells encountered by the virus are respiratory epithelial cells, alveolar macrophages (AMs), DCs, and monocytes in the airways. Because AMs constitute the predominant cell population at the alveolar space in healthy subjects, these cells work as major innate sentinels for the recognition of pathogens. Although adaptive immunity is crucial for viral clearance, AMs are required for the early immune response against hRSV, promoting viral clearance and controlling immunopathology. Furthermore, exposure to hRSV may affect the phagocytic and microbicidal capacity of monocytes and MΦs against other infectious agents. Finally, different studies have addressed the roles of different DC subsets during infection by hRSV. In this review article, we discuss the role of the lung MPS during hRSV infection and their involvement in the development of bronchiolitis.

Immune and inflammatory response in bronchiolitis due to respiratory Syncytial Virus and Rhinovirus infections in infants

Bronchiolitis is a common disease in infancy, mostly due to Respiratory Syncytial Virus and Rhinovirus. In addition to acute infection, viral bronchiolitis is responsible for sequelae including recurrent wheezing and asthma. The analysis of the viral characteristics and of the pathogenesis of the infection shows differences between the two viruses that may be helpful for the development of therapies and preventive strategies.