Hematologically important mutations: leukocyte adhesion deficiency (first update)

Membrane potential dynamics of C5a-stimulated neutrophil granulocytes

Neutrophil granulocytes play a crucial role in host defense against invading pathogens and in inflammatory diseases. The aim of this study was to elucidate membrane potential dynamics during the initial phase of neutrophil activation and its relation to migration and production of reactive oxygen species (ROS). We performed ROS production measurements of neutrophils from healthy C57BL/6J mice after TNFα-priming and/or C5a stimulation. The actin cytoskeleton was visualized with fluorescence microscopy. Furthermore, we combined migration assays and measurements of membrane potential dynamics after stimulating unprimed and/or TNFα-primed neutrophils with C5a. We show that C5a has a concentration-dependent effect on ROS production and chemokinetic migration. Chemokinetic migration and chemotaxis are impaired at C5a concentrations that induce ROS production. The actin cytoskeleton of unstimulated and of ROS-producing neutrophils is not distributed in a polarized way. Inhibition of the phagocytic NADPH oxidase NOX2 with diphenyleneiodonium (DPI) leads to a polarized distribution of the actin cytoskeleton and rescues chemokinetic migration of primed and C5a-stimulated neutrophils. Moreover, C5a evokes a pronounced depolarization of the cell membrane potential by 86.6 ± 4.2 mV starting from a resting membrane potential of -74.3 ± 0.7 mV. The C5a-induced depolarization occurs almost instantaneously (within less than one minute) in contrast to the more gradually developing depolarization induced by PMA (lag time of 3-4 min). This initial depolarization is accompanied by a decrease of the migration velocity. Collectively, our results show that stimulation with C5a evokes parallel changes in membrane potential dynamics, neutrophil ROS production and motility. Notably, the amplitude of membrane potential dynamics is comparable to that of excitable cells.

Analysis of Clinical, Immunological and Molecular Features of Leukocyte Adhesion Deficiency Type I in Egyptian Children

PURPOSE

Leukocyte adhesion deficiency (LAD) represents a rare group of inherited inborn errors of immunity (IEI) characterized by bacterial infections, delayed umbilical stump separation, and autoimmunity. This single-center study aimed at describing the clinical, immunological, and molecular characterizations of 34 LAD-I Egyptian pediatric patients.

METHODS

Details of 34 patients' personal medical history, clinical and laboratory findings were recorded; Genetic material from 28 patients was studied. Mutational analysis was done by Sanger sequencing.

RESULTS

Omphalitis, skin and soft tissue infections with poorly healing ulcers, delayed falling of the umbilical stump, and recurrent or un-resolving pneumonia were the most common presentations, followed by chronic otitis media, enteropathy, periodontitis; and recurrent oral thrush. Persistent leukocytosis and neutrophilia were reported in all patients, as well as CD18 and CD11b deficiency. CD18 expression was < 2% in around 90% of patients. Sixteen different pathological gene variants were detected in 28 patients who underwent ITGß2 gene sequencing, of those, ten were novel and six were previously reported. Three families received a prenatal diagnosis. Patients were on antimicrobials according to culture's results whenever available, and on prophylactic Trimethoprim-Sulfamethoxazole 5 mg/kg once daily, with regular clinical follow up. Hematopoietic stem cell transplantation (HSCT) was offered for 4 patients. However due to severity of the disease and delay in diagnosis, 58% of the patients passed away in the first 2 years of life.

CONCLUSION

This study highlights the importance of early diagnosis and distribution of ITGß2 gene mutation in Egyptian children. Further molecular studies, however, remain a challenging necessity for better disease characterization in the region.

Understanding very early onset inflammatory bowel disease (VEOIBD) in relation to inborn errors of immunity

Inflammatory bowel diseases (IBD) are multifactorial diseases which are caused by the combination of genetic predisposition, exposure factors (environmental and dietary), immune status, and dysbiosis. IBD is a disease which presents at any age, ranging from newborns to the elderly. The youngest of the pediatric IBD population have a more unique presentation and clinical course and may have a different etiology. Very early onset IBD (VEOIBD) patients, designated as those diagnosed prior the age of 6, have distinct features which are more frequent in this patient population including increased incidence of monogenetic causes for IBD (0%-33% depending on the study). This proportion is increased in the youngest subsets, which is diagnosed prior to the age of 2. To date, there are approximately 80 monogenic causes of VEOIBD that have been identified and published. Many of these monogenic causes are inborn errors of immunity yet the majority of VEOIBD patients do not have an identifiable genetic cause for their disease. In this review, we will focus on the clinical presentation, evaluation, and monogenic categories which have been associated with VEOIBD including (1) Epithelial cell defects (2) Adaptive immune defects, (3) Innate Immune/Bacterial Clearance and Recognition defects, and (4) Hyperinflammatory and autoinflammatory disorders. We will highlight differential diagnosis of VEOIBD presentations, as well as evaluation and treatment, which will be helpful for those who study and care for VEOIBD patients outside of the pediatric gastroenterology field. This is a fast-moving field of research which has grown significantly based on knowledge that we gain from our patients. These scientific findings have identified novel mucosal biology pathways and will continue to inform our understanding of gastrointestinal biology.

SKAP2 acts downstream of CD11b/CD18 and regulates neutrophil effector function

Background

The importance of CD11b/CD18 expression in neutrophil effector functions is well known. Beyond KINDLIN3 and TALIN1, which are involved in the induction of the high-affinity binding CD11b/CD18 conformation, the signaling pathways that orchestrate this response remain incompletely understood.

Method

We performed an unbiased screening method for protein selection by biotin identification (BioID) and investigated the KINDLIN3 interactome. We used liquid chromatography with tandem mass spectrometry as a powerful analytical tool. Generation of NB4 CD18, KINDLIN3, or SKAP2 knockout neutrophils was achieved using CRISPR-Cas9 technology, and the cells were examined for their effector function using flow cytometry, live cell imaging, microscopy, adhesion, or antibody-dependent cellular cytotoxicity (ADCC).

Results

Among the 325 proteins significantly enriched, we identified Src kinase-associated phosphoprotein 2 (SKAP2), a protein involved in actin polymerization and integrin-mediated outside-in signaling. CD18 immunoprecipitation in primary or NB4 neutrophils demonstrated the presence of SKAP2 in the CD11b/CD18 complex at a steady state. Under this condition, adhesion to plastic, ICAM-1, or fibronectin was observed in the absence of SKAP2, which could be abrogated by blocking the actin rearrangements with latrunculin B. Upon stimulation of NB4 SKAP2-deficient neutrophils, adhesion to fibronectin was enhanced whereas CD18 clustering was strongly reduced. This response corresponded with significantly impaired CD11b/CD18-dependent NADPH oxidase activity, phagocytosis, and cytotoxicity against tumor cells.

Conclusion

Our results suggest that SKAP2 has a dual role. It may restrict CD11b/CD18-mediated adhesion only under resting conditions, but its major contribution lies in the regulation of dynamic CD11b/CD18-mediated actin rearrangements and clustering as required for cellular effector functions of human neutrophils.

Regulatory features aid interpretation of 3'UTR Variants

Our ability to determine the clinical impact of variants in 3' untranslated regions (UTRs) of genes remains poor. We provide a thorough analysis of 3'UTR variants from several datasets. Variants in putative regulatory elements including RNA-binding protein motifs, eCLIP peaks, and microRNA sites are up to 16 times more likely than other variants to have gene expression and phenotype associations. Heterozygous variants in regulatory motifs result in allele-specific protein binding in cell lines and allele-specific gene expression differences in population studies. In addition, variants in shared regions of alternatively polyadenylated isoforms and those proximal to polyA sites are more likely to affect gene expression and phenotype. Finally, pathogenic 3'UTR variants in ClinVar are 20 times more likely than benign variants to fall in a regulatory site. We incorporated these findings into RegVar, a software tool that interprets regulatory elements and annotations for any 3'UTR variant, and predicts whether the variant is likely to affect gene expression or phenotype. This tool will help prioritize variants for experimental studies and identify pathogenic variants in patients.

Clinical and immunological characteristics of 69 leukocyte adhesion deficiency-I patients

BACKGROUND

In order to support the comprehensive classification of Leukocyte Adhesion Deficiency-I (LAD-I) severity by simultaneous screening of CD11a/CD18, this study assessed clinical, laboratory, and genetic findings along with outcomes of 69 LAD-I patients during the last 15 years.

METHODS

Sixty-nine patients (40 females and 29 males) with a clinical phenotype suspected of LAD-I were referred to Immunology, Asthma, and Allergy research institute, Tehran, Iran between 2007 and 2022 for further advanced immunological screening and genetic evaluations as well as treatment, were enrolled in this study.

RESULTS

The diagnosis median age of the patients was 6 months. Delayed umbilical cord separation was found in 25 patients (36.2%). The median diagnostic delay time was 4 months (min-max: 0-82 months). Forty-six patients (66.7%) were categorized as severe (CD18 and/or CD11a: below 2%); while 23 children (33.3%) were in moderate category (CD18 and/or CD11a: 2%-30%). During the follow-ups, 55.1% of children were alive with a mortality rate of 44.9%. Skin ulcers (75.4%), omphalitis (65.2%), and gingivitis (37.7%) were the most frequent complaints. Genetic analysis of the patients revealed 14 previously reported and three novel pathogenic mutations in the ITGB2 gene. The overall survival of patients with and without hematopoietic stem cell transplantation was 79.3% and 55.6%, respectively.

CONCLUSION

Physicians' awareness of LAD-I considering delayed separation of umbilical cord marked neutrophilic leukocytosis, and variability in CD11 and CD18 expression levels, and genetic analysis leads to early diagnosis and defining disease severity. Moreover, the prenatal diagnosis would benefit families with a history of LAD-I.

Pharmacologic Management of Monogenic and Very Early Onset Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD) is treated with a variety of immunomodulating and immunosuppressive therapies; however, for the majority of cases, these therapies are not targeted for specific disease phenotypes. Monogenic IBD with causative genetic defect is the exception and represents a disease cohort where precision therapeutics can be applied. With the advent of rapid genetic sequencing platforms, these monogenic immunodeficiencies that cause inflammatory bowel disease are increasingly being identified. This subpopulation of IBD called very early onset inflammatory bowel disease (VEO-IBD) is defined by an age of onset of less than six years of age. Twenty percent of VEO-IBDs have an identifiable monogenic defect. The culprit genes are often involved in pro-inflammatory immune pathways, which represent potential avenues for targeted pharmacologic treatments. This review will provide an overview of the current state of disease-specific targeted therapies, as well as empiric treatment for undifferentiated causes of VEO-IBD.

Hematologically important mutations: Leukocyte adhesion deficiency (second update)

Leukocyte adhesion deficiency (LAD) is an immunodeficiency caused by defects in the adhesion of leukocytes (especially neutrophils) to the blood vessel wall. As a result, patients with LAD suffer from severe bacterial infections and impaired wound healing, accompanied by neutrophilia. In LAD-I, characterized directly after birth by delayed separation of the umbilical cord, mutations are found in ITGB2, the gene that encodes the β subunit (CD18) of the β₂ integrins. In the rare LAD-II disease, the fucosylation of selectin ligands is disturbed, caused by mutations in SLC35C1, the gene that encodes a GDP-fucose transporter of the Golgi system. LAD-II patients lack the H and Lewis Le^a and Le^b blood group antigens. Finally, in LAD-III, the conformational activation of the hematopoietically expressed β integrins is disturbed, leading to leukocyte and platelet dysfunction. This last syndrome is caused by mutations in FERMT3, encoding the kindlin-3 protein in all blood cells, involved in the regulation of β integrin conformation. This article contains an update of the mutations that we consider to be relevant for the various forms of LAD.

A Novel Deletion in FERMT3 Causes LAD-III in a Turkish Family

Leukocyte adhesion deficiency-III (LAD-III) is an extremely rare autosomal recessive syndrome caused by mutations in FERMT3, the gene encoding kindlin-3. The genetic alterations in this gene lead to abnormal expression or activity of kindlin-3 in leukocytes and platelets. Kindlin-3 acts as an important regulator of integrin activation. LAD-III has features of the bleeding syndrome of Glanzmann and also of leukocyte adhesion deficiency. In this study, we report on two families, one of Turkish and one of Syrian origin, with clinical features of LAD-III, loss of kindlin-3 protein expression, and a functional leukocyte defect. A novel, homozygous deletion in FERMT3 (c.921delC, p.Ser307Argfs*21) was found in the Turkish patient. The parents were carriers of the mutation, consistent with an autosomal recessive inheritance. A common c.1525C > T (p.Arg509*) mutation was found in the Syrian patient. In conclusion, beside the variant c.1525C > T in the FERMT3 gene, which was previously found in more than 15 patients in Anatolia, our study is the first to identify the novel homozygous variant c.921delC in the FERMT3 gene.

Mechano-Redox Control of Integrins in Thromboinflammation

Significance: How mechanical forces and biochemical cues are coupled remains a miracle for many biological processes. Integrins, well-known adhesion receptors, sense changes in mechanical forces and reduction-oxidation reactions (redox) in their environment to mediate their adhesive function. The coupling of mechanical and redox function is a new area of investigation. Disturbance of normal mechanical forces and the redox balance occurs in thromboinflammatory conditions; atherosclerotic plaques create changes to the mechanical forces in the circulation. Diabetes induces redox changes in the circulation by the production of reactive oxygen species and vascular inflammation. Recent Advances: Integrins sense changes in the blood flow shear stress at the level of focal adhesions and respond to flow and traction forces by increased signaling. Talin, the integrin-actin linker, is a traction force sensor and adaptor. Oxidation and reduction of integrin disulfide bonds regulate their adhesion. A conserved disulfide bond in integrin αlpha IIb beta 3 (αIIbβ3) is directly reduced by the thiol oxidoreductase endoplasmic reticulum protein 5 (ERp5) under shear stress. Critical Issues: The coordination of mechano-redox events between the extracellular and intracellular compartments is an active area of investigation. Another fundamental issue is to determine the spatiotemporal arrangement of key regulators of integrins' mechanical and redox interactions. How thromboinflammatory conditions lead to mechanoredox uncoupling is relatively unexplored. Future Directions: Integrated approaches, involving disulfide bond biochemistry, microfluidic assays, and dynamic force spectroscopy, will aid in showing that cell adhesion constitutes a crossroad of mechano- and redox biology, within the same molecule, the integrin. Antioxid. Redox Signal. 37, 1072-1093.

Three novel homozygous ITGB2 mutations among two patients with leukocyte adhesion defect type-1: Two case reports

BACKGROUND

A leukocyte adhesion defect (LAD) is a rare primary immunodeficiency disorder. LAD type 1 (LAD-1) is the most common, which is caused by ITGB2 mutation resulting in dysfunction of β2 integrin, which impairs leukocyte adherence to the endothelium.

CASE SUMMARY

The first two cases of LAD-1 in Thailand presented with recurrent omphalitis, soft tissue infection, marked leukocytosis, and neutrophilia. One patient experienced delayed umbilical cord separation. Mutation analysis was performed by direct DNA sequencing of the ITGB2 gene. The results revealed two novel homozygous missense mutations, c.920C>T (p.Leu307Pro) in exon 8 and c.758G>A (p.Arg253His) in exon 7, and one novel homozygous nonsense mutation, c.262C>T (p.Gln88Ter) in exon 4, in the genomic DNA of the first and second patients, respectively. Heterozygous mutations were identified in the parents of both patients, suggesting a carrier status. The patients were administered intravenous antibiotics for infections with good clinical responses. Hematopoietic stem cell transplantation could not be performed due to the unavailability of matched donors. However, a significant decline in infections was observed after antibiotic prophylaxis. Several follow-up visits were conducted for both patients. They are currently 6 years old.

CONCLUSION

Molecular analysis is essential for definitive diagnosis, early treatment implementation, and prevention of LAD-1 in future pregnancy.

Preclinical safety and efficacy of lentiviral-mediated gene therapy for leukocyte adhesion deficiency type I

Leukocyte adhesion deficiency type I (LAD-I) is a primary immunodeficiency caused by mutations in the ITGB2 gene, which encodes for the CD18 subunit of β₂-integrins. Deficient expression of β₂-integrins results in impaired neutrophil migration in response to bacterial and fungal infections. Using a lentiviral vector (LV) that mediates a preferential myeloid expression of human CD18 (Chim.hCD18-LV), we first demonstrated that gene therapy efficiently corrected the phenotype of mice with severe LAD-I. Next, we investigated if the ectopic hCD18 expression modified the phenotypic characteristics of human healthy donor hematopoietic stem cells and their progeny. Significantly, transduction of healthy CD34⁺ cells with the Chim.hCD18-LV did not modify the membrane expression of CD18 nor the adhesion of physiological ligands to transduced cells. Additionally, we observed that the repopulating properties of healthy CD34⁺ cells were preserved following transduction with the Chim.hCD18-LV, and that a safe polyclonal repopulation pattern was observed in transplanted immunodeficient NOD scid gamma (NSG) mice. In a final set of experiments, we demonstrated that transduction of CD34⁺ cells from a severe LAD-I patient with the Chim.hCD18-LV restores the expression of β₂-integrins in these cells. These results offer additional preclinical safety and efficacy evidence supporting the gene therapy of patients with severe LAD-I.

Incorporation of fucose into glycans independent of the GDP-fucose transporter SLC35C1 preferentially utilizes salvaged over de novo GDP-fucose

Mutations in the SLC35C1 gene encoding the Golgi GDP-fucose transporter are known to cause leukocyte adhesion deficiency II. However, improvement of fucosylation in leukocyte adhesion deficiency II patients treated with exogenous fucose suggests the existence of an SLC35C1-independent route of GDP-fucose transport, which remains a mystery. To investigate this phenomenon, we developed and characterized a human cell–based model deficient in SLC35C1 activity. The resulting cells were cultured in the presence/absence of exogenous fucose and mannose, followed by examination of fucosylation potential and nucleotide sugar levels. We found that cells displayed low but detectable levels of fucosylation in the absence of SLC35C1. Strikingly, we show that defects in fucosylation were almost completely reversed upon treatment with millimolar concentrations of fucose. Furthermore, we show that even if fucose was supplemented at nanomolar concentrations, it was still incorporated into glycans by these knockout cells. We also found that the SLC35C1-independent transport preferentially utilized GDP-fucose from the salvage pathway over the de novo biogenesis pathway as a source of this substrate. Taken together, our results imply that the Golgi systems of GDP-fucose transport discriminate between substrate pools obtained from different metabolic pathways, which suggests a functional connection between nucleotide sugar transporters and nucleotide sugar synthases.

A humanized β2 integrin knockin mouse reveals localized intra- and extravascular neutrophil integrin activation in vivo

β₂ integrins are leukocyte-specific adhesion molecules that are essential for leukocyte recruitment. The lack of tools for reporting β₂ integrin activation in mice hindered the study of β₂ integrin-related immune responses in vivo. Here, we generated a humanized β₂ integrin knockin mouse strain by targeting the human β₂ integrin coding sequence into the mouse Itgb2 locus to enable imaging of β₂ integrin activation using the KIM127 (extension) and mAb24 (high-affinity) reporter antibodies. Using a CXCL1-induced acute inflammation model, we show the local dynamics of β₂ integrin activation in arresting neutrophils in vivo in venules of the mouse cremaster muscle. Activated integrins are highly concentrated in a small area at the rear of arresting neutrophils in vivo. In a high-dose lipopolysaccharide model, we find that β₂ integrins are activated in association with elevated neutrophil adhesion in lung and liver. Thus, these mice enable studies of β₂ integrin activation in vivo.

Linking Genetic Diagnosis to Therapeutic Approach in Very Early Onset Inflammatory Bowel Disease: Pharmacologic Considerations

Very early onset inflammatory bowel disease (VEO-IBD) is diagnosed in children < 6 years of age, and in rare cases may be due to an identifiable monogenic cause. Recent advances in genetic testing have allowed for more accurate diagnosis, with as many as 100 genes now known to be associated with monogenic inflammatory bowel disease. These genes are involved in many immune pathways and thus may represent potential avenues for targeted precision medicine with pharmacologic treatments aimed at these. This review describes the broad classifications of monogenic disorders known to cause VEO-IBD, as well as empiric and disease-specific medical therapies. These include immune-modulating or immunosuppressant medications, nutritional therapy, surgery, and hematopoietic stem cell transplantation. We aim to provide an overview of the current state of targeted therapy for VEO-IBD.

The Pathogenesis of Giant Condyloma Acuminatum (Buschke-Lowenstein Tumor): An Overview

Giant condyloma acuminatum, also known as Buschke-Lowenstein tumor (BLT), is a rare disease of the anogenital region. BLT is considered a locally aggressive tumor of benign histological appearance, but with the potential for destructive growth and high recurrence rates. BLT development is strongly associated with infection with low-risk human papillomaviruses (HPVs), mostly HPV-6 and -11. Immunity to HPVs plays a crucial role in the natural control of various HPV-induced lesions. Large condyloma acuminata are frequently reported in patients with primary (e.g., DOCK8 or SPINK5 deficiencies) and secondary (e.g., AIDS, solid organ transplantation) immune defects. Individuals with extensive anogenital warts, including BLT in particular, should therefore be tested for inherited or acquired immunodeficiency. Research into the genetic basis of unexplained cases is warranted. An understanding of the etiology of BLT would lead to improvements in its management. This review focuses on the role of underlying HPV infections, and human genetic and immunological determinants of BLT.

Milk Immune Cell Composition in Dromedary Camels With Subclinical Mastitis

Mastitis represents one of the most important infectious diseases in camels with heavy economic losses due to reduced milk quantity and quality. Balanced immune cell composition and function in the mammary gland are essential for effective immune response to mastitis pathogens. The objective of the present study was to characterize the cellular immune response to subclinical mastitis in the mammary gland of dromedary camels. Therefore, immunostaining and flow cytometry were used to compare the cellular composition, leukocyte phenotype, and cell viability in camel milk from healthy she-camels (n = 8) and she-camels with subclinical mastitis (SCM; n = 6). In addition, the ex vivo phagocytic activity of milk phagocytes was compared between healthy and affected animals. The health status of the mammary gland was evaluated based on the California Mastitis Test (CMT) score. SCM (CMT score of ≥3 in the absence of clinical signs of mastitis) was found in six of the 56 sampled quarters (10.7 %) with only one affected quarter per animal. In comparison to milk from healthy camels, milk from SCM animals showed higher somatic cell count (SCC), higher numbers of CD45+ leukocytes with an expanded fraction of CD172a+ myeloid cells. Within the myeloid cell population, there was an increase in the percentage of granulocytes (CD172a⁺CD14^low) with a decreased percentage of macrophages (CD172a⁺CD14^high) in milk from affected animals compared to healthy animals. The decrease in lymphoid cells in SCM milk was mainly due to the decreased fraction of CD4+ helper T cells. Camel SCM was also associated with a stimulated phenotype, increased cell viability, and enhanced phagocytic activity of the milk phagocytes, macrophages and granulocytes. Collectively, the present study identified significant changes in SCC, leukocyte count, phenotype, viability, and function in association with subclinical mastitis in camels. The results of the present study support a better understanding of host-pathogen interaction mechanisms in the camel mammary gland.

Defining the mild variant of leukocyte adhesion deficiency type II (SLC35C1-congenital disorder of glycosylation) and response to l-fucose therapy: Insights from two new families and review of the literature

Leukocyte adhesion deficiency type II (LAD II, also known as SLC35C1-congenital disorder of glycosylation) is an autosomal recessive disorder characterized by growth and cognitive impairment, peripheral neutrophilia, recurrent infections, and the Bombay blood phenotype. A subset of patients with a milder presentation has been described with short stature and developmental delay but minimal immune and hematologic features. Some patients with LAD II benefit from oral fucose therapy, though this has not been previously studied in patients with milder disease. In this study, we describe two new patients from separate families with the milder variant of LAD II and review the published literature on this rare disorder. We demonstrate improvement in speech and cognition, CD15 expression, and core fucosylation of serum glycoproteins after 27 months of oral fucose supplementation in one patient. These patients further support the stratification of this disorder into distinct subtypes, a classical severe and an attenuated variant, and provide preliminary evidence of benefit of fucose therapy in the latter group.

Understanding the Role of LFA-1 in Leukocyte Adhesion Deficiency Type I (LAD I): Moving towards Inflammation?

LFA-1 (Lymphocyte function-associated antigen-1) is a heterodimeric integrin (CD11a/CD18) present on the surface of all leukocytes; it is essential for leukocyte recruitment to the site of tissue inflammation, but also for other immunological processes such as T cell activation and formation of the immunological synapse. Absent or dysfunctional expression of LFA-1, caused by mutations in the ITGB2 (integrin subunit beta 2) gene, results in a rare immunodeficiency syndrome known as Leukocyte adhesion deficiency type I (LAD I). Patients suffering from severe LAD I present with recurrent infections of the skin and mucosa, as well as inflammatory symptoms complicating the clinical course of the disease before and after allogeneic hematopoietic stem cell transplantation (alloHSCT); alloHSCT is currently the only established curative treatment option. With this review, we aim to provide an overview of the intrinsic role of inflammation in LAD I.

Novel ITGB2 Mutation Is Responsible for a Severe Form of Leucocyte Adhesion Deficiency Type 1

Leukocyte adhesion deficiency type 1 (LAD1) is a rare autosomal recessive hereditary disorder characterized by recurrent infections, impaired pus formation, delayed wound healing, omphalitis, and delayed separation of the umbilical cord as hallmark features of the disease. It results from mutations in the integrin β2 subunit gene ITGB2, which encodes the integrin beta chain-2 protein CD18. In this study, we aimed to investigate the case of a five-month-old boy who presented with a clinical phenotype and flow cytometry results suggesting LAD1 disease. Sanger sequencing of all exons and intron boundaries of ITGB2 identified a novel in-frame deletion in exon 7 (ITGB2 c.844_846delAAC, p.Asn282del) in the patient. The p.Asn282del mutation was heterozygous in the child's parents, whereas it was absent in the 96 control individuals from North Africa. This variant was evaluated by two in silico mutation analysis tools, PROVEAN and MutationTaster, which predicted that the mutation was likely to be pathogenic. In addition, molecular modeling with the YASARA View software suggested that this novel mutation may affect the structure of integrin beta-2 and, subsequently, its interaction with integrin alpha-X. In summary, we report a novel pathogenic mutation p.Asn282del associated with LAD1 that expands the mutation diversity of ITGB2 and suggest the combination of flow cytometry and ITGB2 sequencing as a first-line diagnostic approach for LAD disease.

The Impact of Anticoagulation Agent on the Composition and Phenotype of Blood Leukocytes in Dromedary Camels

For the analysis of several cellular biomarkers, blood samples are anticoagulated using different agents with different modes of action. However, for the most commonly used anticoagulants, EDTA and heparin, varying effects on blood components have been reported in different species. As little is known about the impact of anticoagulants on the immunological evaluation of camel leukocytes, the present study analyzed the leukogram, the immunophenotype, and the cell vitality of camel leukocytes separated from blood samples anticoagulated with EDTA or lithium heparin. Using flow cytometry and staining with monoclonal antibodies to several cell surface markers, the composition and immunophenotype of camel leukocytes separated from blood anticoagulated with EDTA or heparin were analyzed. In comparison to EDTA-anticoagulated blood, using lithium heparin as an anticoagulant resulted in reduced numbers of total leukocytes and reduced numbers of neutrophils, which led to a reduced neutrophil to lymphocyte ratio. The analysis of cell necrosis and apoptosis after the staining of leukocytes with the DNA-sensitive dye propidium iodide and the mitochondrial membrane potential probe JC1 revealed a higher fraction of necrotic neutrophils and higher fractions of apoptotic neutrophils and monocytes in heparin blood than in EDTA blood. In addition, monocytes from heparin blood showed higher expression levels of the cell surface markers CD14, CD163, and MHCII when compared to cells from EDTA blood. Similarly, in heparin blood, CD44 and CD172a were expressed higher on neutrophils, while CD11a was expressed higher on lymphocytes in comparison to cells from EDTA blood. The results of the current study indicate the importance of considering the type of anticoagulant when investigating the composition, vitality, and immunophenotype of camel leukocytes.

The Impact of the Animal Housing System on Immune Cell Composition and Function in the Blood of Dromedary Camels

Simple Summary

The present study investigated the impacts of a change in animal housing system on selected parameters of the camel immune system. Samples collected from camels during a free-ranging time were compared with samples collected from the same camels during movement-restricted housing. Movement-restricted camels showed elevated myeloperoxidase activity in their serum, a significant shape-change of their neutrophils, and higher reactive oxygen species content in their monocytes and neutrophils. The leukogram pattern of the camels under restricted housing was characterized by increased numbers of neutrophils, eosinophils, lymphocytes, and monocytes. Within the lymphocyte population, only the helper T cells and B cells were expanded in animals under restricted housing. In addition, restricted housing modulated the expression of several cell surface antigens, including monocyte-polarization markers and cell adhesion molecules. Functional analysis of bacterial phagocytosis indicated impaired antibacterial function of phagocytes in camels under restricted housing. In summary, the present study identified significant changes in blood immune cell composition, phenotype, and function in dromedary camels under restricted-housing conditions, and suggests the development of an excitement leukogram in those animals.

Abstract

Background: The dromedary camel (Camelus dromedarius) is an important livestock animal of desert and semi-desert ecosystems. In recent years, several elements of the camel immune system have been characterized. Stress and excitement induced by animal housing represent the most important environmental factors with potential modulatory effects on the immune system. The present study evaluated the impacts of a restricted-housing system on some phenotypic and functional properties of blood leukocytes in dromedary camels. Methods: Immunofluorescence and flow cytometry were used to comparatively analyze samples collected from camels during a free-ranging time and samples collected from the same camels during movement-restricted housing. Results: In comparison to blood samples collected from the camels during the free-ranging time, samples from movement-restricted camels showed elevated serum myeloperoxidase activity, a significant shape-change in their neutrophils, and higher reactive oxygen species content in their monocytes and neutrophils, indicating increased cellular oxidative stress under movement-restricted housing. The leukogram pattern of the camels under restricted housing was characterized by leukocytosis with increased numbers of neutrophils, eosinophils, lymphocytes, and monocytes, resembling an excitement leukogram pattern. Within the lymphocyte population, only the helper T cells and B cells were expanded in animals under restricted housing. The upregulation of CD163 together with the downregulation of MHC-II on monocytes from excited camels indicate a modulatory potential of animal excitement to polarize monocytes toward an anti-inflammatory phenotype. Functional analysis of bacterial phagocytosis indicates an impaired antibacterial function of phagocytes in excited camels. The downregulation of several cell adhesion molecules on leukocytes from excited camels suggests a role for impaired cell adhesion and tissue migration and leukocyte retention in blood in the observed leukocytosis in animals under excitement. Conclusions: The present study identified significant changes in blood immune cell composition, phenotype, and function in dromedary camels under restricted-housing conditions. The observed changes in leukocyte composition suggest the development of an excitement leukogram pattern in camels under movement-restricted housing. To evaluate the clinical relevance of the observed changes in immune cell phenotype and function for the immune competence of camels under restricted housing, further studies are required.

Binary and ternary complexes of FLNa-Ig21 with cytosolic tails of αMß2 integrin reveal dual role of filamin mediated regulation

BACKGROUND

Cytoskeletal protein filamin A is critical for the outside-in signaling of integrins. Although molecular mechanisms of filamin-integrin interactions are not fully understood. Mostly, the membrane distal (MD) part of the cytosolic tail (CT) of β subunit of integrin is known to interact with filamin A domain 21 (FLNa-Ig2). However, binary and ternary complexes of full-length CTs of leucocyte specific ß2 integrins with FLNa-Ig21 are yet to be elucidated.

METHODS

Binding interactions of the CTs of integrin αMß2 with FLNa-Ig21 are extensively investigated by NMR, ITC, cell-based functional assays and computational docking.

RESULTS

The αM CT demonstrates interactions with FLNa-Ig21 forming a binary complex. Filamin/αM interface is mediated by sidechain-sidechain interactions among non-polar and aromatic residues involving MP helix of αM and the canonical CD face of FLNa-Ig21. Functional assays delineated an interfacial residue Y1137 of αM CT is critical for in-cell binding to FLNa-Ig2. In addition, full-length ß2 CT occupies two distinct binding sites in complex with FLNa-Ig21. A ternary complex of FLNa-Ig21 with CTs has been characterized. In the ternary complex, αM CT moves away to a distal site of FLNa-Ig21 with fewer interactions.

CONCLUSION

Our findings demonstrate a plausible dual role of filamin in integrin regulation. The molecular interactions of the ternary complex are critical for the resting state of integrins whereas stable FLNa-Ig21/αM CT binary complex perhaps be required for the activated state.

GENERAL SIGNIFICANCE

Filamin binding to both α and β CTs of other integrins could be essential in regulating bidirectional signaling mechanisms.

Clinical and laboratory findings in patients with leukocyte adhesion deficiency type I: A multicenter study in Turkey

Leukocyte adhesion deficiency type I is a rare primary immunodeficiency disorder characterized by mutations in the ITGB2 gene encoding CD18. We present clinical and immunological features of 15 patients with leukocyte adhesion deficiency type 1 (LAD-1). Targeted next-generation sequencing was performed with either a primary immunodeficiency gene panel comprising 266 genes or a small LAD-panel consisting of five genes for genetic analysis. To measure the expression level of integrins on the leukocyte surface, flow cytometry analysis was performed. The median age of the patients at diagnosis was 3 (1-48) months. Eleven (73%) of the 15 patients had a LAD-1 diagnosis in their first 6 months and 14 (93%) patients had consanguineous parents. Delayed separation of the umbilical cord was present in 80% (n = 12) of the patients in our cohort, whereas omphalitis was observed in 53% (n = 8) of the patients. Leukocytosis with neutrophil predominance was observed in 73% (n = 11) patients. Nine distinct variants in the ITGB2 gene in 13 of the 15 patients with LAD-1 were characterized, two of which (c.305_306delAA and c.779_786dup) are novel homozygous mutations of ITGB2. Four unrelated patients from Syria had a novel c.305_306delAA mutation that might be a founder effect for patients of Syrian origin. Four (27%) patients underwent hematopoietic stem cell transplantation. Two patients died because of HSCT complications and the other two are alive and well. Early differential diagnosis of the patients is critical in the management of the disease and genetic evaluation provides a basis for family studies and genetic counseling.

The Growing Need to Understand Very Early Onset Inflammatory Bowel Disease

Very Early Onset Inflammatory Bowel Disease (VEO-IBD) represents a cohort of inflammatory bowel disease (IBD) patients diagnosed before 6 years of age. Unlike IBD diagnosed at older ages, VEO-IBD can be associated with underlying primary immunodeficiencies. VEO-IBD has been linked to monogenic variations in over 70 genes involved in multiple pathways of immunity. As sequencing technologies and platforms evolve and become readily available, an increasing number of genes linked to VEO-IBD have emerged. Although monogenic defects are rare in VEO-IBD, diagnosis of these variants can often dictate specific treatment. In this mini-review, we set out to describe monogenic variants previously characterized in multiple patients in the literature that contribute to VEO-IBD, diagnostic tools, unique treatment modalities for specific genetic diagnoses, and future directions in the field of VEO-IBD. Although this mini-review is by no means comprehensive of all the novel monogenic variants linked to VEO-IBD, we hope to provide relevant information that is readily accessible to clinicians and educators.

Changes in Cell Vitality, Phenotype, and Function of Dromedary Camel Leukocytes After Whole Blood Exposure to Heat Stress in vitro

The dromedary camel (Camelus dromedarius) is well-adapted to the desert environment with the ability to tolerate increased internal body temperatures rising daily to 41–42°C during extreme hot. This study was undertaken to assess whether in vitro incubation of camel blood at 41°C, simulating conditions of heat stress, differently alters cell vitality, phenotype, and function of leukocytes, compared to incubation at 37°C (normothermia). Using flow cytometry, the cell vitality (necrosis and apoptosis), the expression of several cell markers and adhesion molecules, and the antimicrobial functions of camel leukocytes were analyzed in vitro. The fraction of apoptotic cells within the granulocytes, lymphocytes, and monocytes increased significantly after incubation of camel whole blood at 41°C for 4 h. The higher increase in apoptotic granulocytes and monocytes compared to lymphocytes suggests higher resistance of camel lymphocytes to heat stress. Functionally, incubation of camel blood at 41°C for 4 h enhanced the phagocytosis and ROS production activities of camel neutrophils and monocytes toward S. aureus. Monocytes from camel blood incubated at 41°C for 4 h significantly decreased their expression level of MHC class II molecules with no change in the abundance of CD163, resulting in a CD163^high MHC-II^low M2-like macrophage phenotype. In addition, heat stress treatment showed an inhibitory effect on the LPS-induced changes in camel monocytes phenotype. Furthermore, in vitro incubation of camel blood at 41°C reduced the expression of the cell adhesion molecules CD18 and CD11a on neutrophils and monocytes. Collectively, the present study identified some heat-stress-induced phenotypic and functional alterations in camel blood leukocytes, providing a paradigm for comparative immunology in the large animals. The clinical relevance of the observed changes in camel leukocytes for the adaptation of the camel immune response to heat stress conditions needs further in vitro and in vivo studies.

Genome editing in human hematopoietic stem and progenitor cells via CRISPR-Cas9-mediated homology-independent targeted integration

Ex vivo gene correction of hematopoietic stem and progenitor cells (HSPCs) has emerged as a promising therapeutic approach for treatment of inherited human blood disorders. Use of engineered nucleases to target therapeutic transgenes to their endogenous genetic loci addresses many of the limitations associated with viral vector-based gene replacement strategies, such as insertional mutagenesis, variable gene dosage, and ectopic expression. Common methods of nuclease-mediated site-specific integration utilize the homology-directed repair (HDR) pathway. However, these approaches are inefficient in HSPCs, where non-homologous end joining (NHEJ) is the primary DNA repair mechanism. Recently, a novel NHEJ-based approach to CRISPR-Cas9-mediated transgene knockin, known as homology-independent targeted integration (HITI), has demonstrated improved site-specific integration frequencies in non-dividing cells. Here we utilize a HITI-based approach to achieve robust site-specific transgene integration in human mobilized peripheral blood CD34+ HSPCs. As proof of concept, a reporter gene was targeted to a clinically relevant genetic locus using a recombinant adeno-associated virus serotype 6 vector and single guide RNA/Cas9 ribonucleoprotein complexes. We demonstrate high levels of stable HITI-mediated genome editing (∼21%) in repopulating HSPCs after transplantation into immunodeficient mice. Our study demonstrates that HITI-mediated genome editing provides an effective alternative to HDR-based transgene integration in CD34+ HSPCs.

Curcuma amarissima Extract Activates Growth and Survival Signal Transduction Networks to Stimulate Proliferation of Human Keratinocyte

Simple Summary

Like many plants in the family of Zingiberaceae, Curcuma amarissima has been traditionally used to induce healing and tissue regeneration. However, there is no scientific evidence to explain how Curcuma amarissima works to accelerate wound healing. Our data clearly proved that Curcuma amarissima extract could potentially accelerate the closure of scratch wounds of human keratinocytes by stimulating cell proliferation. The potential mechanisms underlying these effects were defined to be associated with the activated signal transduction pathways relevant to cell proliferation and survival. This strongly suggests the ability of Curcuma amarissima to enhance the process of keratinocyte reepithelization during wound healing. Our current study provides convincing evidence that supports the possibility to develop an effective wound-healing promoting agent from this plant.

Abstract

Many medicinal plants have been used to treat wounds. Here, we revealed the potential wound healing effects of Curcuma amarissima (CA). Our cell viability assay showed that CA extract increased the viability of HaCaT cells that were cultured in the absence of serum. This increase in cell viability was proved to be associated with the pharmacological activities of CA extract in inducing cell proliferation. To further define possible molecular mechanisms of action, we performed Western blot analysis and immunofluorescence study, and our data demonstrated that CA extract rapidly induced ERK1/2 and Akt activation. Consistently, CA extract accelerated cell migration, resulting in rapid healing of wounded human keratinocyte monolayer. Specifically, the CA-induced increase of cell monolayer wound healing was blocked by the MEK inhibitor (U0126) or the PI3K inhibitor (LY294002). Moreover, CA extract induced the expression of Mcl-1, which is an anti-apoptotic protein, supporting that CA extract enhances human keratinocyte survival. Taken together, our study provided convincing evidence that Curcuma amarissima can promote proliferation and survival of human keratinocyte through stimulating the MAPK and PI3K/Akt signaling cascades. These promising data emphasize the possibility to develop this plant as a wound healing agent for the potential application in regenerative medicine.

Pyoderma Gangrenosum with an Underlying Leukocyte Adhesion Deficiency Type 1 (LAD-1) and Pregnancy in the Shade of COVID-19 Epidemic: A Patient and Physician Experience

In the first part of this article, the anonymous patient diagnosed with leukocyte adhesion deficiency type 1 (LAD-1) and pyoderma gangrenosum (PG) discusses her experience of her medical history and treatment in a foreign country during her pregnancy and the coronavirus disease-19 (COVID-19) pandemic. The patient’s dermatologists, immunologist, and diagnostician refer to the epidemiology, genetics, diagnosis, morphologic manifestations, including skin lesions, treatment, and prognosis in LAD-1. The patient’s diagnostic and therapeutic process was discussed in the last part of this paper.

β2 Integrin Signaling Cascade in Neutrophils: More Than a Single Function

Neutrophils are the most prevalent leukocytes in the human body. They have a pivotal role in the innate immune response against invading bacterial and fungal pathogens, while recent emerging evidence also demonstrates their role in cancer progression and anti-tumor responses. The efficient execution of many neutrophil effector responses requires the presence of β2 integrins, in particular CD11a/CD18 or CD11b/CD18 heterodimers. Although extensively studied at the molecular level, the exact signaling cascades downstream of β2 integrins still remain to be fully elucidated. In this review, we focus mainly on inside-out and outside-in signaling of these two β2 integrin members expressed on neutrophils and describe differences between various neutrophil stimuli with respect to integrin activation, integrin ligand binding, and the pertinent differences between mouse and human studies. Last, we discuss how integrin signaling studies could be used to explore the therapeutic potential of targeting β2 integrins and the intracellular signaling cascade in neutrophils in several, among other, inflammatory conditions in which neutrophil activity should be dampened to mitigate disease.

AA Amyloidosis Secondary to Primary Immune Deficiency: About 40 Cases Including 2 New French Cases and a Systematic Literature Review

BACKGROUND

Primary immune deficiencies (PIDs) are a heterogeneous group of disorders resulting from defects in immune system. They lead to increased susceptibility to infections and immune dysregulation. The resulting chronic inflammation can induce long-term complications, including AA amyloidosis (AAA).

OBJECTIVES

To present the French cases of PID-related AAA and perform a systematic literature review to determine its main features and predisposing factors.

METHODS

A systematic literature review was performed by searching MEDLINE up until 2019. New French cases were identified with the help of the Reference Center for Auto-Inflammatory Diseases and AA Amyloidosis and the Reference Center for Hereditary Immune Deficiencies.

RESULTS

Forty patients were identified including 2 new French cases. PIDs were varied: immunoglobulin deficits (n = 30), chronic granulomatous disease (n = 3), hyper-IgM syndrome (n = 3), hereditary complete C4 deficiency (n = 1), leucocyte adhesion deficiency type 1 (n = 1), hyper-IgE syndrome (n = 1), and Chediak-Higashi syndrome (n = 1). The mean age at PID diagnosis was 22.2 ± 16.02 years. Renal involvement was the most common manifestation of AAA (80%). Infections were extremely heterogeneous; bacterial infection with pulmonary involvement was the most frequent. Bronchiectasis was particularly common (52.5%). The delay between the first symptoms of PID and AAA diagnosis was 16.18 ± 7 years. Thirteen concomitant diagnoses were made. Twenty patients died during follow-up.

CONCLUSION

AAA is a rare life-threatening complication of PID, especially in cases of long diagnostic and therapeutic delays. Bronchiectasis should be considered as a warning sign of chronic inflammation and increased risk of AAA.

Clinical and Genetic Spectrum of a Large Cohort of Patients With Leukocyte Adhesion Deficiency Type 1 and 3: A Multicentric Study From India

Leukocyte adhesion deficiency (LAD) syndrome is a group of inborn errors of immunity characterized by a defect in the cascade of the activation and adhesion leading to the failure of leukocyte to migrate to the site of tissue injury. Three different types of LAD have been described. The most common subtype is LAD type 1 (LAD1) caused due to defects in the ITGβ2 gene. LAD type 2 (LAD2) is caused by mutations in the SLC35C1 gene leading to a generalized loss of expression of fucosylated glycans on the cell surface and LAD type 3 (LAD3) is caused by mutations in the FERMT3 gene resulting in platelet function defects along with immunodeficiency. There is a paucity of data available from India on LAD syndromes. The present study is a retrospective analysis of patients with LAD collated from 28 different centers across India. For LAD1, the diagnosis was based on clinical features and flow cytometric expression of CD18 on peripheral blood leukocytes and molecular confirmation by Sanger sequencing. For patients with LAD3 diagnosis was largely based on clinical manifestations and identification of the pathogenic mutation in the FERMT3 gene by next-generation Sequencing. Of the total 132 cases diagnosed with LAD, 127 were LAD1 and 5 were LAD3. The majority of our patients (83%) had CD18 expression less than 2% on neutrophils (LAD1°) and presented within the first three months of life with omphalitis, skin and soft tissue infections, delayed umbilical cord detachment, otitis media, and sepsis. The patients with CD18 expression of more than 30% (LAD1⁺) presented later in life with skin ulcers being the commonest manifestation. Bleeding manifestations were common in patients with LAD3. Persistent neutrophilic leukocytosis was the characteristic finding in all patients. 35 novel mutations were detected in the ITGβ2 gene, and 4 novel mutations were detected in the FERMT3 gene. The study thus presents one of the largest cohorts of patients from India with LAD, focusing on clinical features, immunological characteristics, and molecular spectrum.

Therapeutic Monosaccharides: Looking Back, Moving Forward

In this review, we focus on the metabolism of mammalian glycan-associated monosaccharides, where the vast majority of our current knowledge comes from research done during the 1960s and 1970s. Most monosaccharides enter the cell using distinct, often tissue specific transporters from the SLC2A family. If not catabolized, these monosaccharides can be activated to donor nucleotide sugars and used for glycan synthesis. Apart from exogenous and dietary sources, all monosaccharides and their associated nucleotide sugars can be synthesized de novo, using mostly glucose to produce all nine nucleotide sugars present in human cells. Today, monosaccharides are used as treatment options for a small number of rare genetic disorders and even some common conditions. Here, we cover therapeutic applications of these sugars and highlight biochemical gaps that must be revisited as we go forward.

When Actin is Not Actin' Like It Should: A New Category of Distinct Primary Immunodeficiency Disorders

An increasing number of primary immunodeficiencies (PIDs) have been identified over the last decade, which are caused by deleterious mutations in genes encoding for proteins involved in actin cytoskeleton regulation. These mutations primarily affect hematopoietic cells and lead to defective function of immune cells, such as impaired motility, signaling, proliferative capacity, and defective antimicrobial host defense. Here, we review several of these immunological "actinopathies" and cover both clinical aspects, as well as cellular mechanisms of these PIDs. We focus in particular on the effect of these mutations on human neutrophil function.

Differential expression patterns of glycosphingolipids and C-type lectin receptors on immune cells in absence of functional regulatory T cells

Background

Glycosylation is a common and complex type of protein posttranslational modification. Altered glycosylation of immunoglobulins in autoimmune diseases has led to the “altered glycan hypothesis” postulating existence of a unique glycan signature on immune cells and extracellular proteins characterized by site‐specific relative abundances of individual glycan structures and glycosylation patterns. However, it is not clear how glycosylation on leukocyte subpopulations differ between states of health or inflammation.

Hypothesis

Glycosphingolipid patterns on immune cells of forkhead‐box‐P3‐deficient scurfy mice differs from those on wild‐type immune cells.

Methods

T cells and dendritic cells were isolated from spleens of either wild‐type or age‐matched scurfy mice. Glycosphingolipids of CD4⁺ T cells and splenic dendritic cells from wild‐type and scurfy mice were then analyzed by multiplexed capillary gel electrophoresis coupled to laser‐induced fluorescence detection (xCGE‐LIF). In addition, flow cytometry and ChipCytometry were used to access expression patterns of various C‐type lectin receptors on antigen‐presenting cells from various organs of both wild‐type and scurfy mice.

Results

We, hereby report differential expression of glycosphingolipids in health and under inflammatory conditions as reflected in wild‐type and scurfy mice. Furthermore, we observed that the absence of functional regulatory T cells correlated with elevated expression of CLEC‐7A and CD205 but a reduction in levels of CLEC12A and CD206 on antigen‐presenting cells.

Conclusion

We hereby show that the absence of functional regulatory T cells affects expression pattern and quantities of glycosphingolipids on immune cells. Thus, glycosphingolipids could serve as biomarkers for mapping genetical and homeostatic perturbances such as those resulting from a diseased condition.

Successful reconstitution of leukocyte adhesion defect after umbilical cord blood stem cell transplant

Leukocyte adhesion deficiencies (LADs) are a type of primary immunodeficiencies characterized by delayed detachment of the umbilical cord, impaired wound healing, leukocytosis, and recurrent infections. The disease is caused by genetic defects affecting different steps in the process of leukocyte adhesion cascade such as rolling, integrin activation, and adhesion of leukocytes, resulting in the impairment of leukocyte trafficking. Till date, three types of LAD have been documented: type I, II and III. Type I LAD is caused by congenital defect in the β2 integrin receptor complex CD11/CD18 on the cell surface of leukocytes, which results in impaired leukocytes connection to endothelial cells and migration. Type II LAD is caused by defect in the fucose metabolism resulting in the absence of fucosylated selectin ligands on neutrophils and impaired rolling phase of the leukocyte adhesion cascade. Type III LAD is caused by mutations in the kindlin-3 gene resulting in defective integrin activation. In this article, we present a review of literature for type I LAD, and successful treatment of patient using umbilical cord blood stem cell transplantation.

Human genetic dissection of papillomavirus-driven diseases: new insight into their pathogenesis

Human papillomaviruses (HPVs) infect mucosal or cutaneous stratified epithelia. There are 5 genera and more than 200 types of HPV, each with a specific tropism and virulence. HPV infections are typically asymptomatic or result in benign tumors, which may be disseminated or persistent in rare cases, but a few oncogenic HPVs can cause cancers. This review deals with the human genetic and immunological basis of interindividual clinical variability in the course of HPV infections of the skin and mucosae. Typical epidermodysplasia verruciformis (EV) is characterized by β-HPV-driven flat wart-like and pityriasis-like cutaneous lesions and non-melanoma skin cancers in patients with inborn errors of EVER1-EVER2-CIB1-dependent skin-intrinsic immunity. Atypical EV is associated with other infectious diseases in patients with inborn errors of T cells. Severe cutaneous or anogenital warts, including anogenital cancers, are also driven by certain α-, γ-, μ or ν-HPVs in patients with inborn errors of T lymphocytes and antigen-presenting cells. The genetic basis of HPV diseases at other mucosal sites, such as oral multifocal epithelial hyperplasia or juvenile recurrent respiratory papillomatosis (JRRP), remains poorly understood. The human genetic dissection of HPV-driven lesions will clarify the molecular and cellular basis of protective immunity to HPVs, and should lead to novel diagnostic, preventive, and curative approaches in patients.

Improved mouse models and advanced genetic and genomic technologies for the study of neutrophils

Mice have been excellent surrogates for studying neutrophil biology and, furthermore, murine models of human disease have provided fundamental insights into the roles of human neutrophils in innate immunity. The emergence of novel humanized mice and high-diversity mouse populations offers the research community innovative and powerful platforms for better understanding, respectively, the mechanisms by which human neutrophils drive pathogenicity, and how genetic differences underpin the variation in neutrophil biology observed among humans. Here, we review key examples of these new resources. Additionally, we provide an overview of advanced genetic engineering tools available to further improve such murine model systems, of sophisticated neutrophil-profiling technologies, and of multifunctional nanoparticle (NP)-based neutrophil-targeting strategies.

EZH2 Cooperates with DNA Methylation to Downregulate Key Tumor Suppressors and IFN Gene Signatures in Melanoma

The histone methylase EZH2 is frequently dysregulated in melanoma and is associated with DNA methylation and silencing of genes involved in tumor suppression. In this study, we used chromatin immunoprecipitation and sequencing to identify key suppressor genes that are silenced by histone methylation in constitutively active EZH2^(Y641) mutant melanoma and assessed whether these regions were also sites of DNA methylation. The genes identified were validated by their re-expression after treatment with EZH2 and DNA methyltransferase inhibitors. The expression of putative EZH2 target genes was shown to be highly relevant to the survival of patients with melanoma in clinical datasets. To determine correlates of response to EZH2 inhibitors, we screened a panel of 53 melanoma cell lines for drug sensitivity. We compared RNA sequencing profiles of sensitive to resistant melanoma cells and performed pathway analysis. Sensitivity was associated with strong downregulation of IFN-γ and IFN-α gene signatures that were reversed by treatment with EZH2 inhibitors. This is consistent with EZH2-driven dedifferentiated invasive states associated with treatment resistance and defects in antigen presentation. These results suggest that EZH2 inhibitors may be most effectively targeted to immunologically cold melanoma to both induce direct cytotoxicity and increase immune responses in the context of checkpoint inhibitor immunotherapy.

β2 Integrin Gene (ITGB2) mutation spectra in Pakistani families with leukocyte adhesion deficiency type 1 (LAD1)

Leukocyte adhesion deficiency I (LADI) is an autosomal recessive type of primary immunodeficiency characterized by occurrence of repeated bacterial infections, impaired pus formation and wound healing. Genetic variations in the β-2 integrin subunit encoding gene ITGB2 have been implicated in causing the disorder. In the present study, we have investigated twelve patients presenting LAD1 features. After collecting clinical and family history, flow cytometry was used to determine levels of CD18 in the patients. Clinical history revealed that umbilical cord separation occurred mostly after 19 days in the patients. Recurrent skin infections were found in seven patients. Eight patients had at least one elder sibling who died due to repeated infections. All patients had marked neutrophilia with only 0.77% of neutrophils expressing CD18. Total 12 patients suffering from LAD1 were Sanger sequenced for ITGB2 gene. Five variants, including a novel p.(Cys286Phe) and four previously reported [p.(Gly273Arg), p.(Asp128Tyr), p.(Cys62*), IVS7 + 1G > A] were identified in 8 cases, while no pathogenic variant was observed in remaining four cases. This study represents the first comprehensive clinical and genetic characterization of LAD1 in Pakistani population. This will facilitate diagnosis and genetic counselling of patients with immunodeficiency disorders in Pakistani population.

Successful umbilical cord blood transplantation in children with leukocyte adhesion deficiency type I

BACKGROUND

This study aims to investigate the efficacy and safety of umbilical cord blood transplantation (UCBT) without serotherapy for treating children with leukocyte adhesion deficiency type I (LAD-I).

METHODS

Clinical characteristics and data of five children with LAD-I who underwent UCBT at our hospital between September 2016 and September 2018 were retrospectively analyzed.

RESULTS

Five (two boys and three girls) patients with LAD-I were included. The median age at UCBT was 9 months (range, 8 to 32 months). The same myeloablative conditioning regimen was administered for each patient and included busulfan, fludarabine, and cyclophosphamide. HLA matching of patients and umbilical cord blood was 8/10 to 10/10. The median dose of total nucleated cells (TNC) infused was 10.2×10⁷/kg (range, 4.5×10⁷ to 20.6×10⁷/kg) and the median dose of CD34+ cells was 3.2×10⁵/kg (range, 1.9×10⁵ to 5.7×10⁵/kg). The median time of neutrophil engraftment was 20 days (range, 13 to 28 days). The median time of platelet engraftment was 36 days (range, 32 to 56 days). All patients received complete donor chimerism (CDC). Four of the five patients developed grade II-IV acute graft-versus-host disease (GvHD). The median follow-up time after transplantation was 19 months (range, 8 to 38 months). Four of the patients survived and achieved complete clinical remission. The other patient died of bronchiolitis obliterans 8 months after UCBT.

CONCLUSIONS

UCBT is an effective treatment method for LAD-I patients. Also, severe LAD-I patients should undergo stem cell transplantation as early as possible.

Novel variants in FERMT3 and RASGRP2-Genetic linkage in Glanzmann-like bleeding disorders

Defects of platelet intracellular signaling can result in severe platelet dysfunction. Several mutations in each of the linked genes FERMT3 and RASGRP2 on chromosome 11 causing a Glanzmann-like bleeding phenotype have been identified so far. We report on novel variants in two unrelated pediatric patients with severe bleeding diathesis-one with leukocyte adhesion deficiency type III due to a homozygous frameshift in FERMT3 and the other with homozygous variants in both, FERMT3 and RASGRP2. We focus on the challenging genetic and functional variant assessment and aim to accentuate the risk of obtaining misleading results due to the phenomenon of genetic linkage.

Neutrophil Defects and Diagnosis Disorders of Neutrophil Function: An Overview

Primary disorders of neutrophil function result from impairment in neutrophil responses that are critical for host defense. This chapter summarizes inherited disorders of neutrophils that cause defects in neutrophil adhesion, migration, and oxidative killing. These include the leukocyte adhesion deficiencies, actin defects and other disorders of chemotaxis, hyperimmunoglobulin E syndrome, Chédiak-Higashi Syndrome, neutrophil specific granule deficiency, chronic granulomatous disease, and myeloperoxidase deficiency. Diagnostic tests and treatment approaches are also summarized for each neutrophil disorder.

Neutrophils Kill Antibody-Opsonized Cancer Cells by Trogoptosis

Destruction of cancer cells by therapeutic antibodies occurs, at least in part, through antibody-dependent cellular cytotoxicity (ADCC), and this can be mediated by various Fc-receptor-expressing immune cells, including neutrophils. However, the mechanism(s) by which neutrophils kill antibody-opsonized cancer cells has not been established. Here, we demonstrate that neutrophils can exert a mode of destruction of cancer cells, which involves antibody-mediated trogocytosis by neutrophils. Intimately associated with this is an active mechanical disruption of the cancer cell plasma membrane, leading to a lytic (i.e., necrotic) type of cancer cell death. Furthermore, this mode of destruction of antibody-opsonized cancer cells by neutrophils is potentiated by CD47-SIRPα checkpoint blockade. Collectively, these findings show that neutrophil ADCC toward cancer cells occurs by a mechanism of cytotoxicity called trogoptosis, which can be further improved by targeting CD47-SIRPα interactions.

Leukocyte adhesion defect: Where do we stand circa 2019?

Migration of polymorphonuclear leukocytes from bloodstream to the site of inflammation is an important event required for surveillance of foreign antigens. This trafficking of leukocytes from bloodstream to the tissue occurs in several distinct steps and involves several adhesion molecules. Defect in adhesion of leukocytes to vascular endothelium affecting their subsequent migration to extravascular space gives rise to a group of rare primary immunodeficiency diseases (PIDs) known as Leukocyte Adhesion Defects (LAD). Till date, four classes of LAD are discovered with LAD I being the most common form. LAD I is caused by loss of function of common chain, cluster of differentiation (CD)18 of β2 integrin family. These patients suffer from life-threatening bacterial infections and in its severe form death usually occurs in childhood without bone marrow transplantation. LAD II results from a general defect in fucose metabolism. These patients suffer from less severe bacterial infections and have growth and mental retardation. Bombay blood group phenotype is also observed in these patients. LAD III is caused by abnormal integrin activation. LAD III patients suffer from severe bacterial and fungal infections. Patients frequently show delayed detachment of umbilical cord, impaired wound healing and increased tendency to bleed. LAD IV is the most recently described class. It is caused by defects in β2 and α4β1 integrins which impairs lymphocyte adhesion. LAD IV patients have monogenic defect in cystic-fibrosis-transmembrane-conductance-regulator (CFTR) gene, resulting in cystic fibrosis. Pathophysiology and genetic etiology of all LAD syndromes are discussed in detail in this paper.

A novel mutation of the ITGB2 gene in a Chinese Zhuang minority patient with leukocyte adhesion deficiency type 1 and glucose-6-phosphate dehydrogenase deficiency

OBJECTIVES

To explore the clinical and molecular characteristics of a Chinese Zhuang minority patient with leukocyte adhesion deficiency type-1 (LAD-1) and glucose-6-phosphate dehydrogenase deficiency (G6PDD).

METHODS

Routine clinical and physical examinations were performed, and patient data was collected and analyzed. Protein expression levels of Itgb2 and glucose-6-phosphate dehydrogenase (G6pd) proteins were assessed by flow cytometry and the glucose-6-phosphate (G6P) substrate method, respectively. Whole exome sequencing was performed to investigate genetic variations of the patient and his parents.

RESULTS

The patient had fester disease and delayed separation of the umbilical cord at birth. Staphylococcus was detected in the fluid secretion of the auditory meatus of the patient. He exhibited a recurrent cheek scab, swollen hand, and swollen gum. Hematological examination indicated dramatic elevation of leukocytes including lymphocytes, monocytes, neutrophils and eosinophils. A novel homozygous mutation was detected in the ITGB2 gene of the patient, which was determined to be a two nucleotide deletion at the site of c.1537-1538 (c.1537-1538delGT), causing a frameshift of 24 amino acids from p.513 and inducing a stop codon (p.V513Lfs*24). A base substitution mutation was identified at c.1466 (c.1466G>T) of G6PD on chromosome X of the patient, which resulted in an amino acid change from arginine to leucine at p.489 (p.R489L). The patient also showed deficient lymphocyte expression of CD18 (2.99%) and significant downregulation of the G6pd protein.

CONCLUSIONS

The patient was diagnosed with G6PDD and moderate LAD-1. The combination of LAD-1 and G6PDD in this case may have been due to the high incidence of genetic disease in this minority ethnic population. Analyzing existing LAD-1 and G6PDD cases from different populations can facilitate disease diagnosis and treatment. Particularly, reporting pathogenic mutations of LAD-1 and G6PDD will be crucial for genetic testing and prenatal diagnosis in an effort to decrease the incidence of these diseases.

A Novel Nonsense Mutation in FERMT3 Causes LAD-III in a Pakistani Family

Leukocyte adhesion deficiency-III (LAD3) is an extremely rare primary immunodeficiency disorder, transmitted with autosomal-recessive inheritance. It is caused by genetic alteration in the FERMT3 gene, which leads to abnormal expression of kindlin-3. This cytoplasmic protein is highly expressed in leukocytes and platelets, and acts as an important regulator of integrin activation. LAD3 has features like bleeding syndrome of Glanzmann-type and leukocyte adhesion deficiency. FERMT3 mutation(s) have not been well characterized in Pakistani patients with LAD3. In this study, an infant and his family of Pakistani origin, presenting with clinical features of LAD, were investigated to determine the underlying genetic defect. Targeted next generation sequencing (TGS) and Sanger sequencing were performed to identify and confirm the causative mutations, respectively, and their segregation within the family. A novel, homozygous FERMT3 nonsense mutation (c.286C > T, p.Q96^∗) was found in the proband, and its co-segregation with LAD3 phenotype within the family was consistent with an autosomal recessive inheritance. Both parents were carriers of the same mutation. This family was offered prenatal diagnosis during first trimester of the subsequent pregnancy; the fetus carried the variant. In conclusion, our study is the first report to identify the novel homozygous variant c.286C > T, p.Q96^∗in the FERMT3 gene, which might be the causative mutation for LAD3 patients of Pakistani origin.