Recurrent viral infections associated with a homozygous CORO1A mutation that disrupts oligomerization and cytoskeletal association

Coronin 1a-mediated F-actin disassembly controls effector function in murine neutrophils

The double-edged role of neutrophils in effective host defense and harmful pathology is an emerging topic in clinical research. Neutrophils release highly potent antimicrobial granule compounds and reactive oxygen species (ROS) that can also be detrimental to the host and promote inflammatory diseases and cancer. Here we show that disassembly of F-actin greatly facilitates ROS production and degranulation in neutrophils. Utilizing neutrophils from Coronin 1a (Coro1a)-deficient mice, our data reveal that the actin-regulatory protein Coro1a controls this spatial F-actin deconstruction and concomitantly forms a signaling complex with Rac-GTPases, thereby promoting activation and translocation of Rac to the membrane during neutrophil activation. This functional activity of Coro1a was critical for neutrophil granule exocytosis and the activation of the NADPH oxidase complex. Consistent with these findings, impaired ROS production in Coro1a-deficient neutrophils was rescued by pharmacological promotion of actin depolymerization or activation of Rac. Together, our findings suggest that the Coro1a/Rac signaling hub acts as a central regulatory element that coordinates actin cytoskeletal reorganization required for the execution of neutrophil effector functions. Since Coro1a is highly conserved between mice and humans and associated with human immunodeficiency, our results are also relevant for human biomedical studies.

Novel hemizygous CORO1A variant leads to combined immunodeficiency with defective platelet calcium signaling and cell mobility

Background

To date, fewer than 20 patients have been identified as having germline biallelic mutations in the coronin-1A gene (CORO1A) and its protein with clinical features of combined immunodeficiency characterized by T-cell lymphopenia ranging from the severe phenotype to the mild phenotype, recurrent infections, and lymphoproliferative disorders. However, the effects of CORO1A protein disruption on actin-dependent functions in primary cells have not been fully delineated.

Objective

We sought to characterize the underlying defects of actin-dependent cellular functions in a female patient with combined immunodeficiency caused by a novel missense variant in the CORO1A gene in combination with a de novo heterozygous microdeletion of chromosome 16p11.2 and also to provide evidence of the pathogenicity of this gene mutation.

Methods

To identify the genetic defect, next-generation sequencing followed by Sanger confirmation and array comparative genomic hybridization were performed. Western blot and quantitative PCR tests were used to assess the effects on the protein. Flow cytometry and live microscopy were performed to investigate cellular motility and immune cell counts and function.

Results

We demonstrated that the CORO1A hemizygous variant c.19C>T, p. A7C induces significant decreases in cellular levels of the CORO1A protein while leaving mRNA concentrations unaffected. The observed mutation resulted in impaired natural killer cell cytotoxicity and platelet calcium signaling. In addition, primary granulocytes and mesenchymal cells showed significant defects in motility.

Conclusion

Collectively, we added new data about the CORO1A gene as a key player in actin cytoskeleton dynamics and cell signaling. Our findings expand the clinical spectrum regarding CORO1A protein deficiency and confirm the importance of a personalized therapeutic approach for each patient.

Monogenic etiologies of persistent human papillomavirus infections: A comprehensive systematic review

PURPOSE

Persistent human papillomavirus infection (PHPVI) causes cutaneous, anogenital, and mucosal warts. Cutaneous warts include common warts, Treeman syndrome, and epidermodysplasia verruciformis, among others. Although more reports of monogenic predisposition to PHPVI have been published with the development of genomic technologies, genetic testing is rarely incorporated into clinical assessments. To encourage broader molecular testing, we compiled a list of the various monogenic etiologies of PHPVI.

METHODS

We conducted a systematic literature review to determine the genetic, immunological, and clinical characteristics of patients with PHPVI.

RESULTS

The inclusion criteria were met by 261 of 40,687 articles. In 842 patients, 83 PHPVI-associated genes were identified, including 42, 6, and 35 genes with strong, moderate, and weak evidence for causality, respectively. Autosomal recessive inheritance predominated (69%). PHPVI onset age was 10.8 ± 8.6 years, with an interquartile range of 5 to 14 years. GATA2,IL2RG,DOCK8, CXCR4, TMC6, TMC8, and CIB1 are the most frequently reported PHPVI-associated genes with strong causality. Most genes (74 out of 83) belong to a catalog of 485 inborn errors of immunity-related genes, and 40 genes (54%) are represented in the nonsyndromic and syndromic combined immunodeficiency categories.

CONCLUSION

PHPVI has at least 83 monogenic etiologies and a genetic diagnosis is essential for effective management.

Whole exome sequencing of patients with varicella-zoster virus and herpes simplex virus induced acute retinal necrosis reveals rare disease-associated genetic variants

Purpose

Herpes simplex virus (HSV) and varicella-zoster virus (VZV) are neurotropic human alphaherpesviruses endemic worldwide. Upon primary infection, both viruses establish lifelong latency in neurons and reactivate intermittently to cause a variety of mild to severe diseases. Acute retinal necrosis (ARN) is a rare, sight-threatening eye disease induced by ocular VZV or HSV infection. The virus and host factors involved in ARN pathogenesis remain incompletely described. We hypothesize an underlying genetic defect in at least part of ARN cases.

Methods

We collected blood from 17 patients with HSV-or VZV-induced ARN, isolated DNA and performed Whole Exome Sequencing by Illumina followed by analysis in Varseq with criteria of CADD score > 15 and frequency in GnomAD < 0.1% combined with biological filters. Gene modifications relative to healthy control genomes were filtered according to high quality and read-depth, low frequency, high deleteriousness predictions and biological relevance.

Results

We identified a total of 50 potentially disease-causing genetic variants, including missense, frameshift and splice site variants and on in-frame deletion in 16 of the 17 patients. The vast majority of these genes are involved in innate immunity, followed by adaptive immunity, autophagy, and apoptosis; in several instances variants within a given gene or pathway was identified in several patients.

Discussion

We propose that the identified variants may contribute to insufficient viral control and increased necrosis ocular disease presentation in the patients and serve as a knowledge base and starting point for the development of improved diagnostic, prophylactic, and therapeutic applications.

Cutaneous Findings in Inborn Errors of Immunity: An Immunologist's Perspective

Cutaneous manifestations are common in patients with inborn errors of immunity (IEI)/primary immunodeficiency and could be due to infections, immune dysregulation, or lymphoproliferative/malign diseases. Immunologists accept some as warning signs for underlying IEI. Herein, we include noninfectious/infectious cutaneous manifestations that we come across in rare IEI cases in our clinic and provide a comprehensive literature review. For several skin diseases, the diagnosis is challenging and differential diagnosis is necessary. Detailed disease history and examination play a vital role in reaching a diagnosis, especially if there is a potential underlying IEI. A skin biopsy is sometimes necessary, especially if we need to rule out inflammatory, infectious, lymphoproliferative, and malignant conditions. Specific and immunohistochemical stainings are particularly important when diagnosing granuloma, amyloidosis, malignancies, and infections like human herpes virus-6, human herpes virus-8, human papillomavirus, and orf. Elucidation of mechanisms of IEIs has improved our understanding of their relation to cutaneous findings. In challenging cases, the immunological evaluation may lead the approach when there is a specific primary immunodeficiency diagnosis or at least help to reduce the number of differential diagnoses. Conversely, the response to therapy may provide conclusive evidence for some conditions. This review raises awareness of concomitant lesions and expands the scope of the differential diagnosis of IEI and the spectrum of skin disease therapy by highlighting frequent forms of IEI-associated cutaneous manifestations. The manifestations given here will guide clinicians to plan for alternative use of diverse therapeutics in a multidisciplinary way for skin diseases.

A History and Atlas of the Human CD4+ T Helper Cell

CD4+ T cells have orchestrated and regulated immunity since the introduction of jawed vertebrates, yet our understanding of CD4+ T cell evolution, development, and cellular physiology has only begun to be unearthed in the past few decades. Discoveries of genetic diseases that ablate this cellular population have provided insight into their critical functions while transcriptomics, proteomics, and high-resolution microscopy have recently revealed new insights into CD4+ T cell anatomy and physiology. This article compiles historical, microscopic, and multi-omics data that can be used as a reference atlas and index to dissect cellular physiology within these influential cells and further understand pathologies like HIV infection that inflict human CD4+ T cells.

Human genetic and immunological determinants of SARS-CoV-2 and Epstein-Barr virus diseases in childhood: Insightful contrasts

There is growing evidence to suggest that severe disease in children infected with common viruses that are typically benign in other children can result from inborn errors of immunity or their phenocopies. Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a cytolytic respiratory RNA virus, can lead to acute hypoxemic COVID-19 pneumonia in children with inborn errors of type I interferon (IFN) immunity or autoantibodies against IFNs. These patients do not appear to be prone to severe disease during infection with Epstein-Barr virus (EBV), a leukocyte-tropic DNA virus that can establish latency. By contrast, various forms of severe EBV disease, ranging from acute hemophagocytosis to chronic or long-term illnesses, such as agammaglobulinemia and lymphoma, can manifest in children with inborn errors disrupting specific molecular bridges involved in the control of EBV-infected B cells by cytotoxic T cells. The patients with these disorders do not seem to be prone to severe COVID-19 pneumonia. These experiments of nature reveal surprising levels of redundancy of two different arms of immunity, with type I IFN being essential for host defense against SARS-CoV-2 in respiratory epithelial cells, and certain surface molecules on cytotoxic T cells essential for host defense against EBV in B lymphocytes.

Multi-omics characterization of RNA binding proteins reveals disease comorbidities and potential drugs in COVID-19

The COVID-19 has led to a devastating global health crisis, which emphasizes the urgent need to deepen our understanding of the molecular mechanism and identifying potential antiviral drugs. Here, we comprehensively analyzed the transcriptomic and proteomic profiles of 178 COVID-19 patients, ranging from asymptomatic to critically ill. Our analyses found that the RNA binding proteins (RBPs) were likely to be perturbed in infection. Interactome analysis revealed that RBPs interact with virus proteins and the viral interacting RBPs were likely to locate in central regions of human protein-protein interaction network. Functional enrichment analysis revealed that the viral interacting RBPs were likely to be enriched in RNA transport, apoptosis and viral genome replication-related pathways. Based on network proximity analyses of 299 human complex-disease genes and COVID-19-related RBPs in the human interactome, we revealed the significant associations between complex diseases and COVID-19. Network analysis also implicated potential antiviral drugs for treatment of COVID-19. In summary, our integrative characterization of COVID-19 patients may thus help providing evidence regarding pathophysiology and potential therapeutic strategies for COVID-19.

Deciphering actin remodelling in immune cells through the prism of actin-related inborn errors of immunity

Actin cytoskeleton remodelling drives cell motility, cell to cell contacts, as well as membrane and organelle dynamics. Those cellular activities operate at a particularly high pace in immune cells since these cells migrate through various tissues, interact with multiple cellular partners, ingest microorganisms and secrete effector molecules. The central and multifaceted role of actin cytoskeleton remodelling in sustaining immune cell tasks in humans is highlighted by rare inborn errors of immunity due to mutations in genes encoding proximal and distal actin regulators. In line with the specificity of some of the actin-based processes at work in immune cells, the expression of some of the affected genes, such as WAS, ARPC1B and HEM1 is restricted to the hematopoietic compartment. Exploration of these natural deficiencies highlights the fact that the molecular control of actin remodelling is tuned distinctly in the various subsets of myeloid and lymphoid immune cells and sustains different networks associated with a vast array of specialized tasks. Furthermore, defects in individual actin remodelling proteins are usually associated with partial cellular impairments highlighting the plasticity of actin cytoskeleton remodelling. This review covers the roles of disease-associated actin regulators in promoting the actin-based processes of immune cells. It focuses on the specific molecular function of those regulators across various immune cell subsets and in response to different stimuli. Given the fact that numerous immune-related actin defects have only been characterized recently, we further discuss the challenges lying ahead to decipher the underlying patho-mechanisms.

Extracellular Vesicles in Diffuse Large B Cell Lymphoma: Characterization and Diagnostic Potential

Diffuse large B cell lymphoma (DLBCL) is an aggressive B cell lymphoma characterized by a heterogeneous behavior and in need of more accurate biological characterization monitoring and prognostic tools. Extracellular vesicles are secreted by all cell types and are currently established to some extent as representatives of the cell of origin. The present study characterized and evaluated the diagnostic and prognostic potential of plasma extracellular vesicles (EVs) proteome in DLBCL by using state-of-the-art mass spectrometry. The EV proteome is strongly affected by DLBCL status, with multiple proteins uniquely identified in the plasma of DLBCL. A proof-of-concept classifier resulted in highly accurate classification with a sensitivity and specificity of 1 when tested on the holdout test data set. On the other hand, no proteins were identified to correlate with non-germinal center B-cell like (non-GCB) or GCB subtypes to a significant degree after correction for multiple testing. However, functional analysis suggested that antigen binding is regulated when comparing non-GCB and GCB. Survival analysis based on protein quantitative values and clinical parameters identified multiple EV proteins as significantly correlated to survival. In conclusion, the plasma extracellular vesicle proteome identifies DLBCL cancer patients from healthy donors and contains potential EV protein markers for prediction of survival.

HPV-Related Skin Phenotypes in Patients with Inborn Errors of Immunity

Patients with inborn errors of immunity (IEI) are prone to develop infections, either due to a broad spectrum of pathogens or to only one microbe. Since skin is a major barrier tissue, cutaneous infections are among the most prevalent in patients with IEI due to high exposures to many microbes. In the general population, human papillomaviruses (HPVs) cause asymptomatic or self-healing infections, but, in patients with IEI, unusual clinical expression of HPV infection is observed ranging from epidermodysplasia verruciformis (EV) (a rare disease due to β-HPVs) to profuse, persistent, and recalcitrant warts (due to α-, γ-, and μ-HPVs) or even tree man syndrome (due to HPV2). Mutations in EVER1, EVER2, and CIB1 are associated with EV phenotype; GATA2, CXCR4, and DOCK8 mutations are typically associated with extensive HPV infections, but there are several other IEI that are less frequently associated with severe HPV lesions. In this review, we describe clinical, immunological, and genetic patterns of IEI related to severe HPV cutaneous infections and propose an algorithm for diagnosis of IEI with severe warts associated, or not, with lymphopenia.

Molecular Tuning of Actin Dynamics in Leukocyte Migration as Revealed by Immune-Related Actinopathies

Motility is a crucial activity of immune cells allowing them to patrol tissues as they differentiate, sample or exchange information, and execute their effector functions. Although all immune cells are highly migratory, each subset is endowed with very distinct motility patterns in accordance with functional specification. Furthermore individual immune cell subsets adapt their motility behaviour to the surrounding tissue environment. This review focuses on how the generation and adaptation of diversified motility patterns in immune cells is sustained by actin cytoskeleton dynamics. In particular, we review the knowledge gained through the study of inborn errors of immunity (IEI) related to actin defects. Such pathologies are unique models that help us to uncover the contribution of individual actin regulators to the migration of immune cells in the context of their development and function.

Epstein-Barr Virus in Inborn Immunodeficiency-More Than Infection

Simple Summary

Epstein–Barr Virus (EBV) is a common virus that is readily controlled by a healthy immune system and rarely causes serious problems in infected people. However, patients with certain genetic defects of their immune system might have difficulties controlling EBV and often develop severe and life-threatening conditions, such as severe inflammation and malignancies. In this review, we provide a summary of inherited immune diseases that lead to a high susceptibility to EBV infection and discuss how this infection is associated with cancer development.

Abstract

Epstein–Barr Virus (EBV) is a ubiquitous virus affecting more than 90% of the world’s population. Upon infection, it establishes latency in B cells. It is a rather benign virus for immune-competent individuals, in whom infections usually go unnoticed. Nevertheless, EBV has been extensively associated with tumorigenesis. Patients suffering from certain inborn errors of immunity are at high risk of developing malignancies, while infection in the majority of immune-competent individuals does not seem to lead to immune dysregulation. Herein, we discuss how inborn mutations in TNFRSF9, CD27, CD70, CORO1A, CTPS1, ITK, MAGT1, RASGRP1, STK4, CARMIL2, SH2D1A, and XIAP affect the development, differentiation, and function of key factors involved in the immunity against EBV, leading to increased susceptibility to lymphoproliferative disease and lymphoma.

Human genetic and immunological dissection of papillomavirus-driven diseases: new insights into their pathogenesis

Human papillomaviruses (HPVs) are responsible for cutaneous and mucosal lesions. Persistent HPV infection remains a leading cause of uterine cancer in women, but also of cutaneous squamous cell carcinoma in patients with epidermodysplasia verruciformis (EV), and of rare and devastating benign tumors, such as 'tree-man' syndrome. HPV infections are usually asymptomatic or benign in the general population. Severe manifestations in otherwise healthy subjects can attest to inherited immunodeficiencies. The human genetic dissection of these cases has identified critical components of the immune response to HPVs, including the non-redundant roles of keratinocyte-intrinsic immunity in controlling β-HPVs, and of T cell-dependent adaptive immunity for controlling all HPV types. A key role of the CD28 T-cell costimulation pathway in controlling common warts due to HPVs was recently discovered. This review summarizes the state of the art in the human genetics of HPV infection, focusing on two key affected cell types: keratinocytes and T cells.

Genetic variants and immune responses in a cohort of patients with varicella zoster virus encephalitis

BACKGROUND

Infection with varicella zoster virus (VZV) may involve different central nervous system (CNS) manifestations, including meningitis, encephalitis, and vasculitis. In cases where otherwise healthy individuals are affected, an inborn error of immunity may underlie increased susceptibility or severity of infection.

METHODS

We collected a cohort of 17 adults who experienced VZV encephalitis and performed whole exome sequencing. Patient PBMCs were infected with VZV and innate antiviral interferon and cytokine responses as well as viral replication was evaluated. Data were analyzed by Mann Whitney U test.

RESULTS

We identified a total of 21 different potentially disease-causing variants in a total of 13 of the 17 patients included. These gene variants were within two major functional clusters: i) innate viral sensors and immune pathways and ii) autophagy pathways. Antiviral interferon (IFN) and cytokine responses were abnormal in the majority of patients, whereas viral replication was increased in only 2/17.

CONCLUSION

This study identifies a list of variants of pathogenic potential, which may serve as a platform for generating hypotheses for future studies addressing genetic and immunological factors associated with susceptibility to VZV encephalitis. Collectively, these data suggest that disturbances in innate sensing and autophagy pathways may predispose to VZV encephalitis.

NCKAP1L defects lead to a novel syndrome combining immunodeficiency, lymphoproliferation, and hyperinflammation

The Nck-associated protein 1–like (NCKAP1L) gene, alternatively called hematopoietic protein 1 (HEM-1), encodes a hematopoietic lineage–specific regulator of the actin cytoskeleton. Nckap1l-deficient mice have anomalies in lymphocyte development, phagocytosis, and neutrophil migration. Here we report, for the first time, NCKAP1L deficiency cases in humans. In two unrelated patients of Middle Eastern origin, recessive mutations in NCKAP1L abolishing protein expression led to immunodeficiency, lymphoproliferation, and hyperinflammation with features of hemophagocytic lymphohistiocytosis. Immunophenotyping showed an inverted CD4/CD8 ratio with a major shift of both CD4⁺ and CD8⁺ cells toward memory compartments, in line with combined RNA-seq/proteomics analyses revealing a T cell exhaustion signature. Consistent with the core function of NCKAP1L in the reorganization of the actin cytoskeleton, patients’ T cells displayed impaired early activation, immune synapse morphology, and leading edge formation. Moreover, knockdown of nckap1l in zebrafish led to defects in neutrophil migration. Hence, NCKAP1L mutations lead to broad immune dysregulation in humans, which could be classified within actinopathies.

Transcriptome analysis of the procession from chronic pancreatitis to pancreatic cancer and metastatic pancreatic cancer

Exploring the underlying mechanisms of cancer development is useful for cancer treatment. In this paper, we analyzed the transcriptome profiles from the human normal pancreas, pancreatitis, pancreatic cancer and metastatic pancreatic cancer to study the intricate associations among pancreatic cancer progression. We clustered the transcriptome data, and analyzed the differential expressed genes. WGCNA was applied to construct co-expression networks and detect important modules. Importantly we selected the module in a different way. As the pancreatic disease deteriorates, the number of differentially expressed genes increases. The gene networks of T cells and interferon are upregulated in stages. In conclusion, the network-based study provides gradually activated gene networks in the disease progression of pancreatitis, pancreatic cancer, and metastatic pancreatic cancer. It may contribute to the rational design of anti-cancer drugs.

Clinical presentation and molecular characterization of a novel patient with variant POC1A-related syndrome

Biallelic pathogenic variants in POC1A result in SOFT (Short-stature, Onychodysplasia, Facial-dysmorphism, and hypoTrichosis) and variant POC1A-related (vPOC1A) syndromes. The latter, nowadays described in only two unrelated subjects, is associated with a restricted spectrum of variants falling in exon 10, which is naturally skipped in a specific POC1A mRNA. The synthesis of an amount of a POC1A isoform from this transcript in individuals with vPOC1A syndrome has been believed as the likely explanation for such a genotype-phenotype correlation. Here, we illustrate the clinical and molecular findings in a woman who resulted to be compound heterozygous for a recurrent frameshift variant in exon 10 and a novel variant in exon 9 of POC1A. Phenotypic characteristics of this woman included severe hyperinsulinemic dyslipidemia, acanthosis nigricans, moderate growth restriction, and dysmorphisms. These manifestations overlap the clinical features of the two previously published individuals with vPOC1A syndrome. RT-PCR analysis on peripheral blood and subsequent sequencing of the obtained amplicons demonstrated a variety of POC1A alternative transcripts that resulted to be expressed in the proband, in the healthy mother, and in controls. We illustrate the possible consequences of the two POC1A identified variants in an attempt to explain pleiotropy in vPOC1A syndrome.

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.

Determinants of neurological syndromes caused by varicella zoster virus (VZV)

Varicella zoster virus (VZV) is a pathogenic human herpes virus which causes varicella as a primary infection, following which it becomes latent in peripheral autonomic, sensory, and cranial nerve ganglionic neurons from where it may reactivate after decades to cause herpes zoster. VZV reactivation may also cause a wide spectrum of neurological syndromes, in particular, acute encephalitis and vasculopathy. While there is potentially a large number of coding viral mutations that might predispose certain individuals to VZV infections, in practice, a variety of host factors are the main determinants of VZV infection, both disseminated and specifically affecting the nervous system. Host factors include increasing age with diminished cell-mediated immunity to VZV, several primary immunodeficiency syndromes, secondary immunodeficiency syndromes, and drug-induced immunosuppression. In some cases, the molecular immunological basis underlying the increased risk of VZV infections has been defined, in particular, the role of POL III mutations, but in other cases, the mechanisms have yet to be determined. The role of immunization in immunosuppressed individuals as well as its possible efficacy in preventing both generalized and CNS-specific infections will require further investigation to clarify in such patients.

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.

Homodimerization of coronin A through the C-terminal coiled-coil domain is essential for multicellular differentiation of Dictyostelium discoideum

Coronin proteins are widely expressed among eukaryotic organisms. Most coronins consist of a WD-repeat domain followed by a C-terminal coiled coil. Dictyostelium discoideum expresses a single short coronin coronin A, which has been implicated in both actin modulation and multicellular differentiation. Whether coronin A's coiled coil is important for functionality, as well as the oligomeric state of coronin A is not known. Here, we show that the coiled-coil domain in Dictyostelium coronin A functions in homodimerization, is dispensable for coronin A stability and localization but essential for multicellular differentiation. These results allow a better understanding of the role for the coiled-coil domain of coronin A in oligomerization and demonstrate that its presence is essential for multicellular differentiation.

Genetic susceptibility to EBV infection: insights from inborn errors of immunity

Epstein-Barr virus (EBV) is a ubiquitous human pathogen, infecting > 90% of the adult population. In the vast majority of healthy individuals, infection with EBV runs a relatively benign course. However, EBV is by no means a benign pathogen. Indeed, apart from being associated with at least seven different types of malignancies, EBV infection can cause severe and often fatal diseases-hemophagocytic lymphohistiocytosis, lymphoproliferative disease, B-cell lymphoma-in rare individuals with specific monogenic inborn errors of immunity. The discovery and detailed investigation of inborn errors of immunity characterized by heightened susceptibility to, or increased frequency of, EBV-induced disease have elegantly revealed cell types and signaling pathways that play critical and non-redundant roles in host-defense against EBV. These analyses have revealed not only mechanisms underlying EBV-induced disease in rare genetic conditions, but also identified molecules and pathways that could be targeted to treat severe EBV infection and pathological consequences in immunodeficient hosts, or even potentially enhance the efficacy of an EBV-specific vaccine.

Human inborn errors of immunity to herpes viruses

Infections with any of the nine human herpes viruses (HHV) can be asymptomatic or life-threatening. The study of patients with severe diseases caused by HHVs, in the absence of overt acquired immunodeficiency, has led to the discovery or diagnosis of various inborn errors of immunity. The related inborn errors of adaptive immunity disrupt α/β T-cell rather than B-cell immunity. Affected patients typically develop HHV infections in the context of other infectious diseases. However, this is not always the case, as illustrated by inborn errors of SAP-dependent T-cell immunity to EBV-infected B cells. The related inborn errors of innate immunity disrupt leukocytes other than T and B cells, non-hematopoietic cells, or both. Patients typically develop only a single type of infection due to HHV, although, again, this is not always the case, as illustrated by inborn errors of TLR3 immunity resulting in HSV1 encephalitis in some patients and influenza pneumonitis in others. Most severe HHV infections in otherwise healthy patients remains unexplained. The forward human genetic dissection of isolated and syndromic HHV-driven illnesses will establish the molecular and cellular basis of protective immunity to HHVs, paving the way for novel diagnosis and management strategies.

Primary immunodeficiencies caused by mutations in actin regulatory proteins

The identification of patients with monogenic gene defects have illuminated the function of different proteins in the immune system, including proteins that regulate the actin cytoskeleton. Many of these actin regulatory proteins are exclusively expressed in leukocytes and regulate the formation and branching of actin filaments. Their absence or abnormal function leads to defects in immune cell shape, cellular projections, migration, and signaling. Through the study of patients' mutations and generation of mouse models that recapitulate the patients' phenotypes, our laboratory and others have gained a better understanding of the role these proteins play in cell biology and the underlying pathogenesis of immunodeficiencies and immune dysregulatory syndromes.

Diagnostic interpretation of genetic studies in patients with primary immunodeficiency diseases: A working group report of the Primary Immunodeficiency Diseases Committee of the American Academy of Allergy, Asthma & Immunology

Genetic testing has become an integral component of the diagnostic evaluation of patients with suspected primary immunodeficiency diseases. Results of genetic testing can have a profound effect on clinical management decisions. Therefore clinical providers must demonstrate proficiency in interpreting genetic data. Because of the need for increased knowledge regarding this practice, the American Academy of Allergy, Asthma & Immunology Primary Immunodeficiency Diseases Committee established a work group that reviewed and summarized information concerning appropriate methods, tools, and resources for evaluating variants identified by genetic testing. Strengths and limitations of tests frequently ordered by clinicians were examined. Summary statements and tables were then developed to guide the interpretation process. Finally, the need for research and collaboration was emphasized. Greater understanding of these important concepts will improve the diagnosis and management of patients with suspected primary immunodeficiency diseases.

Disruption of Coronin 1 Signaling in T Cells Promotes Allograft Tolerance while Maintaining Anti-Pathogen Immunity

The ability of the immune system to discriminate self from non-self is essential for eradicating microbial pathogens but is also responsible for allograft rejection. Whether it is possible to selectively suppress alloresponses while maintaining anti-pathogen immunity remains unknown. We found that mice deficient in coronin 1, a regulator of naive T cell homeostasis, fully retained allografts while maintaining T cell-specific responses against microbial pathogens. Mechanistically, coronin 1-deficiency increased cyclic adenosine monophosphate (cAMP) concentrations to suppress allo-specific T cell responses. Costimulation induced on microbe-infected antigen presenting cells was able to overcome cAMP-mediated immunosuppression to maintain anti-pathogen immunity. In vivo pharmacological modulation of this pathway or a prior transfer of coronin 1-deficient T cells actively suppressed allograft rejection. These results define a coronin 1-dependent regulatory axis in T cells important for allograft rejection and suggest that modulation of this pathway may be a promising approach to achieve long-term acceptance of mismatched allografts.

Inherited Immunodeficiencies With High Predisposition to Epstein-Barr Virus-Driven Lymphoproliferative Diseases

Epstein–Barr Virus (EBV) is a gamma-herpes virus that infects 90% of humans without any symptoms in most cases, but has an oncogenic potential, especially in immunocompromised individuals. In the past 30 years, several primary immunodeficiencies (PIDs) associated with a high risk to develop EBV-associated lymphoproliferative disorders (LPDs), essentially consisting of virus-associated hemophagocytic syndrome, non-malignant and malignant B-cell LPDs including non-Hodgkin and Hodgkin’s types of B lymphomas have been characterized. Among them are SH2D1A (SAP), XIAP, ITK, MAGT1, CD27, CD70, CTPS1, RASGRP1, and CORO1A deficiencies. Penetrance of EBV infection ranges from 50 to 100% in those PIDs. Description of large cohorts and case reports has refined the specific phenotypes associated with these PIDs helping to the diagnosis. Specific pathways required for protective immunity to EBV have emerged from studies of these PIDs. SLAM-associated protein-dependent SLAM receptors and MAGT1-dependent NKG2D pathways are important for T and NK-cell cytotoxicity toward EBV-infected B-cells, while CD27–CD70 interactions are critical to drive the expansion of EBV-specific T-cells. CTPS1 and RASGRP1 deficiencies further strengthen that T-lymphocyte expansion is a key step in the immune response to EBV. These pathways appear to be also important for the anti-tumoral immune surveillance of abnormal B cells. Monogenic PIDs should be thus considered in case of any EBV-associated LPDs.

Molecular Classification of Primary Immunodeficiencies of T Lymphocytes

Proper regulation of the immune system is required for protection against pathogens and preventing autoimmune disorders. Inborn errors of the immune system due to inherited or de novo germline mutations can lead to the loss of protective immunity, aberrant immune homeostasis, and the development of autoimmune disease, or combinations of these. Forward genetic screens involving clinical material from patients with primary immunodeficiencies (PIDs) can vary in severity from life-threatening disease affecting multiple cell types and organs to relatively mild disease with susceptibility to a limited range of pathogens or mild autoimmune conditions. As central mediators of innate and adaptive immune responses, T cells are critical orchestrators and effectors of the immune response. As such, several PIDs result from loss of or altered T cell function. PID-associated functional defects range from complete absence of T cell development to uncontrolled effector cell activation. Furthermore, the gene products of known PID causal genes are involved in diverse molecular pathways ranging from T cell receptor signaling to regulators of protein glycosylation. Identification of the molecular and biochemical cause of PIDs can not only guide the course of treatment for patients, but also inform our understanding of the basic biology behind T cell function. In this chapter, we review PIDs with known genetic causes that intrinsically affect T cell function with particular focus on perturbations of biochemical pathways.

From Phagocytes to Immune Defense: Roles for Coronin Proteins in Dictyostelium and Mammalian Immunity

Microbes have interacted with eukaryotic cells for as long as they have been co-existing. While many of these interactions are beneficial for both the microbe as well as the eukaryotic cell, several microbes have evolved into pathogenic species. For some of these pathogens, host cell invasion results in irreparable damage and thus host cell destruction, whereas others use the host to avoid immune detection and elimination. One of the latter pathogens is Mycobacterium tuberculosis, arguably one of the most notorious pathogens on earth. In mammalian macrophages, M. tuberculosis manages to survive within infected macrophages by avoiding intracellular degradation in lysosomes using a number of different strategies. One of these is based on the recruitment and phagosomal retention of the host protein coronin 1, that is a member of the coronin protein family and a mammalian homolog of coronin A, a protein identified in Dictyostelium. Besides mediating mycobacterial survival in macrophages, coronin 1 is also an important regulator of naïve T cell homeostasis. How, exactly, coronin 1 mediates its activity in immune cells remains unclear. While in lower eukaryotes coronins are involved in cytoskeletal regulation, the functions of the seven coronin members in mammals are less clear. Dictyostelium coronins may have maintained multiple functions, whereas the mammalian coronins may have evolved from regulators of the cytoskeleton to modulators of signal transduction. In this minireview, we will discuss the different studies that have contributed to understand the molecular and cellular functions of coronin proteins in mammals and Dictyostelium.

Defective thymic output in WAS patients is associated with abnormal actin organization

Wiskott-Aldrich syndrome protein (WASp) is a key regulator of the actin cytoskeleton. Defective T - cell function is a major cause for immune deficiency in Wiskott-Aldrich syndrome (WAS) patients. T cells originate in the bone marrow and develop in the thymus, and then migrate to peripheral tissues. TCR excision circles (TRECs) present in thymic output cells stably, which is used as a molecular marker for thymic output. We found that CD8⁺ T naïve cells of classic WAS patients were significantly reduced, and TRECs in patients with classic WAS and X-linked thrombocytopenia (XLT) dramatically decreased compared with that of HCs. TRECs were also reduced in WAS (KO) mice. These suggest that defective thymic output partially accounts for T cell lymphopenia in WAS patients. However, the correlation between the defect of thymic output and actin organization still remains elusive. We found that the subcellular location and the levels of of F-actin were altered in T cells from both WAS and XLT patients compared to that of HCs with or without stimulation. Our study shows that WASp plays a critical role in thymic output, which highly correlates with the subcellular location and level of F-actin in T cells.

Proof of Principle for a T Lymphocyte Intrinsic Function of Coronin 1A

Coronins are evolutionarily conserved proteins that were originally identified as modulators of actin-dependent processes. Studies analyzing complete Coronin 1a knock-out mice have shown that this molecule is an important regulator of naive T cell homeostasis and it has been linked to immune deficiencies as well as autoimmune disorders. Nevertheless, because Coronin 1A is strongly expressed in all leukocyte subsets, it is not conclusive whether or not this phenotype is attributed to a T cell-intrinsic function of Coronin 1A. To address this research question, we have generated a T cell-specific Coronin 1a knock-out mouse (Coro1afl/fl × Cd4[Cre]). Deletion of Coronin 1A specifically in T cells led to a strong reduction in T cell number and a shift toward the effector/memory phenotype in peripheral lymphoid organs when compared with Cd4[Cre] mice expressing wild-type Coronin 1A. In contrast to peripheral lymphoid tissue, thymocyte number and subsets were not affected by the deletion of Coronin 1a Furthermore, T cell-specific Coronin 1a knock-out mice were largely resistant to the induction of autoimmunity when tested in the myelin oligoglycoprotein-induced EAE mouse model of multiple sclerosis. Thus, the phenotype of T cell-specific Coronin 1a deletion resembles the phenotype observed with conventional (whole body) Coronin 1a knock-out mice. In summary, our findings provide formal proof of the predominant T cell-intrinsic role of Coronin 1A.