CD109, a TGF-β co-receptor, attenuates extracellular matrix production in scleroderma skin fibroblasts

Hemophagocytic lymphohistiocytosis (HLH) is a rare life-threatening disease of severe hyperinflammation caused by uncontrolled proliferation of activated lymphocytes and macrophages secreting high amounts of inflammatory cytokines. It is a frequent manifestation in patients with predisposing genetic defects, but can occur secondary to various infectious, malignant, and autoimmune triggers in patients without a known genetic predisposition. Clinical hallmarks are prolonged fever, cytopenias, hepatosplenomegaly, and neurological symptoms, but atypical variants presenting with signs of chronic immunodeficiency are increasingly recognized. Impaired secretion of perforin is a key feature in several genetic forms of the disease, but not required for disease pathogenesis. Despite progress in diagnostics and therapy, mortality of patients with severe HLH is still above 40%. Reference treatment is an etoposide-based protocol, but new approaches are currently explored. Key for a favorable prognosis is the rapid identification of an underlying genetic cause, which has been facilitated by recent immunological and genetic advances. In patients with predisposing genetic disease, hematopoietic stem cell transplantation is performed increasingly with reduced intensity conditioning regimes. Current research aims at a better understanding of disease pathogenesis and evaluation of more targeted approaches to therapy, including anti-cytokine antibodies and gene therapy.     

Pathophysiology and spectrum of diseases caused by defects in lymphocyte cytotoxicity

In experimental settings, lymphocyte cytotoxicity has been recognized as a central mechanism for immune defense against infected and neoplastic cells. More recently, molecular determinants of lymphocyte cytotoxicity have been identified through studies of rare, inherited hyperinflammatory and lymphoproliferative syndromes that include hemophagocytic lymphohistiocytosis (HLH). These studies have unraveled a set of genes pivotal for the biogenesis and directed release of perforin-containing lysosomes that mediate target cell killing, in addition to other pathways including Fas that also contribute to induction of cell death. Furthermore, studies of such human primary immunodeficiencies have highlighted non-redundant roles of perforin for maintenance of immune homeostasis. Besides providing mechanistic insights to lymphocyte cytotoxicity, studies of individuals with rare hyperinflammatory diseases are highlighting the relevance of lymphocyte cytotoxicity to more common human diseases. It is increasingly recognized that mutations abrogating lymphocyte cytotoxicity not only cause HLH, but also are associated with susceptibility to cancer and autoimmune syndromes. In addition, patients may initially be present with neurological symptoms or severe infectious disease masquerading as variable immunodeficiency syndrome. Here, we highlight new knowledge regarding the molecular mechanisms regulating lymphocyte cytotoxicity and review how mutations in genes associated with HLH cause disease. We also discuss the wider implications of impairments in lymphocyte cytotoxicity for human disease predisposition.     

Genetic Features of Late Onset Primary Hemophagocytic Lymphohistiocytosis in Adolescence or Adulthood

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition of uncontrolled immune activation leading to extreme inflammation. Primary HLH was once believed to be a disease that occurred only in infancy or young children, and was rarely diagnosed in adults. It is now understood that patients can develop primary HLH in their adolescence or adulthood. This study included 252 adolescent and adult patients with a clinical diagnosis of HLH from 35 general medical institutions across mainland China. All exons and 50 bp of flanking intronic sequence of six HLH-related genes (PRF1, UNC13D, STX11, STXBP2, SH2D1A, and BIRC4) were sequenced in these patients. We identified mutations in 18/252 (7.1%) of the patients, with changes in PRF1 being most common. Late-onset HLH often features viral infection and other predisposing factors. We conclude that late-onset primary HLH is not as rare as previously thought. Older patients should not be delayed to receive HLH-related genes testing when they are suspected with HLH.     

Incidence and Risk Factors for Developing Dengue-Associated Hemophagocytic Lymphohistiocytosis in Puerto Rico, 2008 - 2013

BackgroundHemophagocytic lymphohistiocytosis (HLH) is a rare, potentially fatal disorder characterized by fever, pancytopenia, hepatosplenomegaly, and increased serum ferritin. HLH is being increasingly reported as a complication of dengue, a common tropical acute febrile illness.Conclusions/SignificanceDuring this cluster of dengue-associated HLH cases that was temporally associated with the 2012–2013 epidemic, most patients with dengue-associated HLH were infants and had higher morbidity than dengue inpatients. Physicians throughout the tropics should be aware of HLH as a potential complication of dengue, particularly in patients with anemia and severe liver injury.     

Human Genetic Predisposition to Diseases Caused by Viruses from Flaviviridae Family

The identification of human predisposition genes to severe forms of infectious diseases is important for understanding the mechanisms of pathogenesis, as well as for the detection of the risk groups. This will allow one to carry out targeted vaccination and preventive therapy. The most common approaches to the genetic risk estimation include conducting association studies, in which the groups of patients and control individuals are compared using both preliminarily selected candidate genes and using genome-wide analysis. To search for genetic variants predisposed to severe forms of infectious diseases, it is expedient to form a control that consists of patients with clinically proven infections with asymptomatic or mild forms of the disease. The examples of the use of these approaches to identify genetic factors that predispose one to severe forms of infections caused by viruses from the Flaviviridae family are considered in the review. At present, a number of genetic markers associated with predisposition to tick-borne encephalitis, West Nile fever, and Dengue fever have already been detected. These associations must be confirmed in independent samples. Genetic variants, for which the association with spontaneous recovery during infection with hepatitis C virus, patient’s reaction on antiviral drugs, and the development of liver fibrosis was established, were also detected. The gene variants with more pronounced phenotypic effects will probably be found during further studies; they can be used in clinical practice as prognostic markers of the course and outcomes of infection with the Flaviviridae, as well as of the response to treatment.     

Lytic viral replication and immunopathology in a cytomegalovirus-induced mouse model of secondary hemophagocytic lymphohistiocytosis

Background

Hemophagocytic lymphohistiocytosis (HLH) is a rare immunological disorder caused by unbridled activation of T cells and macrophages, culminating in a life-threatening cytokine storm. A genetic and acquired subtype are distinguished, termed primary and secondary HLH, respectively. Clinical manifestations of both forms are frequently preceded by a viral infection, predominantly with herpesviruses. The exact role of the viral infection in the development of the hemophagocytic syndrome remains to be further elucidated.

Methods

We utilized a recently developed murine model of cytomegalovirus-associated secondary HLH and dissected the respective contributions of lytic viral replication and immunopathology in its pathogenesis.

Results

HLH-like disease only developed in cytomegalovirus-susceptible mouse strains unable to clear the virus, but the severity of symptoms was not correlated to the infectious viral titer. Lytic viral replication and sustained viremia played an essential part in the pathogenesis since abortive viral infection was insufficient to induce a full-blown HLH-like syndrome. Nonetheless, a limited set of symptoms, in particular anemia, thrombocytopenia and elevated levels of soluble CD25, appeared less dependent of the viral replication but rather mediated by the host’s immune response, as corroborated by immunosuppressive treatment of infected mice with dexamethasone.

Conclusion

Both virus-mediated pathology and immunopathology cooperate in the pathogenesis of full-blown virus-associated secondary HLH and are closely entangled. A certain level of viremia appears necessary to elicit the characteristic HLH-like symptoms in the model.

     

Cystic fibrosis and lipoxins

Dysregulated neutrophilic inflammation and chronic infection lead to progressive destruction of the airways in cystic fibrosis (CF). Despite considerable recent progress in therapy, the median survival of patients with CF remains around 30 years. The lipoxins are endogenous anti-inflammatory lipid mediators that are important regulators of neutrophilic inflammation. Recent data indicate that there is a pathophysiologically important defect in lipoxin-mediated anti-inflammatory activity in the CF airway, suggesting novel approaches to pathogenesis and therapy in this lethal genetic disease.     

HLA-C, DRB1 and DQB1 alleles involved in genetic predisposition to psoriasis vulgaris in the Slovak population

Psoriasis vulgaris is a complex chronic skin disease with immunological and genetic background. The most important predisposing genetic factors in psoriasis are genes of the human leukocyte antigen (HLA) region. Accumulative evidence has shown that several HLA alleles are closely associated with psoriasis; however, they tend to vary in different racial and ethnic backgrounds. One hundred forty-seven unrelated Slovak patients with psoriasis vulgaris (average age at onset 28?±?14 years) were genotyped for the HLA-C, DQB1 and DRB1 alleles by the polymerase chain reaction using sequence-specific primers. Allele frequencies observed in the group of psoriatic patients were compared to those obtained in the ethnically matched control group comprising 194 subjects with no history of psoriasis. Susceptibility to psoriasis vulgaris in our study group is significantly associated with HLA-C*06 (odds ratio (OR)?=?3.85), DRB1*07 (OR?=?2.56) and DQB1*02 (OR?=?1.09), respectively, whereas DRB*01 (OR?=?0.05) is associated negatively. Hereby, we provide the first report on the association of HLA-C, DRB1 and DQB1 alleles with psoriasis in the Slovak population. Our findings confirm HLA-C*06 and DRB1*07 as the most important genetic risk factors for psoriasis. However, the role of HLA genes as causative in the pathogenesis of the disease remains unclear. Identification of genetic factors that increase the risk of psoriasis is a precondition that helps to elucidate the pathogenesis of this troubling disease and identify targets for a more specific and effective therapy.     

A network-informed analysis of SARS-CoV-2 and hemophagocytic lymphohistiocytosis genes’ interactions points to Neutrophil extracellular traps as mediators of thrombosis in COVID-19

Abnormal coagulation and an increased risk of thrombosis are features of severe COVID-19, with parallels proposed with hemophagocytic lymphohistiocytosis (HLH), a life-threating condition associated with hyperinflammation. The presence of HLH was described in severely ill patients during the H1N1 influenza epidemic, presenting with pulmonary vascular thrombosis. We tested the hypothesis that genes causing primary HLH regulate pathways linking pulmonary thromboembolism to the presence of SARS-CoV-2 using novel network-informed computational algorithms. This approach led to the identification of Neutrophils Extracellular Traps (NETs) as plausible mediators of vascular thrombosis in severe COVID-19 in children and adults. Taken together, the network-informed analysis led us to propose the following model: the release of NETs in response to inflammatory signals acting in concert with SARS-CoV-2 damage the endothelium and direct platelet-activation promoting abnormal coagulation leading to serious complications of COVID-19. The underlying hypothesis is that genetic and/or environmental conditions that favor the release of NETs may predispose individuals to thrombotic complications of COVID-19 due to an increase risk of abnormal coagulation. This would be a common pathogenic mechanism in conditions including autoimmune/infectious diseases, hematologic and metabolic disorders.     

Secondary hemophagocytic lymphohistiocytosis versus cytokine release syndrome in severe COVID-19 patients

COVID-19 or SARS-CoV-2 infection can lead to severe acute respiratory distress syndrome/pneumonia with features of cytokine storm reminiscent of secondary hemophagocytic lymphohistiocytosis (HLH), which can be diagnosed by the calculated HScore. Recent reports have suggested favorable responses to the interleukin-1 receptor antagonist, anakinra in patients with COVID-19 associated secondary HLH. In our single institution study, we compared 14 COVID-19 cytokine storm patients with 10 secondary HLH patients seen immediately prior to the pandemic (non-COVID-19), to determine whether diagnostic features of secondary HLH were typically seen in COVID-19 patients presenting with cytokine storm. Although most of our COVID-19 patients did not fulfill diagnostic criteria for HLH, we hypothesize that identification of HLH may relate to the severity or timing of cytokine release. Based on our observations, we would suggest distinguishing between cytokine release syndrome and secondary HLH, reserving the latter term for cases fulfilling diagnostic criteria.Impact statementSevere COVID-19 associated pneumonia and acute respiratory distress syndrome has recently been described with life-threatening features of cytokine storm and loosely referred to as hemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (MAS). Although a recent report indicated favorable responses to the interleukin-1 receptor antagonist, anakinra in eight patients with COVID-19 secondary HLH diagnosed using the HScore calculation, others have suggested that the diagnosis of secondary HLH is uncommon and that the use of the HScore has limited value in guiding immunomodulatory therapy for COVID-19. Here, we provide additional perspective on this important controversy based upon comparisons between 14 COVID-19 cytokine storm patients and 10 secondary HLH patients seen immediately prior to the pandemic. We hypothesize that identification of HLH may relate to the severity or timing of cytokine release and suggest distinguishing between cytokine release syndrome and secondary HLH, reserving the latter term for cases fulfilling diagnostic criteria.     

Dissecting complex epigenetic alterations in human lupus

Systemic lupus erythematosus is a chronic relapsing autoimmune disease that primarily afflicts women, and both a genetic predisposition and appropriate environmental exposures are required for lupus to develop and flare. The genetic requirement is evidenced by an increased concordance in identical twins and by the validation of at least 35 single-nucleotide polymorphisms predisposing patients to lupus. Genes alone, though, are not enough. The concordance of lupus in identical twins is often incomplete, and when concordant, the age of onset is usually different. Lupus is also not present at birth, but once the disease develops, it typically follows a chronic relapsing course. Thus, genes alone are insufficient to cause human lupus, and additional factors encountered in the environment and over time are required to initiate the disease and subsequent flares. The nature of the environmental contribution, though, and the mechanisms by which environmental agents modify the immune response to cause lupus onset and flares in genetically predisposed people have been controversial. Reports that the lupus-inducing drugs procainamide and hydralazine are epigenetic modifiers, that epigenetically modified T cells are sufficient to cause lupus-like autoimmunity in animal models, and that patients with active lupus have epigenetic changes similar to those caused by procainamide and hydralazine have prompted a growing interest in how epigenetic alterations contribute to this disease. Understanding how epigenetic mechanisms modify T cells to contribute to lupus requires an understanding of how epigenetic mechanisms regulate gene expression. The roles of DNA methylation, histone modifications, and microRNAs in lupus pathogenesis will be reviewed here.     

Killer cell immunoglobulin-like receptor gene polymorphisms predispose susceptibility to Epstein-Barr virus associated hemophagocytic lymphohistiocytosis in Chinese children

Epstein-Barr virus associated hemophagocytic lymphohistiocytosis (EBV-HLH) has a high mortality rate among children. The pathogenesis of, and underlying predisposing factors for, EBV-HLH are as yet unclear; however, natural killer cells may play a key role in progression of the disease. This study attempted to determine whether killer cell immunoglobulin-like receptor (KIR) gene polymorphisms are responsible for susceptibility to EBV-HLH. Of the 125 children with EBV infection studied, 59 had EBV-HLH and 66 patients had EBV associated infectious mononucleosis (IM) without HLH. The control group was 146 normal children without immune deficiency. KIR polymorphisms were determined by polymerase chain reaction with sequence-specific primers. KIR polymorphism data were analyzed using the X(2) test or Fisher's exact test. The overall observed carrier frequency (OF) of KIR2DS5 was significantly higher in EBV-HLH patients than in IM patients and normal controls (49.2% versus 31.8%, P = 0.048; 49.2% versus 31.5%, P = 0.018, respectively), and the odds ratios (95% confidence interval) were 2.071 (1.001-4.286) and 2.101(1.132-3.900) respectively. The OF of KIR3DS1 was significantly higher in the EBV-HLH patients than in the IM patients (47.4% versus 24.6%, P = 0.012), but not different from normal controls. In summary, KIR polymorphisms may be involved in the development of EBV-HLH, with KIR2DS5 promoting susceptibility to this disease. The obtained KIR data will enrich the understanding of genetic relationships among diseases associated with EBV infection in children.     

Autoimmune diabetes mellitus, Hodgkin's disease and Graves' ophthalmopathy in a patient with 8.1 ancestral haplotype.

In this report, we describe the case of a 43-year-old woman affected by type 1 diabetes mellitus diagnosed 8 years before, who developed Graves' disease 2 years after chemotherapy and mantle radiotherapy treatment for Hodgkin's disease. Bilateral Graves' ophthalmopathy appeared four months before our observations. Intravenous methyl-prednisolone therapy was started, but was interrupted due to severe metabolic failure. Autoantibodies (anti-islet cells, anti-thyroid, thyroid-stimulating, non-organ-specific) were positive. Since the clinical picture suggested a genetic immunological ground predisposing to autoimmunity, we evaluated her HLA haplotype. Genomic typing of the patient permitted identification of the 8.1 ancestral haplotype, a Caucasoid haplotype unique in its association with many immunopathological diseases. Moreover, we also observed a haplotype unusual in Caucasians, trans DRB1*1101, DQA1*0103, DQB1*0603. To our knowledge, HLA-related genetic risk of developing thyroid autoimmunity after neck irradiation has never been studied. Although we cannot confirm a direct association between the 8.1 ancestral haplotype or DRB1*1101, DQA1*0103, DQB1*0603 and the diseases described, we suggest considering immunological parameters and HLA typing in candidate patients for mantle radiation therapy for Hodgkin's disease or other tumors. HLA haplotype determination could be useful in identifying the patients at raised risk of developing autoimmune diseases after irradiation, thus permitting a more appropriate follow-up schedule.     

Heart failure: advances through genomics

Heart failure is an increasingly prevalent and highly lethal disease that is most often caused by underlying pathologies, such as myocardial infarction or hypertension, but it can also be the result of a single gene mutation. Comprehensive genetic and genomic approaches are starting to disentangle the diverse molecular underpinnings of both forms of the disease and promise to yield much-needed novel diagnostic and therapeutic options for specific subtypes of heart failure.     

Epidermal stem cells and ex vivo cutaneous gene therapy: application to xeroderma pigmentosum

Ex vivo cutaneous gene therapy is an alternative treatment for recessively inherited diseases with cutaneous traits. It relies on the transfer in cultured epidermal keratinocytes of the wild-type allele of the gene whose mutation is responsible for the disease. As for severely burnt patients, epithelial sheets developed from genetically corrected cells may then be grafted back to the patients. Long term correction and graft take depend on the genetic correction of stem cells. Success of such an approach has recently been reported in the case of one patient suffering from a severe case of junctional epidermolysis bullosae. Here we report a method for safely selecting keratinocytes populations after genetic manipulation. The method is non invasive and non immunogenic and allows high enrichment of genetically manipulated stem keratinocytes. This could perhaps contribute to ex vivo gene therapy approaches of cancer prone genodermatoses such as xeroderma pigmentosum.     

A possible role for mitochondrial dysfunction in migraine

Migraine is a common neurological disorder characterised by debilitating head pain and an assortment of additional symptoms which can include nausea, emesis, photophobia, phonophobia and occasionally visual sensory disturbances. Migraine is a complex disease caused by an interplay between predisposing genetic variants and environmental factors. It affects approximately 12?% of studied Caucasian populations with affected individuals being predominantly female. Genes involved in neurological, vascular or hormonal pathways have all been implicated in predisposition towards developing migraine. All of these are nuclear encoded genes, but given the role of mitochondria in a number of neurological disorders and in energy production it is possible that mitochondrial variants may play a role in the pathogenesis of this disease. Mitochondrial DNA has been a useful tool for studying population genetics and human genetic diseases due to the clear inheritance shown through successive generations. Given the clear gender bias found in migraine patients it may be important to investigate X-linked inheritance and mitochondrial-related variants in this disorder. This paper explores the possibility that mitochondrial DNA changes may play a role in migraine. Few variants in the mitochondrial genome have so far been investigated in migraine and new studies should be aimed towards investigating the role of mitochondrial DNA in this common disorder.     

Canine models of Duchenne muscular dystrophy and their use in therapeutic strategies

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder in which the loss of dystrophin causes progressive degeneration of skeletal and cardiac muscle. Potential therapies that carry substantial risk, such as gene- and cell-based approaches, must first be tested in animal models, notably the mdx mouse and several dystrophin-deficient breeds of dogs, including golden retriever muscular dystrophy (GRMD). Affected dogs have a more severe phenotype, in keeping with that of DMD, so may better predict disease pathogenesis and treatment efficacy. Various phenotypic tests have been developed to characterize disease progression in the GRMD model. These biomarkers range from measures of strength and joint contractures to magnetic resonance imaging. Some of these tests are routinely used in clinical veterinary practice, while others require specialized equipment and expertise. By comparing serial measurements from treated and untreated groups, one can document improvement or delayed progression of disease. Potential treatments for DMD may be broadly categorized as molecular, cellular, or pharmacologic. The GRMD model has increasingly been used to assess efficacy of a range of these therapies. A number of these studies have provided largely general proof-of-concept for the treatment under study. Others have demonstrated efficacy using the biomarkers discussed. Importantly, just as symptoms in DMD vary among patients, GRMD dogs display remarkable phenotypic variation. Though confounding statistical analysis in preclinical trials, this variation offers insight regarding the role that modifier genes play in disease pathogenesis. By correlating functional and mRNA profiling results, gene targets for therapy development can be identified.     

Treating hemoglobinopathies using gene-correction approaches: promises and challenges

Hemoglobinopathies are genetic disorders caused by aberrant hemoglobin expression or structure changes, resulting in severe mortality and health disparities worldwide. Sickle cell disease (SCD) and β-thalassemia, the most common forms of hemoglobinopathies, are typically treated using transfusions and pharmacological agents. Allogeneic hematopoietic stem cell transplantation is the only curative therapy, but has limited clinical applicability. Although gene therapy approaches have been proposed based on the insertion and forced expression of wild-type or anti-sickling β-globin variants, safety concerns may impede their clinical application. A novel curative approach is nuclease-based gene correction, which involves the application of precision genome-editing tools to correct the disease-causing mutation. This review describes the development and potential application of gene therapy and precision genome-editing approaches for treating SCD and β-thalassemia. The opportunities and challenges in advancing a curative therapy for hemoglobinopathies are also discussed.     

Treatment of Mitochondrial Disease

Defects of the mitochondrial genome are widely recognized as important causes of disease in man. Patients may present at any age with clinical symptoms that vary from acute episodes of lactic acidosis in infancy to severe neurodegenerative illness in adulthood. While modern molecular genetic techniques have facilitated major advances in the diagnosis and characterization of specific molecular defects, treatment for the majority of patients remains supportive in the absence of definitive biochemical therapies. As a consequence, the possibilities for mitochondrial DNA gene therapy must be considered. In this review, we will evaluate the current biochemical strategies available to clinicians for the management of patients with mitochondrial disease and examine the possible approaches to the gene therapy of mitochondrial DNA defects.