Biallelic variants in POPDC2 cause a novel autosomal recessive syndrome presenting with cardiac conduction defects and variable hypertrophic cardiomyopathy.

POPDC2 encodes for the Popeye domain-containing protein 2 which has an important role in cardiac pacemaking and conduction, due in part to its cAMP-dependent binding and regulation of TREK-1 potassium channels. Loss of Popdc2 in mice results in sinus pauses and bradycardia and morpholino knockdown of popdc2 in zebrafish results in atrioventricular (AV) block. We identified bi-allelic variants in POPDC2 in 4 families that presented with a phenotypic spectrum consisting of sinus node dysfunction, AV conduction defects and hypertrophic cardiomyopathy. Using homology modelling we show that the identified POPDC2 variants are predicted to diminish the ability of POPDC2 to bind cAMP. In in vitro electrophysiological studies we demonstrated that, while co-expression of wild-type POPDC2 with TREK-1 increased TREK-1 current density, POPDC2 variants found in the patients failed to increase TREK-1 current density. While patient muscle biopsy did not show clear myopathic disease, it showed significant reduction of the expression of both POPDC1 and POPDC2, suggesting that stability and/or membrane trafficking of the POPDC1-POPDC2 complex is impaired by pathogenic variants in any of the two proteins. Single-cell RNA sequencing from human hearts demonstrated that co-expression of POPDC1 and 2 was most prevalent in AV node, AV node pacemaker and AV bundle cells. Sinoatrial node cells expressed POPDC2 abundantly, but expression of POPDC1 was sparse. Together, these results concur with predisposition to AV node disease in humans with loss-of-function variants in POPDC1 and POPDC2 and presence of sinus node disease in POPDC2, but not in POPDC1 related disease in human. Using population-level genetic data of more than 1 million individuals we showed that none of the familial variants were associated with clinical outcomes in heterozygous state, suggesting that heterozygous family members are unlikely to develop clinical manifestations and therefore might not necessitate clinical follow-up. Our findings provide evidence for POPDC2 as the cause of a novel Mendelian autosomal recessive cardiac syndrome, consistent with previous work showing that mice and zebrafish deficient in functional POPDC2 display sinus and AV node dysfunction.

An IKBKE variant conferring functional cGAS/STING pathway deficiency and susceptibility to recurrent HSV-2 meningitis.

The mechanisms underlying susceptibility to recurrent herpes simplex virus type 2 (HSV-2) meningitis remain incompletely understood. In a patient experiencing multiple episodes of HSV-2 meningitis, we identified a monoallelic variant in the IKBKE gene, which encodes the IKKε kinase involved in induction of antiviral IFN genes. Patient cells displayed impaired induction of IFN-ß1 (IFNB1) expression upon infection with HSV-2 or stimulation with double-stranded DNA (dsDNA) and failed to induce phosphorylation of STING, an activation marker of the DNA-sensing cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING) pathway. The patient allele encoded a truncated IKKε protein with loss of kinase activity and also capable of exerting dominant-negative activity. In stem cell-derived microglia, HSV-2-induced expression of IFNB1 was dependent on cGAS, TANK binding kinase 1 (TBK1), and IKBKE, but not TLR3, and supernatants from HSV-2-treated microglia exerted IKBKE-dependent type I IFN-mediated antiviral activity upon neurons. Reintroducing wild-type IKBKE into patient cells rescued IFNB1 induction following treatment with HSV-2 or dsDNA and restored antiviral activity. Collectively, we identify IKKε to be important for protection against HSV-2 meningitis and suggest a nonredundant role for the cGAS/STING pathway in human antiviral immunity.

Kinetics of Torque Teno virus in heart transplant patients.

End-stage heart failure often requires heart transplantation as a life-prolonging treatment. Immunosuppressive therapy is necessary to avoid rejection, but is associated with serious adverse effects. New approaches are needed to monitor immune function in heart transplant patients. We here report the kinetics of Torque Teno Virus (TTV) after transplantation in a large cohort of heart transplant patients and examine its possible role in predicting rejection. We included 106 patients from Aarhus University Hospital and Oslo University Hospital. Patients were followed for 3 years with clinical assessments, biopsies, TTV measurements, and flowcytometric phenotyping. We observed TTV levels reaching a maximum 3 months after transplantation for all 106 patients, after which levels gradually declined. 38 patients (38 %) had biopsy-proven rejection within the first year. We did not find evidence of an association between TTV and serum trough levels, events of rejection, nor flow cytometric immunophenotype. We report data on a large cohort of heart transplant patients and contribute to the understanding of how TTV behaves in transplant patients. Despite not finding an association with rejection, our results provide important insights into the kinetics of TTV levels after transplantation, which may be useful in future studies of immune function in heart transplant patients.

Low levels of the innate immune system proteins MASP-2 and MAp44 in patients with common variable immunodeficiency.

Patients with common variable immunodeficiency (CVID) display low antibody levels and associated symptoms, including an increased risk of infections. The causes of CVID are uncertain and likely heterogeneous. The complement system protects against pathogens and plays essential roles in homeostasis and development. The influence of the complement system in CVID is not established. We investigated CVID patients and healthy individuals for plasma levels of the complement proteins: MASP-1, MASP-2, MASP-3, MAp19 and MAp44. We also tested other patients with symptoms similar to the CVID patients. CVID patients had lower average MASP-2 and MAp44 levels than healthy individuals (P < 0.01); the MASP-2 level was 0.73-fold lower, and the MAp44 level was 0.87-fold lower. This was not observed in the other patient cohorts studied. Our findings in this exploratory study provide new insights into CVID and introduce a complement perspective for future investigations into the underlying mechanisms of the disease.

Whole-genome sequencing of Chlamydia trachomatis isolates from persistently infected patients.

BACKGROUND: Current understanding of the causes of treatment failure in Chlamydia trachomatis is poor and antimicrobial susceptibility data are lacking. We used genome sequencing to seek evidence of antimicrobial resistance in isolates sourced from patients who were persistently infected. METHODS: Genomic DNA was extracted from C. trachomatis isolates cultured in McCoy cell monolayers. Sequencing libraries were prepared using the SureSelectXT Illumina paired-end protocol. Paired reads were mapped against a reference genome and single nucleotide variants (SNVs) were identified. RESULTS: Seven isolates from persistently infected patients and five isolates from successfully treated patients were sequenced. No previously reported SNVs associated with antimicrobial resistance were found. A unique SNV was identified in the gyrA gene of one treatment failure isolate but was located outside of the quinolone resistance determining region; this SNV has been previously reported in other members of the Chlamydiaceae family. CONCLUSION: No genomic evidence was found to explain the differences in clinical outcome for our two groups of patients. A mutation unrelated to antimicrobial susceptibility was found in an isolate from a persistently infected patient. The cause of these persistent infections with C. trachomatis remains unclear.

Genetic, Immunological, and Clinical Features of 32 Patients with Autosomal Recessive STAT1 Deficiency.

Autosomal recessive (AR) STAT1 deficiency is a severe inborn error of immunity disrupting cellular responses to type I, II, and III IFNs, and IL-27, and conferring a predisposition to both viral and mycobacterial infections. We report the genetic, immunological, and clinical features of an international cohort of 32 patients from 20 kindreds: 24 patients with complete deficiency, and 8 patients with partial deficiency. Twenty-four patients suffered from mycobacterial disease (bacillus Calmette-Guérin = 13, environmental mycobacteria = 10, or both in 1 patient). Fifty-four severe viral episodes occurred in sixteen patients, mainly caused by Herpesviridae viruses. Attenuated live measles, mumps, and rubella and/or varicella zoster virus vaccines triggered severe reactions in the five patients with complete deficiency who were vaccinated. Seven patients developed features of hemophagocytic syndrome. Twenty-one patients died, and death was almost twice as likely in patients with complete STAT1 deficiency than in those with partial STAT1 deficiency. All but one of the eight survivors with AR complete deficiency underwent hematopoietic stem cell transplantation. Overall survival after hematopoietic stem cell transplantation was 64%. A diagnosis of AR STAT1 deficiency should be considered in children with mycobacterial and/or viral infectious diseases. It is important to distinguish between complete and partial forms of AR STAT1 deficiency, as their clinical outcome and management differ significantly.

Whole-Exome Sequencing of Patients With Recurrent HSV-2 Lymphocytic Mollaret Meningitis.

Recurrent lymphocytic meningitis, also referred to as Mollaret meningitis, is a rare neurological disease characterized mainly by reactivation of herpes simplex virus 2 (HSV-2) from sensory ganglia. However, the underlying host immune determinants and viral factors rendering some individuals unable to maintain HSV-2 latency are largely unknown. We collected a cohort of 15 patients diagnosed with Mollaret meningitis. By whole-exome sequencing we identified rare host genetic variants predicted to be deleterious in molecules involved in (1) ubiquitin-proteasome pathways, (2) the autophagy machinery, and (3) cell proliferation/apoptosis. Moreover, infection of patient cells with HSV-2 or stimulation by virus-derived double-stranded DNA ligands revealed reduced antiviral interferon responses in most patients. These findings may contribute to a better understanding of disease pathogenesis and protective immunity to HSV in the central nervous system, and may ultimately be of importance for identification of targets for development of improved prophylaxis and treatment of this disease.

Defects in LC3B2 and ATG4A underlie HSV2 meningitis and reveal a critical role for autophagy in antiviral defense in humans.

Recurrent herpesvirus infections can manifest in different forms of disease, including cold sores, genital herpes, and encephalitis. There is an incomplete understanding of the genetic and immunological factors conferring susceptibility to recurrent herpes simplex virus 2 (HSV2) infection in the central nervous system (CNS). Here, we describe two adult patients with recurrent HSV2 lymphocytic Mollaret's meningitis that each carry a rare monoallelic variant in the autophagy proteins ATG4A or LC3B2. HSV2-activated autophagy was abrogated in patient primary fibroblasts, which also exhibited significantly increased viral replication and enhanced cell death. HSV2 antigen was captured in autophagosomes of infected cells, and genetic inhibition of autophagy by disruption of autophagy genes, including ATG4A and LC3B2, led to enhanced viral replication and cell death in primary fibroblasts and a neuroblastoma cell line. Activation of autophagy by HSV2 was sensitive to ultraviolet (UV) irradiation of the virus and inhibited in the presence of acyclovir, but HSV2-induced autophagy was independent of the DNA-activated STING pathway. Reconstitution of wild-type ATG4A and LC3B2 expression using lentiviral gene delivery or electroporation of in vitro transcribed mRNA into patient cells restored virus-induced autophagy and the ability to control HSV2 replication. This study describes a previously unknown link between defective autophagy and an inborn error of immunity that can lead to increased susceptibility to HSV2 infection, suggesting an important role for autophagy in antiviral immunity in the CNS.

Idiopathic hypereosinophilic syndrome: A rare diagnosis in children.

Idiopathic hypereosinophilic syndrome (IHES) is one of numerous hypereosinophilic syndromes. The incidence of IHES among children is unknown, but it is considered a rare disease. We report a pediatric case of IHES and the challenges to finding an effective treatment. The patient described here was responsive to prednisolone and thalidomide.

Systemic juvenile idiopathic arthritis and recurrent macrophage activation syndrome due to a CASP1 variant causing inflammasome hyperactivation.

OBJECTIVES: We investigated a patient with systemic juvenile idiopathic arthritis (sJIA) and recurrent macrophage activation syndrome (MAS) to discover genetic and immunological contributing factors. METHODS: Severe recurrent MAS motivated whole exome sequencing (WES) to identify genetic variants potentially involved in disease pathogenesis. In vitro peripheral blood mononuclear cell (PBMC) stimulations for cytokine expression and caspase-1 activity assays as well as NF-κB reporter luciferase assays were performed to functionally characterize variants. RESULTS: WES revealed an extremely rare heterozygous missense variant, c.482G>A, p.R161H in the CASP1 gene encoding pro-caspase-1. Lipopolysaccharide (LPS) stimulation of patient PBMCs induced high levels of IL-6 compared to controls, and activation of the NLRP3 inflammasome resulted in increased production of IL-1ß and IL-18 as well as significantly elevated caspase-1 activity. Constitutive and inducible levels of IL-18 and IFNγ in whole blood were markedly elevated. Expression of the CASP1 variant in an NF-κB reporter luciferase assay induced increased NF-κB activation in a RIP2-dependent manner. The disease course of the patient was complicated by severe recurrent MAS. However, dual IL-1 and IL-6 blockade caused disease remission. CONCLUSION: For the first time, we demonstrate the involvement of a CASP1 variant in sJIA and recurrent MAS. This variant is gain-of-function for both inflammasome and NF-κB activation leading to increased production of IL-6, IL-1ß and IL-18. Although dual IL-1 and IL-6 blockade may be beneficial in patients, in whom single treatment is not sufficient to control MAS, caution should be practiced, since interstitial lung disease may progress despite apparent clinical and biochemical remission.

Detecting mismatched donor HLA types from allograft biopsies - An easily applicable tool for improved individualized risk assessment.

Short-term allograft survival has improved among solid organ transplant (SOT) patients. An increasing number of SOT patients are prepared for re-transplantation because of chronic allograft failure. Lack of HLA typing or incomplete HLA typing of previous donors complicates pretransplant risk assessment, as repeated HLA mismatches may be missed. In addition, a complete HLA type of the donor is essential in the diagnosis of antibody-mediated rejection. We aimed to determine donor HLA types from allograft biopsies from kidney, heart and liver grafts. Graft biopsies were obtained from 13 kidney, heart and liver transplanted patients. HLA typing was performed using q-PCR. Alleles of both donor and recipient origin were detected, and donor HLA type was concluded by deducting known HLA types of the recipient. For all 13 patients, we were able to determine mismatched donor HLA alleles from graft material. These results are promising, because they enable better individualized risk assessment.

HTLV infected individuals have increased B-cell activation and proinflammatory regulatory T-cells.

Human T-lymphotropic virus (HTLV) affects the human immune system in many ways, most notably by inducing proliferation of infected CD4 + T cells, but several other cell types are also affected. To characterize the effects of HTLV infection, we analysed blood samples from HTLV-infected individuals by flow cytometry. Samples were collected from visitors at the HIV clinic in Bissau, Guinea-Bissau. These samples were tested for HTLV and HIV, and 199 were analysed by flow cytometry using panels for B cells, T-cell maturation and activation, regulatory T cells (Tregs) and monocytes. CD80+ cell proportions were significantly higher in HTLV infected than in HTLV uninfected in all B cell subsets. Among T cells, there was no change in cell distribution between maturation stages, but a higher CD25+ proportion among Tregs (61.1 % vs 36.3 %, p < 0.001) in HTLV infected than in HTLV uninfected. The level of CD49d on individual cells was also higher (MFI 2734.5 vs 1,041, p < 0.001). In HTLV infected individuals, CD8 + T cells had a lower proportion of CTLA-4+ (2.5 % vs 3.5 %, 0.048) and higher PD1+ proportion on the CD45RO + subset (81.6 % vs 77.1 %, p < 0.001). Together, these findings point toward reduced regulation in HTLV + patients, which leads to immune activation. This study corroborates previous findings and offers new insight into the effects of HTLV by providing a broad flowcytometric analysis of immune cells in HTLV + individuals.

Autoinflammatory disease with corneal and mucosal dyskeratosis caused by a novel NLRP1 variant.

OBJECTIVES: Here we investigated a patient with inflammatory corneal intraepithelial dyskeratosis, mucosal inflammation, tooth abnormalities and, eczema to uncover the genetic and immunological basis of the disease. METHODS: On suspicion of an autoinflammatory condition, Sanger sequencing of nucleotide-binding oligomerization domain-like, leucine-rich repeat pyrin domain containing 1 (NLRP1) was performed and combined with an in vitro inflammasome reconstitution assay to measure caspase-1-mediated IL-1ß cleavage, stimulation of patient peripheral blood mononuclear cells (PBMCs) and whole blood to measure IL-1ß, IL-18 production and quantification of apoptosis-associated speck-like protein containing CARD (ASC) speck formation as a measure of inflammasome activation by flow cytometry. RESULTS: Sanger sequencing revealed a novel mutation (c.175G>C, p.A59P; NM_33004.4) in the inflammasome molecule NLRP1 segregating with disease, although with incomplete penetrance, in three generations. We found that patient PBMCs produced increased IL-1ß in response to inflammatory stimuli, as well as increased constitutive levels of IL-18. Moreover, we demonstrate that expression of the identified NLRP1 A59P variant caused spontaneous IL-1ß cleavage to mature IL-1ß. In addition, patient PBMCs responded to NLRP1 stimulation with increased ASC speck formation as a reflection of elevated inflammasome activity. CONCLUSION: We demonstrate that this novel NLRP1 A59P variant caused increased activation of the NLRP1 inflammasome, resulting in constitutively and inducibly elevated IL-1ß and IL-18 synthesis. We suggest the NLRP1 mutation underlies the pathogenesis of this rare autoinflammatory dyskeratotic disease inherited in an autosomal dominant manner with incomplete penetrance in the patient and within the family for several generations.

Whole-Genome Sequencing of Chlamydia trachomatis Directly from Human Samples.

Whole-genome sequencing is a powerful, high-resolution tool that can be used to generate accurate data on bacterial population structure, phylogeography and mutations associated with antimicrobial resistance. The ability to sequence pathogen genomes directly from clinical specimens, without the requirement for in vitro culturing, is attractive in terms of time- and labor-saving, especially in the case of slow growing, or obligate intracellular pathogens, such as Chlamydia trachomatis. However clinical samples typically contain too low levels of pathogen nucleic acid, plus relatively high levels of human and natural microbiota DNA/RNA, to make this a viable option. Using a combination of whole-genome enrichment and deep sequencing, which has been proven to be a nonmutagenic approach, we can capture all known variation found within C. trachomatis genomes. The method is a consistent and sensitive tool that enables rapid whole-genome sequencing of C. trachomatis directly from clinical samples and has the potential to be adapted to other pathogens with a similar clonal nature.

Pattern Recognition Molecules of the Lectin Pathway-Screening of Patients with Suspected Immunodeficiency.

PURPOSE: To compare plasma concentrations of all lectin pathway (LP) pattern recognition molecules (PRMs) in patients referred for laboratory evaluation due to recurrent infections with healthy individuals. METHODS: Patients were divided into categories according to referral: recurrent airway infections (RAI), recurrent abscesses, common variable immunodeficiency (CVID), lung transplantation candidates (LTX), and 'other causes'. LP PRMs (mannose-binding lectin (MBL), collectin liver 1 (CL-L1), H-ficolin, L-ficolin, M-ficolin) and C-reactive protein (CRP) were determined in 332 patients and 150 healthy blood donors using time-resolved immunofluorometric assays. RESULTS: None of the LP PRMs was found in lower concentration in the patient categories; however, several PRMs were detected in higher concentrations. M-ficolin was found in higher concentrations in all patient categories. Patients suffering from RAI had higher concentrations of CL-L1 and H-ficolin. Patients suffering from abscesses exhibited higher concentrations of MBL and CL-L1, whereas LTX had higher concentrations of MBL. Patients with other causes of referral had higher concentrations of MBL and CL-L1. Prevalence of combined deficiencies of PRMs in patient categories and controls did not differ. CRP was used as a marker of ongoing inflammation and was significantly higher among all patient categories. Furthermore, CRP was found to correlate with both M-ficolin and L-ficolin. CONCLUSION: The results suggest that neither single nor combined deficiencies of LP PRMs are more frequent among patients referred for an immunological evaluation than in healthy individuals. Future studies are needed and should focus on deficiencies of LP PRMs combined with deficiencies in other parts of the immune system.

Host Genetics, Innate Immune Responses, and Cellular Death Pathways in Poliomyelitis Patients.

PURPOSE: Poliovirus (PV) is one of the most studied viruses. Despite efforts to understand PV infection within the host, fundamental questions remain unanswered. These include the mechanisms determining the progression to viremia, the pathogenesis of neuronal infection and paralysis in only a minority of patients. Because of the rare disease phenotype of paralytic poliomyelitis (PPM), we hypothesize that a genetic etiology may contribute to the disease course and outcome. METHODS: We used whole-exome sequencing (WES) to investigate the genetic profile of 18 patients with PPM. Functional analyses were performed on peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages (MdMs). RESULTS: We identified rare variants in host genes involved in interferon signaling, viral replication, apoptosis, and autophagy. Upon PV infection of MdMs, we observed a tendency toward increased viral burden in patients compared to controls, suggesting reduced control of PV infection. In MdMs from patients, the IFNß response correlated with the viral burden. CONCLUSION: We suggest that genetic variants in innate immune defenses and cell death pathways contribute to the clinical presentation of PV infection. Importantly, this study is the first to uncover the genetic profile in patients with PPM combined with investigations of immune responses and viral burden in primary cells.