Janus kinase inhibition in complement component 1 deficiency

UNC93B1 variants underlie TLR7-dependent autoimmunity

UNC93B1 is critical for trafficking and function of nucleic acid-sensing Toll-like receptors (TLRs) TLR3, TLR7, TLR8, and TLR9, which are essential for antiviral immunity. Overactive TLR7 signaling induced by recognition of self-nucleic acids has been implicated in systemic lupus erythematosus (SLE). Here, we report UNC93B1 variants (E92G and R336L) in four patients with early-onset SLE. Patient cells or mouse macrophages carrying the UNC93B1 variants produced high amounts of TNF-α and IL-6 and upon stimulation with TLR7/TLR8 agonist, but not with TLR3 or TLR9 agonists. E92G causes UNC93B1 protein instability and reduced interaction with TLR7, leading to selective TLR7 hyperactivation with constitutive type I IFN signaling. Thus, UNC93B1 regulates TLR subtype-specific mechanisms of ligand recognition. Our findings establish a pivotal role for UNC93B1 in TLR7-dependent autoimmunity and highlight the therapeutic potential of targeting TLR7 in SLE.

Absence of Type I Interferon Autoantibodies or Significant Interferon Signature Alterations in Adults With Post-COVID-19 Syndrome

Genetic defects in the interferon (IFN) system or neutralizing autoantibodies against type I IFNs contribute to severe COVID-19. Such autoantibodies were proposed to affect post-COVID-19 syndrome (PCS), possibly causing persistent fatigue for >12 weeks after confirmed SARS-CoV-2 infection. In the current study, we investigated 128 patients with PCS, 21 survivors of severe COVID-19, and 38 individuals who were asymptomatic. We checked for autoantibodies against IFN-α, IFN-β, and IFN-ω. Few patients with PCS had autoantibodies against IFNs but with no neutralizing activity, indicating a limited role of type I IFNs in PCS pathogenesis. In a subset consisting of 28 patients with PCS, we evaluated IFN-stimulated gene activity and showed that it did not correlate with fatigue. In conclusion, impairment of the type I IFN system is unlikely responsible for adult PCS.

C-terminal variants in CDC42 drive type I interferon-dependent autoinflammation in NOCARH syndrome reversible by ruxolitinib

C-terminal variants in CDC42 encoding cell division control protein 42 homolog underlie neonatal-onset cytopenia, autoinflammation, rash, and hemophagocytic lymphohistiocytosis (NOCARH). Pyrin inflammasome hyperactivation has been shown to contribute to disease pathophysiology. However, mortality of NOCARH patients remains high despite inflammasome-focused treatments. Here, we demonstrate in four NOCARH patients from three families that cell-intrinsic activation of type I interferon (IFN) is a previously unrecognized driver of autoinflammation in NOCARH. Our data show that aberrant innate immune activation is caused by sensing of cytosolic nucleic acids released from mitochondria, which exhibit disturbances in integrity and dynamics due to CDC42 dysfunction. In one of our patients, treatment with the Janus kinase inhibitor ruxolitinib led to complete remission, indicating that inhibition of type I IFN signaling may have an important role in the management of autoinflammation in patients with NOCARH.

Hemophagocytic lymphohistiocytosis-like hyperinflammation due to a de novo mutation in DPP9

BACKGROUND

Genetic defects in components of inflammasomes can cause autoinflammation. Biallelic loss-of-function mutations in dipeptidyl peptidase 9 (DPP9), a negative regulator of the NLRP1 and CARD8 inflammasomes, have recently been shown to cause an inborn error of immunity characterized by pancytopenia, skin manifestations, and increased susceptibility to infections.

OBJECTIVE

We sought to study the molecular basis of autoinflammation in a patient with severe infancy-onset hyperinflammation associated with signs of fulminant hemophagocytic lymphohistiocytosis.

METHODS

Using heterologous cell models as well as patient cells, we performed genetic, immunologic, and molecular investigations to identify the genetic cause and to assess the impact of the identified mutation on inflammasome activation.

RESULTS

The patient exhibited pancytopenia with decreased neutrophils and T, B, and natural killer cells, and markedly elevated levels of lactate dehydrogenase, ferritin, soluble IL-2 receptor, and triglycerides. In addition, serum levels of IL-1β and IL-18 were massively increased, consistent with inflammasome activation. Genetic analysis revealed a previously undescribed de novo mutation in DPP9 (c.755G>C, p.Arg252Pro) affecting a highly conserved amino acid residue. The mutation led to destabilization of the DPP9 protein as shown in transiently transfected HEK293T cells and in patient-derived induced pluripotent stem cells. Using functional inflammasome assays in HEK293T cells, we demonstrated that mutant DPP9 failed to restrain the NLRP1 and CARD8 inflammasomes, resulting in constitutive inflammasome activation. These findings suggest that the Arg252Pro DPP9 mutation acts in a dominant-negative manner.

CONCLUSIONS

A de novo mutation in DPP9 leads to severe infancy-onset autoinflammation because of unleashed inflammasome activation.

Case Report: Response of cutaneous lupus lesions in SLE to interferon receptor blockade parallels reduction of interferon score in blood

Cutaneous lupus erythematosus (CLE), the main manifestation of systemic lupus erythematosus (SLE), is driven by type I interferons (IFNs) and often only partially responds to conventional therapies. Treatment of seven SLE patients with the monoclonal antibody anifrolumab induced fast and sustained remission of previously refractory CLE lesions, beginning within the first weeks of treatment. Decline in CLASI-A score was paralleled by a reduction in IFN score determined by mRNA expression of seven IFN-stimulated genes (ISGs) in blood. These data suggest that a subset of ISGs could be a valuable biomarker in CLE.

Phenotypic spectrum in recessive STING-associated vasculopathy with onset in infancy: Four novel cases and analysis of previously reported cases

Gain-of-function variants in the stimulator of interferon response cGAMP interactor 1 (STING1) gene cause STING-Associated Vasculopathy with onset in Infancy (SAVI). Previously, only heterozygous and mostly de novo STING1 variants have been reported to cause SAVI. Interestingly, one variant that only leads to SAVI when homozygous, namely c.841C>T p.(Arg281Trp), has recently been described. However, there are no entries in public databases regarding an autosomal recessive pattern of inheritance. Here, we report four additional unrelated SAVI patients carrying c.841C>T in homozygous state. All patients had interstitial lung disease and displayed typical interferon activation patterns. Only one child displayed cutaneous vasculitis, while three other patients presented with a relatively mild SAVI phenotype. Steroid and baricitinib treatment had a mitigating effect on the disease phenotype in two cases, but failed to halt disease progression. Heterozygous c.841C>T carriers in our analysis were healthy and showed normal interferon activation. Literature review identified eight additional cases with autosomal recessive SAVI caused by c.841C>T homozygosity. In summary, we present four novel and eight historic cases of autosomal recessive SAVI. We provide comprehensive clinical data and show treatment regimens and clinical responses. To date, SAVI has been listed as an exclusively autosomal dominant inherited trait in relevant databases. With this report, we aim to raise awareness for autosomal recessive inheritance in this rare, severe disease which may aid in early diagnosis and development of optimized treatment strategies.

The yin and the yang of early classical pathway complement disorders

The classical pathway of the complement cascade has been recognized as a key activation arm, partnering with the lectin activation arm and the alternative pathway to cleave C3 and initiate the assembly of the terminal components. While deficiencies of classical pathway components have been recognized since 1966, only recently have gain-of-function variants been described for some of these proteins. Loss-of-function variants in C1, C4, and C2 are most often associated with lupus and systemic infections with encapsulated bacteria. C3 deficiency varies slightly from this phenotypic class with membranoproliferative glomerulonephritis and infection as the dominant phenotypes. The gain-of- function variants recently described for C1r and C1s lead to periodontal Ehlers Danlos syndrome, a surprisingly structural phenotype. Gain-of-function in C3 and C2 are associated with endothelial manifestations including hemolytic uremic syndrome and vasculitis with C2 gain-of-function variants thus far having been reported in patients with a C3 glomerulopathy. This review will discuss the loss-of-function and gain-of-function phenotypes and place them within the larger context of complement deficiencies.

Precision treatment of Singleton Merten syndrome with ruxolitinib: a case report

BACKGROUND

Singleton-Merten syndrome 1 (SGMRT1) is a rare type I interferonopathy caused by heterozygous mutations in the IFIH1 gene. IFIH1 encodes the pattern recognition receptor MDA5 which senses viral dsRNA and activates antiviral type I interferon (IFN) signaling. In SGMRT1, IFIH1 mutations confer a gain-of-function which causes overactivation of type I interferon (IFN) signaling leading to autoinflammation.

CASE PRESENTATION

We report the case of a nine year old child who initially presented with a slowly progressive decline of gross motor skill development and muscular weakness. At the age of five years, he developed osteoporosis, acro-osteolysis, alveolar bone loss and severe psoriasis. Whole exome sequencing revealed a pathogenic de novo IFIH1 mutation, confirming the diagnosis of SGMRT1. Consistent with constitutive type I interferon activation, patient blood cells exhibited a strong IFN signature as shown by marked up-regulation of IFN-stimulated genes. The patient was started on the Janus kinase (JAK) inhibitor, ruxolitinib, which inhibits signaling at the IFN-α/β receptor. Within days of treatment, psoriatic skin lesions resolved completely and the IFN signature normalized. Therapeutic efficacy was sustained and over the course muscular weakness, osteopenia and growth also improved.

CONCLUSIONS

JAK inhibition represents a valuable therapeutic option for patients with SGMRT1. Our findings also highlight the potential of a patient-tailored therapeutic approach based on pathogenetic insight.

One Gene, Many Facets: Multiple Immune Pathway Dysregulation in SOCS1 Haploinsufficiency

Background

Inborn errors of immunity (IEI) present with a large phenotypic spectrum of disease, which can pose diagnostic and therapeutic challenges. Suppressor of cytokine signaling 1 (SOCS1) is a key negative regulator of cytokine signaling, and has recently been associated with a novel IEI. Of patients described to date, it is apparent that SOCS1 haploinsufficiency has a pleiotropic effect in humans.

Objective

We sought to investigate whether dysregulation of immune pathways, in addition to STAT1, play a role in the broad clinical manifestations of SOCS1 haploinsufficiency.

Methods

We assessed impacts of reduced SOCS1 expression across multiple immune cell pathways utilizing patient cells and CRISPR/Cas9 edited primary human T cells.

Results

SOCS1 haploinsufficiency phenotypes straddled across the International Union of Immunological Societies classifications of IEI. We found that reduced SOCS1 expression led to dysregulation of multiple intracellular pathways in immune cells. STAT1 phosphorylation is enhanced, comparably with STAT1 gain-of-function mutations, and STAT3 phosphorylation is similarly reduced with concurrent reduction of Th17 cells. Furthermore, reduced SOCS1 E3 ligase function was associated with increased FAK1 in immune cells, and increased AKT and p70 ribosomal protein S6 kinase phosphorylation. We also found Toll-like receptor responses are increased in SOCS1 haploinsufficiency patients.

Conclusions

SOCS1 haploinsufficiency is a pleiotropic monogenic IEI. Dysregulation of multiple immune cell pathways may explain the variable clinical phenotype associated with this new condition. Knowledge of these additional dysregulated immune pathways is important when considering the optimum management for SOCS1 haploinsufficient patients.