Real-world treatment patterns and outcomes in patients with primary hemophagocytic lymphohistiocytosis treated with emapalumab

ABSTRACT

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening, hyperinflammatory syndrome. Emapalumab, a fully human monoclonal antibody that neutralizes the proinflammatory cytokine interferon gamma, is approved in the United States to treat primary HLH (pHLH) in patients with refractory, recurrent, or progressive disease, or intolerance with conventional HLH treatments. REAL-HLH, a retrospective study, conducted across 33 US hospitals, evaluated real-world treatment patterns and outcomes in patients treated with ≥1 dose of emapalumab between 20 November 2018 and 31 October 2021. In total, 46 patients met the pHLH classification criteria. Median age at diagnosis was 1.0 year (range, 0.3-21.0). Emapalumab was initiated for treating refractory (19/46), recurrent (14/46), or progressive (7/46) pHLH. At initiation, 15 of 46 patients were in the intensive care unit, and 35 of 46 had received prior HLH-related therapies. Emapalumab treatment resulted in normalization of key laboratory parameters, including chemokine ligand 9 (24/33, 72.7%), ferritin (20/45, 44.4%), fibrinogen (37/38, 97.4%), platelets (39/46, 84.8%), and absolute neutrophil count (40/45, 88.9%). Forty-two (91.3%) patients were considered eligible for transplant. Pretransplant survival was 38 of 42 (90.5%). Thirty-one (73.8%) transplant-eligible patients proceeded to transplant, and 23 of 31 (74.2%) of those who received transplant were alive at the end of the follow-up period. Twelve-month survival probability from emapalumab initiation for the entire cohort (N = 46) was 73.1%. There were no discontinuations because of adverse events. In conclusion, results from the REAL-HLH study, which describes treatment patterns, effectiveness, and outcomes in patients with pHLH treated with emapalumab in real-world settings, are consistent with the emapalumab pivotal phase 2/3 pHLH trial.

Low-dose biliatresone treatment of pregnant mice causes subclinical biliary disease in their offspring: Evidence for a spectrum of neonatal injury

Biliary atresia is a neonatal disease characterized by damage, inflammation, and fibrosis of the liver and bile ducts and by abnormal bile metabolism. It likely results from a prenatal environmental exposure that spares the mother and affects the fetus. Our aim was to develop a model of fetal injury by exposing pregnant mice to low-dose biliatresone, a plant toxin implicated in biliary atresia in livestock, and then to determine whether there was a hepatobiliary phenotype in their pups. Pregnant mice were treated orally with 15 mg/kg/d biliatresone for 2 days. Histology of the liver and bile ducts, serum bile acids, and liver immune cells of pups from treated mothers were analyzed at P5 and P21. Pups had no evidence of histological liver or bile duct injury or fibrosis at either timepoint. In addition, growth was normal. However, serum levels of glycocholic acid were elevated at P5, suggesting altered bile metabolism, and the serum bile acid profile became increasingly abnormal through P21, with enhanced glycine conjugation of bile acids. There was also immune cell activation observed in the liver at P21. These results suggest that prenatal exposure to low doses of an environmental toxin can cause subclinical disease including liver inflammation and aberrant bile metabolism even in the absence of histological changes. This finding suggests a wide potential spectrum of disease after fetal biliary injury.

Disease Course, Treatments, and Outcomes of Children With Systemic Juvenile Idiopathic Arthritis-Associated Lung Disease

OBJECTIVE

Systemic juvenile idiopathic arthritis-associated lung disease (SJIA-LD) is a life-threatening disease complication. Key questions remain regarding clinical course and optimal treatment approaches. The objectives of the study were to detail management strategies after SJIA-LD detection, characterize overall disease courses, and measure long-term outcomes.

METHODS

This was a prospective cohort study. Clinical data were abstracted from the electronic medical record, including current clinical status and changes since diagnosis. Serum biomarkers were determined and correlated with presence of LD.

RESULTS

We enrolled 41 patients with SJIA-LD, 85% with at least one episode of macrophage activation syndrome and 41% with adverse reactions to a biologic. Although 93% of patients were alive at last follow-up (median 2.9 years), 37% progressed to requiring chronic oxygen or other ventilator support, and 65% of patients had abnormal overnight oximetry studies, which changed over time. Eighty-four percent of patients carried the HLA-DRB1*15 haplotype, significantly more than patients without LD. Patients with SJIA-LD also showed markedly elevated serum interleukin-18 (IL-18), variable C-X-C motif chemokine ligand 9 (CXCL9), and significantly elevated matrix metalloproteinase 7. Treatment strategies showed variable use of anti-IL-1/6 biologics and addition of other immunomodulatory treatments and lung-directed therapies. We found a broad range of current clinical status independent of time from diagnosis or continued biologic treatment. Multidomain measures of change showed imaging features were the least likely to improve with time.

CONCLUSION

Patients with SJIA-LD had highly varied courses, with lower mortality than previously reported but frequent hypoxia and requirement for respiratory support. Treatment strategies were highly varied, highlighting an urgent need for focused clinical trials.

Kagami Ogata syndrome: a small deletion refines critical region for imprinting

Kagami-Ogata syndrome is a rare imprinting disorder and its phenotypic overlap with multiple different etiologies hampers diagnosis. Genetic etiologies include paternal uniparental isodisomy (upd(14)pat), maternal allele deletions of differentially methylated regions (DMR) in 14q32.2 or pure primary epimutations. We report a patient with Kagami-Ogata syndrome and an atypical diagnostic odyssey with several negative standard-of-care genetic tests followed by epigenetic testing using methylation microarray and a targeted analysis of whole-genome sequencing to reveal a 203 bp deletion involving the MEG3 transcript and MEG3:TSS-DMR. Long-read sequencing enabled the simultaneous detection of the deletion, phasing, and biallelic hypermethylation of the MEG3:TSS-DMR region in a single assay. This case highlights the challenges in the sequential genetic testing paradigm, the utility of long-read sequencing as a single comprehensive diagnostic assay, and the smallest reported deletion causing Kagami-Ogata syndrome allowing important insights into the mechanism of imprinting effects at this locus.

c-Myc uses Cul4b to preserve genome integrity and promote antiviral CD8+ T cell immunity

During infection, virus-specific CD8+ T cells undergo rapid bursts of proliferation and differentiate into effector cells that kill virus-infected cells and reduce viral load. This rapid clonal expansion can put T cells at significant risk for replication-induced DNA damage. Here, we find that c-Myc links CD8+ T cell expansion to DNA damage response pathways though the E3 ubiquitin ligase, Cullin 4b (Cul4b). Following activation, c-Myc increases the levels of Cul4b and other members of the Cullin RING Ligase 4 (CRL4) complex. Despite expressing c-Myc at high levels, Cul4b-deficient CD8+ T cells do not expand and clear the Armstrong strain of lymphocytic choriomeningitis virus (LCMV) in vivo. Cul4b-deficient CD8+ T cells accrue DNA damage and succumb to proliferative catastrophe early after antigen encounter. Mechanistically, Cul4b knockout induces an accumulation of p21 and Cyclin E2, resulting in replication stress. Our data show that c-Myc supports cell proliferation by maintaining genome stability via Cul4b, thereby directly coupling these two interdependent pathways. These data clarify how CD8+ T cells use c-Myc and Cul4b to sustain their potential for extraordinary population expansion, longevity and antiviral responses.

Improving Outcomes of Pediatric Lupus Care Delivery With Provider Goal-Setting Activities and Multidisciplinary Care Models

OBJECTIVE

The present study was undertaken to evaluate high-quality care delivery in the context of provider goal-setting activities and a multidisciplinary care model using an electronic health record (EHR)-enabled pediatric lupus registry. We then determined associations between care quality and prednisone use among youth with systemic lupus erythematosus (SLE).

METHODS

We implemented standardized EHR documentation tools to autopopulate a SLE registry. We compared pediatric Lupus Care Index (pLCI) performance (range 0.0-1.0; 1.0 representing perfect metric adherence) and timely follow-up 1) before versus during provider goal-setting activities and population management, and 2) in a multidisciplinary lupus nephritis versus rheumatology clinic. We estimated associations between pLCI and subsequent prednisone use adjusted for time, current medication, disease activity, clinical features, and social determinants of health.

RESULTS

We analyzed 830 visits by 110 patients (median 7 visits per patient [interquartile range 4-10]) over 3.5 years. The provider-directed activity was associated with improved pLCI performance (adjusted β 0.05 [95% confidence interval (95% CI) 0.01, 0.09]; mean 0.74 versus 0.69). Patients with nephritis in multidisciplinary clinic had higher pLCI scores (adjusted β 0.06 [95% CI 0.02, 0.10]) and likelihood of timely follow-up than those in rheumatology (adjusted relative risk [RR] 1.27 [95% CI 1.02, 1.57]). A pLCI score of ≥0.50 was associated with 0.72-fold lower adjusted risk of subsequent prednisone use (95% CI 0.53, 0.93). Minoritized race, public insurance, and living in areas with greater social vulnerability were not associated with reduced care quality or follow-up, but public insurance was associated with higher risk of prednisone use.

CONCLUSION

Greater attention to quality metrics is associated with better outcomes in childhood SLE. Multidisciplinary care models with population management may additionally facilitate equitable care delivery.

The 2022 EULAR/ACR Points to Consider at the Early Stages of Diagnosis and Management of Suspected Haemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome (HLH/MAS)

OBJECTIVE

Haemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening systemic hyperinflammatory syndromes that can develop in most inflammatory contexts. They can progress rapidly, and early identification and management are critical for preventing organ failure and mortality. This effort aimed to develop evidence-based and consensus-based points to consider to assist clinicians in optimising decision-making in the early stages of diagnosis, treatment and monitoring of HLH/MAS.

METHODS

A multinational, multidisciplinary task force of physician experts, including adult and paediatric rheumatologists, haematologist/oncologists, immunologists, infectious disease specialists, intensivists, allied healthcare professionals and patients/parents, formulated relevant research questions and conducted a systematic literature review (SLR). Delphi methodology, informed by SLR results and questionnaires of experts, was used to generate statements aimed at assisting early decision-making and optimising the initial care of patients with HLH/MAS.

RESULTS

The task force developed 6 overarching statements and 24 specific points to consider relevant to early recognition of HLH/MAS, diagnostic approaches, initial management and monitoring of HLH/MAS. Major themes included the simultaneous need for prompt syndrome recognition, systematic evaluation of underlying contributors, early intervention targeting both hyperinflammation and likely contributors, careful monitoring for progression/complications and expert multidisciplinary assistance.

CONCLUSION

These 2022 EULAR/American College of Rheumatology points to consider provide up-to-date guidance, based on the best available published data and expert opinion. They are meant to help guide the initial evaluation, management and monitoring of patients with HLH/MAS in order to halt disease progression and prevent life-threatening immunopathology.

The 2022 EULAR/ACR points to consider at the early stages of diagnosis and management of suspected haemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS)

OBJECTIVE

Haemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening systemic hyperinflammatory syndromes that can develop in most inflammatory contexts. They can progress rapidly, and early identification and management are critical for preventing organ failure and mortality. This effort aimed to develop evidence-based and consensus-based points to consider to assist clinicians in optimising decision-making in the early stages of diagnosis, treatment and monitoring of HLH/MAS.

METHODS

A multinational, multidisciplinary task force of physician experts, including adult and paediatric rheumatologists, haematologist/oncologists, immunologists, infectious disease specialists, intensivists, allied healthcare professionals and patients/parents, formulated relevant research questions and conducted a systematic literature review (SLR). Delphi methodology, informed by SLR results and questionnaires of experts, was used to generate statements aimed at assisting early decision-making and optimising the initial care of patients with HLH/MAS.

RESULTS

The task force developed 6 overarching statements and 24 specific points to consider relevant to early recognition of HLH/MAS, diagnostic approaches, initial management and monitoring of HLH/MAS. Major themes included the simultaneous need for prompt syndrome recognition, systematic evaluation of underlying contributors, early intervention targeting both hyperinflammation and likely contributors, careful monitoring for progression/complications and expert multidisciplinary assistance.

CONCLUSION

These 2022 EULAR/American College of Rheumatology points to consider provide up-to-date guidance, based on the best available published data and expert opinion. They are meant to help guide the initial evaluation, management and monitoring of patients with HLH/MAS in order to halt disease progression and prevent life-threatening immunopathology.

Adenovirus is Not Detected in Liver Tissue From a Historical Multicenter Cohort of Children With Acute Liver Failure

There has been a recent surge in cases of pediatric acute hepatitis and pediatric acute liver failure (PALF) of unknown cause. Several reports have described clusters of these children who were positive for adenovirus (AdV) DNA, primarily in peripheral blood but some in liver tissue. We tested archived liver tissue specimens from a historical cohort of 44 children with PALF who were enrolled in a multicenter biorepository between 2007 and 2014 for AdV 40/41 using quantitative polymerase chain reaction. Most children had final diagnosis indeterminate. All samples were negative. Our findings suggest that AdV was unlikely to be an unidentified cause of indeterminate PALF during this past era. The significance of AdV viremia in contemporary cohorts of children with PALF remains unknown and requires further study.

The Liver in Hemophagocytic Lymphohistiocytosis: Not an Innocent Bystander

Hemophagocytic lymphohistiocytosis (HLH) is a rare multisystemic hyperinflammatory disease commonly associated with hepatic dysfunction. Liver injury is mediated by unchecked antigen presentation, hypercytokinemia, dysregulated cytotoxicity by natural killer and CD8 T cells, and disruption of intrinsic hepatic metabolic pathways. Over the past decade, there have been significant advances in diagnostics and expansion in therapeutic armamentarium for this disorder allowing for improved morbidity and mortality. This review discusses the clinical manifestations and pathogenesis of HLH hepatitis in both familial and secondary forms. It will review growing evidence that the intrinsic hepatic response to hypercytokinemia in HLH perpetuates disease progression and the novel therapeutic approaches for patients with HLH-hepatitis/liver failure.

CXCL9 inhibition does not ameliorate disease in murine models of both primary and secondary hemophagocytic lymphohistiocytosis

Hemophagocytic Lymphohistiocytosis (HLH) is a group of disorders culminating in systemic inflammation and multi-organ failure with high incidence of hepatic dysfunction. Overproduction of IFN-γ is the main immunopathological driver in this disorder. Monokine induced by IFN-γ (CXCL9) serves as a biomarker for disease activity and response to treatment in this disorder. However, very little is understood about the actual functional role of CXCL9 in pathogenesis in HLH. In the current study, we sought to determine the role of CXCL9 in pathogenesis in murine models of both Familial HLH (prf1^-/-) and Toll Like Receptor (TLR) 9 repeated stimulation induced Macrophage Activation Syndrome (MAS), a form of secondary HLH. FHL and MAS were induced in both CXCL9 genetically deficient mice (cxcl9^-/-) and controls as well as using AMG487, a pharmacological antagonist of the CXCL9 receptor, CXCR3. Results showed that CXCL9 genetic deficiency did not improve disease parameters or hepatitis in both models. Consistent with genetic ablation of CXCL9, inhibition of its receptor, CXCR3, by AMG487 did not show any significant effects in the FHL model. Taken together, inhibition of CXCL9-CXCR3 interaction does not ameliorate HLH physiology in general, or hepatitis as a classical target organ of disease.

Effector memory CD8 T-cells as a novel peripheral blood biomarker for activated T-cell pediatric acute liver failure

A distinct phenotype of pediatric acute liver failure (PALF) has been identified, labeled activated T-cell hepatitis. These patients, previously included within the indeterminate group, have evidence of systemic immune activation and liver biopsy specimens with dense infiltration of CD8+ T-cells. We aimed to evaluate the peripheral blood T-cell phenotype in PALF patients with activated T-cell hepatitis compared to indeterminate cause. PALF patients with unknown etiology age 1-17 years were prospectively enrolled between 2017-2020. Within the unknown group, patients were classified as either activated T-cell hepatitis if they had a liver biopsy with dense or moderate CD8 staining and an elevated soluble interleukin-2 receptor level, or they were classified as indeterminate if they did not meet these criteria. Whole blood was collected for flow cytometry and T-cell phenotyping. Four patients with activated T-cell hepatitis and 4 patients with indeterminate PALF were enrolled. Activated T-cell hepatitis patients had significantly greater percentage of CD8 T-cells that were effector memory (TEM) phenotype compared to indeterminate PALF patients (median 66.8% (IQR 57.4-68.7) vs 19.1% (IQR 13.4-25.2), P = 0.03). In addition, CD8+ TEM cells in activated T-cell hepatitis patients were significantly more likely to be CD103 positive, a marker of tissue resident memory T-cells, compared to indeterminate PALF patients (median 12.4% (IQR 9.5-14.7) vs 4.7% (IQR 4.5-5.3), P = 0.03). We found patients with activated T-cell hepatitis can be identified by the unique pattern of increased percentage of peripheral blood effector memory CD8+ CD103+ T-cells. These findings will guide future studies exploring the T-cell phenotype for these patients and whether they may respond to directed immunosuppressive therapies.

Improvement of Refractory Systemic Juvenile Idiopathic Arthritis-Associated Lung Disease with Single-Agent Blockade of IL-1β and IL-18

Systemic juvenile idiopathic arthritis associated with interstitial lung disease (SJIA-LD) represents a highly morbid subset of SJIA for which effective therapies are lacking. We report the case of a patient with refractory SJIA-LD who underwent treatment with MAS-825, an investigational bispecific monoclonal antibody targeting IL-1β and IL-18. MAS-825 treatment was associated with a marked reduction in total IL-18 and free IL-18 in both serum and bronchoalveolar lavage fluid (BAL). Baseline oxygen saturation, exercise tolerance, and quality of life metrics improved after treatment with MAS-825, while pulmonary function testing remained stable. Following treatment, the BAL showed no evidence of pulmonary alveolar proteinosis and inflammatory infiltrates were markedly reduced, reflected by decreased numbers of CD4 T-cells, CD8 T-cells, and macrophages. The patient was able to wean entirely off systemic corticosteroids and other biologics after 10 months of treatment with MAS-825 and experienced no side effects of the drug. This case demonstrates improvement in pulmonary symptoms, lung inflammation, and burden of immunomodulatory therapy after treatment with MAS-825 and suggests that simultaneous targeting of both IL-1β and IL-18 may be a safe and effective treatment strategy in SJIA-LD.

BRAF-V600E utilizes posttranscriptional mechanisms to amplify LPS-induced TNFα production in dendritic cells in a mouse model of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is an inflammatory disease characterized by abnormal dendritic cells (DCs) with hyperactive ERK signaling, called "LCH cells." Since DCs rely on ERK signaling to produce inflammatory molecules in response to pathogenic cues, we hypothesized that hyperactive ERK enhances DCs inflammatory responses. We specifically investigated TLR4-induced TNFα production in LCH cells by utilizing the BRAF-V600Efl/+ :CD11c-Cre mouse model of LCH, which hyperactivates ERK in DCs. We measured LPS-induced TNFα production both in vivo and in vitro using splenic CD11c+ cells and bone marrow-derived DCs with or without pharmacologic BRAFV600E inhibition. We observed a reversible increase in secreted TNFα and a partially reversible increase in TNFα protein per cell, despite a decrease in TLR4 signaling and Tnfa transcripts compared with controls. We examined ERK-driven, posttranscriptional mechanisms that contribute to TNFα production and secretion using biochemical and cellular assays. We identified a reversible increase in TACE activation, the enzyme required for TNFα secretion, and most strikingly, an increase in protein translation, including TNFα. Defining the translatome through polysome-bound RNA sequencing revealed up-regulated translation of the LPS-response program. These data suggest hyperactive ERK signaling utilizes multiple posttranscriptional mechanisms to amplify inflammatory responses in DCs, advancing our understanding of LCH and basic DC biology.

The RAG1 Ubiquitin Ligase Domain Stimulates Recombination of TCRβ and TCRα Genes and Influences Development of αβ T Cell Lineages

RAG1/RAG2 (RAG) endonuclease-mediated assembly of diverse lymphocyte Ag receptor genes by V(D)J recombination is critical for the development and immune function of T and B cells. The RAG1 protein contains a ubiquitin ligase domain that stabilizes RAG1 and stimulates RAG endonuclease activity in vitro. We report in this study that mice with a mutation that inactivates the Rag1 ubiquitin ligase in vitro exhibit decreased rearrangements and altered repertoires of TCRβ and TCRα genes in thymocytes and impaired thymocyte developmental transitions that require the assembly and selection of functional TCRβ and/or TCRα genes. These Rag1 mutant mice present diminished positive selection and superantigen-mediated negative selection of conventional αβ T cells, decreased genesis of invariant NK T lineage αβ T cells, and mature CD4+ αβ T cells with elevated autoimmune potential. Our findings reveal that the Rag1 ubiquitin ligase domain functions in vivo to stimulate TCRβ and TCRα gene recombination and influence differentiation of αβ T lineage cells, thereby establishing replete diversity of αβ TCRs and populations of αβ T cells while restraining generation of potentially autoreactive conventional αβ T cells.

Comprehensive Serum Proteome Profiling of Cytokine Release Syndrome and Immune Effector Cell-Associated Neurotoxicity Syndrome Patients with B-Cell ALL Receiving CAR T19

PURPOSE

To study the biology and identify markers of severe cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) in children after chimeric antigen receptor T-cell (CAR T) treatment.

EXPERIMENTAL DESIGN

We used comprehensive proteomic profiling to measure over 1,400 serum proteins at multiple serial timepoints in a cohort of patients with B-cell acute lymphoblastic leukemia treated with the CD19-targeted CAR T CTL019 on two clinical trials.

RESULTS

We identified fms-like tyrosine kinase 3 (FLT3) and mast cell immunoglobulin-like receptor 1 (MILR1) as preinfusion predictive biomarkers of severe CRS. We demonstrated that CRS is an IFNγ-driven process with a protein signature overlapping with hemophagocytic lymphohistiocytosis (HLH). We identified IL18 as a potentially targetable cytokine associated with the development of ICANS.

CONCLUSIONS

We identified preinfusion biomarkers that can be used to predict severe CRS with a sensitivity, specificity, and accuracy superior to the current gold standard of disease burden. We demonstrated the fundamental role of the IFNγ pathway in driving CRS, suggesting CRS and carHLH are overlapping rather than distinct phenomena, an observation with important treatment implications. We identified IL18 as a possible targetable cytokine in ICANS, providing rationale for IL18 blocking therapies to be translated into clinical trials in ICANS.

Hematologic abnormalities in Aicardi Goutières Syndrome

BACKGROUND

Because of the broad clinical spectrum, heritable autoinflammatory diseases present a management and therapeutic challenge. The most common genetic interferonopathy, Aicardi Goutières Syndrome (AGS), is associated with early onset neurologic disability and systemic inflammation. The chronic inflammation of AGS is the result of dysregulation of interferon (IFN) expression by one of nine genes within converging pathways. While each AGS subtype shares common features, distinct patterns of severity and potential for systemic complications amongst the genotypes are emerging. Multilineage cytopenias are a potentially serious, but poorly understood, complication of AGS. As immunomodulatory treatment options are developed, it is important to characterize the role of the disease versus treatment in hematologic abnormalities. This will allow for better understanding and management of cytopenia.

METHODS

In total, 142 individuals with molecularly-confirmed AGS were included. Information on genotype, demographics, and all available hematologic laboratory values were collected from existing medical records. As part of a clinical trial, a subset of this cohort (n = 52) were treated with a janus kinase inhibitor (baricitinib), and both pre- and post-treatment values were included. Abnormal values were graded based on Common Terminology Criteria for Adverse Events (CTCAE v5.0), supplemented with grading definitions for thrombocytosis, and were compared across genotypes and baricitinib exposure.

RESULTS

In total, 11,184 laboratory values were collected over a median of 2.54 years per subject (range 0-22.68 years). To reduce bias from repeated sampling within a limited timeframe, laboratory results were restricted to the most abnormal value within a month (n = 8485). The most common abnormalities were anemia (noted in 24% of subjects prior to baricitinib exposure), thrombocytopenia (9%), and neutropenia (30%). Neutropenia was most common in the SAMHD1 cohort and increased with baricitinib exposure (38/69 measurements on baricitinib versus 14/121 while not on baricitinib). Having an abnormality prior to treatment was associated with having an abnormality on treatment for neutropenia and thrombocytopenia.

CONCLUSION

By collecting available laboratory data throughout the lifespan, we were able to identify novel patterns of hematologic abnormalities in AGS. We found that AGS results in multilineage cytopenias not limited to the neonatal period. Neutropenia, anemia, and thrombocytopenia were common. Moderate-severe graded events of neutropenia, anemia, and leukopenia were more common on baricitinib, but rarely of clinical consequence. Based on these results, we would recommend careful monitoring of hematologic parameters of children affected by AGS throughout the lifespan, especially while on therapy, and consideration of AGS as a potential differential diagnosis in children with neurologic impairment of unclear etiology with hematologic abnormalities. Trial registration ClinicalTrials.gov Identifier: NCT01724580 ClinicalTrials.gov Identifier: NCT03921554.

Familial hemophagocytic lymphohistiocytosis hepatitis is mediated by IFN-γ in a predominantly hepatic-intrinsic manner

Interferon gamma (IFN-γ) is the main cytokine driving organ dysfunction in Familial Hemophagocytic Lymphohistiocytosis (FHL). Blockade of IFN-γ pathway ameliorates FHL hepatitis, both in animal models and in humans with FHL. Hepatocytes are known to express IFN-γ receptor (IFN-γ-R). However, whether IFN-γ induced hepatitis in FHL is a lymphocyte or liver intrinsic response to the cytokine has yet to be elucidated. Using a IFNgR-/- bone marrow chimeric model, this study showed that non-hematopoietic IFN-γ response is critical for development of FHL hepatitis in LCMV-infected Prf1-/- mice. Lack of hepatic IFN-γ responsiveness results in reduced hepatitis as measured by hepatomegaly, alanine aminotransferase (ALT) levels and abrogated histologic endothelial inflammation. In addition, IFN-γ non-hematopoietic response was critical in activation of lymphocytes by soluble interleukin 2 receptor (sIL-2r) and recruitment of CD8+ effector T lymphocytes (CD8+ CD44hi CD62Llo) (Teff) and inflammatory monocytes. Lastly, non-hematopoietic IFN-γ response results in increased hepatic transcription of type 1 immune response and oxidative stress response pathways, while decreasing transcription of genes involved in extracellular matrix (ECM) production. In summary, these findings demonstrate that there is a hepatic transcriptional response to IFN-γ, likely critical in the pathogenesis of FHL hepatitis and hepatic specific responses could be a therapeutic target in this disorder.

The E3 Ubiquitin ligase Cul4b is required for CD8+ T cell-mediated antiviral immunity

CD8+ T cells play crucial roles in cellular immune mechanisms that clear invading viruses and prevent reinfection. Virus specific CD8+ T cells expand approximately 10,000 fold, undergoing up to 20 cell divisions in the first week of infection. While this rapid expansion is needed to reduce viral loads, replication can lead to DNA damage and telomere shortening, resulting in growth arrest. T cells must be equipped with mechanisms that promptly promote DNA repair to protect cells from premature senescence and death. We recently determined that the E3 Ubiquitin ligase Cullin-4b (Cul4b) regulates genome integrity in CD4+ T cells by helping to resolve DNA damage. In keeping with this, aberrant expression of Cul4b and its ortholog Cul4a has been reported in many cancers. However, whether Cul4b is important in controlling CD8+ T cell numbers or viral clearance is not known. To address this, we infected control and Cul4bcKO mice with LCMV. Following infection, virus-specific CD8+ T cells lacking Cul4b failed to expand or acquire effector functions. As a consequence, Cul4bcKO mice were unable to clear LCMV. Furthermore, Cul4b-deficient CD8+ T cells were unable to differentiate into memory T cells. Using IP and tandem mass spectrometry, we found Cul4b associated with the chromatin remodeling BAF complex (SWI/SNF). Specifically, our data supports that Brg1, a component of SWI/SNF complex, is a client of the Cul4b ubiquitin ligase. Loss of Cul4b increased Brg1 binding to chromatin following CD8+ T cell activation, impacting gene expression and/or cell cycle arrest. Together, these data support that Cul4b limits the amount of Brg1 associated with chromatin, and allows the expansion and differentiation of CD8+ T cells thus promoting antiviral immunity.

American College of Rheumatology Clinical Guidance for Multisystem Inflammatory Syndrome in Children Associated With SARS-CoV-2 and Hyperinflammation in Pediatric COVID-19: Version 3

OBJECTIVE

To provide guidance on the management of Multisystem Inflammatory Syndrome in Children (MIS-C), a condition characterized by fever, inflammation, and multiorgan dysfunction that manifests late in the course of SARS-CoV-2 infection. Recommendations are also provided for children with hyperinflammation during COVID-19, the acute, infectious phase of SARS-CoV-2 infection.

METHODS

The Task Force is composed of 9 pediatric rheumatologists and 2 adult rheumatologists, 2 pediatric cardiologists, 2 pediatric infectious disease specialists, and 1 pediatric critical care physician. Preliminary statements addressing clinical questions related to MIS-C and hyperinflammation in COVID-19 were developed based on evidence reports. Consensus was built through a modified Delphi process that involved anonymous voting and webinar discussion. A 9-point scale was used to determine the appropriateness of each statement (median scores of 1-3 for inappropriate, 4-6 for uncertain, and 7-9 for appropriate). Consensus was rated as low, moderate, or high based on dispersion of the votes. Approved guidance statements were those that were classified as appropriate with moderate or high levels of consensus, which were prespecified before voting.

RESULTS

The guidance was approved in June 2020 and updated in November 2020 and October 2021, and consists of 41 final guidance statements accompanied by flow diagrams depicting the diagnostic pathway for MIS-C and recommendations for initial immunomodulatory treatment of MIS-C.

CONCLUSION

Our understanding of SARS-CoV-2-related syndromes in the pediatric population continues to evolve. This guidance document reflects currently available evidence coupled with expert opinion, and will be revised as further evidence becomes available.

Lymphocytes Utilize Somatic Mutations, Epigenetic Silencing, and the Proteasome to Escape Truncated WASP Expression

Wiskott-Aldrich Syndrome Protein (WASP) deficiency causes Wiskott-Aldrich Syndrome (WAS), a sex-linked disorder characterized by combined immunodeficiency, microthrombocytopenia, and eczema. Like WASP-deficient humans, WASP-deficient mice produce normal numbers of functionally defective T cells. Here, we report a WAS patient with a novel germline frameshifting WAS mutation encoding a truncated form of WASP lacking the C-terminal cofilin homology (C) and the acidic region (A) domains (WASPΔCA). Although stably overexpressed in embryonic kidney cell lines, WASPΔCA was undetectable in circulating patient leukocytes. Deep sequencing, transcript profiling, and protein degradation analyses demonstrated patient lymphocytes employ an array of genetic, epigenetic, and proteasomal strategies to avoid expressing WASPΔCA.

Variants in STXBP3 are Associated with Very Early Onset Inflammatory Bowel Disease, Bilateral Sensorineural Hearing Loss and Immune Dysregulation

BACKGROUND AND AIMS

Very early onset inflammatory bowel disease [VEOIBD] is characterized by intestinal inflammation affecting infants and children less than 6 years of age. To date, over 60 monogenic aetiologies of VEOIBD have been identified, many characterized by highly penetrant recessive or dominant variants in underlying immune and/or epithelial pathways. We sought to identify the genetic cause of VEOIBD in a subset of patients with a unique clinical presentation.

METHODS

Whole exome sequencing was performed on five families with ten patients who presented with a similar constellation of symptoms including medically refractory infantile-onset IBD, bilateral sensorineural hearing loss and, in the majority, recurrent infections. Genetic aetiologies of VEOIBD were assessed and Sanger sequencing was performed to confirm novel genetic findings. Western analysis on peripheral blood mononuclear cells and functional studies with epithelial cell lines were employed.

RESULTS

In each of the ten patients, we identified damaging heterozygous or biallelic variants in the Syntaxin-Binding Protein 3 gene [STXBP3], a protein known to regulate intracellular vesicular trafficking in the syntaxin-binding protein family of molecules, but not associated to date with either VEOIBD or sensorineural hearing loss. These mutations interfere with either intron splicing or protein stability and lead to reduced STXBP3 protein expression. Knock-down of STXBP3 in CaCo2 cells resulted in defects in cell polarity.

CONCLUSION

Overall, we describe a novel genetic syndrome and identify a critical role for STXBP3 in VEOIBD, sensorineural hearing loss and immune dysregulation.

Inherited Autoinflammatory Syndromes

Autoinflammation describes a collection of diverse diseases caused by indiscriminate activation of the immune system in an antigen-independent manner. The rapid advancement of genetic diagnostics has allowed for the identification of a wide array of monogenic causes of autoinflammation. While the clinical picture of these syndromes is diverse, it is possible to thematically group many of these diseases under broad categories that provide insight into the mechanisms of disease and therapeutic possibilities. This review covers archetypical examples of inherited autoinflammatory diseases in five major categories: inflammasomopathy, interferonopathy, unfolded protein/cellular stress response, relopathy, and uncategorized. This framework can suggest where future work is needed to identify other genetic causes of autoinflammation, what types of diagnostics need to be developed to care for this patient population, and which options might be considered for novel therapeutic targeting. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Skewed Cytokine Responses Rather Than the Magnitude of the Cytokine Storm May Drive Cardiac Dysfunction in Multisystem Inflammatory Syndrome in Children

Background

Cardiac dysfunction is a prominent feature of multisystem inflammatory syndrome in children (MIS‐C), yet the etiology is poorly understood. We determined whether dysfunction is global or regional, and whether it is associated with the cytokine milieu, microangiopathy, or severity of shock.

Methods and Results

We analyzed echocardiographic parameters of myocardial deformation and compared global and segmental left ventricular strain between 43 cases with MIS‐C ≤18 years old and 40 controls. Primary outcomes included left ventricular global longitudinal strain, right ventricular free wall strain), and left atrial strain. We evaluated relationships between strain and profiles of 10 proinflammatory cytokines, microangiopathic features (soluble C5b9), and vasoactive‐inotropic requirements. Compared with controls, cases with MIS‐C had significant impairments in all parameters of systolic and diastolic function. 65% of cases with MIS‐C had abnormal left ventricular function (|global longitudinal strain|<17%), although elevations of cytokines were modest. All left ventricular segments were involved, without apical or basal dominance to suggest acute stress cardiomyopathy. Worse global longitudinal strain correlated with higher ratios of interleukin‐6 (ρ −0.43) and interleukin‐8 (ρ −0.43) to total hypercytokinemia, but not absolute levels of interleukin‐6 or interleukin‐8, or total hypercytokinemia. Similarly, worse right ventricular free wall strain correlated with higher relative interleukin‐8 expression (ρ −0.59). There were no significant associations between function and microangiopathy or vasoactive‐inotropic requirements.

Conclusions

Myocardial function is globally decreased in MIS‐C and not explained by acute stress cardiomyopathy. Cardiac dysfunction may be driven by the relative skew of the immune response toward interleukin‐6 and interleukin‐8 pathways, more so than degree of hyperinflammation, refining the current paradigm of myocardial involvement in MIS‐C.

Thymic stromal lymphopoietin induces adipose loss through sebum hypersecretion

Emerging studies indicate that the immune system can regulate systemic metabolism. Here, we show that thymic stromal lymphopoietin (TSLP) stimulates T cells to induce selective white adipose loss, which protects against obesity, improves glucose metabolism, and mitigates nonalcoholic steatohepatitis. Unexpectedly, adipose loss was not caused by alterations in food intake, absorption, or energy expenditure. Rather, it was induced by the excessive loss of lipids through the skin as sebum. TSLP and T cells regulated sebum release and sebum-associated antimicrobial peptide expression in the steady state. In human skin, TSLP expression correlated directly with sebum-associated gene expression. Thus, we establish a paradigm in which adipose loss can be achieved by means of sebum hypersecretion and uncover a role for adaptive immunity in skin barrier function through sebum secretion.

Transcriptional Analysis of Liver Tissue Identifies Distinct Phenotypes of Indeterminate Pediatric Acute Liver Failure

Many patients with indeterminate pediatric acute liver failure (PALF) have evidence of T-cell driven immune injury; however, the precise inflammatory pathways are not well defined. We have characterized the hepatic cytokine and transcriptional signatures of patients with PALF. A retrospective review was performed on 22 children presenting with indeterminate (IND-PALF; n = 17) or other known diagnoses (DX-PALF; n = 6) with available archived liver tissue. Specimens were stained for clusters of differentiation 8 (CD8) T cells and scored as dense, moderate, or minimal. Measurement of immune analytes and RNA sequencing (RNA-seq) was performed on whole-liver tissue. Immune analyte data were analyzed by principal component analysis, and RNA-seq was analyzed by unsupervised hierarchical clustering, differential gene expression, and gene-set enrichment analysis. Most patients with IND-PALF (94%) had dense/moderate CD8 staining and were characterized by Th1 immune analytes including tumor necrosis factor α, interferon γ (IFN-γ), interleukin (IL) 1β, IL-12, C-X-C motif chemokine ligand (CXCL) 9, and CXCL12. Transcriptional analyses identified two transcriptional PALF phenotypes. Most patients in group 1 (91%) had IND-PALF and dense/moderate CD8 staining. This group was characterized by increased expression of genes and cell subset-specific signatures related to innate inflammation, T-cell activation, and antigen stimulation. Group 1 expressed significantly higher levels of gene signatures for regulatory T cells, macrophages, Th1 cells, T effector memory cells, cytotoxic T cells, and activated dendritic cells (adjusted P < 0.05). In contrast, patients in group 2 exhibited increased expression for genes involved in metabolic processes. Conclusion: Patients with IND-PALF have evidence of a Th1-mediated inflammatory response driven by IFN-γ. Transcriptional analyses suggest that a complex immune network may regulate an immune-driven PALF phenotype with less evidence of metabolic processes. These findings provide insight into mechanisms of hepatic injury in PALF, areas for future research, and potential therapeutic targets.

Proteomic Profiling of MIS-C Patients Reveals Heterogeneity Relating to Interferon Gamma Dysregulation and Vascular Endothelial Dysfunction

Multi-system Inflammatory Syndrome in Children (MIS-C) is a major complication of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic in pediatric patients. Weeks after an often mild or asymptomatic initial infection with SARS-CoV-2 children may present with a severe shock-like picture and marked inflammation. Children with MIS-C present with varying degrees of cardiovascular and hyperinflammatory symptoms. We performed a comprehensive analysis of the plasma proteome of more than 1400 proteins in children with SARS-CoV-2. We hypothesized that the proteome would reflect heterogeneity in hyperinflammation and vascular injury, and further identify pathogenic mediators of disease. Protein signatures demonstrated overlap between MIS-C, and the inflammatory syndromes macrophage activation syndrome (MAS) and thrombotic microangiopathy (TMA). We demonstrate that PLA2G2A is a key marker of MIS-C that associates with TMA. We found that IFNγ responses are dysregulated in MIS-C patients, and that IFNγ levels delineate clinical heterogeneity.

American College of Rheumatology Clinical Guidance for Multisystem Inflammatory Syndrome in Children Associated With SARS-CoV-2 and Hyperinflammation in Pediatric COVID-19: Version 2

OBJECTIVE

To provide guidance on the management of Multisystem Inflammatory Syndrome in Children (MIS-C), a condition characterized by fever, inflammation, and multiorgan dysfunction that manifests late in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Recommendations are also provided for children with hyperinflammation during coronavirus disease 2019 (COVID-19), the acute, infectious phase of SARS-CoV-2 infection.

METHODS

The Task Force was composed of 9 pediatric rheumatologists and 2 adult rheumatologists, 2 pediatric cardiologists, 2 pediatric infectious disease specialists, and 1 pediatric critical care physician. Preliminary statements addressing clinical questions related to MIS-C and hyperinflammation in COVID-19 were developed based on evidence reports. Consensus was built through a modified Delphi process that involved anonymous voting and webinar discussion. A 9-point scale was used to determine the appropriateness of each statement (median scores of 1-3 for inappropriate, 4-6 for uncertain, and 7-9 for appropriate). Consensus was rated as low, moderate, or high based on dispersion of the votes. Approved guidance statements were those that were classified as appropriate with moderate or high levels of consensus, which were prespecified before voting.

RESULTS

The first version of the guidance was approved in June 2020, and consisted of 40 final guidance statements accompanied by a flow diagram depicting the diagnostic pathway for MIS-C. The document was revised in November 2020, and a new flow diagram with recommendations for initial immunomodulatory treatment of MIS-C was added.

CONCLUSION

Our understanding of SARS-CoV-2-related syndromes in the pediatric population continues to evolve. This guidance document reflects currently available evidence coupled with expert opinion, and will be revised as further evidence becomes available.

Amelioration of Murine Macrophage Activation Syndrome by Monomethyl Fumarate in Both a Heme Oxygenase 1-Dependent and Heme Oxygenase 1-Independent Manner

OBJECTIVE

Macrophage activation syndrome (MAS) is characterized by increased serum levels of ferritin and heme oxygenase 1 (HO-1), and yet no known function is ascribed to these molecules in MAS. Because HO-1 is antiinflammatory, we hypothesized that pharmacologic activation of HO-1 could ameliorate MAS disease activity. Dimethyl fumarate (DMF), a treatment approved by the US Food and Drug Administration for multiple sclerosis, activates HO-1. Monomethyl fumarate (MMF) is the active metabolite of DMF. We therefore evaluated whether MMF could elicit HO-1-dependent therapeutic improvements in a murine model of MAS.

METHODS

We induced MAS by repeated activation of Toll-like receptor 9 (TLR-9) in wild-type and myeloid-specific HO-1-deficient mice. MMF was administered twice daily to test its efficacy. We assessed organ weights, serum cytokine levels, histologic features of the spleen and liver tissue, and complete blood cell counts to evaluate disease activity. Statistical testing was performed using Student's t-test or by 2-way analysis of variance as appropriate.

RESULTS

The presence of HO-1 was required for the majority of TLR-9-induced interleukin-10 (IL-10). IL-10 production in TLR-9-induced MAS was found to correlate with the myeloid-HO-1 gene dose in myeloid cells (P < 0.001). MMF treatment increased the levels of HO-1 in splenic macrophages by ~2-fold (P < 0.01), increased serum levels of IL-10 in an HO-1-dependent manner in mice with TLR-9-induced MAS (P < 0.005), and improved multiple disease parameters in both an HO-1-dependent and HO-1-independent manner.

CONCLUSION

TLR-9-induced production of IL-10 is regulated by HO-1 activity both in vitro and in vivo. Therapeutic enhancement of the HO-1/IL-10 axis in a murine model was able to significantly ameliorate MAS disease activity. These results suggest that HO-1 may be viable as a MAS therapeutic target, and treatment with DMF and MMF should be considered in future investigations of MAS therapy.

Deep immune profiling of MIS-C demonstrates marked but transient immune activation compared to adult and pediatric COVID-19

Pediatric COVID-19 following SARS-CoV-2 infection is associated with fewer hospitalizations and often milder disease than in adults. A subset of children, however, present with Multisystem Inflammatory Syndrome in Children (MIS-C) that can lead to vascular complications and shock, but rarely death. The immune features of MIS-C compared to pediatric COVID-19 or adult disease remain poorly understood. We analyzed peripheral blood immune responses in hospitalized SARS-CoV-2 infected pediatric patients (pediatric COVID-19) and patients with MIS-C. MIS-C patients had patterns of T cell-biased lymphopenia and T cell activation similar to severely ill adults, and all patients with MIS-C had SARS-CoV-2 spike-specific antibodies at admission. A distinct feature of MIS-C patients was robust activation of vascular patrolling CX3CR1+ CD8+ T cells that correlated with the use of vasoactive medication. Finally, whereas pediatric COVID-19 patients with acute respiratory distress syndrome (ARDS) had sustained immune activation, MIS-C patients displayed clinical improvement over time, concomitant with decreasing immune activation. Thus, non-MIS-C versus MIS-C SARS-CoV-2 associated illnesses are characterized by divergent immune signatures that are temporally distinct from one another and implicate CD8+ T cells in the clinical presentation and trajectory of MIS-C.

Colonoids From Patients With Pediatric Inflammatory Bowel Disease Exhibit Decreased Growth Associated With Inflammation Severity and Durable Upregulation of Antigen Presentation Genes

BACKGROUND

Defining epithelial cell contributions to inflammatory bowel disease (IBD) is essential for the development of much needed therapies for barrier repair. Children with very early onset (VEO)-IBD have more extensive, severe, and refractory disease than older children and adults with IBD and, in some cases, have defective barrier function. We therefore evaluated functional and transcriptomic differences between pediatric IBD (VEO and older onset) and non-IBD epithelium using 3-dimensional, biopsy-derived organoids.

METHODS

We measured growth efficiency relative to histopathological and clinical parameters in patient enteroid (ileum) and colonoid (colon) lines. We performed RNA-sequencing on patient colonoids and subsequent flow cytometry after multiple passages to evaluate changes that persisted in culture.

RESULTS

Enteroids and colonoids from pediatric patients with IBD exhibited decreased growth associated with histological inflammation compared with non-IBD controls. We observed increased LYZ expression in colonoids from pediatric IBD patients, which has been reported previously in adult patients with IBD. We also observed upregulation of antigen presentation genes HLA-DRB1 and HLA-DRA, which persisted after prolonged passaging in patients with pediatric IBD.

CONCLUSIONS

We present the first functional evaluation of enteroids and colonoids from patients with VEO-IBD and older onset pediatric IBD, a subset of which exhibits poor growth. Enhanced, persistent epithelial antigen presentation gene expression in patient colonoids supports the notion that epithelial cell-intrinsic differences may contribute to IBD pathogenesis.

Multidisciplinary Guidance Regarding the Use of Immunomodulatory Therapies for Acute Coronavirus Disease 2019 in Pediatric Patients

BACKGROUND

Immune-mediated lung injury and systemic hyperinflammation are characteristic of severe and critical coronavirus disease 2019 (COVID-19) in adults. Although the majority of severe acute respiratory syndrome coronavirus 2 infections in pediatric populations result in minimal or mild COVID-19 in the acute phase of infection, a small subset of children develop severe and even critical disease in this phase with concomitant inflammation that may benefit from immunomodulation. Therefore, guidance is needed regarding immunomodulatory therapies in the setting of acute pediatric COVID-19. This document does not provide guidance regarding the recently emergent multisystem inflammatory syndrome in children (MIS-C).

METHODS

A multidisciplinary panel of pediatric subspecialty physicians and pharmacists with expertise in infectious diseases, rheumatology, hematology/oncology, and critical care medicine was convened. Guidance statements were developed based on best available evidence and expert opinion.

RESULTS

The panel devised a framework for considering the use of immunomodulatory therapy based on an assessment of clinical disease severity and degree of multiorgan involvement combined with evidence of hyperinflammation. Additionally, the known rationale for consideration of each immunomodulatory approach and the associated risks and benefits was summarized.

CONCLUSIONS

Immunomodulatory therapy is not recommended for the majority of pediatric patients, who typically develop mild or moderate COVID-19. For children with severe or critical illness, the use of immunomodulatory agents may be beneficial. The risks and benefits of such therapies are variable and should be evaluated on a case-by-case basis with input from appropriate specialty services. When available, the panel strongly favors immunomodulatory agent use within the context of clinical trials. The framework presented herein offers an approach to decision-making regarding immunomodulatory therapy for severe or critical pediatric COVID-19 and is informed by currently available data, while awaiting results of placebo-controlled randomized clinical trials.

Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) Antibody Responses in Children With Multisystem Inflammatory Syndrome in Children (MIS-C) and Mild and Severe Coronavirus Disease 2019 (COVID-19)

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) antibody responses in children remain poorly characterized. Here, we show that pediatric patients with multisystem inflammatory syndrome in children (MIS-C) possess higher SARS-CoV-2 spike immunoglobulin G (IgG) titers compared with those with severe coronavirus disease 2019, likely reflecting a longer time since the onset of infection in MIS-C patients.

Multisystem inflammatory syndrome in children and COVID-19 are distinct presentations of SARS-CoV-2

BACKGROUNDInitial reports from the severe acute respiratory coronavirus 2 (SARS-CoV-2) pandemic described children as being less susceptible to coronavirus disease 2019 (COVID-19) than adults. Subsequently, a severe and novel pediatric disorder termed multisystem inflammatory syndrome in children (MIS-C) emerged. We report on unique hematologic and immunologic parameters that distinguish between COVID-19 and MIS-C and provide insight into pathophysiology.METHODSWe prospectively enrolled hospitalized patients with evidence of SARS-CoV-2 infection and classified them as having MIS-C or COVID-19. Patients with COVID-19 were classified as having either minimal or severe disease. Cytokine profiles, viral cycle thresholds (Cts), blood smears, and soluble C5b-9 values were analyzed with clinical data.RESULTSTwenty patients were enrolled (9 severe COVID-19, 5 minimal COVID-19, and 6 MIS-C). Five cytokines (IFN-γ, IL-10, IL-6, IL-8, and TNF-α) contributed to the analysis. TNF-α and IL-10 discriminated between patients with MIS-C and severe COVID-19. The presence of burr cells on blood smears, as well as Cts, differentiated between patients with severe COVID-19 and those with MIS-C.CONCLUSIONPediatric patients with SARS-CoV-2 are at risk for critical illness with severe COVID-19 and MIS-C. Cytokine profiling and examination of peripheral blood smears may distinguish between patients with MIS-C and those with severe COVID-19.FUNDINGFinancial support for this project was provided by CHOP Frontiers Program Immune Dysregulation Team; National Institute of Allergy and Infectious Diseases; National Cancer Institute; the Leukemia and Lymphoma Society; Cookies for Kids Cancer; Alex's Lemonade Stand Foundation for Childhood Cancer; Children's Oncology Group; Stand UP 2 Cancer; Team Connor; the Kate Amato Foundations; Burroughs Wellcome Fund CAMS; the Clinical Immunology Society; the American Academy of Allergy, Asthma, and Immunology; and the Institute for Translational Medicine and Therapeutics.

Cellular context of IL-33 expression dictates impact on anti-helminth immunity

Interleukin-33 (IL-33) is a pleiotropic cytokine that can promote type 2 inflammation but also drives immunoregulation through Foxp3⁺T_reg expansion. How IL-33 is exported from cells to serve this dual role in immunosuppression and inflammation remains unclear. Here, we demonstrate that the biological consequences of IL-33 activity are dictated by its cellular source. Whereas IL-33 derived from epithelial cells stimulates group 2 innate lymphoid cell (ILC2)-driven type 2 immunity and parasite clearance, we report that IL-33 derived from myeloid antigen-presenting cells (APCs) suppresses host-protective inflammatory responses. Conditional deletion of IL-33 in CD11c-expressing cells resulted in lowered numbers of intestinal Foxp3⁺T_reg cells that express the transcription factor GATA3 and the IL-33 receptor ST2, causing elevated IL-5 and IL-13 production and accelerated anti-helminth immunity. We demonstrate that cell-intrinsic IL-33 promoted mouse dendritic cells (DCs) to express the pore-forming protein perforin-2, which may function as a conduit on the plasma membrane facilitating IL-33 export. Lack of perforin-2 in DCs blocked the proliferative expansion of the ST2⁺Foxp3⁺T_reg subset. We propose that perforin-2 can provide a plasma membrane conduit in DCs that promotes the export of IL-33, contributing to mucosal immunoregulation under steady-state and infectious conditions.

Convalescent plasma for pediatric patients with SARS-CoV-2-associated acute respiratory distress syndrome

There are no proven safe and effective therapies for children who develop life-threatening complications of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Convalescent plasma (CP) has demonstrated potential benefit in adults with SARS-CoV-2, but has theoretical risks.We present the first report of CP in children with life-threatening coronavirus disease 2019 (COVID-19), providing data on four pediatric patients with acute respiratory distress syndrome. We measured donor antibody levels and recipient antibody response prior to and following CP infusion. Infusion of CP was not associated with antibody-dependent enhancement (ADE) and did not suppress endogenous antibody response. We found CP was safe and possibly efficacious. Randomized pediatric trials are needed.

Deep Immune Profiling of MIS-C demonstrates marked but transient immune activation compared to adult and pediatric COVID-19

Pediatric COVID-19 following SARS-CoV-2 infection is associated with fewer hospitalizations and often milder disease than in adults. A subset of children, however, present with Multisystem Inflammatory Syndrome in Children (MIS-C) that can lead to vascular complications and shock, but rarely death. The immune features of MIS-C compared to pediatric COVID-19 or adult disease remain poorly understood. We analyzed peripheral blood immune responses in hospitalized SARS-CoV-2 infected pediatric patients (pediatric COVID-19) and patients with MIS-C. MIS-C patients had patterns of T cell-biased lymphopenia and T cell activation similar to severely ill adults, and all patients with MIS-C had SARS-CoV-2 spike-specific antibodies at admission. A distinct feature of MIS-C patients was robust activation of vascular patrolling CX3CR1+ CD8 T cells that correlated with use of vasoactive medication. Finally, whereas pediatric COVID-19 patients with acute respiratory distress syndrome (ARDS) had sustained immune activation, MIS-C patients displayed clinical improvement over time, concomitant with decreasing immune activation. Thus, non-MIS-C versus MIS-C SARS-CoV-2 associated illnesses are characterized by divergent immune signatures that are temporally distinct and implicate CD8 T cells in clinical presentation and trajectory of MIS-C.

American College of Rheumatology Clinical Guidance for Multisystem Inflammatory Syndrome in Children Associated With SARS-CoV-2 and Hyperinflammation in Pediatric COVID-19: Version 1

Objective

To provide guidance on the management of multisystem inflammatory syndrome in children (MIS‐C), a condition characterized by fever, inflammation, and multiorgan dysfunction that manifests late in the course of severe acute respiratory syndrome coronavirus 2 (SARS–CoV‐2) infection, and to provide recommendations for children with hyperinflammation during coronavirus disease 2019 (COVID‐19), the acute, infectious phase of SARS–CoV‐2 infection.

Methods

A multidisciplinary task force was convened by the American College of Rheumatology (ACR) to provide guidance on the management of MIS‐C associated with SARS–CoV‐2 and hyperinflammation in COVID‐19. The task force was composed of 9 pediatric rheumatologists, 2 adult rheumatologists, 2 pediatric cardiologists, 2 pediatric infectious disease specialists, and 1 pediatric critical care physician. Preliminary statements addressing clinical questions related to MIS‐C and hyperinflammation in COVID‐19 were developed based on evidence reports. Consensus was built through a modified Delphi process that involved 2 rounds of anonymous voting and 2 webinars. A 9‐point scale was used to determine the appropriateness of each statement (median scores of 1–3 for inappropriate, 4–6 for uncertain, and 7–9 for appropriate), and consensus was rated as low, moderate, or high based on dispersion of the votes along the numeric scale. Approved guidance statements were those that were classified as appropriate with moderate or high levels of consensus, as prespecified prior to voting.

Results

The ACR task force approved a total of 128 guidance statements addressing the management of MIS‐C and hyperinflammation in pediatric COVID‐19. These statements were refined into 40 final clinical guidance statements, accompanied by a flow diagram depicting the diagnostic pathway for MIS‐C.

Conclusion

Our understanding of SARS–CoV‐2–related syndromes in the pediatric population continues to evolve. The guidance provided in this “living document” reflects currently available evidence, coupled with expert opinion, and will be revised as further evidence becomes available.

Human Adenovirus 7-Associated Hemophagocytic Lymphohistiocytosis-Like Illness: Clinical and Virological Characteristics in a Cluster of Five Pediatric Cases

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition of immune dysregulation. Children often suffer from primary genetic forms of HLH, which can be triggered by infection. Others suffer from secondary HLH as a complication of infection, malignancy, or rheumatologic disease. Identifying the exact cause of HLH is crucial, as definitive treatment for primary disease is hematopoietic stem cell transplant. Adenoviruses have been associated with HLH but molecular epidemiology data are lacking.

METHODS

We describe the clinical and virologic characteristics of 5 children admitted with adenovirus infection during 2018-2019 who developed HLH or HLH-like illness. Detailed virologic studies, including virus isolation and comprehensive molecular typing were performed.

RESULTS

All patients recovered; clinical management varied but included immunomodulating and antiviral therapies. A genetic predisposition for HLH was not identified in any patient. Adenovirus isolates were recovered from 4/5 cases; all were identified as genomic variant 7d. Adenovirus type 7 DNA was detected in the fifth case. Phylogenetic analysis of genome sequences identified two clusters - one related to strains implicated in 2016-2017 outbreaks in Pennsylvania and New Jersey, the other related to a 2009 Chinese strain.

CONCLUSIONS

It can be challenging to determine whether HLH is the result of an infectious pathogen alone or genetic predisposition triggered by an infection. We describe 5 children from the same center presenting with an HLH-like illness after onset of adenovirus type 7 infection. None of the patients were found to have a genetic predisposition to HLH. These findings suggest that adenovirus 7 infection alone can result in HLH.

SARS-CoV-2 antibody responses in children with MIS-C and mild and severe COVID-19

SARS-CoV-2 antibody responses in children remain poorly characterized. Here, we show that pediatric patients with multisystem inflammatory syndrome in children (MIS-C) possess higher SARS-CoV-2 spike IgG titers compared to those with severe coronavirus disease 2019 (COVID-19), likely reflecting a longer time since onset of infection in MIS-C patients.

IFNs Drive Development of Novel IL-15-Responsive Macrophages

Disruption in homeostasis of IL-15 is linked to poor maternal and fetal outcomes during pregnancy. The only cells described to respond to IL-15 at the early maternal-fetal interface have been NK cells. We now show a novel population of macrophages, evident in several organs but enriched in the uterus of mice and humans, expressing the β-chain of the IL-15R complex (CD122) and responding to IL-15. CD122+ macrophages (CD122+Macs) are morphologic, phenotypic, and transcriptomic macrophages that can derive from bone marrow monocytes. CD122+Macs develop in the uterus and placenta with kinetics that mirror IFN activity at the maternal-fetal interface. M-CSF permits macrophages to express CD122, and IFNs are sufficient to drive expression of CD122 on macrophages. Neither type I nor type II IFNs are required to generate CD122+Macs, however. In response to IL-15, CD122+Macs activate the ERK signaling cascade and enhance production of proinflammatory cytokines after stimulation with the TLR9 agonist CpG. Finally, we provide evidence of human cells that phenocopy murine CD122+Macs in secretory phase endometrium during the implantation window and in first-trimester uterine decidua. Our data support a model wherein IFNs local to the maternal-fetal interface direct novel IL-15-responsive macrophages with the potential to mediate IL-15 signals critical for optimal outcomes of pregnancy.

Vitamin C deficiency mimicking inflammatory bone disease of the hand

BACKGROUND

Severe vitamin C deficiency, or scurvy, encompasses a syndrome of multisystem abnormalities due to defective collagen synthesis and antioxidative functions. Among the more common presentations is a combination of oral or subcutaneous hemorrhage with lower extremity pain, the latter often exhibiting inflammatory bone changes on magnetic resonance imaging (MRI).

CASE PRESENTATION

A 12-year-old male with anorexia nervosa presented with asymmetric painful swelling of multiple fingers of both hands. Imaging demonstrated soft tissue and bone marrow edema of several phalanges, without arthritis, concerning for an inflammatory process. Extensive imaging and laboratory evaluations were largely unrevealing, with the exception of a severely low vitamin C level and a moderately low vitamin D level. A diagnosis of scurvy was made and supplementation was initiated. Within 3 weeks of treatment, serum levels of both vitamins normalized and the digital abnormalities resolved on physical exam.

CONCLUSIONS

This represents the first description of scurvy manifesting with bone and soft tissue changes limited to the hands. There must be a high index of suspicion for scurvy in children with restricted dietary intake or malabsorption who have bone pain, irrespective of location of the lesions.

Multisystem Inflammatory Syndrome in Children During the Coronavirus 2019 Pandemic: A Case Series

We present a series of 6 critically ill children with multisystem inflammatory syndrome in children. Key findings of this syndrome include fever, diarrhea, shock, and variable presence of rash, conjunctivitis, extremity edema, and mucous membrane changes.

On the Alert for Cytokine Storm: Immunopathology in COVID-19

Poor outcomes in COVID-19 correlate with clinical and laboratory features of cytokine storm syndrome. Broad screening for cytokine storm and early, targeted antiinflammatory therapy may prevent immunopathology and could help conserve limited health care resources. While studies are ongoing, extrapolating from clinical experience in cytokine storm syndromes may benefit the multidisciplinary teams caring for patients with severe COVID-19.

Missense mutation in non-recombinase domain of RAG1 results in B-cell developmental defect

Objective

To examine how a single amino acid change to a region of RAG1 that is not related to VDJ recombination affects B-cell development.

Methods

We studied B-cells within a Rag1 P326G missense mutant mouse (Rag1PG) utilizing flow cytometric analysis to phenotype B-cell development and peripheral populations, as well as biochemical studies examining the B-cell Receptor (BCR) molecular complex and signaling function. We also created a mixed bone marrow chimera to determine which alterations were cell-intrinsic.

Results

We find that overall there is an ~50% decrease in total B-cells in the Rag1PG mouse compared to wildtype (WT) due to a Pro-B to Pre-B-cell developmental block. Peripheral B cell cytopenias are in the Follicular Zone B-cell compartment, with sparing of the Marginal Zone B-cells. There is decreased Syk expression in Rag1PG—however no differences in BCR signaling strength were appreciated in Rag1PG. In the mixed bone marrow chimera, we find a competitive advantage in the WT developing B-cells, but peripheral B cell populations survive equally well.

Conclusion

Despite the Rag1PG protein being a single amino acid change to a region of RAG1 not involved in recombination, we nevertheless find a developmental defect consistent with leaky SCID. Given that there is no evidence of altered BCR signaling, and the developmental block occurs at the stage in B-cell development in which VDJ recombination is first required, these data suggest a recombination defect. The mutation is in a ubiquitin ligase domain, and it is possible this alters currently unappreciated roles of RAG1, such as histone degradation to allow RAG1 access to DNA. Our findings illustrate how mutations in the non-recombinase domain of RAG1 may result in leaky SCID.