Prevalence of Pathogenic and Potentially Pathogenic Inborn Error of Immunity Associated Variants in Children with Severe Sepsis

Are inborn errors of immunity being investigated in the pediatric intensive care unit?

OBJECTIVES

To assess the frequency of diagnostic investigation for inborn errors of immunity (IEI) in the presence of warning signs and clinical outcomes of children hospitalized in the pediatric intensive care unit (PICU) according to age group.

MATERIAL AND METHODS

This retrospective cross-sectional study included children hospitalized in the PICU of a referral hospital over two years. Warning signs were collected according to age group (up to and over one year), and sociodemographic and clinical variables, basic investigation of IEI, follow-up by the immunology service, and hospital discharge and death were also assessed.

RESULTS

Of 680 included children, 330 (48.5%) were aged up to one year, and 350 (51.5%) were over one year. Among those aged up to one year, 108 (32.7%) had two or more warning signs, and only 22 (20.4%) were investigated for IEI. Considering the group aged over one year, 48 (13.7%) had two or more warning signs, and 21 (43.8%) were investigated for IEI. The highest number of deaths occurred among children aged up to one year with two or more warning signs (58.8%).

CONCLUSIONS

Few children with warning signs were investigated for IEI, representing missed opportunities to timely diagnose IEI, which may impact the risk of death.

Genomic sequencing: the case for equity of care in the era of personalized medicine

Over the past two decades, genomic sequencing (exome and genome) has proven to be critical in providing a faster and more accurate diagnosis as well as tailored treatment plans for a variety of populations. Despite its potential, disparities in access to genomic sequencing persist, predominantly among underrepresented and socioeconomically disadvantaged groups and populations. This inequity stems from factors such as: 1) high costs of sequencing, 2) significant gaps in insurance coverage, 3) limited availability of genetic services in many healthcare institutions and geographic areas, and 4) lack of diversity in genetic research and databases. Addressing these barriers is essential to realizing the full benefits of personalized treatment approaches for all individuals. By doing so, healthcare systems can move towards a more inclusive model that delivers optimal care for everyone. This manuscript emphasizes these issues by considering diverse perspectives from various ethnic groups, summarizing findings across different patient populations (adults, pediatrics, critical/non-critical care), and highlighting the importance of collaboration and workforce training in genomic sequencing and interpretation. IMPACT: Presentation of exemplary studies demonstrating the advantages of genomic sequencing in various clinical settings and a variety of high-risk populations. Review of obstacles in providing equitable genomic medical care and the importance of national and international collaborations An overview of the ethical aspects of genomic sequencing is provided.

Application of whole-exome sequencing to predict inborn errors of immunity in pediatric severe infections and sepsis

Increasing evidence supports the involvement of inborn errors of immunity in severe infections, but little is known about the prevalence of these genetic defects in children with sepsis. Due to the limited understanding of the molecular and immunological mechanisms driving sepsis, genetic testing is rarely used in routine diagnostics to identify genetic susceptibility to the condition. We performed a prospective observational study on previously healthy children hospitalized for severe infections, including sepsis. Patients underwent immunophenotyping and whole-exome sequencing, followed by in silico analysis to identify potentially causal variants. We assembled a cohort of 194 previously healthy children, including 149 (77%) patients with severe infection and 45 (23%) with sepsis. Our cohort was marked by a high frequency of respiratory tract infections (35%), bloodstream infections (20%), and central nervous system infections (16%). The genetic investigation identified 28 potentially causal variants, 18 (64%) are classified as variants with uncertain significance, and 10 (36%) are likely pathogenic variants. Of 45 patients with sepsis, 6 (13%) had potentially causal genetic variants. Similarly, 22/149 (15%) patients with severe infection presented potentially causal genetic variants. Whole-exome sequencing predicted the impairment of various immune mechanistic pathways such as immune dysregulation defects, antibody deficiencies, and combined immunodeficiencies (18% each). We found no clear association between genetic variants and the studied parameters: organ failure, microbe identification, immunoglobulin levels, and lymphocyte subset numbers. Although whole-exome sequencing is a valuable tool for detecting inborn errors of immunity underlying sepsis and unexplained severe infections, it could be selectively recommended for patients with a strong clinical suspicion of genetic abnormalities, balancing its diagnostic value with its cost and complexity.

Prevalence of pathogenic variants of inborn errors of immunity in critically ill children admitted to the pediatric intensive care unit for sepsis: A Moroccan cohort study

INTRODUCTION

Pediatric sepsis remains a leading cause of morbidity and mortality in Africa. Nearly half of pediatric sepsis deaths occur in previously healthy children. The role of inborn errors of immunity (IEI) in susceptibility to sepsis is yet to be identified and their prevalence amongst previously healthy children admitted to the pediatric intensive care unit (PICU) is unclear. We aimed to assess prevalence of IEI among a cohort of children admitted to the PICU for community acquired sepsis and to describe demographic, microbiological, and genetic features of this cohort.

METHODS

We listed a cohort of children admitted to our PICU for sepsis from January 2021 to March 2023. Demographic data was collected, and microbiological tests were performed. Written consent was obtained and whole exome sequencing (WES) was performed after DNA extraction.

RESULTS

Thirty cases were included. Mean age at admission was 46 months (1-180), microorganisms were identified in 20 cases (66%). Bacterial sepsis was identified in 8 cases, viral sepsis in 6 cases and fungal sepsis in 2 cases. Mean pediatric sequential sepsis related organ failure assessment (pSOFA) score at admission was 6,46 (2-18). Mechanical ventilation was necessary in 18 cases. Inotropes were used in 17 cases and renal replacement therapy initiated in 3 cases. Pathogenic variants of IEI were identified in 5 out of 30 cases (17%). These variants were identified in the following genes BACH2, TLR7, TINF2, NFK2B and MAGT1. Overall mortality was 50% and mean intensive care unit (ICU) stay was 9,26 (1-60) days.

CONCLUSION

Prevalence of pathogenic variants of IEI among children admitted to the PICU for sepsis was 17%. Our study findings support systematic screening of IEI amongst critically ill children admitted to the PICU for sepsis in order to increase our comprehension of sepsis phenotypes and improve outcomes in this group of critically ill children.

Diagnostic guidelines for familial hemophagocytic lymphohistiocytosis revisited

ABSTRACT

Current hemophagocytic lymphohistiocytosis 2004 (HLH-2004)-based diagnostic criteria for familial hemophagocytic lymphohistiocytosis (FHL) are based on expert opinion. Here, we performed a case-control study to test and possibly improve these criteria. We also developed 2 complementary expert opinion-based diagnostic strategies for FHL in patients with signs/symptoms suggestive of HLH, based on genetic and cellular cytotoxicity assays. The cases (N = 366) were children aged <16 years with verified familial and/or genetic FHL (n = 341) or Griscelli syndrome type 2 (n = 25); 276 from the HLH-94/HLH-2004 databases and 90 from the Italian HLH Registry. All fulfilled the HLH-94/HLH-2004 patient inclusion criteria. Controls were 374 children with systemic-onset juvenile idiopathic arthritis (sJIA) and 329 + 361 children in 2 cohorts with febrile infections that could be confused with HLH and sepsis, respectively. To provide complete data sets, multiple imputations were performed. The optimal model, based on 17 variables studied, revealed almost similar diagnostic thresholds as the existing criteria, with accuracy 99.1% (sensitivity 97.1%; specificity 99.5%); the original HLH-2004 criteria had accuracy 97.4% (sensitivity 99.0%; specificity 97.1%). Because cellular cytotoxicity assays here constitute a separate diagnostic strategy, HLH-2004 criteria without natural killer (NK)-cell function was also studied, which showed accuracy 99.0% (sensitivity, 96.2%; specificity, 99.5%). Thus, we conclude that the HLH-2004 criteria (without NK-cell function) have significant validity in their current form when tested against severe infections or sJIA. It is important to exclude underlying malignancies and atypical infections. In addition, complementary cellular and genetic diagnostic guidelines can facilitate necessary confirmation of clinical diagnosis.

IMPACT OF ABCC8 AND TRPM4 GENETIC VARIATION IN CENTRAL NERVOUS SYSTEM DYSFUNCTION ASSOCIATED WITH PEDIATRIC SEPSIS

ABSTRACT

Background: Sepsis-associated brain injury is associated with deterioration of mental status, persistent cognitive impairment, and morbidity. The SUR1/TRPM4 channel is a nonselective cation channel that is transcriptionally upregulated in the central nervous system with injury, allowing sodium influx, depolarization, cellular swelling, and secondary injury. We hypothesized that genetic variation in ABCC8 (SUR1 gene) and TRPM4 would associate with central nervous system dysfunction in severe pediatric sepsis. Methods: 326 children with severe sepsis underwent whole exome sequencing in an observational cohort. We compared children with and without central nervous system dysfunction (Glasgow Coma Scale <12) to assess for associations with clinical characteristics and pooled rare variants in ABCC8 and TRPM4. Sites of variation were mapped onto protein structure and assessed for phenotypic impact. Results: Pooled rare variants in either ABCC8 or TRPM4 associated with decreased odds of central nervous system dysfunction in severe pediatric sepsis (OR 0.14, 95% CI 0.003-0.87), P = 0.025). This association persisted following adjustment for race, organ failure, viral infection, and continuous renal replacement therapy (aOR 0.11, 95% CI 0.01-0.59, P = 0.038). Structural mapping showed that rare variants concentrated in the nucleotide-binding domains of ABCC8 and N-terminal melastatin homology region of TRPM4 . Conclusion : This study suggests a role for the ABCC8/TRPM4 channel in central nervous system dysfunction in severe pediatric sepsis. Although exploratory, the lack of therapies to prevent or mitigate central nervous system dysfunction in pediatric sepsis warrants further studies to clarify the mechanism and confirm the potential protective effect of these rare ABCC8/TRPM4 variants.

Dysregulated STAT3 signaling and T cell immunometabolic dysfunction define a targetable, high mortality subphenotype of critically ill children

Sepsis is the leading cause of death of hospitalized children worldwide. Despite the established link between immune dysregulation and mortality in pediatric sepsis, it remains unclear which host immune factors contribute causally to adverse sepsis outcomes. Identifying modifiable pathobiology is an essential first step to successful translation of biologic insights into precision therapeutics. We designed a prospective, longitudinal cohort study of 88 critically ill pediatric patients with multiple organ dysfunction syndrome (MODS), including patients with and without sepsis, to define subphenotypes associated with targetable mechanisms of immune dysregulation. We first assessed plasma proteomic profiles and identified shared features of immune dysregulation in MODS patients with and without sepsis. We then employed consensus clustering to define three subphenotypes based on protein expression at disease onset and identified a strong association between subphenotype and clinical outcome. We next identified differences in immune cell frequency and activation state by MODS subphenotype and determined the association between hyperinflammatory pathway activation and cellular immunophenotype. Using single cell transcriptomics, we demonstrated STAT3 hyperactivation in lymphocytes from the sickest MODS subgroup and then identified an association between STAT3 hyperactivation and T cell immunometabolic dysregulation. Finally, we compared proteomics findings between patients with MODS and patients with inborn errors of immunity that amplify cytokine signaling pathways to further assess the impact of STAT3 hyperactivation in the most severe patients with MODS. Overall, these results identify a potentially pathologic and targetable role for STAT3 hyperactivation in a subset of pediatric patients with MODS who have high severity of illness and poor prognosis.

EMERGENCE OF A TECHNOLOGY-DEPENDENT PHENOTYPE OF PEDIATRIC SEPSIS IN A LARGE CHILDREN'S HOSPITAL

ABSTRACT

Objective: To investigate whether pediatric sepsis phenotypes are stable in time. Methods: Retrospective cohort study examining children with suspected sepsis admitted to a Pediatric Intensive Care Unit at a large freestanding children's hospital during two distinct periods: 2010-2014 (early cohort) and 2018-2020 (late cohort). K-means consensus clustering was used to derive types separately in the cohorts. Variables included ensured representation of all organ systems. Results: One thousand ninety-one subjects were in the early cohort and 737 subjects in the late cohort. Clustering analysis yielded four phenotypes in the early cohort and five in the late cohort. Four types were in both: type A (34% of early cohort, 25% of late cohort), mild sepsis, with minimal organ dysfunction and low mortality; type B (25%, 22%), primary respiratory failure; type C (25%, 18%), liver dysfunction, coagulopathy, and higher measures of systemic inflammation; type D (16%, 17%), severe multiorgan dysfunction, with high degrees of cardiorespiratory support, renal dysfunction, and highest mortality. Type E was only detected in the late cohort (19%) and was notable for respiratory failure less severe than B or D, mild hypothermia, and high proportion of diagnoses and technological dependence associated with medical complexity. Despite low mortality, this type had the longest PICU length of stay. Conclusions: This single center study identified four pediatric sepsis phenotypes in an earlier epoch but five in a later epoch, with the new type having a large proportion of characteristics associated with medical complexity, particularly technology dependence. Personalized sepsis therapies need to account for this expanding patient population.

Autoinflammatory Contributors to Cytokine Storm

Cytokine Storm is a complex and heterogeneous state of life-threatening systemic inflammation and immunopathology. Autoinflammation is a mechanistic category of immune dysregulation wherein immunopathology originates due to poor regulation of innate immunity. The growing family of monogenic Systemic Autoinflammatory Diseases (SAIDs) has been a wellspring for pathogenic insights and proof-of-principle targeted therapeutic interventions. There is surprisingly little overlap between SAID and Cytokine Storm Syndromes, and there is a great deal to be inferred from those SAID that do, and do not, consistently lead to Cytokine Storm. This chapter will summarize how illustrations of the autoinflammatory paradigm have advanced the understanding of human inflammation, including the role of autoinflammation in familial HLH. Next, it will draw from monogenic SAID, both those with strong associations with cytokine storm and those without, to illustrate how the cytokine IL-18 links innate immune dysregulation and cytokine storm.

Whole-exome sequencing to identify undiagnosed primary immunodeficiency disorders in children with community-acquired sepsis, admitted in the pediatric intensive care unit

BACKGROUND

Whole-exome sequencing (WES) provides a powerful diagnostic tool for identifying primary immunodeficiency diseases (PIDs). This study explores the utility of this approach in uncovering previously undiagnosed PIDs in children with community-acquired sepsis (CAS), with a medical history of recurrent infections or a family history of PIDs.

METHODS

We performed WES on DNA samples extracted from the blood of the 34 enrolled patients, followed by bioinformatic analysis for variant calling, annotation, and prioritization. We also performed a segregation analysis in available family members to confirm the inheritance patterns and assessed the potential impact of the identified variants on protein function.

RESULTS

From 34 patients enrolled in the study, 29 patients (85%) with previously undiagnosed genetic diseases, including 28 patients with PIDs and one patient with interstitial lung and liver disease, were identified. We identified two patients with severe combined immunodeficiency (SCID), patients with combined immunodeficiency (CID), six patients with combined immunodeficiency with syndromic features (CID-SF), four patients with defects in intrinsic and innate immunity, four patients with congenital defects of phagocyte function (CPDF), and six patients with the disease of immune dysregulation. Autoinflammatory disorders and predominantly antibody deficiency were diagnosed in one patient each.

CONCLUSION

Our findings demonstrate the potential of WES in identifying undiagnosed PIDs in children with CAS. Implementing WES in the clinical evaluation of CAS patients with a warning sign for PIDs can aid in their timely diagnosis and potentially lead to improved patient care.

Hyperferritinemic sepsis, macrophage activation syndrome, and mortality in a pediatric research network: a causal inference analysis

BACKGROUND

One of five global deaths are attributable to sepsis. Hyperferritinemic sepsis (> 500 ng/mL) is associated with increased mortality in single-center studies. Our pediatric research network's objective was to obtain rationale for designing anti-inflammatory clinical trials targeting hyperferritinemic sepsis.

METHODS

We assessed differences in 32 cytokines, immune depression (low whole blood ex vivo TNF response to endotoxin) and thrombotic microangiopathy (low ADAMTS13 activity) biomarkers, seven viral DNAemias, and macrophage activation syndrome (MAS) defined by combined hepatobiliary dysfunction and disseminated intravascular coagulation, and mortality in 117 children with hyperferritinemic sepsis (ferritin level > 500 ng/mL) compared to 280 children with sepsis without hyperferritinemia. Causal inference analysis of these 41 variables, MAS, and mortality was performed.

RESULTS

Mortality was increased in children with hyperferritinemic sepsis (27/117, 23% vs 16/280, 5.7%; Odds Ratio = 4.85, 95% CI [2.55-9.60]; z = 4.728; P-value < 0.0001). Hyperferritinemic sepsis had higher C-reactive protein, sCD163, IL-22, IL-18, IL-18 binding protein, MIG/CXCL9, IL-1β, IL-6, IL-8, IL-10, IL-17a, IFN-γ, IP10/CXCL10, MCP-1/CCL2, MIP-1α, MIP-1β, TNF, MCP-3, IL-2RA (sCD25), IL-16, M-CSF, and SCF levels; lower ADAMTS13 activity, sFasL, whole blood ex vivo TNF response to endotoxin, and TRAIL levels; more Adenovirus, BK virus, and multiple virus DNAemias; and more MAS (P-value < 0.05). Among these variables, only MCP-1/CCL2 (the monocyte chemoattractant protein), MAS, and ferritin levels were directly causally associated with mortality. MCP-1/CCL2 and hyperferritinemia showed direct causal association with depressed ex vivo whole blood TNF response to endotoxin. MCP-1/CCL2 was a mediator of MAS. MCP-1/CCL2 and MAS were mediators of hyperferritinemia.

CONCLUSIONS

These findings establish hyperferritinemic sepsis as a high-risk condition characterized by increased cytokinemia, viral DNAemia, thrombotic microangiopathy, immune depression, macrophage activation syndrome, and death. The causal analysis provides rationale for designing anti-inflammatory trials that reduce macrophage activation to improve survival and enhance infection clearance in pediatric hyperferritinemic sepsis.

DOCK2 Mutation and Recurrent Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome resulting from uncontrolled hyper-inflammation, excessive immune system activation, and elevated levels of inflammatory cytokines. HLH can be caused by the inability to downregulate activated macrophages by natural killer (NK) and CD8 cytotoxic T cells through a process reliant on perforin and granzyme B to initiate apoptosis. Homozygous genetic mutations in this process result in primary HLH (pHLH), a disorder that can lead to multi-system organ failure and death in infancy. Heterozygous, dominant-negative, or monoallelic hypomorphic mutations in these same genes can cause a similar syndrome in the presence of an immune trigger, leading to secondary HLH (sHLH). A genetic mutation in a potential novel HLH-associated gene, dedicator of cytokinesis 2 (DOCK2), was identified in a patient with recurrent episodes of sHLH and hyperinflammation in the setting of frequent central line infections. He required baseline immune suppression for the prevention of sHLH, with increased anti-cytokine therapies and corticosteroids in response to flares and infections. Using a foamy-virus approach, the patient's DOCK2 mutation and wild-type (WT) control DOCK2 cDNA were separately transduced into a human NK-92 cell line. The NK-cell populations were stimulated with NK-sensitive K562 erythroleukemia target cells in vitro and degranulation and cytolysis were measured using CD107a expression and live/dead fixable cell dead reagent, respectively. Compared to WT, the patient's DOCK2 mutation was found to cause significantly decreased NK cell function, degranulation, and cytotoxicity. This study speaks to the importance of DOCK2 and similar genes in the pathogenesis of sHLH, with implications for its diagnosis and treatment.

Mortality Risk in Pediatric Sepsis Based on C-reactive Protein and Ferritin Levels

OBJECTIVES

Interest in using bedside C-reactive protein (CRP) and ferritin levels to identify patients with hyperinflammatory sepsis who might benefit from anti-inflammatory therapies has piqued with the COVID-19 pandemic experience. Our first objective was to identify patterns in CRP and ferritin trajectory among critically ill pediatric sepsis patients. We then examined the association between these different groups of patients in their inflammatory cytokine responses, systemic inflammation, and mortality risks.

DATA SOURCES

A prospective, observational cohort study.

STUDY SELECTION

Children with sepsis and organ failure in nine pediatric intensive care units in the United States.

DATA EXTRACTION

Two hundred and fifty-five children were enrolled. Five distinct clinical multi-trajectory groups were identified. Plasma CRP (mg/dL), ferritin (ng/mL), and 31 cytokine levels were measured at two timepoints during sepsis (median Day 2 and Day 5). Group-based multi-trajectory models (GBMTM) identified groups of children with distinct patterns of CRP and ferritin.

DATA SYNTHESIS

Group 1 had normal CRP and ferritin levels ( n = 8; 0% mortality); Group 2 had high CRP levels that became normal, with normal ferritin levels throughout ( n = 80; 5% mortality); Group 3 had high ferritin levels alone ( n = 16; 6% mortality); Group 4 had very high CRP levels, and high ferritin levels ( n = 121; 11% mortality); and Group 5 had very high CRP and very high ferritin levels ( n = 30; 40% mortality). Cytokine responses differed across the five groups, with ferritin levels correlated with macrophage inflammatory protein 1α levels and CRP levels reflective of many cytokines.

CONCLUSIONS

Bedside CRP and ferritin levels can be used together to distinguish groups of children with sepsis who have different systemic inflammation cytokine responses and mortality risks. These data suggest future potential value in personalized clinical trials with specific targets for anti-inflammatory therapies.

MIS-C: A COVID-19-as sociated condition between hypoimmunity and hyperimmunity

Multisystem inflammatory syndrome in children (MIS-C) is a rare, severe complication of COVID-19. A better knowledge of immunological, cellular, and genetic characteristics of MIS-C could help better understand the pathogenesis of the disease and contribute to identifying specific diagnostic biomarkers and develop targeted therapies. We studied 37 MIS-C children at hospital admission and 24 healthy controls analyzing serum cytokines (IFN-α, IFN-β, IFN-γ, IL-6, IL-10, IL-17A, IL-12p70 and TNF), lymphocyte populations by flow cytometry and 386 genes related to autoimmune diseases, autoinflammation and primary immunodeficiencies by NGS. MIS-C patients showed a significant increase of serum IFNγ (despite a significant reduction of activated Th1) and ILs, even if with a great heterogeneity among patients, revealing different pathways involved in MIS-C pathogenesis and suggesting that serum cytokines at admission may help to select the inflammatory pathways to target in each patient. Flow cytometry demonstrated a relevant reduction of T populations while the percentage of B cell was increased in agreement with an autoimmune pathogenesis of MIS-C. Genetic analysis identified variants in 34 genes and 83.3% of patients had at least one gene variant. Among these, 9 were mutated in more patients. Most genes are related to autoimmune diseases like ATM, NCF1, MCM4, FCN3, and DOCK8 or to autoinflammatory diseases associated to the release of IFNγ like PRF1, NOD2, and MEF. Thus, an incomplete clearance of the Sars-CoV2 during the acute phase may induce tissue damage and self-antigen exposure and genetic variants can predispose to hyper-reactive immune dysregulation events of MIS-C-syndrome. Type II IFN activation and cytokine responses (mainly IL-6 and IL-10) may cause a cytokine storm in some patients with a more severe acute phase of the disease, lymphopenia and multisystemic organ involvement. The timely identification of such patients with an immunocytometric panel might be critical for targeted therapeutic management.

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.