Leukocyte Activation Patterns in Hospitalized Children: Comparing SARS-CoV-2, Bacterial Infections, and Inflammatory Pathologies.

In adults, monocytes and neutrophils play important roles in the hyper-inflammatory responses' characteristic of severe forms of SARS-CoV-2 infection. We assessed leukocyte activation in 55 children attending the emergency department for acute fever between March 2020 and September 2021. The following markers were analyzed by flow cytometry: CD169 and HLA-DR on monocytes, CD64 and CD16 on neutrophils, CD38 on lymphocytes TCD8. Fifteen of the children had SARS-CoV-2 infection, 15 had bacterial infections, 15 had inflammatory diseases. We observed overexpression of CD169 on monocytes and CD38 on lymphocytes T in all patients with a diagnosis of SARS-CoV-2, while overexpression of CD64 on neutrophils was observed with bacterial infections and inflammatory diseases. There was a decrease in the expression of HLA-DR on monocytes in the bacterial infection and inflammatory pathology groups. Leukocyte analysis identifies distinct activation patterns in children during SARS-CoV-2 infections, bacterial infections, and inflammatory diseases.

Pediatric refractory chronic immune thrombocytopenia: Identification, patients' characteristics, and outcome.

Refractory chronic immune thrombocytopenia (r-cITP) is one of the most challenging situations in chronic immune thrombocytopenia (cITP). Pediatric r-cITP is inconsistently defined in literature, contributing to the scarcity of data. Moreover, no evidence is available to guide the choice of treatment. We compared seven definitions of r-cITP including five pediatric definitions in 886 patients with cITP (median [min-max] follow-up 5.3 [1.0-29.3] years). The pediatric definitions identified overlapping groups of various sizes (4%-20%) but with similar characteristics (higher proportion of immunopathological manifestations [IM] and systemic lupus erythematosus [SLE]), suggesting that they adequately captured the population of interest. Based on the 79 patients with r-cITP (median follow-up 3.1 [0-18.2] years) according to the CEREVANCE definition (≥3 second-line treatments), we showed that r-cITP occurred at a rate of 1.15% new patients per year and did not plateau over time. In multivariate analysis, older age was associated with r-cITP. One patient (1%) experienced two grade five bleeding events after meeting r-cITP criteria and while not receiving second-line treatment. The cumulative incidence of continuous complete remission (CCR) at 2 years after r-cITP diagnosis was 9%. In this analysis, splenectomy was associated with a higher cumulative incidence of CCR (hazard ratio: 5.43, 95% confidence interval: 1.48-19.84, p = 7.8 × 10-4). In sum, children with cITP may be diagnosed with r-cITP at any time point of the follow-up and are at increased risk of IM and SLE. Second-line treatments seem to be effective for preventing grade 5 bleeding. Splenectomy may be considered to achieve CCR.

Clinical spectrum and outcome of Takayasu's arteritis in children.

OBJECTIVES: We aimed to compare clinical spectrum and outcome between adults and children with Takayasu's arteritis (TAK) in a European population. METHODS: We made a nationwide retrospective observational study between 1988 and 2019. All adult patients met the ACR diagnostic criteria for TAK and all children met the EULAR/PRINTO/PRES criteria for paediatric TAK. RESULTS: We identified 46 children and 389 adults with TAK. The male to female ratio was 34/46 (0.74) in the paediatric group compared to 241/274 (0.88) in the adult group (P<0.05). Children presented with significantly more systemic symptoms; i.e., fever (P<0.05), fatigue (P<0.001), weight loss (P<0.001), abdominal pain (P<0.05), and myalgia (P<0.05) while adults had more upper limb claudication (P<0.01). Topography of the lesions differed significantly between the two groups: adults had more damage at the cerebral vasculature (P<0.01), upper and lower limbs (P<0.001) while children had more kidney lesions (P<0.05). Children TAK had more frequent (P<0.01) and higher (P<0.001) biological inflammation than adults. Children received higher dose-weight of corticosteroids (P=0.001) and less biotherapy (P<0.010) at diagnosis. Relapses (P<0.05) and death (8.6% vs 4.9%) were more frequent in children TAK than in adults. CONCLUSION: Paediatric TAK seems more severe than adult TAK. Therefore, paediatrics patients may require closer monitoring and systemic use of biological treatment.

Regulatory T and B cells in pediatric Henoch-Schönlein purpura: friends or foes?

BACKGROUND AND OBJECTIVES: Henoch-Schönlein purpura (HSP) is the most common immunoglobulin A-mediated systemic vasculitis in childhood. We studied immune dysregulation in HSP by analyzing regulatory T (Treg), T helper 3 (Th3), and regulatory B cell (Breg) subpopulations that might intervene in immune activation, IgA production, and HSP clinical manifestations. METHODS: This prospective study included 3 groups of children: 30 HSP on acute phase, 30 HSP on remission, and 40 healthy controls (HCs) matched on age. Treg, Breg, and Th3 were analyzed by flow cytometry. Serum immunoglobulin and cytokine levels were quantified by ELISA and Luminex. RESULTS: Treg frequencies were higher in acute HSP than in remitting HSP and HCs (6.53% [4.24; 9.21] vs. 4.33% [3.6; 5.66], p = 0.002, and vs. 4.45% [3.01; 6.6], p = 0.003, respectively). Activated Th3 cells (FoxP3 + Th3 cells) tend to be more abundant in HSP than in HCs (78.43% [50.62; 80.84] vs. 43.30% [40.20; 49.32], p = 0.135). Serum IgA, IL-17, and latency-associated peptide (a marker of the anti-inflammatory cytokine TGF-beta production) were significantly and inflammatory cytokines TNF-alpha, IL-1-beta, and IL-6 were non-significantly higher in HSP than HCs. Bregs were identical between the groups, but, in patients with renal impairment, Breg percentage was lower compared to those without. Treg removal in PBMC culture resulted in an increase in IgA production in HSP proving a negative regulatory role of Tregs on IgA production. CONCLUSIONS: In pediatric HSP, immune activation persists in spite of an increase in Th3 and Tregs. Th3 could be involved in IgA hyperproduction, inefficiently downregulated by Tregs. Lack of Bregs appears linked to renal impairment.

Antinuclear antibody-associated autoimmune cytopenia in childhood is a risk factor for systemic lupus erythematosus.

ABSTRACT: Autoimmune cytopenia (AIC) in children may be associated with positive antinuclear antibodies (ANA) and may progress to systemic lupus erythematosus (SLE). We evaluated the risk of progression to SLE of childhood-onset ANA-associated AIC. In the French national prospective OBS'CEREVANCE cohort, the long-term outcome of children with ANA-associated AIC (ANA titer ≥1/160) and a subgroup of children who developed SLE were described. ANA were positive in 355 of 1803 (20%) children with AIC. With a median follow-up of 5.8 (range, 0.1-29.6) years, 79 of 355 (22%) patients developed SLE at a median age of 14.5 (1.1-21.4) years; 20% of chronic immune thrombocytopenic purpura, 19% of autoimmune hemolytic anemia, and 45% of Evans syndrome. None of the patients with ANA-negative test developed SLE. Severe manifestations of SLE were observed in 21 patients, and 2 patients died. In multivariate analysis including patients with positive ANA within the first 3 months after AIC diagnosis, age >10 years at AIC diagnosis (relative risk [RR], 3.67; 95% confidence interval [CI], 1.18-11.4; P = .024) and ANA titer >1/160 (RR, 5.28; 95% CI, 1.20-23.17; P = .027) were associated with the occurrence of SLE after AIC diagnosis. ANA-associated AIC is a risk factor for progression to SLE, especially in children with an initial ANA titer >1/160 and an age >10 years at AIC diagnosis. ANA screening should be recommended in children with AIC, and patients with ANA should be monitored long-term for SLE, with special attention to the transition period. This trial was registered at www.ClinicalTrials.gov as #NCT05937828.

SARS-CoV-2 nucleocapsid antigen in plasma of children hospitalized for COVID-19 or with incidental detection of SARS-CoV-2 infection.

In hospitalized children, SARS-CoV-2 infection can present as either a primary reason for admission (patients admitted for COVID-19) or an incidental finding during follow-up (patients admitted with COVID-19). We conducted a nested case-control study within a cohort of pediatric patients with confirmed SARS-CoV-2 infection, to investigate the concentration of plasma nucleocapsid antigen (N-Ag) in children admitted for COVID-19 or with COVID-19. While reverse transcriptase polymerase chain reaction Ct values in nasopharyngeal swab were similar between the two groups, children admitted for COVID-19 had a higher rate of detectable N-Ag (12/18 (60.7%) versus 6/18 (33.3%), p = 0.0455) and a higher concentration of N-Ag (medians: 19.51 g/mL vs. 1.08 pg/mL, p = 0.0105). In children hospitalized for COVID-19, the youngest had higher concentration of N-Ag (r = -0.74, p = 0.0004). We also observed a lower prevalence of detectable spike antibodies in children hospitalized for COVID-19 compared to those hospitalized for other medical reasons (3/15 [20%] vs. 13/16 [81.25%], respectively, p = < 0.0011), but similar rates of IgG nucleocapsid antibodies (5/14 [35.7%] vs. 6/17 [35.3%], respectively, p = 0.99). Our findings indicate that N-Ag is associated with COVID-19-related hospitalizations in pediatric patients, and less frequently detected in children tested positive for SARS-CoV-2 but hospitalized for another medical reason. Further studies are needed to confirm the value of N-Ag in identifying COVID-19 disease infections in which SARS-CoV-2 is the main pathogen responsible for symptoms.

Antibiotic therapy for osteoarticular infections in 2023: Proposals from the Pediatric Infectious Pathology Group (GPIP).

Most osteoarticular infections (OAI) occur via the hematogenous route, affect children under 5 years of age old, and include osteomyelitis, septic arthritis, osteoarthritis and spondylodiscitis. Early diagnosis and prompt treatment are needed to avoid complications. Children with suspected OAI should be hospitalized at the start of therapy. Surgical drainage is indicated in patients with septic arthritis or periosteal abscess. Staphylococcus aureus is implicated in OAI in children at all ages; Kingella kingae is a very common causative pathogen in children from 6 months to 4 years old. The French Pediatric Infectious Disease Group recommends empirical antibiotic therapy with appropriate coverage against methicillin-sensitive S. aureus (MSSA) with high doses (150 mg/kg/d) of intravenous cefazolin. In most children presenting uncomplicated OAI with favorable outcome (disappearance of fever and pain), short intravenous antibiotic therapy during 3 days can be followed by oral therapy. In the absence of bacteriological identification, oral relay is carried out with the amoxicillin/clavulanate combination (80 mg/kg/d of amoxicillin) or cefalexin (150 mg/kg/d). If the bacterial species is identified, antibiotic therapy will be adapted to antibiotic susceptibility. The minimum total duration of antibiotic therapy should be 14 days for septic arthritis, 3 weeks for osteomyelitis and 4-6 weeks for OAI of the pelvis, spondylodiscitis and more severe OAI, and those evolving slowly under treatment or with an underlying medical condition (neonate, infant under 3 months of old, immunocompromised patients). Treatment of spondylodiscitis and severe OAI requires systematic orthopedic advice.

Clinical, Radiologic, and Immunologic Features of Patients With CTLA4 Deficiency With Neurologic Involvement.

OBJECTIVES: CTLA4 deficiency (CTLA4d) is a disease with multisystem autoimmune features, including neurologic manifestations. We aimed to describe neurologic involvement in these patients. METHODS: We performed a cross-sectional observational study using the French Reference Centre for Primary Immunodeficiencies (CEREDIH) registry plus a surveillance in national society networks. Participants with confirmed CTLA4d and neurologic involvement were included. Clinical, laboratory, and radiologic features were collected, as well as treatments. Available MRI was double-reviewed. RESULTS: Among 70 patients with CTLA4d, 13 patients (21%) had neurologic involvement. Neurologic symptoms began at a median age of 18 [15-45] years, mostly occurring after systemic manifestations (median delay: 8.5 [4.5-10.5] years). Main symptoms included headaches, focal deficit (54% each), and seizures (38%). MRI detected at least 1 large contrast-enhancing lesion in 8 patients. Lesions reminiscent of multiple sclerosis lesions were found in 6 patients. Cerebellar (6 patients) and large spinal cord lesions (3 patients) were common. Ten patients were treated with abatacept, of whom 9 (90%) showed good clinical and radiologic response. DISCUSSION: Neurologic involvement is common among patients with CTLA4d. Despite its rarity, and considering the suspected efficacy of abatacept, neurologists should be aware of the characteristics of CTLA4d neurologic involvement.

MicroRNAs in inflammasomopathies.

microRNAs (miRNAs) are small non-coding RNA sequences that negatively regulate the expression of protein-encoding genes at the post-transcriptional level. They play a role in the regulation of inflammatory responses by controlling the proliferation and activation of immune cells and their expression is disrupted in several immune-mediated inflammatory disorders. Among these, autoinflammatory diseases (AID) are a group of rare hereditary disorders caused by abnormal activation of the innate immune system and characterized by recurrent fevers. Major groups of AID are inflammasomopathies, which are associated with hereditary defects in the activation of inflammasomes, cytosolic multiprotein signaling complexes regulating IL-1 family cytokine maturation and pyroptosis. The study of the role of miRNAs in AID is only recently emerging and remains scarce in inflammasomopathies. In this review, we describe the AID and inflammasomopathies, and the current knowledge on the role of miRNAs in disease processes.

Chronic Aichi Virus Infection As a Cause of Long-Lasting Multiorgan Involvement in Patients With Primary Immune Deficiencies.

BACKGROUND: Metagenomic next-generation sequencing (mNGS) was used to assess patients with primary or secondary immune deficiencies (PIDs and SIDs) who presented with immunopathological conditions related to immunodysregulation. METHODS: Thirty patients with PIDs or SIDs who presented with symptoms related to immunodysregulation and 59 asymptomatic patients with similar PIDs or SIDs were enrolled. mNGS was performed on organ biopsy. Specific Aichi virus (AiV) reverse-transcription polymerase chain reaction (RT-PCR) was used to confirm AiV infection and screen the other patients. In situ hybridization (ISH) assay was done on AiV-infected organs to identify infected cells. Virus genotype was determined by phylogenetic analysis. RESULTS: AiV sequences were detected using mNGS in tissue samples of 5 patients and by RT-PCR in peripheral samples of another patient, all of whom presented with PID and long-lasting multiorgan involvement, including hepatitis, splenomegaly, and nephritis in 4 patients. CD8+ T-cell infiltration was a hallmark of the disease. RT-PCR detected intermittent low viral loads in urine and plasma from infected patients but not from uninfected patients. Viral detection stopped after immune reconstitution obtained by hematopoietic stem cell transplantation. ISH demonstrated the presence of AiV RNA in hepatocytes (n = 1) and spleen tissue (n = 2). AiV belonged to genotype A (n = 2) or B (n = 3). CONCLUSIONS: The similarity of the clinical presentation, the detection of AiV in a subgroup of patients suffering from immunodysregulation, the absence of AiV in asymptomatic patients, the detection of viral genome in infected organs by ISH, and the reversibility of symptoms after treatment argue for AiV causality.

Molecular and clinicopathologic characterization of pediatric histiocytoses.

The spectrum of somatic mutations in pediatric histiocytoses and their clinical implications are not fully characterized, especially for non-Langerhans cell histiocytosis (-LCH) subtypes. A cohort of 415 children with histiocytosis from the French histiocytosis registry was reviewed and analyzed for BRAFV600E . Most BRAFWT samples were analyzed by next-generation sequencing (NGS) with a custom panel of genes for histiocytosis and myeloid neoplasia. Of 415 case samples, there were 366 LCH, 1 Erdheim-Chester disease, 21 Rosai-Dorfman disease (RDD), 21 juvenile xanthogranuloma (JXG, mostly with severe presentation), and 6 malignant histiocytosis (MH). BRAFV600E was the most common mutation found in LCH (50.3%, n = 184). Among 105 non-BRAFV600E -mutated LCH case samples, NGS revealed mutations as follows: MAP2K1 (n = 44), BRAF exon 12 deletions (n = 26), and duplications (n = 8), other BRAF V600 codon mutation (n = 4), and non-MAP-kinase pathway genes (n = 5). Wild-type sequences were identified in 17.1% of samples. BRAFV600E was the only variant significantly correlated with critical presentations: organ-risk involvement and neurodegeneration. MAP-kinase pathway mutations were identified in seven RDD (mostly MAP2K1) and three JXG samples, but most samples were wild-type on NGS. Finally, two MH samples had KRAS mutations, and one had a novel BRAFG469R mutation. Rarely, we identified mutations unrelated to MAP-kinase pathway genes. In conclusion, we characterized the mutational spectrum of childhood LCH and clinical correlations of variants and subtypes. Variants responsible for JXG and RDD were not elucidated in more than half of the cases, calling for other sequencing approaches.

Impact of age at diagnosis, sex, and immunopathological manifestations in 886 patients with pediatric chronic immune thrombocytopenia.

Pediatric chronic immune thrombocytopenia (cITP) is a heterogeneous condition in terms of bleeding severity, second-line treatment use, association with clinical and/or biological immunopathological manifestations (IMs), and progression to systemic lupus erythematosus (SLE). No risk factors for these outcomes are known. Specifically, whether age at ITP diagnosis, sex, or IMs impact cITP outcomes is unknown. We report the outcomes of patients with pediatric cITP from the French nationwide prospective cohort OBS'CEREVANCE. We used multivariate analyses to investigate the effect of age at ITP diagnosis, sex, and IMs on cITP outcomes. We included 886 patients with a median (min-max) follow-up duration of 5.3 (1.0-29.3) years. We identified an age cutoff that dichotomized the risk of the outcomes and defined two risk groups: patients with ITP diagnosed <10 years (children) and ≥ 10 years (adolescents). Adolescents had a two to four-fold higher risk of grade ≥3 bleeding, second-line treatment use, clinical and biological IMs, and SLE diagnosis. Moreover, female sex and biological IMs were independently associated with higher risks of biological IMs and SLE diagnosis, second-line treatment use, and SLE diagnosis, respectively. The combination of these three risk factors defined outcome-specific risk groups. Finally, we showed that patients clustered in mild and severe phenotypes, more frequent in children and adolescents, respectively. In conclusion, we identified that age at ITP diagnosis, sex, and biological IMs impacted the long-term outcomes of pediatric cITP. We defined risk groups for each outcome, which will help clinical management and further studies.

Late-onset enteric virus infection associated with hepatitis (EVAH) in transplanted SCID patients.

BACKGROUND: Allogenic hematopoietic stem cell transplantation (HSCT) and gene therapy (GT) are potentially curative treatments for severe combined immunodeficiency (SCID). Late-onset posttreatment manifestations (such as persistent hepatitis) are not uncommon. OBJECTIVE: We sought to characterize the prevalence and pathophysiology of persistent hepatitis in transplanted SCID patients (SCIDH+) and to evaluate risk factors and treatments. METHODS: We used various techniques (including pathology assessments, metagenomics, single-cell transcriptomics, and cytometry by time of flight) to perform an in-depth study of different tissues from patients in the SCIDH+ group and corresponding asymptomatic similarly transplanted SCID patients without hepatitis (SCIDH-). RESULTS: Eleven patients developed persistent hepatitis (median of 6 years after HSCT or GT). This condition was associated with the chronic detection of enteric viruses (human Aichi virus, norovirus, and sapovirus) in liver and/or stools, which were not found in stools from the SCIDH- group (n = 12). Multiomics analysis identified an expansion of effector memory CD8+ T cells with high type I and II interferon signatures. Hepatitis was associated with absence of myeloablation during conditioning, split chimerism, and defective B-cell function, representing 25% of the 44 patients with SCID having these characteristics. Partially myeloablative retransplantation or GT of patients with this condition (which we have named as "enteric virus infection associated with hepatitis") led to the reconstitution of T- and B-cell immunity and remission of hepatitis in 5 patients, concomitantly with viral clearance. CONCLUSIONS: Enteric virus infection associated with hepatitis is related to chronic enteric viral infection and immune dysregulation and is an important risk for transplanted SCID patients with defective B-cell function.

Quality of life in monogenic autoinflammatory diseases. A review.

BACKGROUND: Systemic autoinflammatory diseases (SAIDs) are a group of disorders related to defective regulation of the innate immune system. Recurrence of inflammation can severely affect the patients' outcomes with a direct or indirect impact on their physical and mental health and/or global quality of life (QoL). We therefore sought to identify currently available QoL studies for these diseases as well as measurement tools at our disposal. BASIC PROCEDURES: A systematic literature review was carried out with a focus on monogenic SAIDs. We inventoried the study designs developed in the selected publications, grouped them into similar topics, and listed the different outcome measures used for QoL. MAIN FINDINGS: We recorded 53 bibliographic references evaluating the impact of monogenic SAIDs on the patients' QoL. These publications revealed 150 different study designs and 82 outcome measures used for their assessment. The best-explored topics were the overall patients' QoL, followed by the evaluation of their psychosocial and physical functioning. We found fair coverage of familial Mediterranean fever, poor investigation of the mixed hereditary recurrent fever (HRF) group, cryopyrin-associated periodic diseases and cherubism, and almost no study of the other monogenic SAIDs. CONCLUSIONS: This work revealed areas requiring further investigation such as homogenization of concepts, study of uncommon or more recent diseases, and development of more specific and validated outcome measures for SAIDs.