Validation of the IgA1 Detection Method With Gradient Glycosylation by Mass Spectrometry as a Potential Marker of Renal Involvement in Pediatric Rheumatoid Purpura

Study Overview
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Brief Summary
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In this ancillary study on the FoxTreg cohort, the study investigators will select variables to input and thus develop two models (Linear Discriminant Analysis and Decision Tree). The aim of this study is to validate the method in terms of repeatability, reproducibility, control of pre-analytical conditions and sample conservation, to complete the screening of IgA glycosylation in individuals of the FoxTreg cohort and to refine the glycopeptide signature to predict renal involvement.

Official Title
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Recherche d'un Marqueur Pronostique de l'Atteinte rénale du Purpura Rhumatoïde de l'Enfant. Validation de la méthode de détection Des IgA1 Avec Gradient de la Glycosylation Par spectrométrie de Masse

Conditions
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Rheumatoid Purpura, Pediatric ALL

Intervention / Treatment
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* Other: Mass Sepctrometry


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patient sera from biobank of the FoxTreg study (NCT02317133)

Ages Eligible for Study
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Minimum Age: 3 Years
Maximum Age: 16 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Acute Rheumatoid Purpura<br> | Other: Mass Sepctrometry<br>* Mass spectrometry (LC/MS) of purified immunoglobulins<br>|
| Rheumatoid Purpura in Remission<br> | Other: Mass Sepctrometry<br>* Mass spectrometry (LC/MS) of purified immunoglobulins<br>|
| Controls<br>Without infection, inflammatory or auto-immune pathology | Other: Mass Sepctrometry<br>* Mass spectrometry (LC/MS) of purified immunoglobulins<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Glycopeptide signature of serum from children with Rheumatoid Purpura | Mass spectrometry to identify the glycopeptides present and their level | Day 0 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Repeatability of mass spectrometry in measuring glycopeptide signature | Mass spectrometry to identify the glycopeptides present and their level | Day 0 | 
| Reproducibility of mass spectrometry in measuring glycopeptide signature | Mass spectrometry to identify the glycopeptides present and their level | Day 0 | 
| Control of conservation of samples for measuring glycopeptide signature | Mass spectrometry to identify the glycopeptides present and their level | Day 0 | 
| Glycopeptide signature of serum from all patients of the cohort | Mass spectrometry to identify the glycopeptides present and their level | Day 0 | 
| Difference between a normally glycosylated IgA and an IgA with GalNac polymer in Rheumatoid Purpura patients with / without renal impairment versus controls | Mass spectrometry to identify the glycopeptides present and their level | Day 0 | 
| Number of subjects with IgA glycosylation abnormalities in Rheumatoid Purpura patient population with renal impairment polymer in Rheumatoid Purpura patients with / without renal impairment versus controls | Mass spectrometry of IgA | Day 0 | 
| Percentage of subjects with IgA glycosylation abnormalities in Rheumatoid Purpura patient population with renal impairment polymer in Rheumatoid Purpura patients with / without renal impairment versus controls | Mass spectrometry of IgA | Day 0 | 
| Number of subjects with IgA glycosylation abnormalities in each group | Mass spectrometry of IgA | Day 0 | 
| Percentage of subjects with IgA glycosylation abnormalities in each group | Mass spectrometry of IgA | Day 0 | 
| Serum immunoglobulin levels in patients with acute Rheumatoid Purpura and in remission | Mass spectrometry of immunoglobulins IgA, IgM and IgG (g/L) | Day 0 | 
| Quantification of blood cell lines in patients with acute Rheumatoid Purpura and in remission. | Blood cell lines, particularly Treg and Breg (number/mm3) | Day 0 | 
| Serum cytokine levels in patients with acute Rheumatoid Purpura and in remission | pg/ml of TGF-β, IL-1, IL-6, TNF-α, IL-8, IL-10 and IL-17 | Day 0 | 
| Bacterial Translocation in patients with Rheumatoid Purpura | Plasma levels of 16S rDNA (copies/µl) | Day 0 | 
| Plasma levels of LBP in patients with Rheumatoid Purpura | µg/ml | Day 0 | 
| Plasma levels of CD14s in patients with Rheumatoid Purpura | µg/ml | Day 0 | 
| Bacterial diversity in the gut microbiota in patients with Rheumatoid Purpura | Diversity Index | Day 0 |