Welcome to the ESID 2022 Meeting Interactive Programme

Background and Aims

CTLA-4 insufficiency and LRBA-deficiency are both complex immune dysregulation syndromes with an underlying regulatory T cell dysfunction due to the lack of CTLA-4 protein. As anticipated, the clinical phenotypes of CTLA-4 insufficiency and LRBA deficiency are similar. Main manifestations include hypogammaglobulinemia, lymphoproliferation, autoimmune cytopenia, immune-mediated respiratory, gastrointestinal, neurological, and skin involvement, which can be severe and disabling. The rationale of this clinical trial is to improve clinical outcomes of affected patients by substituting the deficient CTLA-4 by administration of CTLA4-Ig (abatacept) as a causative personalized treatment.

Our objective is to assess the safety and efficacy of abatacept for patients with CTLA-4 insufficiency or LRBA deficiency. The study will also establish a CTLA4- and LRBA-specific disease-severity scoring system and investigate how treatment with abatacept affects the patients’ quality of life.

Methods

ABACHAI is a phase IIa prospective, non-randomized, open-label, single arm multi-center trial. Altogether 20 adult patients will be treated with abatacept 125 mg s.c. on a weekly basis for 12 months, including (1) patients already pretreated with abatacept, and (2) patients not pretreated, starting with abatacept therapy at the baseline study visit. For the evaluation of drug safety infection control during the trial, for efficacy, a newly developed CHAI-Morbidity Score will be used.

Results

The trial was fully recruited in March 2022; altogether 18 CTLA-4 and 2 LRBA patients were included.

Conclusions

The trial is registered in the German Clinical Trials Register (Deutsches Register Klinischer Studien, DRKS) with the identity number DRKS00017736. Final results of this clinical trial are expected for 2023.

Background and Aims

The Autoimmune Lymphoproliferative Syndrome (ALPS) is a rare genetic disorder with early-onset non-infectious non-malignant lymphoproliferative disease and autoimmune cytopenia. The main genetic defects involved in ALPS are mutations affecting the death receptor FAS or its ligand (FASLG). CASPASE 10 (CASP10) variants have been also described in ALPS patients, but their causal role remains debated given their high frequencies in the general population. The aim of this work was to elucidate the impact of those CASP10 variants on the apoptosis function of lymphocytes from healthy individuals.

Methods

By using the in-house IMAGINE- bioinformatic tool “Polyweb” (including more than 70 000 samples) we identified healthy carriers of CASPASE 10 mutations. By using a well described and routinely used apoptosis assays, we compared the apoptosis function in B-EBV and in activated T cells from healthy individuals carrying wild-type (wt) CASP10 or one of the 3 controversial CASP10 variants: p.401fs (c.1202-1208 del), p.Y446 (c.1337 A>G) and p.V410I (c.1228 G>A), either heterozygous or homozygous.

Results

The proportions of FAS- or TRAIL-sensitive lymphocytes were strictly similar between the CASP10 wt and mutated cells. Moreover, the apoptosis function remained totally preserved in lymphocytes carrying a homozygous deletion leading to a complete CASPASE 10 expression defect.

Conclusions

The results showed that CASPASE 10 is dispensable for the FAS- and TRAIL-induced apoptosis in lymphocytes from healthy individuals, thereby ruling-out a functional role of the previously described CASP10 variants in ALPS patients.

Background and Aims

SAVI (STING associated vasculopathy with onset in infancy) is an interferonopathy characterized by inflammation of several organs. SAVI is due to mutations in STING1, which codes for STING, whose activation by cytosolic dsDNA triggering the production of type-I interferon (IFN). These mutations lead to constitutive IFN signalling and sustained inflammation.

To better understand SAVI, we aim to define which pathways are dysregulated in PBMCs of patients and identified the ones that are under the direct and/or indirect control of this excessive and uncontrolled type-I IFN production. These dysregulated pathways could later be used for a better understanding of SAVI pathophysiology and open new areas of research and potential therapeutic treatments.

Methods

Two single-cell RNAseq datasets have been generated on PBMCs. A first dataset on SAVI patients revealed some cell-type specific molecular mechanisms of SAVI. A second dataset was created to establish the kinetic of response to type-I IFN: PBMCs from healthy blood donors were stimulated at several timepoints using IFNβ. The transcriptome from 100,000 single cells allowed us to identify the molecular pathways and transcription factors specific to IFN and compare them to SAVI patients.

Results

SAVI patients were found to have drastic lymphopenia, associated with a T cell hyperactivation, exhaustion and apoptosis. This T cell hyperactivation was not reproduced by type-I IFN stimulation. We also observed strong hyperinflammation in monocytes associated with ER stress.

Conclusions

Our results suggest an hyperinflammation of monocytes associated with cellular/ER stress which triggers T lymphocytes hyperactivation, senescence and apoptosis

Background and Aims

The Multisystem Inflammatory Syndrome in Children (MIS-C), is a serious inflammatory condition characterized by a systemic inflammation with multiorgan failure, that can occur in children and young adults after COVID-19 infection.

Ain of the study is to create an International multicenter collection of patients with MIS-C involving the main pediatric networks committed in the care of patients with hyperinflammatory conditions.

Methods

a steering committee constituted by representatives of ERN-RITA, PRES, ESID and ISSAID and with the coordination of PRINTO developed a shared form to collect clinical manifestations, laboratory features, response to treatment and outcome of patients with MIS-C. The registry is available online on PRINTO and ESID websites (www.printo.it , www.ESID.org).

Results

Currently, more than 1000 patients from 44 centers of 20 countries worldwide have been included in the study; completed data are available for 688 patients. 56 (8%) patients were younger than 2 years, 173 (25%) 2-6 years, 279 (41%) between 6-12 years, while 180 (26%) patients were older than 12 years. 234 (34%) patients required ICU admission; 51 (7.4%) patients presented long term sequaele and 7 (1%) patients died.

Mucocutaneous manifestation were observed in 85.2% of patients, hematological in 84.7%, gastrointestinal in 80.8%, cardiovascular in 52.3%, lymphoid organ in 51.7%, respiratory in 34.6%, musculoskeletal in 31.5%, neurological in 19%, genito-urinary in 10.9%.

576 patients (84%) recieved Ig infusions and 572 (83%) corticosterois; 78 (11%) were treated with biologics.

Conclusions

The first analysis confirms that MISC is a severe inflammatory condition, requiring anti-inflammatory treatment. Even if the mortality rate is low, one third of patients required ICU admission.

Background and Aims

Systemic lupus erythematosus is an autoimmune disease characterized by the production of antibodies against nucleic acids and an upregulation of type-I interferon in most patients. The etiology of the disease is unexplained in most cases but is thought to involve both genetic and environmental factors.

Methods

We selected from our national lupus biobank patients fulfilling at least one of the following criteria: (1) male patients, (2) onset of the disease < 12 years old, (3) family history of autoimmune diseases and we performed whole exome sequencing in 118 families using Illumina technology. We used in silico panels in a diagnosis-based approach and explore the whole data to identify new disease-causing genes.

Results

We identified pathogenic or probably pathogenic variations (according to ACMG classification) in genes related to inborn errors of immunity in 6 patients (ADAR, C1QA, PSTPIP1, IRAK4, PTPN11, COPA). A genetic diagnosis involving a gene never related to lupus (MAN1B1, ETV6, BAZ2B, IGHMBP2) was identified in 4 patients (3,3%). Ten percent of families present a variation of undetermined significance. Besides, the research approach revealed many candidate genes, among which SOCS1 and PTPN2 were confirmed as disease causing thanks to collaboration and functional studies.

Conclusions

This study confirms the interest of exome sequencing in preselected lupus patients with a diagnosis rate of 13% of monogenic SLE. It demonstrates the superiority of the exome over panel sequencing in lupus, with a genetic diagnosis in unexpected genes in 3,3% percent of cases and the possibility of discovery-based approaches.

Background and Aims

Mutations in RAC2, were first identified in neonates carrying RAC2 dominant negative, p.D57N, who presented with severe neutrophil defects and T-cell lymphopenia. Subsequently, dominant-activating mutations were reported in patients with combined immunodeficiency/immunodysregulation (CIID) or SCID. We assembled an international cohort of 48 published and unpublished patients with RAC2 mutations to characterize the spectrum of disease.

Methods

Clinical and immunologic phenotypes of 48 germline-mutant RAC2 patients were obtained from referring physicians and literature reports. Heterologous expression assays including superoxide production, PAK1 binding, AKT activation were used to characterize RAC2 variant effects. Protein stability was determined by western blot.

Results

Patient presentation varied by mutation; five patients presented as SCID with reticular dysgenesis, five as neonatal neutrophil deficiency (D57N), and 38 as CIID. Patients with dominant, active RAC2 variants with high protein stability (Q61R, Q61K) presented in the first days of life with SCID and absent lymphocytes. Activating variants with lower stability (I21S, E62K, N92K, N92S) presented as CIID with lymphopenia, detectable by newborn screening but presenting later with recurrent sinopulmonary and viral infections. A third class of mutations with unstable transcript or protein were phenotypic only in homozygosity (W56*, R68W). Severity of phenotype and initial clinical presentation was correlated with protein stability - increased stability led to neonatal presentation and dominant mutations with decreased stability had later clinical onset.

Conclusions

Clinical presentation of RAC2 mutation-bearing patients is determined by a combination of protein activity and stability. Heterologous expression and analysis is useful for deciphering the molecular basis of the clinical phenotype.

Background and Aims

Biallelic mutations in lipopolysaccharide responsive beige-like anchor protein (LRBA) lead to a severe clinical syndrome presenting with immunodeficiency and immunodysregulation. Previously, we suggested reduced autophagy as the biological cause for the aberrant humoral response in LRBA-deficient patients; however, the molecular mechanisms and its impact on autophagy-dependent immune functions remained unknown.

Methods

Hence, we screened for LRBA-interacting proteins using in silico and proteome-wide approaches.

Results

We found that LRBA interacts with the phosphoinositide 3-kinase regulatory subunit 4 (PIK3R4) and the FYVE And Coiled-Coil Domain Autophagy Adaptor 1 (FYCO-1). Interestingly, both proteins play essential roles during early and late autophagy, respectively. Specifically, PIK3R4 facilitates the production of phosphatidylinositol-3 phosphate (PI(3)P) and thereby the recruitment of DFCP-1 and WIPI2. In fact, LRBA-KO cells showed impaired production of PI(3)P leading to reduced autophagosome formation. In addition, blockade of the autophagosome-lysosome fusion and accumulation of enlarged autophagosomes, accompanied by an atypical lysosomal positioning, were observed in LRBA-KO cells; possibly due to loss of LRBA-FYCO1 interaction. Immunologically, we observed that accumulation of enlarged autophagosomes led to an enhanced antigen presentation and a strong T-cell response. Noteworthy, autophagy is a major intracellular degradation system that delivers cytoplasmic proteins to lysosomes for MHC class II loading.

Conclusions

Taken together, our data suggests that i) LRBA is part of a large protein machinery serving at different stages of autophagy, and ii) loss of LRBA impacts the targeting of cytosolic antigens for autophagy degradation, enhancing antigen presentation. The latter could contribute to the exacerbated T-cell infiltration and autoimmune manifestations in LRBA-deficient patients.