POS0072 COMPREHENSIVE IMMUNE PROFILING OF 20 CHILDREN WITH MULTISYSTEM INFLAMMATORY SYNDROME
Authors: M. Zajc Avramovic, N. Emersic, A. N. Kopitar, M. Korva, T. Avsic-Zupanc, A. Ihan, T. Avcin
Journal: Annals of the Rheumatic Diseases (2021)

Background: Multisystem inflammatory syndrome in children (MIS-C) is a rare complication of SARS-CoV-2 infection in the pediatric population, caused by extensive activation of immune system. The understanding of the distorted immune response is still in the early stages. Objectives: To analyze comprehensively immune profile in MIS-C patients including detailed serologic response to SARS-CoV-2 in comparison with control groups. Methods: Blood samples of consecutive MIS-C patients were collected at admission. Flow cytometric analysis of all lymphocyte populations including T and B cell differentiation was performed. Immunophenotyping was performed by six-color panels for the detection of lymphocyte subpopulations. Anti-SARS-CoV-2 specific antibodies were measured in the patients serum. The IgA and IgG antibodies against S protein, the IgG S1 and S2 specific antibodies, antibodies against nucleoprotein and neutralising antibodies were measured. Patients were assessed for a wide range of auto-antibodies, namely ANA, anti-ENA (Jo-1, PL-7, PL-12, SRP, Mi-2, Ku, Pm/Scl 100, Scl-70), myositis specific antibodies (EJ, MDA-5, TIH-Y, Ro52, SAE-1, SAE-2, NXP-2), anti-dsDNA, anti-phopholipid antibodies (aCl IgA, IgG, IgM, antiβ2GPI IgG, IgM) and ANCA. Control groups to compare specific antibody response consisted of 14 healthy children and 19 healthy adults, who had SARS-CoV-2 infection in the last 2 months. Results: Samples of 20 patients were included (14/20 boys, median age 12.4 years). Patients had higher percentage of double negative T cells and low numbers of of cytokine producing T cells Th1, Th2 and Th17. . Numbers of immune competent and CD21+ transitional B cells were also lowered. All patients had positive antibodies against SARS-CoV-2 including neutralising antibodies. Nine (9/19; 47 %) patients had high titer (≥1:160) of neutralising antibodies. Results were compared with 2 control groups; 14 healthy children (7/14 boys; median age 8 years,) and 19 healthy adults, who all experienced SARS-CoV-2 infection in the last two months. Patients with MIS-C had significantly higher levels of anti-S IgA (p&lt;0.0001), patients with MIS-C and healthy children had significantly higher titers of anti-S1 (p=0.001) and significantly lower titers of anti-S2 (p=0.016) in comparison to adults (Figure 1). No differences were found in the titers of neutralising antibodies and anti-N antibodies. All patients were ANA negative, 19/20 patients were anti-ENA negative, whereas 1 patient had anti-Ro antibodies in low titre. Three patients had aCL IgG in medium titre and 2 patients anti-beta2GPI IgG in low titre. Patients were negative for all other autoantibodies. Conclusion: The immune response in MIS-C patients is specific with most prominent differences in elevated percentage of double negative T cells and low numbers of Th1, Th2, Th17 and CD21+ transitional B cells. MIS-C patients have distinct serologic response with high anti-S IgA, high anti-S1 and low anti-S2 titres. Figure 1. Antibody titres in patient group and control groups. Mean value with SEM s shown. Disclosure of Interests: None declared.