Evaluation of Autoantibody Binding to Cardiac Tissue in Multisystem Inflammatory Syndrome in Children and COVID-19 Vaccination-Induced Myocarditis

Abstract

Importance: Cardiac dysfunction and myocarditis have emerged as serious complications of multisystem inflammatory syndrome in children (MIS-C) and vaccines against SARS-CoV-2. Understanding the role of autoantibodies in these conditions is essential for guiding MIS-C management and vaccination strategies in children.

Objective: To investigate the presence of anticardiac autoantibodies in MIS-C or COVID-19 vaccine-induced myocarditis.

Design, setting, and participants: This diagnostic study included children with acute MIS-C or acute vaccine myocarditis, adults with myocarditis or inflammatory cardiomyopathy, healthy children prior to the COVID-19 pandemic, and healthy COVID-19 vaccinated adults. Participants were recruited into research studies in the US, United Kingdom, and Austria starting January 2021. Immunoglobulin G (IgG), IgM, and IgA anticardiac autoantibodies were identified with immunofluorescence staining of left ventricular myocardial tissue from 2 human donors treated with sera from patients and controls. Secondary antibodies were fluorescein isothiocyanate-conjugated antihuman IgG, IgM, and IgA. Images were taken for detection of specific IgG, IgM, and IgA deposits and measurement of fluorescein isothiocyanate fluorescence intensity. Data were analyzed through March 10, 2023.

Main outcomes and measures: IgG, IgM and IgA antibody binding to cardiac tissue.

Results: By cohort, there were a total of 10 children with MIS-C (median [IQR] age, 10 [13-14] years; 6 male), 10 with vaccine myocarditis (median age, 15 [14-16] years; 10 male), 8 adults with myocarditis or inflammatory cardiomyopathy (median age, 55 [46-63] years; 6 male), 10 healthy pediatric controls (median age, 8 [13-14] years; 5 male), and 10 healthy vaccinated adults (all older than 21 years, 5 male). No antibody binding above background was observed in human cardiac tissue treated with sera from pediatric patients with MIS-C or vaccine myocarditis. One of the 8 adult patients with myocarditis or cardiomyopathy had positive IgG staining with raised fluorescence intensity (median [IQR] intensity, 11 060 [10 223-11 858] AU). There were no significant differences in median fluorescence intensity in all other patient cohorts compared with controls for IgG (MIS-C, 6033 [5834-6756] AU; vaccine myocarditis, 6392 [5710-6836] AU; adult myocarditis or inflammatory cardiomyopathy, 5688 [5277-5990] AU; healthy pediatric controls, 6235 [5924-6708] AU; healthy vaccinated adults, 7000 [6423-7739] AU), IgM (MIS-C, 3354 [3110-4043] AU; vaccine myocarditis, 3843 [3288-4748] AU; healthy pediatric controls, 3436 [3313-4237] AU; healthy vaccinated adults, 3543 [2997-4607] AU) and IgA (MIS-C, 3559 [2788-4466] AU; vaccine myocarditis, 4389 [2393-4780] AU; healthy pediatric controls, 3436 [2425-4077] AU; healthy vaccinated adults, 4561 [3164-6309] AU).

Conclusions and relevance: This etiological diagnostic study found no evidence of antibodies from MIS-C and COVID-19 vaccine myocarditis serum binding cardiac tissue, suggesting that the cardiac pathology in both conditions is unlikely to be driven by direct anticardiac antibody-mediated mechanisms.

Figure 1.. Immunohistochemistry Images of Cardiac Tissue From Donor A Treated With Serum From Patients and Controls and Stained With Fluorescein Isothiocyanate (FIT-C)–Conjugated Antihuman Immunoglobulin G

Images were taken on wide-field microscope using a 20× (0.8 NA) objective. Cardiac tissue was treated with serum diluted at 1:50. MIS-C indicates multisystem inflammatory syndrome in children; PBS, phosphate-buffered saline.

Figure 2.. Immunohistochemistry Images of Cardiac Tissue From Donor B Treated With Serum From Patients and Controls and Stained With Fluorescein Isothiocyanate (FIT-C)–Conjugated Antihuman Immunoglobulin G

Images were taken on wide-field microscope using a 20× (0.8 NA) objective. Cardiac tissue was treated with serum diluted at 1:50. MIS-C indicates multisystem inflammatory syndrome in children; PBS, phosphate-buffered saline.

Figure 3.. Fluorescence Intensity of Fluorescein Isothiocyanate (FITC) Conjugated With Antihuman Immunoglobulin G (IgG), IgM, and IgA in Cardiac Tissue

Cohorts included 10 healthy prepandemic pediatric controls, 10 healthy COVID-19–vaccinated adults, 10 patients with COVID-19 vaccine myocarditis, 10 patients with multisystem inflammatory syndrome in children (MIS-C), 1 adult with myocarditis (positive control for immunoglobulin G [IgG]), 7 patients with adult myocarditis or inflammatory cardiomyopathy, and 2 to 4 phosphate buffered saline–negative controls. Only IgG measurements were taken for the adult myocarditis or inflammatory cardiomyopathy cases. No significant difference seen between MIS-C, vaccine myocarditis, adult myocarditis or inflammatory cardiomyopathy, and healthy pediatric and adult controls on Kruskal-Wallis analysis. PBS indicates phosphate-buffered saline.