535 - Comparison of humoral immunity in Kawasaki Disease (KD) and COVID-19 related Multisystem Inflammatory Syndrome of Childhood (MIS-C)

Poster Number: 535
Publication Number: 535.327

Mark Hicar, Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, Buffalo, NY, United States; Sarah Baron, Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, Buffalo, NY, United States

Background:
Multisystem Inflammatory Syndrome of Children (MISC), a post infectious sequelae of SARS CoV-2 infection, shares enough features with Kawasaki Disease (KD) that some have postulated they share an immunologic basis. A number of studies have shown lack of cross-reactive antibodies in KD samples with SARS-CoV-2 proteins.

Objective: Due to the similarities in KD and MISC, we sought to further explore shared humoral immune response between these conditions.

Design/Methods: We used ELISA assays to delineate SARS-CoV-2 antibody responses, 10x genomics immune profiling with single-cell RNA seq to study the B cell compartment, and meme analysis to compare these sequences to other published SARS-CoV-2 antibody sequences.

Results:
In testing SARS-Cov-2 RBD and Spike antibody targeting on serial MISC samples, titers were higher than acute pediatric and adult cases. Stable antibody levels in pre-treatment, post-treatment and convalescence samples, relative to presentation of timing of MISC, support that there was a lack of ongoing viral replication in the MISC phase.  Pre-pandemic KD subjects had little cross-reactivity to SARS-CoV-2 proteins. The S2 region showed the most cross-reactivity which correlated with reactivity to the common cold coronavirus, OC43.  We then compared in depth antibody gene sequences from MISC, KD, and a child with acute SARS-CoV-2 (COVID) infection using 10x genomics. KD showed the most clonal expansions, and there were distinct V-J pairings shown. Detailing the plasmablast compartments using BLIMP-1 expression showed that COVID and KD both had two high expression clusters, but BLIMP-1 cells were more broadly distributed at lower levels in MIS-C. Eleven public clonotypes, antibodies from different individuals that share the same variable gene and are highly similar in their third complementarity determining region, have been described for SARS-CoV-2. To explore if our individuals had similar antibodies, we then compared the CDR3 usage in our samples using MEME analysis. Two such antibodies were identified in MISC and none in the KD. Compared more broadly to known published sequences, CDR3 sequence motifs were shown in seven instances in acute COVID-19, two instances in MISC, and none were shown in the child with KD. No shared clones were seen in KD when compared to samples from eight other children with KD.
Conclusion(s):
Overall, support for an antigen driven similarity in the immune response of KD and MISC is lacking, and distinct B cell compartment phenotypes support that KD and MISC are distinct entities.

B cell compartment comparison using 10x immune profiling and single cell RNAseqFigure, A) COVID and MISC have limited clonal diversity in Ig sequence in comparison to KD, which
shows high variability in clonotypes. B) MISC have very little Blimp1 expressing cells in all clusters