196 - SPECIFIC LINEAR AMINO ACID MOTIF TARGETED BY KAWASAKI DISEASE PLASMABLAST DERIVED ANTIBODY

Background:

The cause of KD remains a mystery, but studies suggest it has an infectious origin. Plasmablasts are a subset of B cells that acutely respond to and are enriched for specific antibodies to a preceding illness or immunization. In prior studies, we showed that plasmablasts are elevated in KD in a similar fashion to other infections. We hypothesized that plasmablast derived antibodies that had characteristics of maturation against an infectious disease would be specific for the etiology of KD.

Methods:

Sequencing of heavy and light chains was performed with Human B cell Single Cell V(D)J Enrichment Kit by Chromium Single Cell Gene Expression (10x Genomics, Pleasanton, CA). Peptide screening was performed by interrogation of a peptide microarray (PEPperCHIP® Human Epitome Microarray), which includes 29,127 linear peptides printed in duplicate, 5,656 of which are human. We also examined interactions on full-length expressed proteins via HuProt array (CDI labs), a yeast-derived expression library of 23,059 human proteins.

Results:

Of 964 paired heavy and light chains from subject 24, we further characterized five (KD24-1, -29, -67, -377, -595) antibodies. These antibodies were chosen due to sequence characteristics consistent with response to an infectious agent: exhibited class switching, increased mutation rates, and targeted mutations (high replacement to silent ratios). Peptide array screens show antibody KD24-67 binds multiple peptides that all included an exact five amino acid linear sequence motif in common. On screening human protein expression arrays for autoantibody potential, KD24-377 showed a moderately specific target involved in facial morphology. KD24-67 showed one potential autoantigen target involved in T cell maturation.

Conclusion:

There is a potential for antibody responses to both autoantigens and prior infections during KD.

Ongoing work is directed at confirming these potential autoantigens. We are using Phip-SEQ to further assess targeting of the linear five amino acid sequence and to define potential infectious etiologies that led to this antibody response.