A protein epitope targeted by the antibody response in children with Kawasaki disease has been identified, according to study results published in The Journal of Infectious Diseases.

Kawasaki disease has clinical and epidemiologic features that may be infectious in nature, but the etiology of the disease is unknown. Identification of disease-specific antigens may help develop diagnostic tools and improved therapies.

Study researchers prepared monoclonal antibodies from peripheral blood plasmablasts isolated from children with Kawasaki disease for the identification of specific target antigens. Peripheral blood plasmablasts were isolated from 11 children with Kawasaki disease who were being treated at the Ann & Robert H. Lurie Children’s Hospital of Chicago, Illinois, 8 to 24 days after onset of fever. Clonally related plasmablasts (n=42 sets) were identified in 10 patients; the remaining patient did not have clonally related plasmablasts, but did have immunoglobulin A plasmablasts with many germline mutations.

Antibodies from the plasmablasts were screened against lung tissue from a child with Kawasaki disease; 10 monoclonal antibodies with strong positive staining were identified. When screened against a database of animal virus epitopes, binding to multiple similar peptides within the hepacivirus protein, nonstructural protein 4A was observed. Bioinformatic analysis identified a shared motif within the top peptide hits, which was reduced to an 8 amino acid epitope using an amino acid substation assay. This epitope did not match sequences from any known hepaciviruses.

Each of the 60 identified monoclonal antibodies was screened against a peptide containing the identified epitope in an enzyme-linked immunosorbent assay. The assay identified 5 antibodies, isolated from 3 patients, which reacted with the peptide. All 5 antibodies also exhibited positive immunohistochemical staining of Kawasaki disease inclusion bodies in ciliated bronchial epithelium. Preincubation of the tissue with the epitope-containing peptide blocked binding of the antibodies to inclusion bodies.

A western blot was performed to determine whether sera from 8 patients with Kawasaki disease and 17 control participants (aged 5-9 months) recognized the Kawasaki disease peptide. Compared with 0 infants in the control group, sera from 5 patients with Kawasaki disease (62.5%) recognized the Kawasaki disease peptide (P <.01).

Researchers acknowledged that the investigation of the immune response in patients from a single center in the United States may limit the generalizability of results to patients in other regions around the world; however, they also noted that the identified antibodies reacted with tissue samples from children with Kawasaki disease from other regions of US and Japan, and spanning multiple decades.

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“Here, we identified a peptide that is recognized by antibodies that develop during acute [Kawasaki disease],” the researchers concluded. “This is the first discovery of a specific antigen recognized by the immune response to [Kawasaki disease].”

Researchers posited that the etiologic agent of Kawasaki disease was likely to be viral in origin. Although the antibodies screened did not recognize epitopes present in any known hepaciviruses, they argued that this did not preclude the possibility of a novel hepacivirus as the source of the antigen. “Whether the protein epitope identified in this study derives from a previously unidentified virus remains to be determined,” they noted.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Rowley AH, Baker SC, Arrollo D, et al. A protein epitope targeted by the antibody response to Kawasaki disease [published online February 13, 2020]. J Infect Dis. doi:10.1093/infdis/jiaa066

This article originally appeared on Rheumatology Advisor