Fine specificities of natural regulatory T cells after IVIG therapy in patients with Kawasaki disease

Abstract

The activation of natural regulatory T cells (nTreg) recognizing the heavy constant region (Fc) of IgG is an important mechanism of action of intravenous immunoglobulin (IVIG) therapy in Kawasaki disease (KD). Lack of circulating Fc-specific nTreg in the sub-acute phase of KD is correlated with the development of coronary artery abnormalities (CAA). Here, we characterize the fine specificity of nTreg in sub-acute (2- to 8-week post-IVIG) and convalescent (1- to 10-year post-IVIG) KD subjects by testing the immunogenicity of 64 peptides, 15 amino acids in length with a 10 amino acid-overlap spanning the entire Fc protein. About 12 Fc peptides (6 pools of 2 consecutive peptides) were recognized by nTreg in the cohorts studied, including two patients with CAA. To test whether IVIG expands the same nTreg populations that maintain vascular homeostasis in healthy subjects, we compared these results with results obtained in healthy adult controls. Similar nTreg fine specificities were observed in KD patients after IVIG and in healthy donors. These results suggest that T cell fitness rather than T cell clonal deletion or anergy is responsible for the lack of Fc-specific nTreg in KD patients who develop CAA. Furthermore, we found that adolescents and adults who had KD during childhood without developing CAA did not respond to the Fc protein in vitro, suggesting that the nTreg response induced by IVIG in KD patients is short-lived. Our results support the concept that peptide epitopes may be a viable therapeutic approach to expand Fc-specific nTreg and more effectively prevent CAA in KD patients.

• Immunotherapy
• immune-regulation
• IVIG
• Kawasaki disease
• natural Treg

Acknowledgements

We thank DeeAnna Scherrer, Joan Pancheri and Erika Berry for technical assistance. The article is dedicated to the loving memory of Dr. Eli Sercarz, father of immune-regulation.

Declaration of interest

The authors have no financial conflict of interest. This work was supported by NIH R01 HL103536-01 to A.F. and J.C.B., a grant from UCSD – UL1 RR031980 to A.F., NIH iDASH grant U54Hl108460 to J.C.B.