Kawasaki Disease (KD) is the leading cause of acquired heart disease in children in developed nations. KD can result in coronary artery aneurysms that can lead to lifelong heart disease, myocardial infarction, and death. The clinical and epidemiologic features support an infectious etiology in genetically susceptible children, but the cause has eluded more than 50 years of study. Delayed and missed diagnoses increase the risk of coronary artery aneurysms. The development of urgently needed diagnostic tests and improved therapies are dependent upon identifying the etiology. In preliminary studies, we analyzed the peripheral blood plasmablast response at 1-3 weeks after KD fever onset using single cell RT-PCR and made 60 monoclonal antibodies (Mab) from these plasmablasts. We used these Mab to determine their target antigens. We found that 32/60 Mab, derived from 9/11 KD patients, identify intracytoplasmic virus-like inclusion bodies (ICI) in ciliated bronchial epithelium of KD children but not infant controls. Using peptide arrays to identify binding epitope(s), amino acid substitution arrays, and ELISA, we found that 5 of the 32 (16%) Mab, derived from 3 KD patients with coronary artery aneurysms, recognize KD peptide epitope 1. KD peptide 1 completely blocks binding of these Mab to KD ICI, indicating that a protein with the binding epitope sequence is present in the ICI. Moreover, pre-treatment sera from 5/8 KD patients >day 8 after fever onset but 0/17 infant control sera have IgG antibody to the peptide epitope. We recently identified two additional epitopes using this approach that require further study. These findings support our hypothesis that at least a subset of KD cases results from infection with a presently unidentified, ubiquitous viral causative agent containing the KD peptide epitope 1 sequence. In this proposal, we hypothesize that identification of antigens targeted by the plasmablast response to KD can lead to identification of the etiology(ies) and development of KD serologic tests. To test these hypotheses, we will: 1) identify the specific proteins recognized by our panel of KD Mab that bind to KD tissues, 2) screen for additional antigenic targets recognized by the immune response to KD, and 3) evaluate the antibody responses of KD and control sera to KD antigens. Our findings will inform pathogenesis of KD, with the long-term goals of improving diagnosis and treatment of KD, enabling prevention, and reducing healthcare costs from the long-term consequences of coronary artery aneurysms arising in young childhood.
Kawasaki Disease (KD) is an increasingly recognized, potentially fatal illness of young childhood that is the most common cause of acquired heart disease in children in the developed world. The most likely cause is an infection in genetically susceptible children, but the etiology has eluded 50 years of study, hampering the development of a diagnostic test and specific therapies. We have found that children with KD make antibodies against a specific protein. In this proposal we will identify more proteins that children with KD make antibodies against, determine whether these proteins are all present in one causative agent of KD or in multiple different causes, and develop assays for specific antibody responses to KD. These studies could have a major impact on the field of pediatrics by enabling improved diagnosis, treatment, and prevention of KD.
