Introduction: Kawasaki Disease (KD) is a multi-system vasculitis leading to coronary artery damage. Previous work has shown that co-stimulatory signals can rescue a subset of superantigen (SAg) reactive T-cells from apoptosis and one of the major pathways responsible for delivery of this co-stimulatory signal is CD28 signaling on T-cells. Lactobacillus casei cell wall extract (LCWE) contains a SAg among its active ingredients, leading to induction of coronary arteritis in mice that closely resembles human KD.
Methods: Flow cytometry was used to measure the expression of pro-survival molecules and markers of apoptosis. In vivo studies were performed with C57BL/6 mice (4-5 weeks) injected i.p. with either LCWE, or LCWE and anti-4-1BB or Isotype control antibody. Cardiac tissue isolated, processed, stained and scored as per protocol. Gene expression analysis in KD patients was performed using the Illumina HumanHT-12v4.
Results: Despite the fact that SAg-activated T-cells undergo apoptosis and are deleted, T-cells persist and are central to ongoing inflammation in affected arteries. Stimulation of CD28 leads to upregulation of pro-survival molecules cFLIP and BCLxL and reduction of caspase 3-annexinV double positive cells (markers of apoptosis) after SAg-stimulation, as detected by flow cytometry. In animals co-injected with anti-4-1BB (co-stimulation agonist), the incidence of coronary arteritis was dramatically increased to 94% compared to 54% with LCWE alone. Analysis of gene expression profile from 171 children with KD show elevated levels of molecules specific to the CD28 signaling cascade through Grb2, and VAV1 leading to the upregulation of Rac1 and CDC42, together with upregulation of pro-survival molecules cFLIP, MCL1 and NAIP. Interestingly, increased expression of cell survival molecules was associated with IVIG failure, with statistically significant elevation of NAIP and CDC42 and a trend towards increased expression for cFLIP and MCL, in IVIG non-responders compared to responders.
Conclusions: Enhanced co-stimulation contributes to T-cell survival after SAg-stimulation leading to persistent coronary artery inflammation and poor treatment response in KD.