Children undergoing heart transplantation are at risk of developing rejection. Rejection is the process by which the body’s immune system attacks the donor heart, which may lead to heart failure and sometimes death. To help reduce the risk of rejection, all transplant recipients must take medications to suppress their immune system. Currently, the best way of diagnosing rejection is with a heart catheterization procedure that involves taking a heart biopsy (collecting tissue samples). Catheterization based procedures are costly and have associated risks. Our goal is to develop a blood test that reliably identifies the presence of rejection in children without the need for a catheterization procedure. Our proposal focuses on collecting blood at the time of a heart biopsy and using that blood sample to perform an analysis on genes regulating the immune system. The results of the analysis are then compared to the results of the heart biopsy. The presence of rejection should be identified by a specific pattern of activation in immune related genes. Other advantages of our proposed study are that it may help identify children at risk of developing rejection, it may help monitor the treatment of rejection, and it may expand our knowledge and understanding of the mechanisms involved in rejection.

Development of graft rejection after cardiac transplantation is a key clinical issue. Acute cellular rejection affects 20% to 40% of patients in the first year after transplantation, and acute antibody-mediated rejection occurs in 10% of cases. Chronic rejection is a multifactorial process that manifests as cardiac allograft vasculopathy and accounts for 30% of recipient deaths. Cardiac catheterization with coronary angiography and myocardial biopsies is currently the gold standard for diagnosing and classifying rejection. However, catheterization may underdiagnose rejection, and it is an invasive procedure with associated complications. Gene expression studies have been investigated in adults for rejection surveillance, which yielded poor sensitivity or required invasive tissue samples. Furthermore, there is limited reported data on transcriptional analysis as a marker of rejection in the pediatric heart transplant population. New measures are needed to define the immune states associated with pediatric heart transplantation, how they relate to immunosuppressive regimens, and whether they predict onset of rejection. We have developed a sensitive bioassay where subject plasma is used to induce transcription in a well-controlled peripheral blood mononuclear cell population. This technique has successfully been used to investigate inflammatory states in pediatric disease, such as Type 1 diabetes mellitus and inflammatory bowel disease.

Institutional Review Board approval has already been obtained, and subjects are actively being recruited. Subjects ages 0-17 undergoing cardiac catheterization after heart transplantation will have plasma samples collected. Patient plasma will be used to induce a transcriptional response in commercially available peripheral blood mononuclear cells. An analysis performed on 54,000 inflammatory and regulatory genes will determine if plasma-induced transcriptional signatures can identify rejection, stratify the risk of developing rejection, and demonstrate responsiveness to immune intervention.