Study of Heart Transplant Rejection

Cardiac transplantation has been successful in improving survival in end stage heart failure. But graft rejection has limited survival after transplantation. In the first year, acute cellular rejection and infection remain the most common causes of morbidity and mortality. Afterwards, cardiac allograft vasculopathy (CAV), as a result of chronic vascular rejection, is the major cause of morbidity and mortality. Within the first year post-transplantation, almost two-thirds of recipients will experience at least one rejection episode. At five years post-transplantation, nearly 50% of survivors will have CAV. Clinically, the symptoms of acute rejection are relatively nonspecific (fatigue, dyspnea, fever). Most CAV patients remain asymptomatic until they develop serious problems such as myocardial infarction, heart failure, ventricular dysrhythmias or sudden cardiac death. Presently, the gold standard for diagnosing acute cardiac allograft rejection is right ventricular endomyocardial biopsy. This is an invasive method of diagnosis subject to morbidity and random sampling and interpretation error. Likewise, the gold standard for diagnosing CAV is cardiac catheterization with intravascular ultrasound, an invasive procedure also subject to morbidity. Noninvasive methods such as electrocardiography, echocardiography, and nuclear studies all have been studied, but have been unsuccessful, thus far, for either condition. Peripheral blood evaluations of cytokines and cytoimmunologic markers have also been unsuccessful in either condition. This clinical trial studies the feasibility of using functional genomics and proteomics to identify genes and proteins respectively that can serve as reliable biomarkers of acute cardiac cellular rejection and CAV. We plan to recruit subjects who are on the transplant waiting list. We will analyze the blood of these patients pre-transplant and serially post-transplant over one year and then regularly on a yearly basis. By correlating putative biomarkers with clinical, histological, and imaging based evidence of allograft disease we hope to build a database comprised of functional genomics, cytokine, cytoimmunologic and proteomics data relevant to the immunologic relationship between the donor organ and recipient. With this database we hope to obtain a minimal subset of differentially expressed genes, cytokines, cytoimmunologic and protein change profiles that is most predictive of both acute allograft rejection and CAV. This will eventually serve as the basis for a diagnostic blood test. Thus, with the application of functional genomics, cytokine, and cytoimmunologic analysis and proteomics we hope to derive a noninvasive method to detect both acute cellular cardiac allograft rejection and CAV, thereby minimizing the need for invasive methods of diagnosis. Further better understanding the genetic programs triggered and protein changes induced during rejection may lead to the identification of target pathways for developing new therapeutic approaches aimed at prevention.

Recently, several published reports have established that detection of donor DNA in recipient s blood can serve as a diagnostic tool of graft injury. The level of donor DNA measured as percentage of circulating cell-free donor DNA (%ccfdDNA) accurately diagnoses acute rejection with a high sensitivity and specificity, at times several months before the diagnosis by examining endomyocardial biopsies. The ability of cell free DNA to diagnose graft injury early opens a new window to re-examine markers of rejection. These markers are traditionally evaluated using biopsy results, often positive late during rejection. %ccfdDNA offers an opportunity to better characterize our analyses.