Abstract 18729: Serum Heat Shock Protein-70 is Associated With Decreased Frequency and Severity of Cellular Rejection in Cardiac Transplant Patients

Abstract

Background: Heat Shock Protein-70 (HSP70) is a highly conserved intracellular protein that is up-regulated in cells undergoing stressful stimuli. A recent study demonstrated an inverse relationship between HSP70 expression and cellular rejection grade in endomyocardial biopsies (EBx)from cardiac transplant patients. Peripheral blood based HSP70 levels have not been studied in such individuals. We hypothesized that serum HSP70 levels will be associated with severity of cellular rejection in cardiac transplant patients. Methods: 177 cardiac transplant patients (56 ± 13 years; 8.5 ± 5 years mean time from transplant) were recruited from the Emory Cardiovascular Biobank from 2004-2012. Cellular rejection was defined based on revised International Society of Heart and Lung Transplant (ISHLT) grade of 1R or higher seen on EBx. Frequency of rejection was collected from time of transplant to enrollment date. Serum HSP70 was measured using ELISA and analyzed as detectable vs non-detectable. Nonparametric correlations and ANOVA were used to study univariate relationships while linear and ordinal logistic regression (adjusted for age, gender, race, length of time since transplant, and immunosuppressant medications) were performed to analyze the relationship between HSP70 levels and frequency and severity of cellular rejection respectively. Results: HSP70 was detectable in 35% of patients with grade 0R ISHLT class, 33% for grade 1R, 16% for Grade 2R, 0% for Grade 3R (p for group=0.005). There was an inverse correlation between HSP70 and frequency of rejection (r= -0.2, p= 0.03) with 34% of those with detectable HSP70 in the lowest quintile based on frequency of rejection whereas 9% was detected in the highest quintile (p=0.019). In adjusted regression models, HSP70 remained a significant independent predictor of a) ISHLT class with an OR of 0.43 (p=0.02) and b) frequency of rejection (β=-1.5, p=0.05). Conclusion: Detectable serum HSP70 is associated with decreased frequency and severity of cellular rejection in post cardiac transplant patients. The utility of HSP70 as a marker of graft function needs further study.