CD8+ T Cell Transcriptional Profiles of Pediatric Heart Transplant Recipients That Carry EBV Loads in Peripheral Blood.

Abstract

Pediatric heart transplant (HTx) recipients display impaired CD8+ T cellular immune surveillance due to chronic immunosuppression and thus are at increased risk of EBV-associated post-transplant lymphoproliferative disorders (PTLD). Approximately 70% of asymptomatic pediatric HTx patients who seroconvert after HTx carry EBV loads in peripheral blood. One third of these patients display high chronic EBV loads (> 16,000 genomic copies/ml), and have up to 45% rate of progression to late onset PTLD. Here we used microarray analyses to investigate the hypothesis that CD8+ T cell transcriptional signatures are different between asymptomatic pediatric HTx patients that carry EBV loads vs. asymptomatic patients that do not carry EBV loads in peripheral blood. Six EBV seropositive asymptomatic, gender-, age-, and immunosuppression-matched pediatric HTx recipients were recruited to the study and consisted of: (i) undetectable viral load (UVL, n=2) carriers, resembling “normal” EBV latency; (ii) low viral load (LVL n=2) carriers; (iii) high viral load (HVL n=2) carriers. RNA was extracted from highly purified CD8+ T cells, amplified and hybridized to the Affymetrix H133 2.0 Plus Array. Perfect match data were normalized using the RMA method as implemented in BRB Array Tools. Differentially expressed genes were found for each comparison using the J5 test at threshold |J5|>12. Impacted pathways were studied using Pathway Express. Transcriptional signatures (transcripts, pathways, and networks) for pro-inflammatory cytokines and chemokines were significantly increased in CD8+ T cells from LVL and HVL carriers as compared to UVL carriers. In addition, CD8+ T cell from HVL carriers uniquely revealed up-regulation of transcripts relevant for apoptosis and for cross-talk to B lymphocytes, as well as macrophage-specific transcripts critical for cell migration and inflammation. These results indicate significant differences in the transcriptional profiles of CD8+ T cells from patients that carry EBV loads suggesting that these transcriptional signatures could be used as early surrogate biomarkers to monitor and assess patients at risk of complications that may benefit for prompt clinical intervention.