Background: EBV infection and post-transplant lymphoproliferative disorders (PTLD) are life-threatening complications of pediatric solid organ transplantation (Tx). The risk for PTLD varies by transplanted organ, with pediatric heart chronic high EBV load (HVL) carriers displaying a higher incidence of PTLD than pediatric liver HVL carriers (45% vs 3%). Previously we reported the presence of exhausted EBV-specific CD8⁺ T cell phenotypes, the increase in effector memory CD8⁺T cells paralleled by the loss of the naïve subset in the heart HVL carriers and not in liver HVL carriers, suggestive of different cellular mechanisms of viral control in the two settings. Therefore, we pursued transcriptomics on circulating CD8⁺ T cells to elucidate the pathways involved in EBV viral control after pediatric heart and liver Tx.

Methods: We defined HVL as detection of > 16,000 EBV genomic copies/mL blood with the qPCR assay at our institution. Previously banked 20 PBMC samples from EBV-load matched heart and liver Tx recipients were FACS-sorted to obtain CD8⁺ T cell. RNA expression was performed with Affymetrix® gene array kit and signals were processed with transcriptome analysis console. Differently expressed genes with fold change >2 and FDR p-value <0.05 were further analyzed by ingenuity pathway analysis (IPA) software, with p-value<0.01 and activation Z score>2 considered to be significant.

Results: We identified 625 differentially expressed genes in paired comparison between heart HVL (n=3) and Liver HVL (n=3) carriers. Upstream analysis algorithms identified activated molecules such as TLR3, STAT1, IFI16 by both measurement and prediction with inhibition of STAT3 and RELA in their downstream cascades in the heart HVL compared to liver HVL carriers.

Conclusion: Our results suggest a potential differential role for elevated types of EBV dsRNA binding to TLR3, with down-steam imbalanced signals via STAT1/STAT3. These may explain, in part, the failure of EBV protective memory development due to STAT3 impairment, leading to chronic memory phenotypic changes and subsequent CD8⁺ T cell exhaustion in the heart HVL carriers.

CITATION INFORMATION: Yamada M., Macedo C., Gu X., Michaels M., Green M., Nguyen C., Chandran U., Feingold B., Mazariegos G., Metes D. Detection of Different Gene Expression Profiles in CD8⁺ T Cells from Chronic High EBV Load Carriers after Pediatric Heart and Liver Transplantation Am J Transplant. 2017;17 (suppl 3).

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