EBV load in whole blood correlates with LMP2 gene expression after pediatric heart transplantation or allogeneic hematopoietic stem cell transplantation

BACKGROUND Epstein-Barr virus (EBV) is associated with posttransplant lymphoproliferative disease (PTLD), and EBV load measurement is an important tool to monitor transplant patients. Although EBV DNA quantification has high sensitivity to identify patients at risk for PTLD, it lacks specificity. We examined whether EBV gene expression in peripheral B cells can increase specificity or correlates with EBV load. METHODS Altogether, 220 blood samples were collected from pediatric patients after heart transplantation (HTx, n=57), renal transplantation (n=1), or hematopoietic stem cell transplantation (n=21). In each blood sample, EBV load was quantified in whole blood, plasma, and B cells using qPCR. Additionally EBV gene expression (EBNA2, LMP1, LMP2, and BZLF1) in B cells was analyzed using relative quantitative RT-qPCR. RESULTS Positive expression of at least one gene was detected in 112 (51%) of 220 samples. Patients with PTLD or chronic high viral loads after solid organ transplantation exhibited no homogeneous EBV gene expression pattern. Expression of LMP2, LMP1, or EBNA2 was only observed when EBV load exceeded 1000 copies/mL. A high correlation between the level of LMP2 expression and EBV load in B cells or whole blood was observed (ρ=0.72 or ρ=0.6, HTx population). CONCLUSION The analysis of EBV gene expression in peripheral B cells does not provide additional information about patients' risk of developing PTLD. As EBV load in whole blood correlates well with LMP2 gene expression in EBV-infected B cells, EBV DNA quantification in whole blood alone seems to be a sufficient tool to monitor these patients.