Epstein-Barr virus-specific T-cell response in pediatric liver transplant recipients: a cross-sectional study by multiparametric flow cytometry.

Background: Epstein-Barr virus (EBV) specific T-cell response measurement can help adjust immunosuppression in transplant patients with persistent infections. We aim to define T-cell responses against EBV in a cohort of pediatric liver-transplant patients.

Methods: Thirty-eight immunosuppressed pediatric liver-transplant patients (IP) and 25 EBV-seropositive healthy-adult controls (HC) were included in our cross-sectional study. Based on their EBV serological (S) and viral load (VL) status, patients were categorized into IP-S, IP-SVL and IP-SVL groups. T-cell response was assessed at two timepoints by stimulating cells with EBV peptides (PepTivator) and performing intracellular-cytokine and activation-induced marker staining. Background subtraction was used to determine EBV-specific T-lymphocyte frequency.

Results: Polyfunctional CD8+ T cells indicated previous EBV contact (IP-S 0.00% vs IP-S 0.04% and HC 0.02%; p=0.001 and p=0.01, respectively). Polyfunctional CD8+CD107a+IFNɣ+IL2-TNFα- profile was increased in serology-positive (IP-S 0.01% vs IP-S 0.13% and HC 0.03%; p=0.01 and p=0.50, respectively) and viral-load positive (IP-SVL 0.43% vs IP-SVL 0.07% and HC 0.03%; p=0.03 and p=0.001, respectively) patients. Central-memory cells were increased among serology-positive adults (IP-S 0.00% vs IP-S 0.13% and HC 4.33%; p=0.58 and p=0.002, respectively). At the second timepoint, IP-S patients remained negative (first visit 0.01% vs second visit 0.00%, p=0.44). On the other hand, IP-SVL patients had cleared viral loads and, subsequently, decreased polyfunctional CD8+CD107a+IFNɣ+IL2-TNFα- cells (first visit 0.43% vs second visit 0.10%, p=0.81).

Conclusion: Polyfunctional CD8+ EBV-specific T-cell response allows detecting EBV previous contact in liver-transplant children. %CD8+CD107a+IFNɣ+IL2-TNFα- is increased in patients with positive viral loads. Central memory CD4+ T-cell population more effectively determines prior EBV-exposure in adults.