Diagnostic utility of human cytomegalovirus-specific T-cell response monitoring in predicting viremia in pediatric allogeneic stem-cell transplant patients

BACKGROUND: Several studies proved that virus-specific T-cells play a pivotal role in controlling cytomegalovirus (CMV) infection in adult allogeneic hematopoietic stem-cell transplant (HSCT) patients. Fewer data are available in pediatric HSCT settings, when immature and inexperienced immune system may affect antiviral immune reconstitution. METHODS: We analyzed prospectively the CMV-specific T-cell reconstitution in a cohort of 31 pediatric allogeneic HSCT recipients at 30, 60, 90, 120, 180, and 360 days after HSCT. RESULTS: Depending on donor-recipient CMV serostatus, we observed distinct patterns and kinetics of CMV-specific T-cell immune reconstitution: during the early time-points, patients displayed a severe reduction in CMV-specific T-cell recovery in both CMV seropositive donor (D+) group and CMV seronegative donor (D-) on CMV seropositive recipients (R+). From day 90 onward, statistical significant differences in the profile of T-cell immune reconstitution emerged between D+ and D-. The pattern of immune reconstitution was characterized by heterogeneous kinetics and efficiencies: we report cases of: (1) spontaneous antiviral T-cell recovery with no previous viremia, (2) immune T-cell recovery anticipated by CMV viremia, and (3) no T-cell immune reconstitution despite previous viremia episodes. CONCLUSIONS: Given the heterogeneous scenarios of antiviral T-cell immune recovery in pediatric allogeneic HSCT, we conclude that the evaluation of the antiviral immune reconstitution is a promising and appealing system for identifying patients at higher risk of CMV infection. The use of interferon-γ ELISPOT test is a valid tool for immunological monitoring and predicting CMV viremia in pediatric HSCT.