The Impact of Monitoring Epstein Barr Virus PCR in Paediatric Bone Marrow Transplant Patients: Can It Successfully Predict Outcome and Guide Intervention.

Epstein Barr Virus (EBV) associated Lymphoproliferative Disease (LPD) is a complication of allogeneic haemopoietic stem cell tranplantation (HSCT). In certain groups (congenital immunodeficiency, unrelated and mismatched donor transplants, T cell depletion) the risk may be as high as 25% with significant morbidity and mortality. Strategies to predict such illlness and allow early intervention have therefore assumed importance.

We have routinely screened peripheral blood of paediatric, transplanted patients by quantitiative PCR. We report the results of such analysis of 28 successive patients and the EBV serial quantitation in 4 patients with EBV LPD. The median age at time of transplant was 6.5 years. 17 patients received an unrelated donor transplant and one patient received a haplo-identical transplant. The remainder (n=9) received a matched family donor transplant. 23 patients received either Alemtuzumab (n=19) or ATG (n=4). 13 patients had leukaemia, 5 had mucopolysaccharide syndrome, 4 for congential immune deficiency and 6 for non malignant haeamtological conditions.

9 (32%) patients showed no evidence of EBV reactivation using serial PCR monitoring. 10 patients had low level EBV reactivation as defined with a PCR log[copy number] <4.5 copies/ml. 9 patients had a higher level of EBV reactivation. 2 patients had clinical EBV LPD and 2 additional LPD patients with LPD and with archived serial blood samples were also analysed.

All patients with clinical LPD fell in the high level reactivation group. All patients with high level reactivation had received either Alemtuzumab or ATG. Patients within this high level group with LPD had a higher PCR log value again than those without LPD (all patients with EBV LPD had levels > 6, whilst the highest level without disease was 5.2). All 4 patients responded to therapy for EBV LPD, with a combination of rituximab, withdrawal of immune suppression or administration of donor lymphocytes - DLI). At higher EBV levels the quantitative PCR had increasing positive predictive value for clinical LPD.

We therefore conclude that EBV serial quantitative PCR is useful in discriminating those who will develop LPD from those that will not. Our data suggest that it is possible to use EBV PCR quantitation further to discriminate asymptomatic EBV reactivation that will resolve without therapy from EBV reactivation that will require intervention. This prevents over exposure of patients to treatments (rituximab, DLI, immune suppression withdrawal) with significant associated toxicity (prolonged B cell aplasia, graft versus host disease).