Methyl-qPCR : a New Predictive Marker for Epstein-Barr Virus-associated Lymphoproliferations During Allogeneic Hematopoietic Stem Cell Transplantation

Scientific context Epstein-Barr virus has a causal role in the pathogenesis of multiple distinct lymphomas. Post-transplant lymphoproliferative diseases (PTLD) are the most frequent EBV-induced proliferations. PTLD after allogeneic stem cell transplantation has an incidence lower than 5% but may increase up to 10-20% in patients with established risk factors. EBV-DNAemia is predictive of EBV-PTLD and is routinely performed using qPCR on whole blood. Preemptive therapeutic strategies with anti-CD20 antibody are used when patients are above a defined EBV-DNAemia threshold. This approach remains limited since it does not discriminate between an EBV-induced lymphoproliferation (latent cycle) and/or a replicating virus (replicative cycle). Epigenetic modifications plays a central role in regulating the switch from latent to lytic gene expression. Specific DNA modifications can be regarded as molecular signatures for EBV genomes associated with the status of the viral infection (latent vs lytic). Accordingly, these signatures may be envisioned as a potent tool to characterize the state of the viral infection in vivo. Description of the project Our primary objective is to estimate the respective percentages of EBV-lytic and EBV-latent genomes (proliferating cells) in patients presenting with a high EBV-DNAemia after allogeneic stem cell transplantation HSCT by analysing the epigenetic modifications of EBV genome on specific sites. Our secondary objectives are i) to determine risk factors associated with each "latent versus lytic EBV" profiles and ii) to correlate the "latent versus lytic EBV" profiles with response to rituximab infusion and patient outcomes. For this purpose, a retrospective study (n=80) and a prospective study (estimation n=58) will be established. The different steps of this project are: 1. To study epigenetic modifications. The laboratory is developing a new approach to distinguish between latent and lytic genomes. 2. To realize quantitative analys