Identification of rare Epstein-Barr virus infected memory B cells and plasma cells in non-monomorphic post-transplant lymphoproliferative disorders and the signature of viral signaling.

BACKGROUND AND OBJECTIVES In early and polymorphic post-transplant lymphoproliferative disorders (PTLD) Epstein-Barr virus (EBV), through its latency proteins, drives the proliferation of B lymphocytes, a process which in immunocompetent individuals leads to the establishment of latently infected memory B cells. DESIGN AND METHODS We analyzed 11 cases, which included early and polymorphic PTLD, and 12 controls for latency of EBV infection and their antigenic profile. RESULTS We identified a minority of terminally differentiated EBER+ IRTA1+ memory B cells and EBER+ CD138+ PRDM1+ plasma cells in these samples. These elements were identified both in PTLD and in tumor-free tonsils from post-transplant patients but not in EBV- control tonsils. The expression of EBV latency proteins is heterogeneous, and is associated with activation of the NF-kB pathway. EBV signaling (through EBNA2, LMP1 and LMP2A) and NF-kB activation correlated with upregulation of target proteins: cMYC, JunB, CCL22, TRAF1 and IRF4. EBV-infected lymphocytes in early and polymorphic PTLDs represent a mixture of latencies II, III and, in at least 1/3 of infected cells, of latency 0. INTERPRETATION AND CONCLUSIONS EBV infection correlates with NF-kB activation, with EBV-dependent cell signaling, and lastly, with the presence of EBV-infected plasma cells and memory cells.