Are Differences Between Pediatric EBV-Associated Lymphomas and Carriers Regarding Latency Profile and Microenvironment Composition Involved in Lymphomagenesis?

VISTAROP A; COHEN, M; JIMENEZ O; HUAMAN F; DE MATTEO E; PRECIADO MV; PAOLA ANDREA CHABAY

Madrid

Congreso; 22nd Congress of the European Hematology Association; 2017

Introduction: In Argentina, 90% of patients are seropositive for Epstein?Barr virus (EBV) by 3 years old, whereas EBV presence is statistically associated with Hodgkin lymphoma (HL) and Diffuse Large B cell lymphoma (DLBCL) in patients younger than 10 years, suggesting a relationship between low age of infection and B-cell lymphoma development. Aim: to compare viral latent proteins and microenvironment composition in EBV-associated lymphomas derived from the germinal center (GC) and post-GC with the same areas in tonsils from EBV carriers, to investigate whether an alteration of this scenario could be related to pediatric lymphomagenesis. Methods: formalin fixed paraffin embedded (FFPE) biopsy samples from 26 DLBCL, 55 HL and 41 tonsils from EBV carriers were analyzed. Immunohistochemistry for LMP1, EBNA2, CD4, CD8, Foxp3 and GrB, and EBERs in situ hybridization were performed. Positive cells were counted within EBV+ milieu. Results: Latency II pattern (LMP1+ EBNA2-) was predominant in HL (100%), DLBCL (55%), as well as in pediatric carriers (90%). CD4+ cell count displayed no differences between EBV+ and EBV- HL or DLBCL (p>0.05, Mann Whitney (MW) test), whereas statistically higher CD4+ cells were counted at the EBV+ GC in pediatric carriers (p=0.014, MW test). CD8+ cells did not exhibit statistical differences neither in EBV-associated lymphomas nor in benign conditions at the CG, and the same was observed for Foxp3 regulatory cells (p>0.05, MW test). In contrast, CD8+ cell count were statistically higher exclusively at EBV+ subepithelial region in tonsils, compared to EBV- (p=0.0039, MW test). Finally, higher cytotoxic activity evaluated by GrB expression displayed a trend in EBV+ DLBCL (p=0.057, MW test) but no in HL. In pediatric carriers, GrB did not shown differences in cytotoxic activity according to EBV presence at the CG (p>0.05, MW test). In fact, GrB cytotoxic activity was prevalent only at the EBV+ subepithelial region (p= 0.042, MW test). Conclusions: Latency II pattern prevails in both EBV-associated lymphomas and in EBV+ GC from carriers, indicating that LMP1 expression may collaborate in the lymphomagenesis process at the GC in pediatric patients from our country. Cytotoxic activity against EBV infection may be only relevant in DLBCL, and in EBV+ subepithelial regions in pediatric carriers, whereas in EBV+ HL is not increased, in contrast to previously described. CD4+T helper cell response plays a key role at the GC region in EBV carriers, by helping to the overall immune response in the control of viral infection and restricting latency expression to type II pattern, and ultimately, by limiting cell outgrowth. Failure in this process may trigger malignant transformation in pediatric EBV-associated lymphomas.