Identification of Epstein-Barr Virus (EBV) lytic products involved in B cell-mediated immune evasion

Abstract

The Epstein-Barr virus (EBV), formally designated human herpesvirus 4 (HHV-4) - is a ubiquitous virus that causes lifelong latent infection in over 90% of the world's human adult population. EBV infection is regarded as carcinogenic to humans and associated with a variety of human cancers, especially endemic Burkitt Lymphoma (BL) and nasopharyngeal carcinomas (NPC). Following primary infection, EBV transiently runs a short lytic program before it establishes a predominant latent infection. Although the EBV oncogenic effects are mostly regarded to viral latency products, the viral lytic cycle plays pivotal roles in the development and maintenance of EBV-associated cancers, but its mechanisms remain largely elusive. EBV early lytic factors were found to target cell-surface and intracellular B-cell receptor (BCR) for ubiquitination and subsequently proteasomal degradation. Therefore, this study aims to investigate whether the expression of BZLF1 or BRLF1 early immediate genes by EBV impact the expression and/or activity of the B-cell receptor complex (BCR). EBV mutants lacking BZLF1 or BRLF1 early immediate genes will be produced by CRISPR/Cas9-mediated knockout in P3HR1 BL cell line. Changes in the levels of BCR and other associated proteins will be assessed by immunoblots. Once BCR downregulation is observed, phenotype rescue experiments will be performed by ectopic expression of either BZLF1 and BRFL1 early immediate genes in EBV-negative BL cell line BJAB. The data obtained will contribute to better understanding of possible EBV-mediated immunoevasion mechanisms during lytic reactivation and its implications for the pathogenesis of EBV-associated lymphomas. (AU)