Epstein-Barr virus EBNA1 IgA as a biomarker in nasopharyngeal carcinoma risk prediction

University Of Pittsburgh At Pittsburgh, Pittsburgh PA

Investigators

Abstract

ABSTRACT Southeast Asian and immigrant Chinese communities across the globe have disproportionately high NPC incidence, averaging 25-30 times higher than the general population in neighboring areas. EBV infection is extremely common and more than 95% of adults have seroconverted, but only a subset of chronic carriers will develop EBV-associated nasopharyngeal carcinoma (NPC). Latent and clonal EBV infection occurs in the tumor cells, and a variant of a key EBV protein (EBNA1 Val487) required for co-infection with the host has been identified as a cancer risk-variant because it is found in nearly all (98.8%) NPC tumors from NPC-endemic areas. Both EBV serology and EBV DNA sequencing are informative. Early detection screening programs by one of two screening methods (IgA serology, or next-gen sequencing of plasma cell-free EBV DNA) have been recommended for NPC-endemic populations. However, the screening time-interval for routine early detection is not known. A biomarker that can identify high-risk individuals several years before clinical onset would greatly benefit from an early detection screening program. Antibodies to EBV proteins rise several years before NPC onset. IgA serology is a sentinel for aberrant EBV infection at mucosal sites. We previously surveyed EBV IgA/IgG/IgM serology from the serum of incident NPC cases in a Singapore prospective cohort (discovery cohort) and tested the leading biomarker (EBNA1 IgA) in an additional validation cohort from Shanghai, China. The sojourn time for the custom EBNA1 IgA assay was 4 years before NPC diagnosis (100% sensitivity, 100% specificity in 20 case-controls). False-positives emerged in the expanded control samples which is likely attributed to periodic EBV reactivation but background signal could be minimized by removing cross-reactive epitopes yielding a satisfactory EBNA1 IgA assay (93.7% specificity at 100% sensitivity). Following on from the case-control study performed on a low-throughput but highly accurate multiplex immunoblot assay, the goal of this proposal is to develop a high-throughput EBNA1 IgA assay using a prototypic slot blot assay and applying the principles from EBNA1 mapping studies. By leveraging EBV serology, this work is expected to produce a high-throughput assay for NPC risk assessment. Identified high-risk individuals would benefit from an NPC early detection screening program and/or clinical follow-up.