Analysis of Epstein-Barr virus infection in nasopharyngeal biopsies from a group at high risk of nasopharyngeal carcinoma.

Although Epstein-Barr virus (EBV) is consistently associated with the epithelial malignancy nasopharyngeal carcinoma (NPC), it is not clear to what extent the normal virus carrier state involves infection of nasopharyngeal epithelium. We attempted to examine this question by screening 26 nasopharyngeal punch biopsies from EBV-carrying Chinese Malaysians who had presented with clinical symptoms possibly indicative of NPC, but in whom histological analysis of an adjacent biopsy had revealed no evidence of tumour. Assays included (i) in situ hybridization with 35S-labelled riboprobes specific for EBERs (rather than with BamHI W DNA probes which can give false-positive results); (ii) cDNA amplification across defined splice junctions of the EBNA1 and BamHI A transcripts expressed in latently-infected NPC cells and of the BHRF1 lytic-cycle transcript; and (iii) immunostaining for the immediate early lytic-cycle protein BZLF1. Of the 26 biopsies examined, all 23 showing normal nasopharyngeal histology were consistently negative for both latent and lytic-cycle markers. The other 3 cases were all positive for EBNA1 and BamHI A transcripts; these RNAs were almost certainly of tumour rather than normal-cell origin since these particular biopsies were the only ones to reveal localized foci of EBER-positive NPC cells; such biopsies were again negative for lytic-cycle markers. We provisionally conclude that EBV infection of the normal nasopharynx is not a regular feature of the virus carrier state and that screening nasopharyngeal biopsies for viral RNA markers of the latent cycle could be useful in NPC diagnosis.