Search

Epstein-Barr virus (EBV) is the cause of infectious mononucleosis and is associated with a variety of life-threatening diseases in humans. Therefore the development of an effective vaccine is an important objective. Many of the initial studies of vaccine efficacy analyse the ability of vaccine preparations to prevent the induction of lymphomas in cottontop tamarins by the B95-8 strain of EBV. We used a vaccinia virus recombinant expressing gp340, vMA1, tested previously in the cotton-top tamarin, to evaluate a common marmoset model in which the challenge virus, M81, resembles more closely the wild-type strains of EBV in the general population than does the standard B95-8 strain. We characterised the M81 strain of EBV with respect to the sequence of its gp340/220 gene and in regard to the presence of a region deleted in B95-8. Replication of the challenge virus in the group vaccinated with vMA1 was decreased when compared to control groups.

Anti-Epstein-Barr Virus (EBV) vaccines are being developed which are based on the gp340/220 membrane antigen (MA) gene products from the B95-8 strain. Some proteins are known to be immunologically quite different between type-A (1) and type-B (2) strains of EBV and therefore from a vaccine point of view it was critical to evaluate the degree of conservation of gp340/220. The complete MA coding sequence was determined for two B-type viruses, AG876 and P3HR-1, for comparison with the A-type B95-8. A variable region within MA was sequenced from several other strains. In addition the other open reading frames within the MA-containing BamHI-L fragment of AG876 were sequenced and compared. The results show that there is a high degree of homology between all strains examined. Although some differences were found within the MA coding sequence the only major site of variation was within the repeat region and no consistent A/B changes were found. Monoclonal antibodies generated against A-type MA and representing six epitope groups along the length of the gp340 molecule were found to recognize B-type gp340, thereby demonstrating functional homology. We conclude that, as a vaccine antigen, B95-8 gp340/220 should be equally effective against both types of EBV.

The association between EBV and nasopharyngeal carcinoma (NPC) has been well documented although the precise role of the virus in the genesis of the tumour is not understood. We undertook this study to examine the prevalence of EBV infection in nasopharyngeal tissue obtained from 33 healthy individuals not considered to be at risk of developing NPC. Using polymerase chain amplification (PCR) and in situ hybridization we have identified EBV DNA in 70% (23/33) of the tissues examined. Our data demonstrate that EBV is present at the site of tumour development in the low-risk population and by inference that the virus is also present before the onset of disease in the high-risk group. This survey supports the concept of NPC pathogenesis as a multifactorial process.