Pattern of Epstein-Barr virus infection in human tonsils

Motta, James David (2008) Pattern of Epstein-Barr virus infection in human tonsils. (MSc(R) thesis), Kingston University, .


Epstein-Barr virus (EBV) is a B-cell tropic herpesvirus which infects over 90% of the adult population worldwide without causing disease in the vast majority. It has the remarkable ability to persist for the lifetime of the infected host, in the face of a competent immune system. It has been proposed that the oropharyngeal epithelium plays a central role in viral persistence and replication and that the site of latency is a resting B cell that evades the immune response by expressing very limited viral proteins. However, demonstration of EBV in non-malignant epithelial has never been satisfactory demonstrated. Our objective was to study EBV latency by sectioning and screening entire tonsils to determine the distribution and cellular tropism of EBV in non-malignant tissues. We examined a total of 2136 sections from tonsillectomies of four patients aged between 19 and 43 years. Although human tonsils have been previously examined, sequential analysis of entire tonsils has never been studied. The cellular localisation of EBV-infected cells was determined using specific non-isotopic in situ hybridisation (NISH) procedure; digoxigenin labelled anti-sense oligonucleotides corresponding to sequences in two low molecular weight RNA probes: EBER-l and EBER-2. A morphologically distinct EBV¬RNA hybridisation signal was detected in scattered cells throughout the tonsils. As expected, EBER-positive signals were noted in lymphoid cells. More importantly, we also saw EBV¬positivity in epithelial cells. This is, to the best of our knowledge, the first report showing the presence of EBV in non-malignant epithelial cells and warrants re-examination of the role of these cells in EBV latency and persistence in healthy individuals. These findings may also shed light on the relationship of the virus to EBV-associated epithelial malignancies such as nasopharyngeal carcinoma.

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