Persistence of Epstein-Barr virus in salivary gland biopsies from healthy individuals and patients with Sjögren's syndrome.

Salivary gland biopsies from 12 patients with primary Sjögren's syndrome and 10 controls were examined for Epstein-Barr virus (EBV) DNA by in-situ hybridization and for EBV proteins by immunofluorescence and peroxidase techniques. Viral DNA was found in biopsies from two out of 12 patients with primary Sjögren's syndrome and six out of the 10 controls. The DNA and early antigen were in epithelial cells lining the ducts and acini, early antigen expression being limited to the luminal side of the epithelium. In eight biopsies studied with other antibodies, membrane antigen was identified in both acini and ducts but viral capsid antigen and Epstein-Barr nuclear antigen were not detected. EBV was found in biopsies from five of the controls without inflammation or Class II expression. This suggests that, in health, persistence and replication occur without inducing an immune response, possibly due to the restricted expression of early antigen on the luminal of the epithelium, away from immune surveillance. The inflammation in Sjögren's syndrome could be due to a breakdown of this unusual mechanism for viral persistence leading to a vigorous immune response to the virus. However our study provides no evidence to suggest that EBV infection load is increased in this disease.