[Studies on tissue distribution and expression of Epstein-Barr virus using polymerase chain reaction]

Epstein-Barr virus (EBV), a widespread human herpesvirus, establishes a life-long carrier state after primary infection. It is known that EBV infects mainly B lymphocytes and oral epithelia in vivo. However, other potential sites of EBV latent and/or permissive infection in human body have not been fully clarified. To investigate this, systemic autopsied tissues from 18 EBV-seropositive individuals without apparent EBV-related diseases were examined for EBV genomic DNA and virus-specific mRNA, by using the polymerase chain reaction technique. EBV DNA was frequently detected in oral mucosa/tongue/salivary gland, esophagus, stomach, lymph node and spleen; less frequently in bronchi, lung, kidney, adrenal gland, bone marrow and small intestine. In contrast, liver, gall bladder, pancreas, colon, heart muscle and urinary bladder contained no detectable EBV DNA. Reverse transcription-PCR analysis revealed that the latent membrane protein (LMP) 2A gene was expressed in all lymph nodes of the three cases studied, with LMP2B and EBV-determined nuclear antigen (EBNA) 1 transcripts in the lymph node and the LMP2A transcript in the stomach of one case. EBNA2 and LMP1 mRNA were not detected in any of the tissue specimens. The immediate early Bam HI-Z open reading frame no. 1 (BZLF1) gene, a key gene for EBV replicative cycle, was also expressed in the lymph nodes, but not in the spleen nor the stomach. These results indicate that EBV preferentially resides in the upper gastrointestinal tract and lympho-hemopoietic tissues where the cells harbor functionally active viral genomes. Moreover, the selective expression of the viral latent infection genes may provide advantages for EBV persistence in the setting of a host immune response. In addition, the localized detection of BZLF1 mRNA suggests that lymph nodes are another possible site of EBV replication in the asymptomatic virus carrier state in vivo.