Evidence for lytic infection by Epstein-Barr virus in mucosal lymphocytes instead of nasopharyngeal epithelial cells in normal individuals.
✍ Scribed by Qian Tao; Gopesh Srivastava; Alexander C. L. Chan; Lap Ping Chung; Shee Loong Loke; Faith C. S. Ho
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 989 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0146-6615
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✦ Synopsis
Normal nasopharyngeal tissues from 23 individuals who died of causes unrelated to the upper respiratory system and had no evidence of Epstein-Barr virus (EBV)-related diseases were studied using in situ hybridisation (ISH) and immunohistochemistry for the detection of EBV RNA and expression of EBV proteins, respectively. ISH using 35S-labelled riboprobe for EBV EBER RNA showed occasional to a few EBER+ lymphocytes in the stroma of nasopharyngeal mucosa in 14/16 cases with available paraffinembedded tissues. In addition, very rare intraepithelial EBER+ lymphocytes were also detected in 3/16 cases. However, in none of these cases was EBER detected in the epithelial cells. Similar results were obtained using a nonradioactive ISH method for EBER (Dako). In 3/23 cases, immunostaining using monoclonal antibodies for EBV proteins on cryostat sections showed occasional cells in the stroma expressing EBV nuclear antigen 2 (EBNA2), latent membrane protein-1 (LMP), and switch protein encoded by BZLFl gene (ZEBRA) in two cases and onlyvery rare LMP+ and ZEBRA+ cells in one other case. Double immunostaining combining alkaline phosphatase anti-alkaline phosphatase (APAAP) for CD markers and indirect im mu nofluorescence for LM P showed that the LMP+ cells were either CD19+ or less frequently CD3+, but none were CD68+. These results show that both B and T lymphocytes harbouring EBV can be found in the normal nasopharyngeal tissues. Interestingly, EBV proteins associated with lytic viral replication-diffuse early antigen (EA-D), viral capsid antigen (VCA), or membrane antigen (MA)-were also detected in rare cells in the stroma in one case, and in another case only one MA+ cell was detected. These results provide evidence for a lytic type of infection by EBV in the normal nasopharynx involving a very small proportion of stromal lymphocytes and support the view that nasopharyngeal lymphocytes can act as a reservoir for EBV in normal individuals. o 1995 Wi~ey-Liss, Inc.