Demonstration of Epstein-Barr virus genomes, using polymerase chain reaction in situ hybridization in paraffin-embedded lymphoid tissues.

We used the polymerase chain reaction (PCR) in situ hybridization (ISH) (PCR-ISH) on sections of malignant lymphoma and nonspecific lymphadenitis to detect small amounts of Epstein-Barr virus (EBV), a DNA virus of the herpes virus family. We first surveyed the EBV DNA by Southern blot analysis and PCR, and then compared results of the two PCR/ISH methodologies with the results of simplified/sensitive ISH for the positive cases. The target of the simplified in situ (DNA-ISH) was a few copies of EBV DNA per cell, and the target of the sensitive in situ (RNA-ISH) was as many as 10(7) copies of EBV RNA per cell. When EBV DNA was detected by Southern blot, DNA-ISH, RNA-ISH and PCR-ISH all revealed EBV genomes. When PCR revealed only amplified EBV DNA, DNA-ISH showed no EBV genomes, but PCR-ISH and RNA-ISH showed EBV genomes in a few cells. When PCR showed no detectable amplified EBV DNA, all of DNA-ISH, RNA-ISH and PCR-ISH showed no genomes. These findings indicate that PCR-ISH consistently detected a few copies of the EBV virions. The PCR-ISH was as sensitive as RNA-ISH. The RNA-ISH could not detect virus if RNA was not expressed, but the PCR-ISH could detect virus without such expression. The ability to detect a single copy of a specific gene in situ has many advantages and multiple applications in molecular biology, pathology, and cell biology.