DETECTION OF TRANSCRIPTS OF MAREKS-DISEASE VIRUS SEROTYPE-1 ICP4 HOMOLOG (MDV1 ICP4) BY IN-SITU HYBRIDIZATION

Homologues of herpes simplex virus ICP4 are important genes for the ac tivation of many herpesviruses. We detected transcripts of the Marek's disease virus serotype I homologue of ICP4 (MDV1 ICP4) by in situ hyb ridization (ISH). Using a digoxigenin-labeled-RNA (DIG-RNA) probe, MDV 1 ICP4 transcripts were detected in c.a. 90% of MDV1-infected chicken embryo fibroblasts (CEF) cells when cytopathic effect was reached to 9 0% of the CEF cells and in 0.35% of MDCC-MSB-1 (MSB-1) cells, at a fre quency similar to that for MD antigen-positive MSB-1 cells. Using the same in situ procedure, we detected abundant MDV1 ICP4 transcripts in the feather follicle epithelium (FFE) and some lymphoid cells in the l iver, kidney and peripheral nerve of infected chickens. The subcellula r localization of the transcripts appeared to vary: MSB-1 cells had th em in the nucleus, infected CEF cells and FFE had them in the nucleus and cytoplasm, and lymphoid cells contained them in the cytoplasm. The MDV1 ICP4 transcripts were also detected in the FFE and lymphoid cell s in the liver by reverse-transcriptase polymerase chain reaction (RT- PCR). Detection of MDV1 ICP4 transcripts by RT-PCR indicated the exist ance of MDV1 ICP4 transcripts-positive cells in these tissues. And the se data suggested that DIG-RNA-ISH can detect MDV transcripts on paraf fin sections and provide information about their subcellular localizat ion.