Transcriptional Analysis of Marek's Disease Virus (MDV) Genes in MDV-Transformed Lymphoblastoid Cell Lines without MDV-Activated Cells

Abstract

Spontaneously activated MDV is rarely included in MDV-transformed cells, while it may influence the result of transcriptional analysis. A population consisting of 103 MDV-transformed cells probably did not include spontaneously activated MDV, since the estimated frequency of MDV-transformed cells including activated MDV was below 0.01% according to limiting-dilution polymerase chain reaction (PCR) and the presence of the major early antigen pp38 in 6 transformed cell lines. Reverse transcriptase-PCR (RT-PCR) products corresponding to ICP27, pol, TK, US3, A41, gA, gB and UL50 genes were undetectable in 103 cells by Southern hybridization of the RT-PCR products. Transcripts of the VP16 and SORF2 genes were detected in the 103 cells of MSB-1, and the pp14 gene transcript was found in 103 Cells of RPL-1 but not in 103 cells of HPRS-1, MOGA-1, MOGA-2, MSB-1 or MTB-1. A transcript corresponding to the ICP4 sequence was detected as a 0.7 kbp RT-PCR product in 103 cells of these MDV cell lines but not in the retrovirus-transformed 1104B1 cell line. The transcript corresponding to the 0.7 kbp RT-PCR product suggested a splice by its size and sequence. Thus, transcriptional analysis of 103 MDV-transformed cells revealed that the transcript corresponding to the ICP4 sequence was a common transcript in latently infected MDV-transformed cells, while most of the genes did not transcribe in these cells.