Impact of deletions within the Bam HI-L fragment of attenuated Marek's disease virus on vIL-8 expression and the newly identified transcript of open reading frame LORF4.
Marek's disease (MD) in chickens is caused by MD herpesvirus (MDV), which induces T cell lymphomas. The early pathogenesis of MDV infection is characterized by a primary infection in B lymphocytes followed by infection of activated T lymphocytes. It has been speculated that a MDV-encoded homologue of interleukin-8 (vIL-8) may be important to attract activated T lymphocytes to infected B lymphocytes. Recently, more virulent strains of MDV have emerged, named very virulent plus (vv+)MDV, that cause earlier and more prolonged cytolytic infections compared to less virulent strains. In this report, it was found that vIL-8 mRNA expression in vivo was increased in very virulent (vv) and vv+MDV strains compared to mild (m) and virulent (v) strains, and could not be detected in two attenuated MDV strains examined using very sensitive real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays. In order to identify potential mechanisms for the increased vIL-8 mRNA expression in more virulent strains, and lack thereof in attenuated strains, the vIL-8 gene and putative promoter sequences upstream of the vIL-8 gene were compared from 10 different MDV strains, including attenuated derivatives. Only the JM-16 strain (both non-attenuated and attenuated) and attenuated 584A (584Ap80C) encoded a predicted vIL-8 gene sequence different from all other strains examined. Within the putative vIL-8 gene promoter sequence, there was little difference among the non-attenuated strains; however significant deletions were identified in the attenuated JM-16/p71, Md11 (R2/23), and 584Ap80C strains. Additionally, these deletions were located within a previously hypothetical open reading frame (ORF) named LORF4. Rapid amplification of cDNA ends identified a full-length transcript of LORF4 in the MDV-transformed lymphoblastoid cell line MSB-1, and deletions within this ORF caused truncated predicted proteins in 4 out of 6 attenuated MDV strains examined.
Jarosinski
Keith William
KW
Unit of Avian Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. kwj4@cornell.edu
O'Connell
Priscilla Helene
PH
Schat
Karel Antoni
KA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002645:Chickens; D015245:Deoxyribonuclease BamHI / Q000378:metabolism*; D017353:Gene Deletion; D008381:Herpesvirus 2, Gallid / Q000235:genetics / Q000472:pathogenicity*; D016209:Interleukin-8 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008380:Marek Disease / Q000821:virology; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics / Q000502:physiology*; D011201:Poultry Diseases / Q000821:virology; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014774:Virulence
D016209:Interleukin-8; D015245:Deoxyribonuclease BamHI