title: Association between rate of viral genome replication and virulence of Marek's disease herpesvirus strains.
abstract: The early pathogenesis of Marek's disease virus (MDV) infection is characterized by a lytic infection followed by the induction of latency. Genetically resistant N2a and susceptible P2a chickens were infected with the less virulent JM-16 or the very virulent plus (vv+) RK-1 MDV strains to examine the relationship between virulence and resistance on virus replication during 1-10 days postinfection (dpi) using real-time quantitative polymerase chain reaction (qPCR) and quantitative reverse transcriptase (qRT)-PCR assays. The numbers of copies of the viral DNA or transcripts amplified by these assays were normalized relative to cellular controls and subjected to three-way ANOVA. Viral DNA but not RNA was present in spleens at 1-3 dpi in decreasing quantities, and at 4 dpi, viral DNA started to increase concomitant with the initiation of viral transcription independently of virus strain and genetic resistance. At 6 dpi, JM-16 became latent in resistant N2a and susceptible P2a chickens with low levels of viral transcripts, but transcriptional activity increased in susceptible P2a chickens at 9 and 10 dpi. In contrast, infection with vv+ RK-1 never went into latency in both chicken lines. Viral transcripts were present from 4 to 10 dpi showing a higher and more persistent viral activity that may lead to severe damage to the lymphoid organs resulting in increased immunosuppression and increased incidence of MD. The use of qPCR and qRT-PCR to determine viral DNA load and transcriptional activity may offer an alternative to the current system of pathotyping to characterize new MDV isolates.
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, United States.
authors.forename: Reem
authors.initials: R
authors.lastname: Yunis
authors.forename: Keith W
authors.initials: KW
authors.lastname: Jarosinski
authors.forename: Karel A
authors.initials: KA
authors.lastname: Schat
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000235:genetics; D002645:Chickens; D004261:DNA Replication; D004279:DNA, Viral / Q000032:analysis / Q000096:biosynthesis; D004195:Disease Models, Animal; D020022:Genetic Predisposition to Disease; D025922:Mardivirus / Q000472:pathogenicity / Q000502:physiology; D008380:Marek Disease / Q000235:genetics / Q000821:virology*; D009687:Nuclear Proteins / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D012367:RNA, Viral / Q000032:analysis; D013045:Species Specificity; D013154:Spleen / Q000821:virology; D015534:Trans-Activators / Q000235:genetics; D014759:Viral Envelope Proteins / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics; D014774:Virulence; D017735:Virus Latency; D014779:Virus Replication
chemical_list: D000956:Antigens, Viral; D004279:DNA, Viral; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012367:RNA, Viral; D015534:Trans-Activators; D014759:Viral Envelope Proteins; D014764:Viral Proteins; C072811:glycoprotein B, Marek's disease virus; C075882:ICP4 protein, Gallid herpesvirus 2