Equine herpesvirus-4 kinetics in peripheral blood leukocytes and nasopharyngeal secretions in foals using quantitative real-time TaqMan PCR.
Based on the hypothesis that the viral load of cells infected with EHV-4 will likely change during the course of disease, TaqMan PCR was used to investigate and characterize the kinetics of EHV-4 viral DNA load (glycoprotein B gene) and transcriptional activity (glycoprotein B and latency-associated transcripts) in peripheral blood leukocytes (PBLs) and nasopharyngeal secretions (NSs) collected from 11 foals during a field outbreak of respiratory disease. The EHV-4 DNA load in PBLs was low and of short duration after onset of clinical signs. In contrast, the EHV-4 load in NSs remained high for the majority of the foals over a period of 4 weeks. Viral replication determined by detection of mRNA expression of the structural glycoprotein B was detected only in NSs during the first 7 days after onset of clinical signs for most foals. The majority of foals expressed latency-associated transcripts in NS sonly during the first 7 days after onset of clinical signs. Persistence of the expression of latency-associated transcripts in NS, as a reflection of a latent viral state, was not documented during the 28-day study period. Based on these results, it was concluded that lytic infection with EHV-4 can be diagnosed either by high EHV-4 DNA load of glycoprotein B gene or by detection of transcriptional activity of glycoprotein B.
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
Nicola
N
Pusterla
Christian M
CM
Leutenegger
W David
WD
Wilson
Johanna L
JL
Watson
Gregory L
GL
Ferraro
John E
JE
Madigan
D000818:Animals; D002140:California / Q000453:epidemiology; D004196:Disease Outbreaks / Q000662:veterinary; D005260:Female; D006566:Herpesviridae Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology*; D023141:Herpesvirus 4, Equid / Q000235:genetics* / Q000302:isolation & purification*; D006734:Horse Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000821:virology*; D006736:Horses / Q000097:blood / Q000821:virology; D007962:Leukocytes / Q000821:virology*; D008297:Male; D009093:Mucus / Q000378:metabolism / Q000821:virology; D009305:Nasopharynx / Q000378:metabolism / Q000821:virology*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D014779:Virus Replication