title: Application of real-time RT-PCR for the quantitation and competitive replication study of H5 and H7 subtype avian influenza virus.
abstract: Avian influenza (AI) viruses are endemic in wild birds and if transmitted to poultry can cause serious economic losses. In the study of AI, the quantitation of virus shed from infected birds is valuable in pathogenesis studies and to determine the effectiveness of vaccines, and is performed routinely by cultivation of virus containing samples using embryonating chicken eggs (ECE) and expressed by 50% egg infectious dose (EID(50)). Although, this assay is accurate and is the standard test for infectious virus titration, the method is laborious, requires a large number of ECE, and takes at least 7 days to determine results. In this study, a one-tube hydrolysis fluorescent probe based real-time RT-PCR (RRT-PCR) was applied for the quantitation of AI virus and compared with conventional virus titration method. A strong positive correlation was observed between the amount of RNA determined by quantitative RRT-PCR and the EID(50)s determined by conventional methods. This RRT-PCR test was further applied in the study of competitive replication of co-infected H5 and H7 subtype viruses in chickens. Using hemagglutinin subtype specific probes, we were able to determine the amount of individual subtype virus, which could not have easily been done with conventional methods. This RRT-PCR based quantitation of AI virus, which is specific, sensitive, easy to perform, and rapid, will be useful for virological, pathogenesis, and protection studies.
authors.affiliation: Southeast Poultry Research Laboratory, USDA-ARS, 934 College Station Road, Athens, GA 30605, USA.
authors.forename: Chang-Won
authors.initials: CW
authors.lastname: Lee
authors.forename: David L
authors.initials: DL
authors.lastname: Suarez
mesh_terms: D000818:Animals; D005456:Fluorescent Dyes; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000032:analysis; D009980:Influenza A virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D011200:Poultry; D011201:Poultry Diseases / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D014779:Virus Replication
chemical_list: D005456:Fluorescent Dyes; D019267:Hemagglutinin Glycoproteins, Influenza Virus