Isolation And Identification Of Infectious Bursal Disease Virus In Pu Yang City Of Henan Province And The Full Genome Sequence Analysis Of Isolated Strains PY-03

Infectious bursal disease（IBD） is an acute, highly contagious viralinfectious of young chickens caused by infectious bursal disease virus. Since thebursa of Fabficius is important organ to the maturatio of B-lymphoid cells，a mountof B cells in the lymphoid follicle of bursa Fabricius is lytic，atroph of bursa causingimmunosuppression，leading to increased susceptibility to other pathogens anddecrease immunological response to vaccine. In recent years, the emergence ofvvIBDV and vIBDV, subtype diversity and antigenic variation that promote thenew features of the incidence and prevalence of this disease and bring great economiclosses to the poultry industry.15samples were collected from PuYang.Viruses were isolated by9-11daychicken embryo inoculation via chorio-allantoic membrane（CAM） and wereidentificated by the agar diffusion test,the result suggested that six IBDV that werenamed PY-01、PY-02、PY-03、PY-04、PY-05、PY-06were isolated. Which four IBDVfor studying on biological characteristics of physical and chemical properties,hemagglutination, EID50. The results were that their physical and chemical propertiesmeet the basic characteristics of the infectious bursal disease viruse. Their results ofEID₅₀were10^-7.51、10^-7.60、10^-8.5、10^-7.68EID₅₀/0.2ml.In order to understand the molecular epidemiology of infectious bursal diseasevirus in PuYang of Henan Province, we have been sequencing whole genomenucleotide sequence of PY-03strain. Then comparated and analyzed nucleotide anddeduced amino acid sequences of PY-03strain to the representatives of IBDV strainsin GenBank, and multi-the polyprotein VP2/VP4/VP3gene encoding amino acidhydrophilic and antigenic epitope were analyzed. This strain had the followingcharacteristics:it had a conserved heptapeptide SWSARGS,222P,249Q,254G,theseexplained its antigenicity had not yet mutated and this strain didn’t belong to thevariat strains;222P、242V、253H、279N、284T, these were fully consistent with theattenuated strains.The result of segment A nucleotide sequence and deduced aminoacid sequence homology analysis was that PY-03had the high homology with theattenuated strains CEF94、Cu-1、 Gt and the homology was99.5-99.9%,but it hadthe low homology with the very virulent strains HK46、UK661、Gx，the homologywas95.6-95.9%. Evolutionary relationship, the PY-03strain belonged to a smallbranch and it had the closer relationship with attenuated CEF84、 variant strain NB,but the distantly related with the very virulent strains HK46,、UK661、Gx and theclassics strains T09, UPM94/273. For the VP1gene nucleotide sequence and deduced amino acid sequence homology analysis,we found that the PY-03strain had thehighest homology with the very virulent strains UK661and it had the low homologywith the attenuated strains Cu-1, CEF94, B87, Edgar, Gt. Evolutionaryrelationship,PY-03neither belonged to the very virulent strains nor the attenuatedstrains, it formed a separate branch between them.So we speculated PY-03strain wasa recombinant virus. These results provided the technical foundation for the molecularepidemiology, differential diagnosis and prevention research of Infectious BursalDisease Virus in PuYang of Henan Province.