Construction and immunological evaluation of rGtHLJVP2 expressing VP2 protein of prevalent infectious bursal disease virus strain HLJ0504

In response to the emergency of variant and very virulent infectious bursal disease virus(IBDV)strains and to solve the problem of time-consuming in screening of the conventional live vaccines,a recombinant virus rGtHLJVP2was generated based on the epidemiological investigation with its VP2gene cloned from a prevalent very virulent IBDV(vvIBDV)strain HLJ0504.To adapt this virus to CEF cells,two mutations of Q253Hand A284Twere introduced in its VP2gene.It was then used to replace the corresponding region of the attenuated IBDV vaccine strain Gt.The constructed virus rGtHLJVP2had comparable replication ability to its parental virus Gt in vitro and in vivo.The animal experiments showed that rGtHLJVP2had no pathogenicity in chickens with bursa index above 0.7and no significant bursal atrophy.The recombinant virus induced a good immune response with the antibody titer significantly higher than that induced by the parental virus Gt,and it provided full protection against vvIBDV challenge.In addition,the recombinant virus rGtHLJVP2had good genetic stability.This study provides the solid foundation for the development of IBD vaccines and is significant for the prevention of IBDV infection.