Construction Of Recombinant Fowlpox Virus Expressing Glycoprotein B Gene Of Infectious Laryngotracheitis Virus And Its Protective Efficacy

Infectious laryngotracheitis (ILT) is an acute upper respiratory infection of chickens. The disease occurs worldwide and can result in severe production losses characterized by signs of high mortality and decreased egg production which has been classified as one of the list B animal diseases by the Office International des Epizooties (OIE) . Furthermore, while current modified live vaccines for ILT can offer good protection, the vaccines remain insufficient attenuation as immunogenicity of ILTV is usually correlated with its virulence and the strains of ILTV used in vaccines can also produce latent infections, as well as ILT disease following bird-to-bird spread and increasing virulence during in vivo passage. Although there is commercial recombinant fowlpox virus vaccine expressing glycoprotein B gene of infectious laryngotracheitis virus in china, the FPV maternal antibodies present in production chickens usually exert substantial interference to the efficacy of the rFPV vaccine. There is an urgent demand for more efficient and safer vaccines that could be used to control and eradicate ILT.The previous study of our lab suggests that different nonessential regions for insertion of foreign gene influence the ability of recombinant fowlpox viruses to resist the interference of maternal antibodies, and all the rFPVs used p12LS as transfer vector, which was constructed in our lab through selecting suitable FPV nonessential regions, show superior performance in commercial chickens with high maternal antibodies. Glycoprotein B (gB) , a 205kDa protein complex, is a major protective immunogen of ILTV and is required for ILTV infectivity mediating attachment and penetration. In the study, a gene coding for glycoprotein B (gB) was amplified from ILTV virulent strain WG by using a pair of specific primers based on its published sequence by polymerase chain reaction (PCR). The gB gene was then cloned into pGEM-T easy vector and sequenced. The cloned gB gene was inserted into p12LS to form the transfer vector p12LSgB. The transfer vector was transfected into CEF pre-infected with large plaque (LP) strain of FPV. The rFPV-ILTVgB was successfully generated and purified by blue plaque selection.