A Recombinant Fowlpox Virus Expressing The HN Gene Of Newcastle Disease Virus And Its Protective Efficacy

Newcastle disease (ND) is one of the List A diseases categorized by OIE that can cause severe economic losses in the poultry industry all over the world. The pathogen of the disease is NDV, which is a number of the Paramyxovidae and contains a non-segmented negative strand RNA genome.There are two kinds of glycoproteins on the envelope of the NDV, which are the fusion (F) protein and the hemagglutinin-neuraminidase (HN) protein. The surface glycoprotein HN is a multifunctional protein as well as being the major antigenic determinant of the NDV. Now in our country, the prevention and control of ND is mainly by the way of vaccination. However the traditional vaccines, including the avirulent or attenuated live vaccine and inactivated killed vaccine, usually can not efficiently prevent from occurrence of ND, and severely interfere serological surveillance because we can not defferentiate the antibody responses between vaccination and nature infection. In order to avert the above shortcomings of the conventional vaccine, we constructed the recombinant rFPV282E4-HN containing the HN gene of NDV. Using polymerase chain reaction C PCR) and inderected immunofluorecence assay (IFA) techniques, we detected that the HN gene was expressed in the recombinant fowlpox virus. Moreover, in this study we described the genetic stability and compared the protective efficacy of rFPV282E4-HN with that ofrFPVLP-HN.The rFPV282E4-HN virus was serially passaged up to the 20th generation on chicken embryo fibroblast (CEF) monolayers. The HN genes from passages 0, 10, and 20 were amplified by PCR and sequenced while the expression of HN genes from passages 0, 10, and 20 was detected by IFA. The results showed the recombinant virus was genetically stable without any change in amino acid sequence of HN during20 passeges.To evaluate the protective efficacy against Newcastle disease, we compared the protective efficacy of the rFPV282E4-HN virus with that of rFPVLP-HN virus which was constructed by Weizhong Liu on the SPF chickens and commercial broiler chickens. We tested the growth of the SPF chicken groups and the commercial broiler chicken groups. The results of hemagglution-inhibition(HI) test showed that the titer of each rFPV-HN vaccinated group was significantly lower than that of inactivated oil vaccination group, whereas, there was not apparent difference between the rFPV282E4-HN virus and rFPVLP-HN virus. The protective efficacy and the weight of the two groups which were vaccinated with viruses of rFPV282E4-HN and rFPVLP-HN were independently analyzed by statistic software and the result indicated that no obvious difference existed. In order to obtain better protection in commercial broiler chickens, further related work should be carried out.