Construction of a novel DNA vaccine candidate targeting F gene of genotype VII Newcastle disease virus and chicken IL-18 delivered by Salmonella.

AIMS: Genotype VII Newcastle disease (ND) is one of the most epidemic and serious infectious diseases in the poultry industry. A novel vaccine targeting VII NDV is still in requirement.

METHODS AND RESULTS: In this study, we constructed recombinant regulate delayed lysis Salmonella strains expressing either fusion protein (F) alone under eukaryotic CMV promoter or together with chicken IL-18 (chIL-18) as a molecular adjuvant under prokaryotic Ptrc promoter, named pYL1 and pYL23, respectively. Oral immunization with recombinant strains induced NDV specific serum IgG antibodies in both pYL1 and pYL23 immunized chickens. The presence of chIL-18 significantly increased the lymphocyte proliferation in immunized chickens, as well as the percentages of CD3+ CD4+ and CD3+ CD8+ T cells in serum, even though without statistic difference. After a virulent challenge, the pYL23 immunization provided about 80% percentages protection at day 10 post infection, compared with 60% of pYL1 immunization and 100% of inactivated vaccine group, indicating the enhanced immune response provided by chIL-18, which was also confirmed by the histochemical analysis.

CONCLUSIONS: Recombinant lysis Salmonella vectored DNA vaccine could provide us a novel potential option for controlling NDV infection.

SIGNIFICANCE AND IMPACT OF STUDY: This study firstly took use of regulated delayed lysis Salmonella vector for a design of orally administrated vaccine against NDV. This article is protected by copyright. All rights reserved.