Abstract
The Cre-recombinase mediated in vivo minicircle DNA vaccine platform (CRIM) provided a novel option to replace a traditional DNA vaccine. To further improve the immune response of our CRIM vaccine, we designed a dual promoter expression plasmid named pYL87 which could synthesize short HN protein under a prokaryotic in vivo promoter PpagC and full length HN protein of genotype VII Newcastle disease virus (NDV) under the previous eukaryotic CMV promoter at the same time. Making use of the self-lysed Salmonella strain as a delivery vesicle, chickens immunized with the pYL87 construction showed an increased serum haemagglutination inhibition antibody response, as well as an increased cell proliferation level and cellular IL-4 and IL-18 cytokines, compared with the previous CRIM vector pYL47. After the virus challenge, the pYL87 vector could provide 80% protection compared to 50% protection against genotype VII NDV in pYL47 immunized chickens, indicating a promising dual promoter strategy used in vaccine design.
Highlights
Newcastle disease virus (NDV) has posed severe economic threats to poultry production worldwide since its first discovery in 1926
It is worth noting that the genotype VII of NDV has been considered to be the dominant strain in China during the last decade, which has resulted in significant economic loss for poultry production [1]
The serum samples were collected at 21 dpv, 35 dpv, and 49 dpv to determine the HI antibody levels using 1% chicken red blood cells (RBCs) with 4 hemagglutination (HA) units of the NDV-specific antigen (NA-1, Jilin University, Changchun, China)
Summary
Newcastle disease virus (NDV) has posed severe economic threats to poultry production worldwide since its first discovery in 1926. The high levels of antigen synthesis can result in a metabolic burden to the vaccine strain, leading to a number of unwanted effects, including hyper attenuation, loss of viability, loss of plasmid, modified or poorly expressed antigen genes, and reduction in colonizing ability, resulting in poor immunogenicity [9] To avoid these side effects, a series of in vivo induced promoters such as PPagC , PnirB , and PssaG have been employed, which could drive gene expression in cultured macrophages or in host tissues but poorly express in common laboratory media [10]. The Salmonella strains can gradually lyse in vivo after oral immunization due to the absence of arabinose in vivo, yielding the release of produced protein antigens or plasmid DNA, resulting in an increased humoral immune response compared with a traditional attenuated Salmonella vectored vaccine. Vaccines 2021, 9, 723 vaccine at the same time, which would provide us with an option to improve the immune response of the DNA vaccine
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