College of Animal Medicine, Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Provincial Key Laboratory of Animal Microecology and Healthy Breeding, Key Lab of Animal Production, Product Quality and Security, Ministry of Education, Jilin Agricultural University, Changchun 130118, China.
College of Animal Medicine, Jilin Provincial Engineering Research Center of Animal Probiotics, Jilin Provincial Key Laboratory of Animal Microecology and Healthy Breeding, Key Lab of Animal Production, Product Quality and Security, Ministry of Education, Jilin Agricultural University, Changchun 130118, China.
Vet Microbiol. 2022 Jul;270:109474. doi: 10.1016/j.vetmic.2022.109474. Epub 2022 May 22.
Genotype VII Newcastle disease virus (NDV) is still one of the most important virus threats severely affecting poultry production worldwide. Although inactivated vaccines are commercially available, there is still an urgent need to develop novel vaccine candidates for convenient and affordable vaccine application. Oral immunization using live attenuated bacteria such as Salmonella has recently attracted increasing interest, and in a previous study, we used a regulated delayed lysis Salmonella vector to deliver a DNA vaccine encoding the F protein and chicken IL-18 adjuvant together, named pYL23. To further improve its efficiency, we employed a novel in vivo minicircle DNA (mcDNA) platform to construct pYL58, which could maintain the complete plasmid during in vitro culture conditions and then transform into mcDNA in vivo whenever the plasmid was delivered by Salmonella into host cells. Compared with immunization with the parental strain harboring plasmid pYL23, immunization with Salmonella with pYL58 induced increased levels of serum IgY and mucosal sIgA in chickens, especially the intestinal and tracheal sIgA levels. Production of cytokines, including IL-4, IFN-γ, IL-18 and IFN-α, was also determined in serum and spleen cell culture supernatants after the 3rd immunization, and the results showed that the production of IFN-γ in the pYL58 group was significantly increased compared with that in the negative control group. Interestingly, compared with pYL23, significantly increased production of IFN-α in the cell supernatants from the pYL58 group was also observed. In addition, the CCK-8 assay results showed that the minicircle pYL58 significantly increased spleen cell proliferation. After virulent VII NDV challenge, pYL58 immunization could provide 70% protection compared with 50% protection in the pYL23 group, together with decreased virus titers in chicken lung samples at Day 5 and virus shedding at Days 3 and 5 post-challenge. This study demonstrated that the application of mcDNA technology dramatically increased the DNA vaccine efficiency, providing additional support for the use of our mcDNA platform in the veterinary field.
基因 VII 型新城疫病毒（NDV）仍然是全球范围内严重影响家禽生产的最重要病毒威胁之一。尽管已商业化生产灭活疫苗，但仍迫切需要开发新型疫苗候选物，以方便和负担得起的疫苗应用。使用活减毒细菌（如沙门氏菌）进行口服免疫最近引起了越来越多的关注，在之前的研究中，我们使用一种受调控延迟裂解的沙门氏菌载体，共同传递编码 F 蛋白和鸡 IL-18 佐剂的 DNA 疫苗，命名为 pYL23。为了进一步提高其效率，我们采用了一种新型的体内微小环 DNA（mcDNA）平台构建了 pYL58，该平台可以在体外培养条件下保持完整质粒，然后在沙门氏菌将质粒递送至宿主细胞时在体内转化为 mcDNA。与用携带质粒 pYL23 的亲本菌株免疫相比，用携带 pYL58 的沙门氏菌免疫诱导鸡血清 IgY 和黏膜 sIgA 水平增加，尤其是肠道和气管 sIgA 水平。在第 3 次免疫后，还在血清和脾细胞培养上清液中测定了细胞因子的产生，包括 IL-4、IFN-γ、IL-18 和 IFN-α，结果表明，与阴性对照组相比，pYL58 组 IFN-γ 的产生显著增加。有趣的是，与 pYL23 相比，pYL58 组细胞上清液中 IFN-α 的产生也显著增加。此外，CCK-8 检测结果表明，微小环 pYL58 显著增加了脾细胞的增殖。在强毒 VII NDV 攻毒后，与 pYL23 组的 50%保护相比，pYL58 免疫可提供 70%的保护，同时在攻毒后第 5 天鸡肺样本中的病毒滴度降低，在攻毒后第 3 天和第 5 天病毒脱落减少。本研究表明，mcDNA 技术的应用显著提高了 DNA 疫苗的效率，为我们的 mcDNA 平台在兽医领域的应用提供了额外的支持。
