鸡传染性支气管炎病毒多表位嵌合病毒样颗粒的构建及其免疫应答机制研究

Avian infectious bronchitis (IB) causes massive economic losses to poultry industry. Vaccination is still the major measure for prevention and control of IB. However, traditional vaccines have defects in safety or immunogenicity. In addition, the serotypes of infectious bronchitis virus (IBV) epidemic strains are complex and there is little or no cross-protection between different serotypes of IBVs or circulating variant viruses. Therefore, there is an urgent need to develop new vaccines that are safe, effective and broad-spectrum. Virus-like particles (VLPs) have the advantages of safety, good immunogenicity and displaying epitopes. The multi-epitopes chimeric VLPs will be constructed through co-infection with three recombinant baculoviruses separately encoding M, E and the recombinant S gene containing the three dominant epitopes tandem of S1 gene of the vaccine strain H120, the S1 gene and the transmembrane and cytoplasmic tail (TM/CT) of the S2 gene of Guangxi predominant strain GX-YL5. The effect on the maturation of dendritic cell (DC), the recruiting of DC in vivo, the induction of humoral immunity, cellular immunity and mucosal immune responses of the multi-epitopes chimeric VLPs as well as the protection against different serotype virulent strains will be analyzed. The objectives of the present study are to explore the construction technology and immune response mechanism of multi-epitopes chimeric VLPs of IBV, providing a theoretical basis and technology platform for the future development of new multivalent vaccines that are safe, efficient, and broad-spectrum for different serotype IBVs.

鸡传染性支气管炎经济危害严重，疫苗免疫是重要防控措施，但传统疫苗在安全性或免疫原性方面存在缺陷。此外，鸡传染性支气管炎病毒(IBV)流行株血清型复杂，各型之间交叉保护弱，故研发安全高效广谱的新型疫苗非常重要。病毒样颗粒（VLPs）有安全、免疫原性好、可展示抗原表位优点。本研究将H120 S1蛋白的3个抗原优势表位串联后，与广西地方优势流行株GX-YL5的S1蛋白以及S2蛋白的跨膜区和胞质尾区（TM/CT）融合构建重组杆状病毒表达载体，与表达GX-YL5毒株M和E蛋白的重组杆状病毒共感染Sf9细胞，组装多表位嵌合VLPs，并围绕其对树突状细胞（DC）成熟的影响、招募体内DC的能力、诱导体液、细胞和粘膜免疫及其对不同血清型强毒株的保护作用进行研究，旨在探索IBV多表位嵌合VLPs的构建技术及其诱导的免疫应答机制，为开展针对不同血清型IBV的安全高效广谱的新型多价疫苗研发提供理论基础和技术平台。

鸡传染性支气管炎（Infectious bronchitis, IB）是由传染性支气管炎病毒（Infectious bronchitis virus, IBV）引起的鸡的一种急性、高度接触性的呼吸道传染病，IBV非常容易发生变异，血清型复杂，给该病防控带来了很大困难。IB防控最有效的措施是疫苗接种，但传统疫苗在安全性或免疫原性方面存在不足。因此，非常有必要研发针对当地优势流行株的安全、高效、广谱的新型IBV疫苗。病毒样颗粒（Virus-like particles, VLPs）安全、免疫原性好、具有高效展示有效的抗原表位等优点，已成为新型IBV疫苗研发的热点。目前缺乏IBV嵌合表位VLPs的相关研究。本项目将疫苗株H120的3个抗原表位与IBV广西优势基因型和优势血清型代表性毒株GX-YL5的S1基因、S2基因的跨膜区和胞质尾区（TM/CT）以柔性肽串联，构建并获得了表达嵌合多表位的重组S蛋白的重组杆状病毒rHBM-rS-EB-Th-CTL；将rHBM-rS-EB-Th-CTL、rHBM-M和rHBM-E共感染Sf9细胞制备rS-EB-Th-CTLME-VLPs，并围绕其对树突状细胞（DC）成熟的影响，诱导固有免疫激活、体液免疫、细胞免疫和黏膜免疫应答以及免疫保护效果进行研究，旨在探索IBV多表位嵌合VLPs的构建技术及其诱导的免疫应答机制。结果显示成功构建了IBV多表位嵌合病毒样颗粒rS-EB-Th-CTLME-VLPs，且能有效地刺激DC的成熟和激活固有免疫、细胞免疫、体液免疫和黏膜免疫，对三种不同血清型GX-YL5、M41和GX-QZ181028的攻毒均能起到较好的保护作用，且在一定程度优于未嵌合表位的rSME-VLPs、灭活H120疫苗和GX-YL5疫苗。本项目为今后开展针对不同血清型IBV的安全高效广谱的新型多价苗的研发提供理论基础和技术平台，具有重要的理论意义和应用前景。