法氏囊活性肽BP5和BP7促进B细胞分化成熟为浆细胞的功能及信号机制研究

Pathogenic avian influenza not only causes the serious economic losses on the healthy development of animal husbandry in China, but also causes grave public health risks. Bursa of Fabricius is the acknowledged central humoral immune organ, and various bursal-derived active peptides were reported to promote the antibody level after immunization with H9N2 avian influenza vaccine. However, the mechanism of bursal peptides on humoral immune enhancement remains unclear. The differentiation and mature of B cells into plasma cells is the identification of humoral immune response. In the project, the bursal-derived peptides BP5 and BP7 will be used as the biological active peptides and different developmental stage B cells will be used as immune cell model to explore the mechanism on B cell differentiation and development. The first work will employed to study the regulatory function of bursal bioactive peptides on differentiation of B cells at early stage, and then to detect the enhancing roles on the differentiation and maturation of B cells from the immunized mice into plasmocyte and the mechanism of bursal-derived peptides on antibody production through AMPK/mTOR/Stat3 signals. Furthermore, the roles of T cells on B cell development after bursal-derived peptides treatment will be investigated in different kinds of B cells. Finally, the different B cell deletion or T cell deletion mice and chicken will be used as animal model to explore the functions of bursal-derived peptides on immune response enhancement, respectively. These work will be expected to clarify the regulatory functions on signal mechanism of the differentiation and maturation of B cells and the enhancing roles on the humoral immune response of bursal bioactive peptides, which will lay a good foundation for the successful development of new vaccine adjuvants, and provide the theoretical basis and technical support for the prevention and control of avian influenza in clinical practice, which will have the important practical guiding significance on prevention and control of epidemic disease.

禽流感造成了惨重的经济损失以及严峻的公共卫生隐患。法氏囊是公认的中枢体液免疫器官，其来源活性肽能够促进H9N2禽流感疫苗抗体水平，但其增强动物体液免疫反应的机制尚不清楚。B细胞分化成熟为浆细胞是体液免疫的标识。本项目拟以法氏囊活性肽BP5和BP7等为材料，以不同发育阶段的B细胞为模型，研究法氏囊活性肽对早期阶段B细胞分化的调节功能，进而研究其促进免疫小鼠体内B细胞分化及其成熟为浆细胞，并通过AMPK/mTOR/Stat3信号调节抗体产生的机制，以及T细胞在此B细胞发育过程的影响；并以B细胞或T细胞缺失的小鼠和鸡为模型，探索其增强免疫反应的功能。研究成果有望阐明法氏囊活性肽调控B细胞分化成熟的信号机制及其促进疫苗体液免疫反应的功能，为成功开发新型疫苗佐剂打下良好的基础，为临床上禽流感的防控提供理论研究依据及技术支撑，具有重要的实践指导意义。

法氏囊是鸟类特有的公认的中枢体液免疫器官，对B 细胞分化发育至关重要，其源活性分子调控 B 细胞分化及成熟为浆细胞的功能机制具有重要的科学意义。本项目以新型法氏囊活性肽 BP5、 BP7和BP9 等为研究素材，通过分子生物学、生物化学、免疫学及动物免疫试验证实BP5不仅促进体外B细胞分化及活化，而且促进体内B细胞分化和成熟。转录组分析证实，BP5体内刺激B细胞，主要参与细胞因子与细胞因子受体的相互作用、抗原递呈、NK细胞介导的细胞毒性等免疫过程，提示BP5能激活小鼠体内的多种免疫途径，且不同浓度的BP5所激活的通路也各有差异。而且发现，BP7能够诱导鸡未成熟B细胞分泌IgM产生，诱导DT40细胞中基因差异表达，且细胞因子受体互作是BP7刺激的关键通路。小鼠免疫试验证实，BP7不仅能够促进体外B细胞的活性和细胞因子产生，诱导前B细胞分化及活化，而且能够调节体内B细胞活力，并刺激体内B细胞分化，同时能够诱导鼠源未成熟B细胞发生细胞自噬。此外，BP9能够增强禽流感疫苗免疫小鼠体内的B细胞分化，并诱导B细胞的增殖活性。BP9能激活mTOR通路和STAT3通路，而BP7只能激活mTOR通路。研究还发现，BP7和BP9均能提高活化T细胞的活力水平，促进活化T细胞增殖分化，能抑制T淋巴早期凋亡。总之，本项目证实了法氏囊活性肽调节早期B 细胞分化功能，阐明了活性肽增强禽流感疫苗免疫小鼠体内的 B 细胞分化及其其促进 B 细胞分化为浆细胞，并通过 mTOR/Stat3 信号调节抗体产生的功能机制，以及 T 细胞对 B 细胞分化的影响，并探索其在不同动物模型中调节免疫反应的功能。该研究结果揭示了新型法氏囊活性肽增强机体体液免疫保护及体液免疫的作用机制，为成功开发新型疫苗佐剂打下良好的基础，对当前临床疫病防治具有重要的实践指导意义。