基于透明四带无须鲃感染模型的鱼类诺卡氏菌致病机理研究

Nocardiosis is a long-term and problematic bacterial disease that can infect a wide range of fish and cause great economic losses to the aquaculture. Fish nocardiosis is characterized with typical granuloma occurred in internal organs. Due to its difficulty for observation externally, it is partly hamper the research in nocardiosis prevention. We found that Nocardia can infect transparent mutants of tiger barb Puntius tetrazna via artificial infection, and duplicate the typical symptoms of fish nocardiosis. The transparent mutant is superior to other conventional model owning to its clear visualization of internal organs of fish, it facilitates continual acquisition of a series of dynamics experimental data without sacrificing the experimental fish. Granulomas are bene?ted the host by restricting bacteria, and also be the habitat of the pathogen. As the cardinal cells in granulomas,macrophages may play important role in Nocardia infection. Nocardia seriolae will be traced via the green fluorescent protein-marked, immunohistochemical staining or acid fast staining method, the infection, amplification or distribution of Nocardia seriolae will be investigated with the help of the transparent tiger barb model, and the pathogen-host interactions will also be explored. In this study, we sought to determine the process of granulomatous formation and its role of granuloma expansion or dissemination in real time, to probe the contributions of macrophages in Nocardia infection and granulomatous formation. The unique visual access to internal organs afforded by the transparent tiger barb allow us to investigate conveniently the mechanisms and consequences of granulomatous formation at intravital level. Using the bacteria traced with different protein-marked, the interactions relationship between accumulation, spread, persistence of Nocardia seriolae and macrophages aggregation will be studied. This work will provide fundamental scientific basis for nocardiosis prevention and control in fish.

鱼类诺卡氏菌病病程极其漫长，也给水产养殖业带来巨大危害。该病的典型症状为体内多器官的肉芽肿病变，从体外难以观测，一定程度上影响了该病的防治。实验发现，诺卡氏菌可感染四带无须鲃透明品系，并复制出自然发病的症状，且体内肉芽肿病变可直接观察，在不处死动物情况下能获得一系列动态试验数据，具无法比拟的应用优势。肉芽肿形成虽是宿主控制病原的策略，也为病原在宿主体内提供了栖息地和庇护所，肉芽肿的主要构成巨噬细胞在诺卡氏菌病发展过程起关键作用。本项目通过对诺卡氏菌的荧光标记，结合免疫组化和抗酸染色等技术，研究诺卡氏菌在四带无须鲃体内感染、增殖、扩散的实时情况及其与巨噬细胞的相互作用关系，了解肉芽肿形成的动态过程及其在不同组织的分布规律；通过不同标记菌株在巨噬细胞和肉芽肿中的相互作用研究，明确巨噬细胞和肉芽肿在诺卡氏菌控制、隔离和转运过程中的作用，揭示鱼类诺卡氏菌的致病机制，为该病的有效防控提供基础。