Pathogenesis and immune gene expression of the iridescent shark catfish Pangasianodon hypophthalmus to experimental Edwardsiella tarda infection was studied. Healthy Pangasianodon were inoculated intramuscularly with a sub-lethal dose of 1.77 × 10⁷ cells/fish of E. tarda to induce edwardsiellosis. Petechial haemorrhages, inflammation at the site of injection, vertical hanging from the water surface, swollen abdomen and anorexia were the common signs observed in challenged catfish fingerlings. The morbid catfish also exhibited typical signs of septicaemia with haemorrhages on ventral parts of the body and fin bases and congested vent prior to death. The mortality was observed 48 h post injection. The average percent morality was 42 % in fish exposed to 1.77 × 10⁷ cells of E. tarda, whereas, only6.6 % mortality was observed in placebo control (catfish received 0.1 mL of 0.85 % sterile physiological saline) and no mortality in negative control group (catfish received no injection) over an observational period of 20 days. The kidney and liver of moribund fish demonstrated different necrobiotic changes. In kidney, cellular and cloudy swelling, degeneration of renal tubules, necrosis of glomerulus, dilation of Bowman’s space, hypertrophy, fibrosis of renal tubules and increased melano-macrophage reaction were frequently observed. In liver, disorganized hepatocytes, blood congestion and nuclear pyknosis were evident. To ascertain the host response to E. tarda infection, mRNA levels of three different classes of innate immune components viz. cytokine interleukin-1β (IL-1β), acute phase protein transferrrin and complement C3 were assessed by quantitative real-time PCR. Significant up-regulation (P < 0.05) of IL-1β and C3 gene expression was observed in infected fish upto 15 days post infection (dpi) in liver, kidney, spleen and blood though the level of increase differed among organs and dpi. Significant up-regulation (P < 0.05) of transferrin gene expression was seen at 1 dpi in kidney, spleen and blood while no significant variation could be observed in liver. The tissue specific pathology and changes in immune gene expression may help to improve the knowledge of E. tarda pathogenesis and role of the innate immune genes in this tropical catfish. The innate immune response of host to E. tarda which is evident from increased expression of innate immune genes may be further enhanced through immunostimulants and nutraceuticals to prevent disease onset and use of antibiotics.

发病机理和虹彩鲨鱼鲶鱼的免疫基因表达Pangasianodon hypophthalmu s至实验迟钝爱德华氏菌感染进行了研究。健康Pangasianodon用1.77×10的子致死剂量肌肉内接种⁷细胞/鱼E.氏菌诱发爱德华氏菌病。在受挑战的cat鱼鱼种中观察到的常见症状是儿科出血，注射部位发炎，水面垂直悬挂，腹部肿胀和厌食。病态cat鱼还表现出典型的败血病迹象，身体腹鳍和鳍基部出血，死前发泄物充血。注射后48小时观察到死亡率。暴露于1.77×10 ^7个塔氏大肠杆菌的鱼中的平均道德百分率是42％，而在20天的观察期内，安慰剂对照组（cat鱼接受0.1 mL的0.85％无菌生理盐水）的死亡率仅为6.6％，阴性对照组（cat鱼未接受注射）的死亡率为6.6％。垂死鱼类的肾脏和肝脏表现出不同的坏死性变化。在肾脏中，经常观察到细胞和阴囊肿胀，肾小管变性，肾小球坏死，鲍曼氏空间扩张，肥大，肾小管纤维化和黑色素巨噬细胞反应增加。在肝脏中，肝细胞杂乱无章，血液充血和核固缩明显。为了确定宿主对大肠杆菌感染的反应，三种不同类别的先天免疫成分的mRNA水平。通过定量实时PCR评估细胞因子白介素1β（IL-1β），急性期蛋白转铁蛋白和补体C3。在感染后15天（dpi），肝脏，肾脏，脾脏和血液中IL-1β和C3基因的表达显着上调（P <0.05），尽管器官和dpi的升高水平有所不同。在肾脏，脾脏和血液中，在1 dpi时发现转铁蛋白基因表达显着上调（P <0.05），而在肝脏中未观察到明显的变化。组织特异性病理学和免疫基因表达的变化可能有助于提高对塔氏大肠杆菌的发病机理的了解，并了解先天免疫基因在这种热带cat鱼中的作用。宿主对迟发性大肠杆菌的天然免疫反应 从先天免疫基因表达的增加可以明显看出这一点，可以通过免疫刺激剂和营养药品来进一步预防疾病的发作和使用抗生素。