Yohannes T, Sharma A K, Singh S D, Goswami T K
College of Veterinary Medicine, Mekelle University, 231, Mekelle, Ethiopia.
Vet Immunol Immunopathol. 2012 May 15;146(3-4):245-53. doi: 10.1016/j.vetimm.2012.03.001. Epub 2012 Mar 10.
A total of 128 1-week-old chicks were classified into four groups; T-2 toxin fed (T-2), IBV infected (IBV), T-2 toxin fed and co-infected with IBV (T-2+IBV), and untreated (control) for a period of 6 weeks. Within their respective groups, the birds belonged to T-2 and T-2+IBV were exposed to 2 ppm of T-2 toxin contaminated feed for 6 weeks, and 0.2 ml of 10 EID(50) (10(5.69)/0.2 ml) inoculums of IBV isolate (India/LKW/56/IVRI/08) was used to challenge the chicks belonged to IBV alone and T-2+IBV groups after 3 weeks of the experiment. To study immunopathological effects, parameters such as lymphocyte stimulation indices (SI), haemagglutination inhibition, enzyme linked immunosorbant assay (ELISA), peripheral lymphocytes CD(4)(+) and CD(8)(+) analysis, and histopathological examination of lymphoid organs were done. Accordingly, SI values were significantly (P<0.05) lower in all the treatment groups as compared to control, however, the SI values of IBV infected group were significantly higher than the values in toxin fed groups. The mean HI titres to ND vaccine was significantly (P<0.05) lower in the toxin groups at all the intervals, and the antibody titres in IBV infected group were significantly (P<0.05) higher than that of T-2 toxin fed and co-infected with IBV group but were significantly (P<0.05) lower than the control at 21 (3) and 28 (10) days of toxin feeding (DTF) (days post infection (DPI)). Similarly, the mean IBV ELISA antibody titres in the toxin fed groups were significantly (P<0.01) reduced as compared with the IBV ELISA antibody titres of IBV infected but not toxin fed group, at all intervals. Peripheral CD(4)(+):CD(8)(+) ratios in T-2+IBV group and number of CD(4)(+) and CD(8)(+) peripheral lymphocytes in all treatment groups were significantly reduced as compared to the values in control birds. However, CD(4)(+):CD(8)(+) ratios of IBV infected group at 42 (21) DTF (DPI) were found significantly (P<0.05) higher than the values in control birds. Histopathologically, lymphoid organs (bursa of Fabricius, spleen, thymus, caecal tonsils and Harderian glands) showed moderate to severe necrosis (lymphocytolysis) and extensive lymphocyte depletion in all the toxin groups (T-2 and T-2+IBV groups) where the severity and extent of the lesions were more in T-2+IBV group. The findings of the present experiment revealed immunosuppressive effects of T-2 toxin and aggravated the pathology and pathogenesis of IBV infection.
总共128只1周龄雏鸡被分为四组；喂食T-2毒素组（T-2）、感染传染性支气管炎病毒组（IBV）、喂食T-2毒素并同时感染IBV组（T-2+IBV）以及未处理对照组，实验为期6周。在各自的组内，属于T-2组和T-2+IBV组的鸡被喂食含2 ppm T-2毒素污染的饲料6周，在实验3周后，用0.2 ml含10个鸡胚感染剂量（50）（10(5.69)/0.2 ml）的IBV毒株（印度/LKW/56/IVRI/08）接种物对仅属于IBV组和T-2+IBV组的雏鸡进行攻毒。为研究免疫病理学效应，进行了淋巴细胞刺激指数（SI）、血凝抑制、酶联免疫吸附测定（ELISA）、外周淋巴细胞CD(4)(+)和CD(8)(+)分析以及淋巴器官组织病理学检查等参数检测。相应地，与对照组相比，所有处理组的SI值均显著降低（P<0.05），然而，IBV感染组的SI值显著高于毒素喂食组。在所有时间点，毒素组对新城疫疫苗的平均血凝抑制效价均显著降低（P<0.05），且在毒素喂食21（3）天和28（10）天（感染后天数（DPI））时，IBV感染组的抗体效价显著高于T-2毒素喂食并同时感染IBV组，但显著低于对照组（P<0.05）。同样，在所有时间点，与未喂食毒素的IBV感染组的IBV ELISA抗体效价相比，毒素喂食组的平均IBV ELISA抗体效价显著降低（P<0.01）。与对照鸡相比，T-2+IBV组外周血CD(4)(+):CD(8)(+)比值以及所有处理组外周血CD(4)(+)和CD(8)(+)淋巴细胞数量均显著减少。然而，在毒素喂食42（21）天（DPI）时，IBV感染组的CD(4)(+):CD(8)(+)比值显著高于对照鸡（P<0.05）。组织病理学上，所有毒素组（T-2组和T-2+IBV组）的淋巴器官（法氏囊、脾脏、胸腺、盲肠扁桃体和哈德氏腺）均显示中度至重度坏死（淋巴细胞溶解）和广泛的淋巴细胞缺失，其中T-2+IBV组的病变严重程度和范围更大。本实验结果揭示了T-2毒素的免疫抑制作用，并加重了IBV感染的病理学和发病机制。
