Greer A W, McKenzie J L, McAnulty R W, Huntley J F, McNeilly T N
Faculty of Agriculture and Life Sciences, Lincoln University, Canterbury, New Zealand.
Haematology Research Group. Pathology Dept, University of Otago, Christchurch, New Zealand.
Vet Parasitol. 2018 Jan 30;250:60-67. doi: 10.1016/j.vetpar.2017.12.013. Epub 2017 Dec 19.
Immunological and performance characteristics were explored in Romney sheep from lines selected for either resistance or resilience to parasite infection. At a mean 78 days-of-age, twin lambs from a line selected for resistance (RT) and lambs from a line selected for resilience (RL) were infected with the intestinal nematode Trichostrongylus colubriformis for 100 days (I) while their twin remained as an uninfected control (C). Compared with RL, RT animals had lower levels of circulating CD4 T-cells (P = 0.003) but a greater proportion of these were activated (CD4CD25) in response to infection (P = 0.007). Differences between the lines in humoral immune responses to nematode infection varied with higher levels of T. colubriformis specific immunoglobulin (Ig) E in RT-I than RL-I (P = 0.002) but similar levels of both IgG (P = 0.926) and IgA (P = 0.321) responses. Temporal differences in the immune response also existed between the lines with RT-I animals displaying an earlier peak and more rapid reduction in FEC and an earlier peak in T. colubriformis specific IgA. In addition, compared with their RT-C and RL-C counterparts, infection caused a 22% reduction in feed intake from day 56 (P = 0.001) with total feed intake reduced by 15% and 9% for RT-I and RL-I, respectively. Cumulative liveweight gain was greatest for RL animals (P = 0.026) and relative to RT-C and RL-C was reduced by 5.8 kg and 4.9 kg for RT-I and RL-I, respectively. Overall, the selection lines appear to have differences in immunological characteristics that are both dependent on, and independent of parasite infection. Further, the difference in growth in the uninfected animals coupled with the similar cost of infection suggests the lower liveweight gain of RT-I compared with RL-I may be due to inherent differences between the lines in their growth potential, rather than a greater cost of infection in animals selected for resistance.
在对寄生虫感染具有抗性或恢复力的罗姆尼羊品系中探索了免疫和生产性能特征。在平均78日龄时，来自抗性选择品系（RT）的双羔和来自恢复力选择品系（RL）的羔羊感染肠道线虫蛇形毛圆线虫100天（I），而它们的双胞胎作为未感染对照（C）。与RL相比，RT动物循环CD4 T细胞水平较低（P = 0.003），但其中有更大比例的细胞在感染后被激活（CD4CD25）（P = 0.007）。品系之间对线虫感染的体液免疫反应差异各不相同，RT-I中蛇形毛圆线虫特异性免疫球蛋白（Ig）E水平高于RL-I（P = 0.002），但IgG（P = 0.926）和IgA（P = 0.321）反应水平相似。品系之间在免疫反应上也存在时间差异，RT-I动物的粪便虫卵计数（FEC）峰值出现更早且下降更快，蛇形毛圆线虫特异性IgA峰值出现更早。此外，与它们的RT-C和RL-C对应物相比，感染导致从第56天起采食量下降22%（P = 0.001），RT-I和RL-I的总采食量分别下降15%和9%。RL动物的累积体重增加最大（P = 0.026），相对于RT-C和RL-C，RT-I和RL-I分别减少了5.8千克和4.9千克。总体而言，选择品系在免疫特征上似乎存在差异，这些差异既取决于寄生虫感染，也独立于寄生虫感染。此外，未感染动物的生长差异以及相似的感染成本表明，与RL-I相比，RT-I体重增加较低可能是由于品系之间生长潜力的固有差异，而不是抗性选择动物的感染成本更高。
