Cooperative Research Centre for Beef Genetic Technologies, Armidale, NSW, Australia.
Int J Parasitol. 2013 Aug;43(9):739-52. doi: 10.1016/j.ijpara.2013.04.005. Epub 2013 Jun 5.
The attachment to host skin by Rhipicephalus microplus larvae induces a series of physiological events at the attachment site. The host-parasite interaction might induce a rejection of the larvae, as is frequently observed in Bos taurus indicus cattle, and under certain conditions in Bos taurus taurus cattle. Ticks deactivate the host rejection response by secreting specific proteins and lipids that play an essential role in manipulation of the host immune response. The available genomic information on the R. microplus tick was mined using bioinformatics approaches to identify R. microplus lipocalins (LRMs). This in silico examination revealed a total of 12 different putative R. microplus LRMs (LRM1-LRM12). The identity of the LRM family showed high sequence variability: from 6% between LRM7 and LRM8 to 55.9% between LRM2 and LRM6. However, the three-dimensional structure of the lipocalin family was conserved in the LRMs. The B and T cell epitopes in these lipocalins were then predicted, and six of the LRMs (5, 6, 9, 10, 11 and 12) were used to examine the host immune interactions with sera and peripheral blood mononuclear cells (PBMCs) collected from tick-susceptible and tick-resistant cattle challenged with R. microplus. On days 28-60 after tick infestation, the anti-LRM titres were higher in the resistant group compared with the susceptible cattle. After 60 day, the anti-LRM titres (except LRM9 and LRM11) decreased to zero in the sera of both the tick-resistant and tick-susceptible cattle. Using cell proliferation assays, the PBMCs challenged with some of the predicted T cell epitopes (LRM1_T1, T2; LRM_T1, T2 and LRM12_T) exhibited a significantly higher number of IFN-γ-secreting cells (Th1) in tick-susceptible Holstein-Friesians compared with tick-resistant Brahman cattle. In contrast, expression of the Th2 cytokine (IL-4) was lower in Holstein-Friesians cattle compared with Brahman cattle. Moreover, this study found that LRM6, LRM9 and LRM11 play important roles in the mechanism by which R. microplus interferes with the host's haemostasis mechanisms.
硬蜱幼虫附着在宿主皮肤时会在附着部位引发一系列生理事件。宿主-寄生虫的相互作用可能会导致幼虫被排斥，这在印度野牛中经常观察到，在某些情况下在欧洲野牛中也会观察到。蜱通过分泌特定的蛋白质和脂质来使宿主的免疫反应失活，从而使幼虫得以附着在宿主身上，这些蛋白质和脂质在宿主免疫反应的操纵中起着至关重要的作用。使用生物信息学方法从已有的关于硬蜱的基因组信息中挖掘出硬蜱的脂联素（LRM）。通过这种计算机分析，共鉴定出 12 种不同的硬蜱脂联素（LRM1-LRM12）。LRM 家族的身份表明其序列高度可变：LRM7 和 LRM8 之间的差异为 6%，LRM2 和 LRM6 之间的差异为 55.9%。然而，脂联素家族的三维结构在 LRMs 中是保守的。然后预测了这些脂联素中的 B 细胞和 T 细胞表位，使用其中的 6 种脂联素（5、6、9、10、11 和 12）来检查对感染有硬蜱的易感和抗蜱牛的血清和外周血单核细胞（PBMC）与硬蜱的免疫相互作用。在感染硬蜱后 28-60 天，抗 LRM 滴度在抗蜱牛中高于易感牛。60 天后，抗 LRM 滴度（除 LRM9 和 LRM11 外）在抗蜱和易感牛的血清中均降至零。使用细胞增殖测定法，用一些预测的 T 细胞表位（LRM1_T1、T2；LRM_T1、T2 和 LRM12_T）刺激 PBMC，在易感的荷斯坦-弗里西亚牛中，与抗蜱的婆罗门牛相比，分泌 IFN-γ的细胞（Th1）数量明显增加。相比之下，荷斯坦-弗里西亚牛的 Th2 细胞因子（IL-4）表达水平低于婆罗门牛。此外，这项研究发现 LRM6、LRM9 和 LRM11 在硬蜱干扰宿主止血机制的过程中起着重要作用。
