PDF(Pubmed)
Abstract：
Background: Variation in parasite burdens among hosts is typically related to differences in adaptive immunity. Comprehension of underlying mechanisms is hence necessary to gain better insights into endemic transmission cycles. Here we investigate whether wild songbirds that have never been exposed to ticks develop adaptive humoral immunity against endemic Ixodes ricinus ticks. Methods: Blue tits were exposed three times in succession to wild Ixodes ricinus ticks. For each infestation, serum samples were obtained. An enzyme-linked immunosorbent assay was developed, using tick salivary antigens, in order to quantify the bird\'s IgY response against ticks. In addition, at every sampling occasion the birds\' body weight (corrected for body size) and haematocrit level was determined. Results: Individual IgY levels against the ticks\' salivary proteins increased over three consecutive tick infestations, and large among-individual variation was observed. The responses were specifically directed against I. ricinus; cross-reactivity against the congeneric tree-hole tick Ixodes arboricola was negligibly low. IgY responses did not impinge on tick feeding success (engorgement weight and attachment success). Yet, those birds with the highest immune responses were more capable to reduce the acute harm (blood depletions) by compensating erythrocyte loss. Furthermore, at the end of the experiment, these birds had gained more body weight than birds with lower IgY levels. Conclusions: Latter observations can be considered as an effect of host quality and/or tolerance mechanisms. Birds anticipate the (future) costs of the activation of the immune system by ticks and/or ongoing tick-borne pathogen infections. Furthermore, although unsuccessful against tick feeding, the IgY responses may indirectly protect birds against tick-borne disease by acting against salivary protein secretions on which pathogens rely for transmission.
摘要：
背景：宿主之间寄生虫负担的变化通常与适应性免疫的差异有关。因此，有必要理解潜在机制，以更好地了解地方性传播周期。在这里，我们调查从未暴露于蜱的野生鸣鸟是否会对地方性的蓖麻蜱产生适应性体液免疫。方法：将蓝雀连续暴露于野生蓖麻蜱中3次。对于每一次侵扰，获得血清样本。开发了一种酶联免疫吸附试验，使用蜱唾液抗原，以量化鸟类对蜱的IgY反应。此外,在每次采样时，都测定了鸟类的体重（根据体型校正）和血细胞比容水平。结果：在连续三次蜱侵染过程中，针对蜱唾液蛋白的个体IgY水平增加，并观察到很大的个体差异。反应是专门针对蓖麻的；对同系树孔蜱Ixodesarboricola的交叉反应性低至可忽略。IgY反应不影响蜱喂食成功(充血体重和依恋成功)。然而，那些免疫反应最高的鸟类更有能力通过补偿红细胞损失来减少急性伤害(血液耗尽)。此外，在实验结束时,与IgY水平较低的鸟类相比，这些鸟类的体重增加更多。结论：后期观察可以被认为是宿主质量和/或耐受机制的影响。鸟类预测通过蜱和/或持续的蜱传播病原体感染激活免疫系统的(未来)成本。此外，尽管对蜱虫喂食没有成功，IgY反应可以通过对抗病原体赖以传播的唾液蛋白分泌物来间接保护鸟类免受蜱传播疾病。
