Heylen Dieter, Bisaglia Beatrice, Fracasso Gerardo, Prinsen Els, Müller Wendt, Matthysen Erik
Eco-Epidemiology Group, Institute of Tropical Medicine, Antwerp, Belgium.
Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Diepenbeek, Belgium.
Open Res Eur. 2021 Sep 23;1:8. doi: 10.12688/openreseurope.13204.2. eCollection 2021.
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 ticks. : Blue tits were exposed three times in succession to wild 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. 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 ; cross-reactivity against the congeneric tree-hole tick 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. 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.
宿主之间寄生虫负荷的差异通常与适应性免疫的差异有关。因此，了解潜在机制对于更好地洞察地方病传播周期是必要的。在这里，我们研究从未接触过蜱虫的野生鸣禽是否会产生针对地方病蜱虫的适应性体液免疫。蓝山雀连续三次接触野生蜱虫。每次感染后，采集血清样本。利用蜱虫唾液抗原来开发一种酶联免疫吸附测定法，以量化鸟类针对蜱虫的IgY反应。此外，在每次采样时，测定鸟类的体重（根据体型校正）和血细胞比容水平。针对蜱虫唾液蛋白的个体IgY水平在连续三次蜱虫感染过程中有所增加，并且观察到个体间存在较大差异。这些反应是特异性针对的；与同属的树洞蜱虫的交叉反应性极低。IgY反应并未影响蜱虫的取食成功率（饱食重量和附着成功率）。然而，那些免疫反应最强的鸟类更有能力通过补偿红细胞损失来减轻急性伤害（血液消耗）。此外，在实验结束时，这些鸟类比IgY水平较低的鸟类体重增加更多。后一种观察结果可被视为宿主质量和/或耐受机制的影响。鸟类预计蜱虫和/或持续蜱传病原体感染激活免疫系统的（未来）成本。此外，尽管对蜱虫取食没有效果，但IgY反应可能通过作用于病原体传播所依赖的唾液蛋白分泌而间接保护鸟类免受蜱传疾病的侵害。
