Data from: House finch populations differ in early inflammatory signaling and pathogen tolerance at the peak of Mycoplasma gallisepticum infection

Host individuals and populations often vary in their responses to infection, with direct consequences for pathogen spread and evolution. While considerable work has focused on the mechanisms underlying differences in resistance—the ability to kill pathogens—we know little about the mechanisms underlying tolerance—the ability to minimize fitness losses per unit pathogen. Here, we examine patterns and mechanisms of tolerance between two populations of house finches (Haemorhous [formerly Carpodacus] mexicanus) with different histories with the bacterial pathogen Mycoplasma gallisepticum (MG). After infection in a common environment, we assessed two metrics of pathology, mass loss and eye lesion severity, as proxies for fitness. We calculated tolerance using two methods, one based on pathology and pathogen load at the peak of infection (point tolerance) and the other based on the integrals of these metrics over time (range tolerance). Alabama birds, which have a significantly longer history of exposure to MG, showed more pronounced point tolerance than Arizona birds, while range tolerance did not differ between populations. Alabama birds also displayed lower inflammatory cytokine signaling and lower fever early in infection. These results suggest that differences in inflammatory processes, which can significantly damage host tissues, may contribute to variation in tolerance among house finch individuals and populations. Such variation can affect pathogen spread and evolution in ways not predictable by resistance alone and sheds light on the costs and benefits of inflammation in wild animals.

宿主个体与种群对感染的应答往往存在差异，这会直接影响病原体的传播与演化进程。尽管已有大量研究聚焦于抗病性（resistance）差异背后的调控机制——即宿主杀灭病原体的能力——但我们对耐受性（tolerance）的调控机制却知之甚少：耐受性指的是宿主在单位病原体负荷下最小化自身适合度损失的能力。本研究以两种经历过不同鸡毒支原体（Mycoplasma gallisepticum, MG）感染史的家朱雀（Haemorhous [原分类为Carpodacus] mexicanus）种群为研究对象，探究其耐受性的表现形式与调控机制。在统一可控的环境中完成感染实验后，我们通过两项病理指标——体重下降量与眼部损伤严重程度——作为适合度的替代指标进行评估。我们采用两种方法计算耐受性：一种基于感染峰值时刻的病理指标与病原体载量（即点耐受性（point tolerance）），另一种基于上述指标随时间的积分值（即区间耐受性（range tolerance））。相较于经历鸡毒支原体暴露史更久的阿拉巴马种群家朱雀，亚利桑那种群展现出更显著的点耐受性；而两种群的区间耐受性并无显著差异。此外，阿拉巴马种群在感染早期的炎症细胞因子信号通路活性更低，体温升高程度也更弱。上述结果表明，可对宿主组织造成显著损伤的炎症过程差异，或许是家朱雀个体与种群间耐受性存在差异的重要成因。这类耐受性差异可通过仅依靠抗病性无法预测的方式影响病原体的传播与演化，同时也为野生动物体内炎症反应的成本与收益提供了新的研究视角。