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。尽管已有大量研究聚焦于抗性（resistance，即杀灭病原体的能力）差异的内在机制，但我们对耐受性（tolerance，即最小化每单位病原体引发的宿主适合度损失的能力）差异的内在机制却所知甚少。本研究针对对鸡毒支原体（Mycoplasma gallisepticum, MG）接触历史不同的两个家朱雀（Haemorhous [原Carpodacus] mexicanus）种群，探究其耐受性的模式与机制。在统一环境下完成感染后，我们以体重下降量和眼部病变严重程度这两项病理学指标作为适合度的替代指标进行评估。本研究采用两种方法计算耐受性：一种基于感染峰值时刻的病理学指标与病原体载量（时点耐受性（point tolerance）），另一种基于上述指标随时间的积分（区间耐受性（range tolerance））。接触MG历史显著更长的阿拉巴马州种群，其时点耐受性较亚利桑那州种群更为显著，但二者的区间耐受性并无差异。阿拉巴马州种群在感染早期的炎症细胞因子信号水平与体温升高程度也更低。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，可能是家朱雀个体与种群间耐受性差异的成因之一。这类耐受性差异可通过仅以抗性无法预测的方式影响病原体的传播与演化，同时也为野生动物炎症反应的代价与收益提供了新的见解。