Immune Mechanisms of Disease Resistance in Amphibian Skin

许多种类的两栖动物（青蛙、蟾蜍和蝾螈）目前都在减少，而且灭绝的速度比鸟类或哺乳动物都要快。有许多可能的原因，包括栖息地的丧失、污染和疾病。最近的下降与一种由壶菌引起的致命皮肤病有关。疾病暴发继续以一种与新病原体向易感人群传播相一致的模式发生。这场全球性的生态危机为研究野生动物物种抗病的免疫机制提供了一个独特的机会。目前的研究表明，一些物种对这种疾病的易感性比其他物种低，这些易感性的差异与皮肤防御的差异有关。该项目将研究两栖动物皮肤分泌物中的抗菌肽是否是针对壶菌的主要免疫防御机制，以及抗性越强的物种是否具有更有效的抗菌肽防御机制。这将通过从巴拿马和美国选定的已知易受疾病影响或耐疾病的物种中提取抗菌肽并确定其抗壶菌效力来进行测试。另一个要解决的问题是，是否强大的选择压力的壶菌感染可能选择个体，由于遗传变异，可以表达罕见的有益的抗菌肽。如果是这样，与幼稚易感人群相比，可能在幸存者人群中检测到有益肽。这将在没有壶菌的两栖动物种群存在的地区进行测试，以及在发生疾病和种群减少的地区进行测试，但仍有一些幸存者存在。这个为期四年的项目在培养博士后、研究生和本科生（包括代表性不足的少数民族）方面具有很大的潜力。它将加强与一个由生态学家、生理学家、生化学家和两栖动物疾病专家组成的国际小组的持续伙伴关系，以解决全球两栖动物数量下降的问题。对抗菌肽防御和病原体相互作用的动力学的更深入了解可能为两栖动物进化出对皮肤病原体的抗性机制提供见解。结果可能表明，对壶菌病特别脆弱的物种应该成为更大保护努力的重点。

Immune Mechanisms of Disease Resistance in Amphibian SkinLouise A. Rollins-SmithVanderbilt University Medical Center Many species of amphibians (frogs, toads, and salamanders) are currently in decline, and the rate of extinctions is more rapid than for birds or mammals. There are many possible causes including loss of habitat, pollution, and disease. Recent declines are linked to a lethal skin disease that is caused by a chytrid fungus. Disease outbreaks continue to occur in a pattern consistent with the spread of a new pathogen into susceptible populations. This global ecological crisis provides a unique opportunity to study immune mechanisms of disease resistance in a wildlife species. Current studies suggest that some species are less susceptible to this disease than others, and these differences in susceptibility are correlated with differences in skin defenses. This project will examine the question of whether antimicrobial peptides in the skin secretions of amphibians are a major immune defense mechanism against the chytrid fungus and whether species that are more resistant will have more effective antimicrobial peptide defenses. This will be tested by characterizing the antimicrobial peptides from selected species in Panama and the U.S. that are known to be susceptible or resistant to disease and determining their anti-chytrid potency. Another question that will be addressed is whether the strong selection pressure of a chytrid infection may select for individuals that, due to genetic variation, can express rare beneficial antimicrobial peptides. If so, beneficial peptides may be detectable in survivor populations in comparison with naive susceptible populations. This will be tested where amphibian populations exist in a chytrid-free zone as well as being present in areas where a wave of disease and population losses has occurred, yet some survivors exist. This four-year project has great potential for training students (including under-represented minorities) at the postdoctoral, graduate, and undergraduate levels. It will enhance ongoing partnerships with an international group of ecologists, physiologists, biochemists, and amphibian disease specialists addressing the problem of global amphibian declines. A greater understanding of the dynamics of antimicrobial peptide defenses and pathogen interactions may provide insights into mechanisms by which amphibians evolve resistance to skin pathogens. Results may suggest species that are especially vulnerable to chytrid fungal disease and should be the focus of greater conservation efforts.