蝙蝠狂犬病毒的维持、传播和演化 (系列之二) (The maintenance, transmission, and evolution of lyssaviruses in Bats) 二、 蝙蝠的免疫生物学和病毒携带状态假说 (Bat immunobiology and the carrier state hypothesis) 蝙蝠的基本免疫生物学状态,特别是其与狂犬病毒传播的关联,目前还知之甚少。随着最近在蝙蝠中发现多种人畜共患的病原体,现在有相当多的研究正集中在蝙蝠生态学及与病原体的相互作用。在这种新的宿主-病原体相互作用领域,早期的研究主要集中在蝙蝠基因组学研究,希望从中找到免疫调节因子的指征,并与其他已有充分研究的实验动物模型中所获得的明确结果进行比较。 在多年前就已提出 在蝙蝠中可能存在狂犬病毒的携带状态 这个概念。这个假说认为,蝙蝠在某种程度上能够支持狂犬病毒在其体内某个尚未确定的组织中增殖,但仍然能在很长一段时间不表现出临床症状,并能感染同一栖息地内的同一种蝙蝠。但是, 几乎没有实验证据能支持这一假说 。而且,相当肯定的是,在免疫功能降低期间, 蝙蝠可能最终死于狂犬病 ;狂犬病毒的潜伏期相当长,可能说明狂犬病毒与其他典型的急性RNA病毒感染相比,其免疫状态会随时间的推移而有更多样化的表现。 显然,目前对蝙蝠的基本免疫学特性及感染后的免疫应答仍知之甚少。多种蝙蝠的生命周期都与众多的生态因子有着内在的联系,这些因子决定蝙蝠生物学的关键阶段,如休眠和/或迟钝状态、迁移的需要、交配及随后的后代出生时间。环境的作用,包括温度、湿度、食物供应、寄生虫负荷,以及其他蝙蝠病原体的感染,都可能影响暴露于狂犬病毒后的结果。例如,通过实验证明了迟钝状态的影响,迟钝状态本身的持续时间会延长狂犬病的平均潜伏期。蝙蝠物种内的生物多样性意味着这些因素和要求在不同的蝙蝠物种间差别更大;如此说来, 有理由推断经历了一个潜伏阶段后,可能存在病毒的携带状态和/或病毒再激活的可能,但没有任何证据来支持这种说法。 然而,对大量此类因素的影响力的知识都还很欠缺,所以 病毒在健康蝙蝠内维持的机制仍属未知 。一个有趣的假设是:环境的改变可能会影响蝙蝠对病毒的抵抗力、传播,甚至可以通过溢出事件而感染其他哺乳动物群体。在终端宿主(如人群)中发现有更长的潜伏期。也有实例表明,抓获的蝙蝠当时看起来健康,在囚禁过程中发病,偶尔会表现出较长的潜伏期。这可能反映了潜伏期是可变动的,也可能是宿主-病原体关系的反映,其中免疫状态可能是对抗病毒主动复制必不可少的;但是, 这些结果也可能与暴露的途径、所接受的病毒剂量、复制的起始位点,以及其他未知因素有关。 因此, 为了更深入地理解这些独特的哺乳动物宿主与病原体的关系,继续研究蝙蝠的基础免疫生物学是很有必要的。 参考文献: C. Jackson: Advances in virus research---research advances in rabies, Elsevier, 2011.
Pheromones a myth in mammals 哺乳动物有信息素吗?一本新书说没有,或者说没有那么一种生物分子会引起同类的某种反应。化学感知的特性与昆虫不同? December 2nd, 2010 in Biology / Plants Animals Something just didnt smell right to Richard Doty. It was 1976 when the director of the Smell and Taste Center at Penns School of Medicine first started raising a stink about the existence of pheromones. When his latest book, The Great Pheromone Myth, was released earlier this year, it reignited the debate over the science of these supposed smells. Even the definition of the word is controversial. Generally defined as a biological chemical that induces a well-defined response in the same animal , the concept of pheromone s in mammals has been around since the late 1950s. The term has lingered in both scientific circles and pop culture since then. Weve all heard tales of how pheromones cause sparks to fly between people who almost subconsciously follow their noses even before their hearts toward a potential sweetheart. Theres only one problem: According to Doty, mammals ( in contrast to insects【as an example see this new paper 】 ), do not have pheromones. The pheromone term seems to have mainly attracted perfume manufacturers and people looking for the fountain of youth, Doty says. Its just not the way things are. It would be like saying a particular color is why we choose a mate. Thats just not how relationships are formed. The fallacy of the pheromone is not a position Doty has carved out only recently. He has spent decades researching the chemical senses (smell and taste) from both basic and clinical perspectives. We looked at the literature relative to the set of criteria that would distinguish a pheromone from a chemical, says Doty, a professor in the School of Medicines Department of Otorhinolaryngology. In reality, almost everything you could show that almost all the situations of changed behavior were learned. Animals are very good at learning the meaning of chemicals. Doty objects to the idea that a single chemical emitted by one mammal can induce a behavioral change in another of the same species, and therefore little or no more scientific study about the cause and effect of the relationship is needed. Its an oversimplification of how chemicals work in the environment and how animals are affected by them, he says. People have oversimplified the nature of the olfactory system. Its the brain that interprets what meaning is . Conditioning plays a very significant role in all aspects of human and mammal behavior. Though it deals with a testy topic, Dotys book generally has been received well. The Great Pheromone Myth is a lovely mural of important developmental questions and phenomena, reads a recent review in Developmental Psychobiology. The book is also an excellent guide to a field of inquiry, a conceptual framework and an admirable product of scholarship. It offers much to professionals and advanced students in a wide range of sensory, behavioral, ecological, physiological and even clinical fields. Those whove criticized Dotys book range from the militantly pro-pheromone, many of whom Doty says have stated they will not read it, to those who say the whole argument is a tussle over semantics. Its erroneous to infer that all these mammalian behaviors are determined in an invariant way by a single response to a single chemical, Doty says. Its not just semantics , its the whole conceptualization. Doty has spent countless hours throughout his career working to debunk myths surrounding pheromones. This book may be his crowning achievement, yet the concept seems to never dissipate. People want to exist, he says. Its part of our need as humans to have belief in the unknown . We have the need to believe that certain things are happening beyond our senses. Provided by Pennsylvania State University Pheromones a myth in mammals. December 2nd, Commentsby: JVKohl Disclaimer: I have a commercial interest in all this; as does Dr. Doty. Each of us has presented and published on our topics. Dr. Doty has redefined the term pheromone so that not only can they not exist in mammals, they cannot exist in nature. He also fails to account for the obvious effects on physiology and behavior that have been attributed to pheromones since before they were first defined. Is there an alternative stimulus that is linked to olfactory/pheromonal cause and effect (e.g., on hormones)? The terms he uses as qualifiers are largely inappropriate (e.g., innate / unlearned / invariant ) even when used in discussions of insect responses. In my opinion, he has either a careless disregard for molecular biology, or no knowledge of molecular biology (e.g., epigenetics), because he misrepresents facts to make it appear his position bears consideration. Some people will think his book offers current information on research in olfaction and pheromones. He is, after all, an authority, and perhaps he should be considered seriously -- if only because he is so completely wrong. His book attests to the fact that some authorities may not be familiar with their topic (or minimally, aspects that are critical to their topic's discussion), and that some may deliberately misrepresent what is known. Addressing the journalist's comments: I am not militantly pro-pheromone, and I have read and reviewed his book when it first became available. Addressing the quote from Dr. Doty: An oversimplification of howchemicals work in our environment and how they affect our behavior is: We see the food we like, and we eat it. Yet, many people might initially think that the visual appeal of the food is primarily responsible for eliciting our response, sans conditioning. The same oversimplification applies to mate choice, which in all species that sexually reproduce, including mammals, is a function of pheromones that condition our response to visual input. Is there sufficient experiential evidence for this accurate conceptualization of the facts? Try to eat something that doesn't smell right, or mate with someone whose odor is unappealing. Animals don't do this. If you've evolved into a non-mammalian species that does not respond to pheromones, please write a book about it so that we can compare what you say to what Dr. Doty would like us to believe about mammalian pheromones. Here's a link to a paper linking pheromones to neuroendocrinology and ethology (e.g., in mammals including humans). http://www.nel.edu/22_5/NEL220501R01_Review.htm Here's a link to my lengthy review of his book that details the problems he incorporated.: http://pheromones.com/the-great-pheromone-myth-opinionreview And here's a link to the author's copy of my book chapter in The Handbook of the Evolution of Human Sexuality; http://www2.hu-berlin.de/sexology/BIB/kohl.htm James V. Kohl www.pheromones.com