Cizauskas Carrie A, Bellan Steven E, Turner Wendy C, Vance Russell E, Getz Wayne M
Department of Environmental Science, Policy & Management, University of California, Berkeley, Berkeley, CA, USA.
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
J Anim Ecol. 2014 Sep;83(5):1078-90. doi: 10.1111/1365-2656.12207. Epub 2014 Mar 14.
Few studies have examined host-pathogen interactions in wildlife from an immunological perspective, particularly in the context of seasonal and longitudinal dynamics. In addition, though most ecological immunology studies employ serological antibody assays, endpoint titre determination is usually based on subjective criteria and needs to be made more objective. Despite the fact that anthrax is an ancient and emerging zoonotic infectious disease found world-wide, its natural ecology is not well understood. In particular, little is known about the adaptive immune responses of wild herbivore hosts against Bacillus anthracis. Working in the natural anthrax system of Etosha National Park, Namibia, we collected 154 serum samples from plains zebra (Equus quagga), 21 from springbok (Antidorcas marsupialis) and 45 from African elephants (Loxodonta africana) over 2-3 years, resampling individuals when possible for seasonal and longitudinal comparisons. We used enzyme-linked immunosorbent assays to measure anti-anthrax antibody titres and developed three increasingly conservative models to determine endpoint titres with more rigourous, objective mensuration. Between 52 and 87% of zebra, 0-15% of springbok and 3-52% of elephants had measurable anti-anthrax antibody titres, depending on the model used. While the ability of elephants and springbok to mount anti-anthrax adaptive immune responses is still equivocal, our results indicate that zebra in ENP often survive sublethal anthrax infections, encounter most B. anthracis in the wet season and can partially booster their immunity to B. anthracis. Thus, rather than being solely a lethal disease, anthrax often occurs as a sublethal infection in some susceptible hosts. Though we found that adaptive immunity to anthrax wanes rapidly, subsequent and frequent sublethal B. anthracis infections cause maturation of anti-anthrax immunity. By triggering host immune responses, these common sublethal infections may act as immunomodulators and affect population dynamics through indirect immunological and co-infection effects. In addition, with our three endpoint titre models, we introduce more mensuration rigour into serological antibody assays, even under the often-restrictive conditions that come with adapting laboratory immunology methods to wild systems. With these methods, we identified significantly more zebras responding immunologically to anthrax than have previous studies using less comprehensive titre analyses.
很少有研究从免疫学角度研究野生动物中的宿主 - 病原体相互作用，特别是在季节性和纵向动态的背景下。此外，尽管大多数生态免疫学研究采用血清学抗体检测，但终点滴度的确定通常基于主观标准，需要更加客观。尽管炭疽是一种在全球范围内发现的古老且新出现的人畜共患传染病，但其自然生态尚未得到充分了解。特别是，关于野生食草动物宿主对炭疽芽孢杆菌的适应性免疫反应知之甚少。在纳米比亚埃托沙国家公园的自然炭疽系统中，我们在两到三年的时间里收集了154份平原斑马（Equus quagga）的血清样本、21份跳羚（Antidorcas marsupialis）的血清样本和45份非洲象（Loxodonta africana）的血清样本，并尽可能对个体进行重新采样以进行季节性和纵向比较。我们使用酶联免疫吸附测定法来测量抗炭疽抗体滴度，并开发了三种越来越保守的模型，以更严格、客观的测定方法来确定终点滴度。根据所使用的模型，52%至87%的斑马、0%至15%的跳羚和3%至52%的大象具有可测量的抗炭疽抗体滴度。虽然大象和跳羚产生抗炭疽适应性免疫反应的能力仍不明确，但我们的结果表明，埃托沙国家公园的斑马经常能在亚致死性炭疽感染中存活下来，在雨季接触到大多数炭疽芽孢杆菌，并且可以部分增强它们对炭疽芽孢杆菌的免疫力。因此，炭疽并非仅仅是一种致命疾病，在某些易感宿主中它常常以亚致死性感染的形式出现。尽管我们发现对炭疽的适应性免疫会迅速减弱，但随后频繁的亚致死性炭疽芽孢杆菌感染会导致抗炭疽免疫的成熟。通过触发宿主免疫反应，这些常见的亚致死性感染可能作为免疫调节剂，并通过间接的免疫和共感染效应影响种群动态。此外，通过我们的三种终点滴度模型，即使在将实验室免疫学方法应用于野生系统时经常受到限制的条件下，我们也为血清学抗体检测引入了更严格的测定方法。通过这些方法，我们发现对炭疽有免疫反应的斑马数量比以前使用不太全面的滴度分析的研究显著更多。
