Tracy Allison M, Weil Ernesto, Burge Colleen A
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, United States.
Department of Marine Sciences, University of Puerto Rico, Mayagüez, PR, United States.
Front Immunol. 2021 Jan 11;11:608066. doi: 10.3389/fimmu.2020.608066. eCollection 2020.
The interplay among environment, demography, and host-parasite interactions is a challenging frontier. In the ocean, fundamental changes are occurring due to anthropogenic pressures, including increased disease outbreaks on coral reefs. These outbreaks include multiple parasites, calling into question how host immunity functions in this complex milieu. Our work investigates the interplay of factors influencing co-infection in the Caribbean sea fan octocoral, , using metrics of the innate immune response: cellular immunity and expression of candidate immune genes. We used existing copepod infections and live pathogen inoculation with the fungus, detecting increased expression of the immune recognition gene Tachylectin 5A (T5A) in response to both parasites. Cellular immunity increased by 8.16% in copepod infections compared to controls and single infections. We also detected activation of cellular immunity in reef populations, with a 13.6% increase during copepod infections. Cellular immunity was similar in the field and in the lab, increasing with copepod infections and not the fungus. Amoebocyte density and the expression of T5A and a matrix metalloproteinase (MMP) gene were also positively correlated across all treatments and colonies, irrespective of parasitic infection. We then assessed the scaling of immune metrics to population-level disease patterns and found random co-occurrence of copepods and fungus across 15 reefs in Puerto Rico. The results suggest immune activation by parasites may not alter parasite co-occurrence if factors other than immunity prevail in structuring parasite infection. We assessed non-immune factors in the field and found that sea fan colony size predicted infection by the copepod parasite. Moreover, the effect of infection on immunity was small relative to that of site differences and live coral cover, and similar to the effect of reproductive status. While additional immune data would shed light on the extent of this pattern, ecological factors may play a larger role than immunity in controlling parasite patterns in the wild. Parsing the effects of immunity and ecological factors in octocoral co-infection shows how disease depends on more than one host and one parasite and explores the application of co-infection research to a colonial marine organism.
环境、人口统计学以及宿主 - 寄生虫相互作用之间的相互影响是一个具有挑战性的前沿领域。在海洋中，由于人为压力正在发生根本性变化，包括珊瑚礁上疾病爆发的增加。这些爆发涉及多种寄生虫，这使得宿主免疫在这种复杂环境中的功能受到质疑。我们的研究利用先天免疫反应指标：细胞免疫和候选免疫基因的表达，来研究影响加勒比海扇八放珊瑚共感染的因素之间的相互作用。我们利用现有的桡足类感染以及用该真菌进行活病原体接种，检测到免疫识别基因速激肽5A（T5A）在对两种寄生虫的反应中表达增加。与对照组和单一感染相比，桡足类感染时细胞免疫增加了8.16%。我们还在珊瑚礁种群中检测到细胞免疫的激活，在桡足类感染期间增加了13.6%。野外和实验室中的细胞免疫情况相似，随着桡足类感染而增加，而非真菌感染。在所有处理和菌落中，不论寄生虫感染情况如何，变形细胞密度以及T5A和基质金属蛋白酶（MMP）基因的表达也呈正相关。然后，我们评估了免疫指标与种群水平疾病模式的关系，发现桡足类和真菌在波多黎各的15个珊瑚礁上随机共现。结果表明，如果在构建寄生虫感染的过程中免疫以外的因素占主导，那么寄生虫引发的免疫激活可能不会改变寄生虫的共现情况。我们在野外评估了非免疫因素，发现海扇群落大小可预测桡足类寄生虫的感染情况。此外，相对于地点差异和活珊瑚覆盖率，感染对免疫的影响较小，与繁殖状态的影响相似。虽然更多的免疫数据将有助于揭示这种模式的程度，但在野外控制寄生虫模式方面，生态因素可能比免疫发挥更大的作用。剖析八放珊瑚共感染中免疫和生态因素的影响，展示了疾病如何依赖于不止一种宿主和一种寄生虫，并探索了共感染研究在一种群体海洋生物中的应用。
