Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland ; Biodiversity and Conservation Biology, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland.
PLoS One. 2013 Oct 22;8(10):e78427. doi: 10.1371/journal.pone.0078427. eCollection 2013.
Vertebrate hosts often defend themselves against several co-infecting parasite genotypes simultaneously. This has important implications for the ecological dynamics and the evolution of host defence systems and parasite strategies. For example, it can drive the specificity of the adaptive immune system towards high genotype-specificity or cross-reactivity against several parasite genotypes depending on the sequence and probability of re-infections. However, to date, there is very little evidence on these interactions outside mammalian disease literature. In this study we asked whether genotype-specific or cross-reactive responses dominate in the adaptive immune system of a fish host towards a common macroparasite. In other words, we investigated if the infection success of a parasite genotype is influenced by the immunization genotype. We reciprocally immunized and re-exposed rainbow trout (Oncorhynchus mykiss) to a range of genotypes of the trematode eye fluke Diplostomum pseudospathaceum, and measured infection success of the parasite. We found that the infection success of the parasite genotypes in the re-exposure did not depend on the immunization genotype. While immunization reduced average infection success by 31%, the reduction was not larger against the initial immunization genotype. Our results suggest significant cross-reactivity, which may be advantageous for the host in genetically diverse re-exposures and have significant evolutionary implications for parasite strategies. Overall, our study is among the first to demonstrate cross-reactivity of adaptive immunity against genetically diverse macroparasites with complex life cycles.
脊椎动物宿主通常会同时抵御几种共同感染的寄生虫基因型。这对生态动态和宿主防御系统以及寄生虫策略的进化具有重要意义。例如，它可以根据再感染的序列和概率，使适应性免疫系统的特异性朝着高度基因型特异性或针对几种寄生虫基因型的交叉反应性发展。然而，迄今为止，除了哺乳动物疾病文献之外，关于这些相互作用的证据非常少。在这项研究中，我们询问了在鱼类宿主的适应性免疫系统中，针对一种常见的大型寄生虫，是基因型特异性反应还是交叉反应占主导地位。换句话说，我们研究了寄生虫基因型的感染成功率是否受到免疫基因型的影响。我们互惠地免疫并重新暴露虹鳟（Oncorhynchus mykiss），使其接触一系列吸虫眼吸虫 Diplostomum pseudospathaceum 的基因型，并测量寄生虫的感染成功率。我们发现，再暴露时寄生虫基因型的感染成功率并不取决于免疫基因型。虽然免疫使平均感染成功率降低了 31%，但对初始免疫基因型的降低并不更大。我们的结果表明存在显著的交叉反应性，这可能对宿主在遗传多样化的再暴露中有利，并且对寄生虫策略具有重要的进化意义。总的来说，我们的研究是首批证明针对具有复杂生命周期的遗传多样化大型寄生虫的适应性免疫交叉反应性的研究之一。
