Université de Bourgogne, UMR CNRS 5561 Biogéosciences, Equipe Ecologie Evolutive, 6 Bd Gabriel, 21000 Dijon, France.
Proc Biol Sci. 2009 Dec 7;276(1676):4229-36. doi: 10.1098/rspb.2009.1299. Epub 2009 Sep 2.
Parasites often manipulate host immunity for their own benefit, either by exacerbating or suppressing the immune response and this may directly affect the expression of parasite virulence. However, genetic variation in immunodepression, which is a prerequisite to its evolution, and the relationship between immunodepression and virulence, have rarely been studied. Here, we investigated the variation among sibships of the acanthocephalan parasite, Pomphorhynchus laevis, in infecting and in immunodepressing its amphipod host, Gammarus pulex. We also assessed the covariation between infectivity, parasite-induced immune depression and host mortality (parasite virulence). We found that infectivity, the intensity of immunodepression and virulence were variable among parasite sibships. Infectivity and the level of immunodepression were not correlated across parasite sibships. Whereas infectivity was unrelated to host mortality, we found that gammarids that were exposed to the parasite sibships that immunodepressed their hosts the most survived better. This positive covariation between host survival and immunodepression suggests that gammarids exposed to the less immunodepressive parasites could suffer from damage imposed by a higher activity of the phenoloxidase.
寄生虫经常为了自身利益而操纵宿主的免疫反应，无论是加剧还是抑制免疫反应，这可能直接影响寄生虫的毒力表达。然而，免疫抑制的遗传变异（这是其进化的前提）及其与毒力之间的关系很少被研究。在这里，我们研究了寄生性棘头虫 Pomphorhynchus laevis 在感染其十足目宿主卤虫（Gammarus pulex）并免疫抑制宿主时，其兄弟姐妹之间的变异。我们还评估了感染性、寄生虫引起的免疫抑制和宿主死亡率（寄生虫毒力）之间的共变关系。我们发现，寄生虫的兄弟姐妹之间的感染性、免疫抑制的强度和毒力都是可变的。寄生虫兄弟姐妹之间的感染性和免疫抑制水平没有相关性。虽然感染性与宿主死亡率无关，但我们发现，暴露于对宿主免疫抑制最严重的寄生虫兄弟姐妹的卤虫存活得更好。宿主存活和免疫抑制之间的这种正共变关系表明，暴露于免疫抑制较低的寄生虫的卤虫可能会受到酚氧化酶活性更高所带来的损害。
