Shikano Ikkei, Hua Kevin Ngoc, Cory Jenny S
Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A1S6, Canada.
Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A1S6, Canada.
J Invertebr Pathol. 2016 May;136:35-42. doi: 10.1016/j.jip.2016.03.001. Epub 2016 Mar 2.
Invertebrate hosts that survive pathogen challenge can produce offspring that are more resistant to the same pathogen via immune priming, thereby improving the fitness of their offspring in the same pathogen environment. Most evidence for immune priming comes from exposure to bacteria and there are limited data on other groups of pathogens. Poor parental nutrition has also been shown to result in the transgenerational transfer of pathogen resistance and increased immunocompetence. Here, we combine exposure to an insect DNA virus with a change in the parental diet to examine both parental costs and transgenerational immune priming. We challenged the cabbage looper, Trichoplusia ni, with a low dose of the baculovirus, Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and altered dietary protein to carbohydrate ratio (p:c ratio) after virus exposure. Insects fed a low protein diet had lower haemolymph protein concentrations, and exhibited costs of smaller pupae and slower development, while survivors of virus challenge developed more slowly, irrespective of p:c ratio, and those that were virus-challenged and fed on a low protein diet showed a reduction in haemocyte density. In addition, AcMNPV-challenged parents laid fewer eggs earlier in egg laying although egg size was the same as for unchallenged parents. There was no evidence for increased resistance to AcMNPV (immune priming) or changes in haemocyte number (as proxy for constitutive cellular immunity) in the offspring either as a result of parental AcMNPV-challenge or low dietary p:c ratio. Therefore, although pathogen-challenge and nutritional changes can affect host development and reproduction, this does not necessarily translate into transgenerational immune priming. Our findings contrast with an earlier study on another type of baculovirus, a granulovirus, where immune priming was suggested. This indicates that transgenerational immune priming is not universal in invertebrates and is likely to depend on the host-pathogen system, or the level of pathogen exposure and the type of dietary manipulation. Identifying whether immune priming or transgenerational effects are relevant in field populations, remains a challenge.
在病原体挑战中存活下来的无脊椎动物宿主能够通过免疫致敏产生对相同病原体更具抗性的后代，从而在相同病原体环境中提高其后代的适应性。免疫致敏的大多数证据来自于对细菌的接触，而关于其他病原体组的数据有限。研究还表明，亲本营养不足会导致病原体抗性的跨代传递和免疫能力的增强。在这里，我们将接触昆虫DNA病毒与亲本饮食的改变相结合，以研究亲本成本和跨代免疫致敏。我们用低剂量的杆状病毒——苜蓿银纹夜蛾多角体病毒（AcMNPV）对甘蓝夜蛾（Trichoplusia ni）进行挑战，并在病毒暴露后改变饮食中的蛋白质与碳水化合物比例（p:c比）。喂食低蛋白饮食的昆虫血淋巴蛋白浓度较低，表现出蛹体较小和发育较慢的代价，而病毒挑战的幸存者发育较慢，与p:c比无关，那些受到病毒挑战并喂食低蛋白饮食的昆虫血细胞密度降低。此外，受到AcMNPV挑战的亲本在产卵早期产卵较少，尽管卵的大小与未受挑战的亲本相同。无论是亲本受到AcMNPV挑战还是饮食p:c比低，其后代均未表现出对AcMNPV的抗性增强（免疫致敏）或血细胞数量变化（作为组成性细胞免疫的指标）。因此，尽管病原体挑战和营养变化会影响宿主的发育和繁殖，但这不一定会转化为跨代免疫致敏。我们的研究结果与早期关于另一种杆状病毒——颗粒体病毒的研究形成对比，后者的研究表明存在免疫致敏现象。这表明跨代免疫致敏在无脊椎动物中并不普遍，可能取决于宿主 - 病原体系统，或病原体暴露水平和饮食操纵类型。确定免疫致敏或跨代效应在野外种群中是否相关仍然是一个挑战。
