中华蜜蜂囊状幼虫病毒和东方蜜蜂微孢子虫顺序感染对中华蜜蜂营养和免疫的影响

Effects of sequential infection of Chinese sacbrood virus and Nosema ceranae on nutrition and immunity of Apis cerana cerana

【目的】中华蜜蜂囊状幼虫病毒(Chinese sacbrood virus,CSBV)和东方蜜蜂微孢子虫Nosema ceranae都是严重威胁蜜蜂健康的重要病原,本研究旨在探究2种病原顺序感染对中华蜜蜂Apiscerana cerana存活率、营养代谢和免疫的影响。【方法】设置中华蜜蜂取食正常食物、先喂食CSBV后喂食东方蜜蜂微孢子虫和先喂食东方蜜蜂微孢子虫后喂食CSBV3个处理,利用PCR检测中华蜜蜂在取食第2天和第4天后体内病原增殖情况;通过RT-qPCR检测中华蜜蜂感染病原后第2天和第4天后体内CSBV数量以及营养代谢基因(ilp1、ilp2、hexamerin70b和hexamerin70c)和免疫应答基因(toll、relish、jra、apidaecin、abaecin、defensin、hymenoptaecin和JAK)的表达情况。【结果】先喂食CSBV后喂食东方蜜蜂微孢子虫组的中华蜜蜂体内孢子量高于先喂食东方蜜蜂微孢子虫后喂食CSBV组,而先喂食CSBV后喂食东方蜜蜂微孢子虫组的中华蜜蜂体内CSBV拷贝数显著高于先喂食东方蜜蜂微孢子虫后喂食CSBV组。先喂食CSBV后喂食东方蜜蜂微孢子虫组的中华蜜蜂营养代谢基因ilp1、ilp2、hexamerin70c和hexamerin70b的表达水平随感染时间延长逐渐呈现下调,而先喂食东方蜜蜂微孢子虫后喂食CSBV组中显著上调。先喂食CSBV后喂食东方蜜蜂微孢子虫组中华蜜峰免疫基因toll和relish表达量呈现先增加后下降,而jra、JAK、apidaecin、abaecin、defensin和hymenoptaecin的表达量显著增加,而先喂食东方蜜蜂微孢子虫后喂食CSBV组中8个免疫基因的表达量均显著增加。【结论】在顺序感染过程中,东方蜜蜂微孢子虫的感染抑制CSBV的增殖,而CSBV的感染则有助于东方蜜蜂微孢子虫的增殖。先喂食CSBV比先喂食东方蜜蜂微孢子虫对中华蜜蜂营养和生长发育的影响更显著,且更易引起宿主的免疫防御,表明CSBV与东方蜜蜂微孢子虫顺序感染中蜂后引起的免疫应答及营养代谢更为复杂。

[Objectives]To examine the effects of sequential infection by the Chinese sacbrood virus and Nosema ceranae on the survival rate,nutritional metabolism and immunity of Apis cerana cerana.[Methods]The three groups of bees were fed normal food,CSBV first and then N.ceranae,N.ceranae first and then CSBV and the proliferation of CSBV and N.ceranae in each group was detacted with PCR.The number of CSBV and the expression of nutritional metabolism genes(ilp1,ilp2,hexamerin70b,hexamerin70c)and immune genes(toll,relish,jra,apidaecin,abaecin,defensin,hymenoptaecin,JAK)were detected by RT-qPCR.[Results]CSBV and N.ceranae infection significantly reduced the survival of A.cerana cerana,and the number of spores in the group fed CSBV first was higher than that in the group fed N.ceranae first.At the time of CSBV inoculation,the proliferation of CSBV in the group fed CSBV first was significantly higher than that in the group fed N.ceranae first.The expression levels of nutritional metabolism genes decreased gradually over time in the group fed CSBV first,but increased significantly in the group fed N.ceranae first.In the group fed CSBV first and then N.ceranae,the expression of immune genes toll and relish increased first and then decreased,and the expression of jra,apidaecin,abaecin,defensin and hymenoptaecin increased significantly,while the expression of these eight immune genes increased significantly in the group fed N.ceranae first and then CSBV.[Conclusion]Infection with N.ceranae inhibited the proliferation of CSBV to a certain extent,whereas infection with CSBV accelerated the proliferation of N.ceranae.Infection with CSBV first has a stronger impact on the nutrition,growth and development of honeybees than feeding N.ceranae first.Bees that were first infected with CSBV mobilized their immune defense more effectively than those that were infected with N.ceranae first.This illustrates the complexity of the interaction between the immune response and the nutritional metabolism caused by the sequential infection of workerbees by CSBV and N.ceranae.