Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada.
J Invertebr Pathol. 2019 Oct;167:107232. doi: 10.1016/j.jip.2019.107232. Epub 2019 Aug 21.
Understanding how hosts respond to pathogen attack is crucial to disease management. The response of a host can be particularly important if hosts have to defend against multiple pathogens which could either benefit from or be suppressed by prior pathogen exposure. Insect defence against viruses is less well understood than responses to other entomopathogens and much of the information available relates to in vitro studies and model systems. Baculoviruses are natural pathogens of insects, particularly Lepidoptera, and have been well-studied in terms of their ecology, pest control potential and molecular biology. In order to examine how an insect reacts to baculovirus challenge, we measured components of the cellular and humoral immune response of the cabbage looper Trichoplusia ni to Trichoplusia ni SNPV, a narrow-host range nucleopolyhedrovirus (NPV), over four doses and three times after pathogen challenge (18, 42 and 90 h). We found that total haemocyte numbers peaked at 42 h post-exposure at all doses, and declined linearly with increasing dose after the 18 h time point. Two immune-related enzymes, phenoloxidase (PO) and FAD-glucose dehydrogenase (GLD), showed very different responses. PO levels were lowest at the 42 h time point and were not influenced by virus dose when each time point was examined separately. GLD levels declined over time but they interacted with virus dose in a non-linear manner, such that there was an increase in levels at intermediate virus doses after 18 h, no effect at 42 h, and then declined as infection progressed at 90 h post-infection. These data suggest that baculoviruses can rapidly infect haemocytes (or cause a reduction in their numbers) in a dose-dependent manner once the infection is systemic, likely reducing the ability of the host to counter subsequent infections. However, the data do not support a direct role for PO in defence against baculoviruses. Whether GLD plays a role in virus defence is still unclear.
了解宿主如何应对病原体攻击对于疾病管理至关重要。如果宿主必须抵御多种病原体，而这些病原体要么受益于先前的病原体暴露，要么被其抑制，那么宿主的反应尤其重要。与对其他昆虫病原体的反应相比，昆虫对病毒的防御作用了解得较少，并且可用的信息大多与体外研究和模型系统有关。杆状病毒是昆虫，特别是鳞翅目昆虫的天然病原体，其生态学、害虫防治潜力和分子生物学已得到充分研究。为了研究昆虫对杆状病毒挑战的反应，我们测量了小菜蛾斜纹夜蛾细胞和体液免疫反应的成分，小菜蛾斜纹夜蛾 SNPV 是一种窄宿主范围的核多角体病毒（NPV），在四种剂量和三种时间后进行了病原体挑战（18、42 和 90 h）。我们发现，在所有剂量下，总血细胞数量在暴露后 42 h 时达到峰值，并在 18 h 后随着剂量的增加呈线性下降。两种与免疫相关的酶，酚氧化酶（PO）和 FAD-葡萄糖脱氢酶（GLD），表现出非常不同的反应。PO 水平在 42 h 时间点最低，当分别检查每个时间点时，不受病毒剂量的影响。GLD 水平随时间下降，但与病毒剂量呈非线性相互作用，即在 18 h 后中间病毒剂量下水平增加，在 42 h 时没有影响，然后在感染后 90 h 时随着感染的进展而下降。这些数据表明，一旦感染系统性，杆状病毒可以以剂量依赖的方式快速感染血细胞（或导致其数量减少），可能会降低宿主抵抗随后感染的能力。然而，这些数据并不支持 PO 在防御杆状病毒方面的直接作用。GLD 是否在病毒防御中起作用仍不清楚。
