Washburn J O, Kirkpatrick B A, Volkman L E
Department of Environmental Science, Policy and Management, University of California, Berkeley 94720, USA.
Virology. 1995 Jun 1;209(2):561-8. doi: 10.1006/viro.1995.1288.
We compared early viral pathogenesis and dose-mortality relationships for larvae of two highly susceptible hosts, Trichoplusia ni and Heliothis virescens, using a construct of AcMNPV containing the lacZ reporter gene. Larvae were inoculated either as newly molted fourth instars (4(0)) or 15 hr after the molt (4(15)). In 4(0)-inoculated larvae, first lacZ expression was detected in the midgut epithelium of T. ni at 4 hr postinoculation (hpi) compared to 18 hpi in H. virescens, and systemic infections were initiated from tracheole cells servicing the midgut epithelia beginning at 12 and 20 hpi, respectively. The longer viral tenure within the midgut and the slower progression of systemic infections within H. virescens ultimately contributed to its longer time to death. For 4(0)-inoculated H. virescens, proportions of lacZ-expressing larvae increased from 18 hpi until the onset of the molt to the fifth instar at 36 hpi; at this time point, the proportion of signaling insects equaled the final larval mortality. Viral infections within the midgut epithelium of H. virescens were lost during the molt to the fifth instar. Dose-mortality relationships suggested that the peritrophic membrane provided little protection from AcMNPV infections for either species.
我们使用含有lacZ报告基因的苜蓿银纹夜蛾核型多角体病毒（AcMNPV）构建体，比较了两种高度易感宿主粉纹夜蛾（Trichoplusia ni）和烟芽夜蛾（Heliothis virescens）幼虫的早期病毒发病机制和剂量-死亡率关系。幼虫接种时分别为刚蜕皮的四龄幼虫（4(0)）或蜕皮后15小时（4(15)）。在4(0)接种的幼虫中，接种后4小时（hpi）在粉纹夜蛾的中肠上皮中首次检测到lacZ表达，而在烟芽夜蛾中为18 hpi，并且分别在12 hpi和20 hpi时从中肠上皮的气管细胞开始引发全身感染。烟芽夜蛾中病毒在中肠内持续时间更长以及全身感染进展较慢最终导致其死亡时间更长。对于4(0)接种的烟芽夜蛾，表达lacZ的幼虫比例从18 hpi增加到36 hpi蜕皮至五龄幼虫时；在这个时间点，发出信号的昆虫比例等于最终幼虫死亡率。烟芽夜蛾蜕皮至五龄幼虫时，中肠上皮内的病毒感染消失。剂量-死亡率关系表明，围食膜对这两种物种的AcMNPV感染几乎没有保护作用。
