Song Jingjiao, Wang Ranran, Deng Fei, Wang Hualin, Hu Zhihong
State Key Laboratory of Virology and Joint Laboratory of Invertebrate Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, PR China.
J Gen Virol. 2008 Sep;89(Pt 9):2331-2338. doi: 10.1099/vir.0.2008/002352-0.
A combined functional investigation on the four per os infectivity factors (PIFs) of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus (HearNPV) was conducted in this study. HearNPV bacmids with deletions of p74 (Ha20), pif1 (Ha111), pif2 (Ha132) and pif3 (Ha98) were constructed individually by homologous recombination in Escherichia coli cells. Repaired bacmids with respective pifs were also constructed. Western blot analyses revealed that all four PIFs were structural components of the envelope of HearNPV occlusion-derived virus (ODV). Electron microscopy showed that deletion of the pifs did not have any obvious effects on the morphology of the occlusion bodies (OBs). Bioassay analyses indicated that deletion of any of the above pifs resulted in loss of oral infectivity of OBs. The mixtures of the four pif-deletion mutants also resulted in deficiency of oral infectivity, implying that the four PIFs must be structural components of the same ODV to accomplish their function. Repairing of the respective genes into the pif-deletion bacmids could rescue the oral infectivity of the pif-deletion viruses. Calcofluor, which can damage the peritrophic membrane (PM), could not rescue the defects of the oral infectivity of the pif-deletion viruses, indicating that the PM is not likely to be the functional target of the PIFs.
本研究对棉铃虫单粒包埋核多角体病毒（HearNPV）的四种经口感染因子（PIFs）进行了联合功能研究。通过在大肠杆菌细胞中进行同源重组，分别构建了缺失p74（Ha20）、pif1（Ha111）、pif2（Ha132）和pif3（Ha98）的HearNPV杆粒。还构建了带有各自pif的修复杆粒。蛋白质免疫印迹分析表明，所有四种PIFs都是HearNPV多角体衍生病毒（ODV）包膜的结构成分。电子显微镜显示，缺失pif对多角体（OBs）的形态没有明显影响。生物测定分析表明，缺失上述任何一种pif都会导致OBs经口感染性丧失。四种pif缺失突变体的混合物也导致经口感染性缺陷，这意味着四种PIFs必须是同一ODV的结构成分才能完成其功能。将各自的基因修复到pif缺失杆粒中可以挽救pif缺失病毒的经口感染性。能破坏围食膜（PM）的荧光增白剂不能挽救pif缺失病毒经口感染性的缺陷，表明PM不太可能是PIFs的功能靶点。
