Baculoviruses are a family of arthropod-specific large DNA viruses that infect insect species belonging to the orders Lepidoptera,Hymenoptera and Diptera.In nature,occlusion-derived viruses(ODVs) initiate baculovirus ...Baculoviruses are a family of arthropod-specific large DNA viruses that infect insect species belonging to the orders Lepidoptera,Hymenoptera and Diptera.In nature,occlusion-derived viruses(ODVs) initiate baculovirus primary infection in the midgut epithelium of insect hosts,and this process is largely dependent on a number of ODV envelope proteins designated as per os infectivity factors(PIFs).Interestingly,PIF homologs are also present in other invertebrate large DNA viruses,which is indicative that per os infection is an ancient and phylogenetically conserved entry mechanism shared by these viruses.Here,we review the advances in the knowledge of the functions of individual PIFs and recent discoveries about the PIF complex,and discuss the evolutionary implications of PIF homologs in invertebrate DNA viruses.Furthermore,future research highlights on the per os infection mechanism are also prospected.展开更多
Effective oral infection is set off by interaction of a group of conserved per os infectivity factors(PIFs) with larval midgut columnar epithelial cells. We constructed pseudotyped viruses by substituting pif1, pif2 o...Effective oral infection is set off by interaction of a group of conserved per os infectivity factors(PIFs) with larval midgut columnar epithelial cells. We constructed pseudotyped viruses by substituting pif1, pif2 or pif3 genes of Helicoverpa armigera nucleopolyhedrovirus(Hear NPV) with their homologs from Mamestra bracissae multiple nucleopolyhedrovirus and tested their infectivity to tissue culture cells and to larvae. Transfection and infection assays revealed that all recombinant viruses generated infectious budded virus in both cell culture and in larvae. Electron microscopy showed synthesized occlusion body and occlusion derived virus(ODV) were morphologically indistinguishable from those of the parental virus. By contrast, feeding assays revealed that pseudotyped viruses could not rescue oral infectivity except for pif3 pseudotyped virus that only partially rescued oral infectivity but at a mortality rate much lower than that of the parental Hear NPV. Consistent with the bioassay result, PIF complex was detected in ODVs of pif3 pseudotyped virus only but not in pif1 or pif2 pseudotyped viruses. Our results suggest that PIF complex is essential for oral infectivity, and in the formation of the PIF complex, PIF1, 2 are virus-specific while PIF3 does not appear to be as specific and can function in heterologous environment, albeit to a much more limited extent.展开更多
Apis mellifera filamentous virus(Am FV)is a large DNA virus that is endemic in honeybee colonies.The genome sequence of the Am FV Swiss isolate(Am FV CH–C05)has been reported,but so far very few molecular studies hav...Apis mellifera filamentous virus(Am FV)is a large DNA virus that is endemic in honeybee colonies.The genome sequence of the Am FV Swiss isolate(Am FV CH–C05)has been reported,but so far very few molecular studies have been conducted on this virus.In this study,we isolated and purified Am FV(Am FV CN)from Chinese honeybee(Apis mellifera)colonies and elucidated its genomics and proteomics.Electron microscopy showed ovoid purified virions with dimensions of 300–500×210–285 nm,wrapping a 3165×40 nm filamentous nucleocapsid in three figure-eight loops.Unlike Am FV CH–C05,which was reported to have a circular genome,our data suggest that Am FV CN has a linear genome of approximately 493 kb.A total of 197 ORFs were identified,among which36 putative genes including 18 baculoviral homologs were annotated.The overall nucleotide similarity between the CN and CH–C05 isolates was 96.9%.Several ORFs were newly annotated in Am FV CN,including homologs of per os infectivity factor 4(PIF4)and a putative integrase.Phylogenomic analysis placed Am FVs on a separate branch within the newly proposed virus class Naldaviricetes.Proteomic analysis revealed 47 Am FV virionassociated proteins,of which 14 had over 50%sequence coverage,suggesting that they are likely to be main structural proteins.In addition,all six of the annotated PIFs(PIF-0–5)were identified by proteomics,suggesting that they may function as entry factors in Am FV infection.This study provides fundamental information regarding the molecular biology of Am FV.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB11030400)the National Natural Science Foundation of China(31130058,31621061)+1 种基金the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(QYZDJ-SSW-SMC021)the Virology Key Frontier Science Program of the State Key Laboratory of Virology(klv-2016-03)
文摘Baculoviruses are a family of arthropod-specific large DNA viruses that infect insect species belonging to the orders Lepidoptera,Hymenoptera and Diptera.In nature,occlusion-derived viruses(ODVs) initiate baculovirus primary infection in the midgut epithelium of insect hosts,and this process is largely dependent on a number of ODV envelope proteins designated as per os infectivity factors(PIFs).Interestingly,PIF homologs are also present in other invertebrate large DNA viruses,which is indicative that per os infection is an ancient and phylogenetically conserved entry mechanism shared by these viruses.Here,we review the advances in the knowledge of the functions of individual PIFs and recent discoveries about the PIF complex,and discuss the evolutionary implications of PIF homologs in invertebrate DNA viruses.Furthermore,future research highlights on the per os infection mechanism are also prospected.
基金supported by grants from the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (grant No.QYZDJ-SSW-SMC021)the National Natural Science Foundation of China (grants No.31621061 and 31130058)+2 种基金the Virology Key Frontier Science Program of State Key Laboratory of Virology (grant No.klv-2016-03)the National Key R&D Program of China (2017YFD0200400)sponsored by CAS-TWAS President’s Fellowship for International PhD Students
文摘Effective oral infection is set off by interaction of a group of conserved per os infectivity factors(PIFs) with larval midgut columnar epithelial cells. We constructed pseudotyped viruses by substituting pif1, pif2 or pif3 genes of Helicoverpa armigera nucleopolyhedrovirus(Hear NPV) with their homologs from Mamestra bracissae multiple nucleopolyhedrovirus and tested their infectivity to tissue culture cells and to larvae. Transfection and infection assays revealed that all recombinant viruses generated infectious budded virus in both cell culture and in larvae. Electron microscopy showed synthesized occlusion body and occlusion derived virus(ODV) were morphologically indistinguishable from those of the parental virus. By contrast, feeding assays revealed that pseudotyped viruses could not rescue oral infectivity except for pif3 pseudotyped virus that only partially rescued oral infectivity but at a mortality rate much lower than that of the parental Hear NPV. Consistent with the bioassay result, PIF complex was detected in ODVs of pif3 pseudotyped virus only but not in pif1 or pif2 pseudotyped viruses. Our results suggest that PIF complex is essential for oral infectivity, and in the formation of the PIF complex, PIF1, 2 are virus-specific while PIF3 does not appear to be as specific and can function in heterologous environment, albeit to a much more limited extent.
文摘家蚕核型多角体病毒（Bm NPV）包涵体衍生型病毒粒子（ODV）被家蚕幼虫食下后通过侵染中肠上皮细胞引发全身性感染,这个过程称为经口感染。已知有多种ODV囊膜蛋白在经口感染中发挥关键作用,被称为经口感染因子（PIF）。P74作为最早被鉴定的PIF,与ODV结合中肠上皮细胞有关。为了鉴定宿主家蚕中肠细胞中与P74互作的蛋白质,构建家蚕中肠酵母文库,并以P74作为诱饵进行酵母双杂交筛选。初步筛选到7种互作候选蛋白,分别为U3小核仁核糖核蛋白IMP3、60S核糖体蛋白L5、JAB-MPN结构域蛋白、细胞质肌动蛋白A3、35 k D蛋白酶、富半胱氨酸和组氨酸蛋白1-B和真核翻译起始因子1A。免疫共沉淀实验结果表明JAB-MPN结构域蛋白和P74之间存在强烈互作,该蛋白质可能是ODV结合中肠细胞的关键宿主因子。研究结果为进一步阐明Bm NPV经口感染的详细分子机制提供了新的线索。
基金the Open Research Fund Program of the State Key Laboratory of Virology of China(Grant No.2019IOV004)the key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.QYZDJ-SSW-SMC021)the National Natural Science Foundation of China(Grant No.31900154 and 31572471)。
文摘Apis mellifera filamentous virus(Am FV)is a large DNA virus that is endemic in honeybee colonies.The genome sequence of the Am FV Swiss isolate(Am FV CH–C05)has been reported,but so far very few molecular studies have been conducted on this virus.In this study,we isolated and purified Am FV(Am FV CN)from Chinese honeybee(Apis mellifera)colonies and elucidated its genomics and proteomics.Electron microscopy showed ovoid purified virions with dimensions of 300–500×210–285 nm,wrapping a 3165×40 nm filamentous nucleocapsid in three figure-eight loops.Unlike Am FV CH–C05,which was reported to have a circular genome,our data suggest that Am FV CN has a linear genome of approximately 493 kb.A total of 197 ORFs were identified,among which36 putative genes including 18 baculoviral homologs were annotated.The overall nucleotide similarity between the CN and CH–C05 isolates was 96.9%.Several ORFs were newly annotated in Am FV CN,including homologs of per os infectivity factor 4(PIF4)and a putative integrase.Phylogenomic analysis placed Am FVs on a separate branch within the newly proposed virus class Naldaviricetes.Proteomic analysis revealed 47 Am FV virionassociated proteins,of which 14 had over 50%sequence coverage,suggesting that they are likely to be main structural proteins.In addition,all six of the annotated PIFs(PIF-0–5)were identified by proteomics,suggesting that they may function as entry factors in Am FV infection.This study provides fundamental information regarding the molecular biology of Am FV.
