バキュロウイルスによる宿主行動操作メカニズムの研究

学位の種別: 課程博士審査委員会委員 : (主査)東京大学准教授 勝間 進, 東京大学教授 石川 幸男, 東京大学教授 嶋田 透, 東京大学准教授 松尾 隆嗣, 宇都宮大学准教授 岩永 将司University of Tokyo(東京大学

The Baculovirus Uses a Captured Host Phosphatase to Induce Enhanced Locomotory Activity in Host Caterpillars

The baculovirus is a classic example of a parasite that alters the behavior or physiology of its host so that progeny transmission is maximized. Baculoviruses do this by inducing enhanced locomotory activity (ELA) that causes the host caterpillars to climb to the upper foliage of plants. We previously reported that this behavior is not induced in silkworms that are infected with a mutant baculovirus lacking its protein tyrosine phosphatase (ptp) gene, a gene likely captured from an ancestral host. Here we show that the product of the ptp gene, PTP, associates with baculovirus ORF1629 as a virion structural protein, but surprisingly phosphatase activity associated with PTP was not required for the induction of ELA. Interestingly, the ptp knockout baculovirus showed significantly reduced infectivity of larval brain tissues. Collectively, we show that the modern baculovirus uses the host-derived phosphatase to establish adequate infection for ELA as a virion-associated structural protein rather than as an enzyme

バキュロウイルスの全身感染効率を規定する新たな分子メカニズムの解明

金沢大学理工研究域生命理工学系 / 東京大学バキュロウイルスは全身感染性の昆虫ウイルスで、actin rearrangement-inducing factor 1 遺伝子（arif-1）により宿主体内における感染拡大効率を飛躍的に向上させているが、その詳細な分子メカニズムは不明であった。本研究では、ARIF-1に様々な変異を導入することで、ARIF-1の機能に重要なアミノ酸領域を同定した。また、感染組織の詳細な観察から、これまで想定されていなかった新規の感染ルートを発見し、ARIF-1が新規感染ルートからの感染に必須な因子であることを突き止めた。Baculoviruses are insect viruses that establish systemic infection in the body of host larvae. Previously we found that viral actin rearrangement-inducing factor 1 gene (arif-1) dramatically enhances systemic infection, but its molecular mechanism remains unknown. In this study, we introduced several mutations in arif-1 and identified amino acid regions responsible for its function. In addition, detailed observation of infected tissues revealed the previously unknown infection route that required ARIF-1.研究課題/領域番号:15H06155, 研究期間(年度):2015-08-28 – 2017-03-3

ウイルスは宿主の脳を操るか？: 脳特異的ウイルス制御機構を用いた脳機能操作の実証

金沢大学理工研究域生命理工学系申請者は、カイコ核多角体病ウイルス（BmNPV）が宿主昆虫であるカイコ幼虫の脳に感染することで、カイコの行動を操っていると着想した。そこで、本研究ではGAL4/UASシステムを用いることで、カイコの中枢神経系のみでウイルス増殖を抑制できる遺伝子組換えカイコを作出することで、この仮説の実証を試みた。結果として、ウイルス増殖を大幅に抑制できるカイコ系統は作出できたが、その効果を中枢神経系のみに限定するカイコ系統の作出に難航している。We hypothesized that baculoviruses manipulate host behavior by directly infecting and controlling host central nervous system (CNS). To demonstrate this, we have tried to generate GAL4/UAS transgenic silkworm strains that can suppress viral propagation in specific tissues including CNS. We obtained UAS strains, which express CRISPR-Cas9 system for the cleavage of viral DNA. In the F1 hybrid of these UAS strains and the ActinA3-GAL4 strain, viral propagation significantly delayed. Also, we tried to generate CNS-specific GAL4 strains by GAL4 knock-in into neuron-specific gene loci, but no strains can induce neuron-specific expression so far.研究課題/領域番号:18K14471, 研究期間(年度):2018-04-01 – 2021-03-31出典：「ウイルスは宿主の脳を操るか？：脳特異的ウイルス制御機構を用いた脳機能操作の実証」研究成果報告書　課題番号18K14471（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/report/KAKENHI-PROJECT-18K14471/18K14471seika/）を加工して作

Infectious Virions of <i>Bombyx Mori Latent Virus</i> Are Incorporated into <i>Bombyx Mori Nucleopolyhedrovirus</i> Occlusion Bodies

The Bombyx mori latent virus (BmLV) belongs to the unassigned plant virus family Tymoviridae and contains a positive-sense, single-stranded RNA genome. BmLV has infected almost all B. mori-derived cultured cell lines through unknown routes. The source of BmLV infection and the BmLV life cycle are still unknown. Here, we examined the interaction between BmLV and the insect DNA virus Bombyx mori nucleopolyhedrovirus (BmNPV). Persistent infection with BmLV caused a slight delay in BmNPV propagation, and BmLV propagation was enhanced in B. mori larvae via co-infection with BmNPV. We also showed that BmLV infectious virions were co-occluded with BmNPV virions into BmNPV occlusion bodies. We propose a new relationship between BmLV and BmNPV

Reduced expression of viral genes in tissues of larvae infected with a <i>ptp</i>-disrupted virus.

<p>(A) Heatmaps of viral gene expression in 16 tissues of 5^th instar <i>B. mori</i> infected with BmNPV (WT) or BmPTPD (PTPD). The tissues were dissected from virus-infected larvae at 1, 2, 3, and 4 d p.i., and the expression of the early/late and very late genes <i>gp64</i> and <i>polh</i>, respectively, were quantified by qRT-PCR. Tissues from 5 to 30 larvae were mixed and used for the preparation of cDNAs. Abbreviations: FB, fat body; TR, trachea; BR, brain; CN, central nerve; PG, prothoracic gland; CA, corpora allata; HE, hemocyte; ASG, anterior silk gland; MSG, middle silk gland; PSG, posterior silk gland; MI, midgut; MT, Malpighian tubule; MU, muscle; IN, integument; OV, ovary; and TE, testis. (B) Expression of <i>polh</i> in fat body, trachea, central nerve, and brain. Tissues were dissected from four individual larvae at 4 d p.i. First strand cDNAs were generated from individual larvae and qRT-PCR was performed using primers that targeted the <i>polh</i> gene. Data shown are means ± SD (N = 4). *<i>p</i><0.05, Student's t-test.</p

BmPTPD produces fewer progeny in 5^th instar <i>B. mori</i> and shows a delay in late gene expression in BmN cells.

<p>Production of OBs (A) and BVs (B) in the hemolymph of larvae infected with BmNPV, BmPTPD, BmPTPDR or BmPTP-C119S at 4 d p.i. Data shown are means ± standard deviation (SD) (N = 4). *<i>p</i><0.05, one-way ANOVA with Tukey's post test in comparison to BmPTPD. (C) Western blot analysis of the expression of viral gene products in BmN cells infected with BmNPV, BmPTPD or BmPTPDR. The proteins were separated by SDS-PAGE, transferred to a nitrocellulose membrane, and immunoblotted with antibodies that recognize BmNPV early-expressed (DBP, BRO, and LEF3) or late-expressed (V-CHIA) proteins or actin. Similar results were obtained in two independent experiments. Abbreviations: WT, BmNPV; PTPD, BmPTPD; DR, BmPTPDR; and CS, BmPTPD-C119S.</p

PTP is an envelope-associated protein required for the production of normal virions.

<p>(A) Localization of PTP in the envelope and capsid fractions of budded virus. Western blot analysis of envelope (E) and capsid (C) fractions of budded virus (BV) of BmNPV or BmPTPD-wt were performed with anti-FLAG, anti-GP64 or anti-ORF1629 antibodies. (B) Localization of GP64 and ORF1629 in PTP-deficient BV. Western blot analysis of envelope (E) and capsid (C) fractions of BV of BmNPV, BmPTPD, and BmPTPDR were performed with anti-GP64 or anti-ORF1629 antibody.</p