Researchers Database

ohba kenji

    CenterforMolelucarMedicine(DivisionofGeneticTherapeutics) Assistant Professor
Last Updated :2021/12/07

Researcher Information

Degree

  • Ph.D.(Tokyo Medical and Dental University)

Research funding number

  • 20759576

J-Global ID

Research Interests

  • Genetic Therapy   Immunology   Oncology   Molecular biology   Cell competition   Virology   

Research Areas

  • Life sciences / Tumor diagnostics and therapeutics
  • Life sciences / Medical biochemistry
  • Life sciences / Genomics / Genetic therapy
  • Life sciences / Cell biology
  • Life sciences / Molecular biology
  • Life sciences / Immunology
  • Life sciences / Pathobiochemistry
  • Life sciences / Physiology
  • Life sciences / Tumor biology
  • Life sciences / Virology / HIV, HTLV, Influenza virus, Flavivirus, Oncovirus, AAV, etc

Academic & Professional Experience

  • 2015/03 - 2018/10  Hokkaido UniversityDivision of Molecular Oncology, Institute for Genetic MedicineProject Assistant Professor
  • 2010/04 - 2015/03  National University of SingaporeYong Loo Lin School of Medicine, Department of MicrobiologyResearch Fellow
  • 2008/04 - 2010/03  National Institute of Infectious DiseasesAIDS Research CenterPostdoctoral Fellow
  • 2004/04 - 2008/03  Tokyo Medical and Dental UniversitySchool of MedicinePh.D.
  • 2002/04 - 2004/03  Yokohama City UniversitySchool of MedicineMaster

Education

  • 2004/04 - 2008/03  Tokyo Medical and Dental University  Graduate School of Medical and Dental Science  Doctral Program for Medical and Dental Science (Medical Doctor Course)
  • 2002/04 - 2004/03  Yokohama-city University  Graduate School of Medicine  Master Course for Medical Science
  • 1998/04 - 2002/03  Rikkyo University  College of Science  Department of Life Science

Association Memberships

  • International Society on Aptamers   日本ウイルス学会   The Molecuar Biology Society of Japan   

Published Papers

  • Shiyu Ayukawa, Nagisa Kamoshita, Jun Nakayama, Ryohei Teramoto, Novalia Pishesha, Kenji Ohba, Nanami Sato, Kei Kozawa, Hikari Abe, Kentaro Semba, Nobuhito Goda, Yasuyuki Fujita, Takeshi Maruyama
    Nature Immunology 22 (11) 1391 - 1402 1529-2908 2021/11
  • Yoshihide Sehara, Yuka Hayashi, Kenji Ohba, Ryosuke Uchibori, Masashi Urabe, Ayumu Inutsuka, Kuniko Shimazaki, Kensuke Kawai, Hiroaki Mizukami
    Human Gene Therapy 1043-0342 2021/09 [Refereed]
  • Kei Kozawa, Miho Sekai, Kenji Ohba, Shoko Ito, Hiroaki Sako, Takeshi Maruyama, Mai Kakeno, Takanobu Shirai, Keisuke Kuromiya, Tomoko Kamasaki, Koki Kohashi, Shinya Tanaka, Susumu Ishikawa, Nanami Sato, Shota Asano, Hironori Suzuki, Nobuyuki Tanimura, Yohei Mukai, Noriko Gotoh, Mishie Tanino, Shinya Tanaka, Ken Natsuga, Tomoyoshi Soga, Tomonori Nakamura, Yukihiro Yabuta, Mitinori Saitou, Takahiro Ito, Kenkyo Matsuura, Makoto Tsunoda, Toyone Kikumori, Tadashi Iida, Yasuyuki Mizutani, Yuki Miyai, Kozo Kaibuchi, Atsushi Enomoto, Yasuyuki Fujita
    Current Biology 31 (14) 3086 - 3097.e7 0960-9822 2021/07 [Refereed]
  • Koji Ichiyama, Chuan Yang, Lakshmi Chandrasekaran, Shaoqiong Liu, Lijun Rong, Yue Zhao, Shujun Gao, Ashlynn Lee, Kenji Ohba, Youichi Suzuki, Yoshiyuki Yoshinaka, Kunitada Shimotohno, Kei Miyakawa, Akihide Ryo, James Hedrick, Naoki Yamamoto, Yi Yan Yang
    MACROMOLECULES 49 (7) 2618 - 2629 0024-9297 2016/04 [Refereed][Not invited]
     
    Treatment of viral infections continues to be elusive owing to the variance in virus structure (RNA, DNA, and enveloped and nonenveloped viruses) together with their ability to rapidly mutate and garner resistance. Here we report a general strategy to prevent viral infection using multifunctional macromolecules that were designed to have mannose moieties that compete with viruses for immune cells, and basic amine groups that block viral entry through electrostatic interactions and prevent viral replication by neutralizing the endosomal pH. We showed that cells treated with the antiviral polymers inhibited TIM receptors from trafficking virus, likely from electrostatic and hydrogen bonding interactions, with EC50 values ranging from 2.6 to 6.8 mg/L, depending on the type of TIM receptors. Molecular docking computations revealed an unexpected, and general, specific hydrogen-bonding interactions with viral surface proteins, and virus and cell binding assay demonstrated a significant reduction in infection after incubating virus or cells with the antiviral polymers. Moreover, the mannose-functionalized macromolecules effectively prevented the virus from infecting the immune cells. Representative viruses from each category including dengue, influenza, Chikungunya, Enterovirus 71, Ebola, Marburg, and herpes simplex were surveyed, and viral infection was effectively prevented at polymer concentrations as low as 0.2 mg/L with very high selectivity (>5000) over mammalian cells. The generality of these cooperative orthogonal interactions (electrostatic and hydrogen-bonding) provides broad-spectrum antiviral activity. As the antiviral mechanism is based on nonspecific supramolecular interactions between the amino acid residues and mannose/cationic moieties of the macromolecule, the ability to form the virus polymer and polymer cell assemblies can occur regardless of viral mutation, preventing drug resistance development.
  • Darren Qiancheng Tan, LiFeng Zhang, Kenji Ohba, Min Ye, Koji Ichiyama, Naoki Yamamoto
    EUROPEAN JOURNAL OF IMMUNOLOGY 46 (4) 919 - 928 0014-2980 2016/04 [Refereed][Not invited]
     
    Tumor-associated macrophages (TAMs) are known to regulate tumor response to many anti-cancer therapies, including oncolytic virotherapy. Oncolytic virotherapy employing oncolytic paramyxoviruses, such as attenuated measles (MeV) and mumps (MuV) viruses, has demonstrated therapeutic potential against various malignancies. However, the response of TAMs to oncolytic paramyxoviruses and the consequent effect on virotherapeutic efficacy remains to be characterized. Here, we demonstrate that the presence of human monocyte-derived macrophages (MDMs), irrespective of initial polarization state, enhances the virotherapeutic effect of MeV and MuV on breast cancer cells. Notably, our finding contrasts those of several studies involving other oncolytic viruses, which suggest that TAMs negatively impact virotherapeutic efficacy by impeding virus replication and dissemination. We found that the enhanced virotherapeutic effect in the presence of MDMs was due to slightly delayed proliferation and significantly elevated cell death that was not a result of increased virus replication. Instead, we found that the enhanced virotherapeutic effect involved several macrophage-associated anti-tumor mediators, and was associated with the modulation of MDMs towards an anti-tumor phenotype. Our findings present an alternative view on the role of TAMs in oncolytic virotherapy, and highlight the immunotherapeutic potential of oncolytic paramyxoviruses; possibly contributing towards the overall efficacy of oncolytic virotherapy.
  • Sundararaj Stanley Jeremiah, Kenji Ohba, Naoki Yamamoto
    CURRENT DRUG TARGETS 17 (6) 678 - 692 1389-4501 2016 [Refereed][Not invited]
     
    The global Human Immunodeficiency Virus (HIV) pandemic is still spreading due to the lack of ideal anti-retroviral measures and their availability. Till date, all attempts to produce an efficient vaccine have ended with unsatisfactory results. The highly active anti-retroviral therapy (HAART) is the only effective weapon currently available and is widely being used for curtailing the HIV pandemic. However, the HAART is also expected to fail in the near future due to the emergence and dissemination of antiviral resistance. This review sheds light on the reasons for the failure of the conventional anti-viral measures against HIV and the novel anti-retroviral strategies currently being developed. The various principles to be considered for the success of a novel anti-retroviral strategy are elaborately emphasized and an innovative concept is proposed on these lines. The proposed concept intends to use receptor decoy traps (RDT) called cancellers which are erythrocytes expressing the HIV entry receptors on their surface. If successfully developed, the cancellers would be capable of active targeting of the free HIV particles leading to the trapping of the viruses within the canceller, resulting in the neutralization of infectivity of the trapped virus. The possible ways of translating this concept into reality and the probable hurdles that can be encountered in the process are subsequently discussed. Also, the scope of cancellers in therapeutic and/or preventive strategies against HIV infection is envisaged upon their successful development.
  • Youichi Suzuki, Wei-Xin Chin, Qi'En Han, Koji Ichiyama, Ching Hua Lee, Zhi Wen Eyo, Hirotaka Ebina, Hirotaka Takahashi, Chikako Takahashi, Beng Hui Tan, Takayuki Hishiki, Kenji Ohba, Toshifumi Matsuyama, Yoshio Koyanagi, Yee-Joo Tan, Tatsuya Sawasaki, Justin Jang Hann Chu, Subhash G. Vasudevan, Kouichi Sano, Naoki Yamamoto
    PLOS PATHOGENS 12 (1) e1005357  1553-7366 2016/01 [Refereed][Not invited]
     
    Dengue virus (DENV) is one of the most important arthropod-borne pathogens that cause life-threatening diseases in humans. However, no vaccine or specific antiviral is available for dengue. As seen in other RNA viruses, the innate immune system plays a key role in controlling DENV infection and disease outcome. Although the interferon (IFN) response, which is central to host protective immunity, has been reported to limit DENV replication, the molecular details of how DENV infection is modulated by IFN treatment are elusive. In this study, by employing a gain-of-function screen using a type I IFN-treated cell-derived cDNA library, we identified a previously uncharacterized gene, C19orf66, as an IFN-stimulated gene (ISG) that inhibits DENV replication, which we named Repressor of yield of DENV (RyDEN). Overexpression and gene knockdown experiments revealed that expression of RyDEN confers resistance to all serotypes of DENV in human cells. RyDEN expression also limited the replication of hepatitis C virus, Kunjin virus, Chikungunya virus, herpes simplex virus type 1, and human adenovirus. Importantly, RyDEN was considered to be a crucial effector molecule in the IFN-mediated anti-DENV response. When affinity purificationmass spectrometry analysis was performed, RyDEN was revealed to form a complex with cellular mRNA-binding proteins, poly(A)-binding protein cytoplasmic 1 (PABPC1), and La motif-related protein 1 (LARP1). Interestingly, PABPC1 and LARP1 were found to be positive modulators of DENV replication. Since RyDEN influenced intracellular events on DENV replication and, suppression of protein synthesis from DENV-based reporter construct RNA was also observed in RyDEN-expressing cells, our data suggest that RyDEN is likely to interfere with the translation of DENV via interaction with viral RNA and cellular mRNA-binding proteins, resulting in the inhibition of virus replication in infected cells.
  • Li Feng Zhang, Darren Qian Cheng Tan, Anand D. Jeyasekharan, Wen Son Hsieh, Anh Son Ho, Koji Ichiyama, Min Ye, Brendan Pang, Kenji Ohba, Xin Liu, Sanjay de Mel, Bui Khac Cuong, Wee Joo Chng, Akihide Ryo, Youichi Suzuki, Khay Guan Yeoh, Nguyen Linh Toan, Naoki Yamamoto
    CANCER LETTERS 354 (2) 272 - 280 0304-3835 2014/11 [Refereed][Not invited]
     
    Through combining vaccine-derived measles and mumps viruses (MM), we efficiently targeted a wide range of hematopoietic cancer cell lines. MM synergistically killed many cell lines including acute myeloid leukemia (AML) cell lines. Further investigation suggested that enhanced oncolytic effect of MM was due to increased apoptosis induction. In an U937 xenograft AML mouse model, MM displayed greater tumor suppression and prolonged survival. Furthermore, MM efficiently killed blasts from 16 out of 20 AML patients and elicited more efficient killing effect on 11 patients when co-administered with Ara-C. Our results demonstrate that MM is a promising therapeutic candidate for hematological malignancies. (C) 2014 Elsevier Ireland Ltd. All rights reserved.
  • Kenji Ohba, Koji Ichiyama, Misako Yajima, Nobuhiro Gemma, Masaru Nikaido, Qingqing Wu, PeiPei Chong, Seiichiro Mori, Rain Yamamoto, John Eu Li Wong, Naoki Yamamoto
    PLOS ONE 9 (5) e97787  1932-6203 2014/05 [Refereed][Not invited]
     
    High prevalence of infection with high-risk human papilloma virus (HPV) ranging from 25 to 100% (average 31%) was observed in breast cancer (BC) patients in Singapore using novel DNA chip technology. Early stage of BC demonstrated higher HPV positivity, and BC positive for estrogen receptor (ER) showed significantly higher HPV infection rate. This unique association of HPV with BC in vivo prompted us to investigate a possible involvement of HPV in early stages of breast carcinogenesis. Using normal breast epithelial cells stably transfected with HPV-18, we showed apparent upregulation of mRNA for the cytidine deaminase, APOBEC3B (A3B) which is reported to be a source of mutations in BC. HPV-induced A3B overexpression caused significant gamma H2AX focus formation, and DNA breaks which were cancelled by shRNA to HPV18 E6, E7 and A3B. These results strongly suggest an active involvement of HPV in the early stage of BC carcinogenesis via A3B induction.
  • Wataru Nomura, Akemi Masuda, Asami Kondo, Kenji Ohba, Naoki Yamamoto, Akihide Ryo, Hirokazu Tamamura
    PROTEIN SCIENCE 21 215 - 215 0961-8368 2012/08 [Refereed][Not invited]
  • Wataru Nomura, Akemi Masuda, Kenji Ohba, Arisa Urabe, Nobutoshi Ito, Akihide Ryo, Naoki Yamamoto, Hirokazu Tamamura
    BIOCHEMISTRY 51 (7) 1510 - 1517 0006-2960 2012/02 [Refereed][Not invited]
     
    Artificial zinc finger proteins (ZFPs) consist of Cys(2)-His(2)-type modules composed of similar to 30 amino acids with a beta beta alpha structure that coordinates a zinc ion. ZFPs that recognize specific DNA target sequences can substitute for the binding domains of enzymes that act on DNA to create designer enzymes with programmable sequence specificity. The most studied of these engineered enzymes are zinc finger nucleases (ZFNs). ZFNs have been widely used to model organisms and are currently in human clinical trials with an aim of therapeutic gene editing. Difficulties with ZFNs arise from unpredictable mutations caused by nonhomologous end joining and off-target DNA cleavage and mutagenesis. A more recent strategy that aims to address the shortcomings of ZFNs involves zinc finger recombinases (ZFRs). A thorough understanding of ZFRs and methods for their modification promises powerful new tools for gene manipulation in model organisms as well as in gene therapy. In an effort to design efficient and specific ZFRs, the effects of the DNA binding affinity of the zinc finger domains and the linker sequence between ZFPs and recombinase catalytic domains have been assessed. A plasmid system containing ZFR target sites was constructed for evaluation of catalytic activities of ZFRs with variable linker lengths and numbers of zinc finger modules. Recombination efficiencies were evaluated by restriction enzyme analysis of isolated plasmids after reaction in Escherichia coli and changes in EGFP fluorescence in mammalian cells. The results provide information relevant to the design of ZFRs that will be useful for sequence-specific genome modification.
  • Akemi Masuda, Wataru Nomura, Kenji Ohba, Naoki Yamamoto, Hirokazu Tamamura
    BIOPOLYMERS 96 (4) 434 - 434 0006-3525 2011 [Refereed][Not invited]
  • Hirokazu Tamamura, Wataru Nomura, Toru Nakahara, Chie Hashimoto, Kenji Ohba, Tetsuo Narumi, Naoki Yamamoto
    BIOPOLYMERS 96 (4) 489 - 490 0006-3525 2011 [Refereed][Not invited]
  • Toru Nakahara, Wataru Nomura, Kenji Ohba, Aki Ohya, Tomohiro Tanaka, Chie Hashimoto, Tetsuo Narumi, Tsutomu Murakami, Naoki Yamamoto, Hirokazu Tamamura
    BIOCONJUGATE CHEMISTRY 21 (4) 709 - 714 1043-1802 2010/04 [Refereed][Not invited]
     
    A synthetic antigen targeting membrane-fusion mechanism of HIV-1 has a newly designed template with C3-symmetric linkers mimicking N36 trimeric form. The antiserum produced by immunization of the N36 trimeric form antigen showed structural preference in binding to N36 trimer and stronger inhibitory activity against HIV-1 infection than the N36 monomer. Our results suggest an effective strategy of HIV vaccine design based on a relationship to the native structure of proteins involved in HIV fusion mechanisms.
  • Kei Miyakawa, Akihide Ryo, Tsutomu Murakami, Kenji Ohba, Shoji Yamaoka, Mitsunori Fukuda, John Guatelli, Naoki Yamamoto
    PLOS PATHOGENS 5 (12) e1000700  1553-7366 2009/12 [Refereed][Not invited]
     
    Host cell factors can either positively or negatively regulate the assembly and egress of HIV-1 particles from infected cells. Recent reports have identified a previously uncharacterized transmembrane protein, tetherin/CD317/BST-2, as a crucial host restriction factor that acts during a late budding step in HIV-1 replication by inhibiting viral particle release. Although tetherin has been shown to promote the retention of nascent viral particles on the host cell surface, the precise molecular mechanisms that occur during and after these tethering events remain largely unknown. We here report that a RING-type E3 ubiquitin ligase, BCA2 ( Breast cancer-associated gene 2; also called Rabring7, ZNF364 or RNF115), is a novel tetherin-interacting host protein that facilitates the restriction of HIV-1 particle production in tetherin-positive cells. The expression of human BCA2 in "tetherin-positive" HeLa, but not in "tetherin-negative" HOS cells, resulted in a strong restriction of HIV-1 particle production. Upon the expression of tetherin in HOS cells, BCA2 was capable of inhibiting viral particle production as in HeLa cells. The targeted depletion of endogenous BCA2 by RNA interference (RNAi) in HeLa cells reduced the intracellular accumulation of viral particles, which were nevertheless retained on the plasma membrane. BCA2 was also found to facilitate the internalization of HIV-1 virions into CD63(+) intracellular vesicles leading to their lysosomal degradation. These results indicate that BCA2 accelerates the internalization and degradation of viral particles following their tethering to the cell surface and is a co-factor or enhancer for the tetherin-dependent restriction of HIV-1 release from infected cells.
  • Kenji Ohba, Akihide Ryo, Md. Zahidunnabi Dewan, Mayuko Nishi, Toshio Naito, Xiaohua Qi, Yoshio Inagaki, Yoji Nagashima, Yuetsu Tanaka, Takashi Okamoto, Kazuo Terashima, Naoki Yamamoto
    JOURNAL OF IMMUNOLOGY 183 (1) 524 - 532 0022-1767 2009/07 [Refereed][Not invited]
     
    Follicular dendritic cells (FDCs) are located in the lymphoid follicles of secondary lymphoid tissues and play a pivotal role in the selection of memory B lymphocytes within the germinal center, a major site for HIV-1 infection. Germinal centers are composed of highly activated B cells, macrophages, CD4(+)T cells, and FDCs. However, the physiological role of FDCs in HIV-1 replication remains largely unknown. We demonstrate in our current study that FDCs can efficiently activate HIV-1 replication in latently infected monocytic cells via an intercellular communication network mediated by the P-selectin/P-selectin glycoprotein ligand 1 (PSGL-1) interaction. Upon coculture with FDCs, HIV-1 replication was significantly induced in infected monocytic cell lines, primary monocytes, or macrophages. These cocultures were found to synergistically induce the expression of P-selectin in FDCs via NF-kappa B activation and its cognate receptor PSGL-1 in HIV-1-infected cells. Consistent with this observation, we find that this response is significantly blocked by antagonistic Abs against PSGL-1 and almost completely inhibited by PSGL-1 small interfering RNA. Moreover, a selective inhibitor for Syk, which is a downstream effector of PSGL-1, blocked HIV-1 replication in our cultures. We have thus elucidated a novel regulatory mechanism in which FDCs are a potent positive bystander that facilitates HIV-1 replication in adjacent infected monocytic cells via a juxtacrine signaling mechanism. The Journal of Immunology, 2009, 183: 524-532.
  • Mayuko Nishi, Akihide Ryo, Naomi Tsurutani, Kenji Ohba, Tatsuya Sawasaki, Ryo Morishita, Kilian Perrem, Ichiro Aoki, Yuko Morikawa, Naoki Yamamoto
    FEBS LETTERS 583 (8) 1243 - 1250 0014-5793 2009/04 [Refereed][Not invited]
     
    Suppressor of cytokine signaling 1 (SOCS1) is a recently identified host factor that positively regulates the intracellular trafficking and stability of HIV-1 Gag. We here examine the molecular mechanism by which SOCS1 regulates intercellular Gag trafficking and virus particle production. We find that SOCS1 colocalizes with Gag along the microtubule network and promotes microtubule stability. SOCS1 also increases the amount of Gag associated with microtubules. Both nocodazole treatment and the expression of the microtubule-destabilizing protein, stathmin, inhibit the enhancement of HIV-1 particle production by SOCS1. SOCS1 facilitates Gag ubiquitination and the co-expression of a dominant-negative ubiquitin significantly inhibits the association of Gag with microtubules. We thus propose that the microtubule network plays a role in SOCS1-mediated HIV-1 Gag transport and virus particle formation.
  • Hiroshi Tsutsumi, Wataru Nomura, Seiichiro Abe, Tomoaki Mino, Akemi Masuda, Nami Ohashi, Tomohiro Tanaka, Kenji Ohba, Naoki Yamamoto, Kazunari Akiyoshi, Hirokazu Tamamura
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 48 (48) 9164 - 9166 1433-7851 2009 [Refereed][Not invited]
  • Wataru Nomura, Yasuaki Tanabe, Hiroshi Tsutsumi, Tomohiro Tanaka, Kenji Ohba, Naoki Yamamoto, Hirokazu Tamamura
    BIOCONJUGATE CHEMISTRY 19 (9) 1917 - 1920 1043-1802 2008/09 [Refereed][Not invited]
     
    Development of CXCR4-specific ligands is an important issue in chemotherapy of HIV infection, cancer metastasis, and rheumatoid arthritis, and numerous potential ligands have been developed to date. However, it is difficult to assess their binding mode and specificity because of uncertainties in the structure of the CXCR4-ligand complexes. To address this problem, we have synthesized fluorophore labeled Ac-TZ14011, which is derived from T140, a powerful CXCR4 antagonist. Binding of Ac-TZ14011 to CXCR4 on the cell membrane was observed by fluorescence microscope, and analysis of the binding data produced IC50 values of several ligands comparable to those obtained in RI-based assays. This fluorescence-based assay is applicable to explore new pharmacophores of CXCR4-specific ligands with high-throughput screening and also to screening of the other GPCR binding ligands.
  • Akihide Ryo, Naomi Tsurutan, Kenji Ohba, Ryuichiro Kimura, Jun Komano, Mayuko Nishi, Hiromi Soeda, Shinichiro Hattori, Kilian Perrem, Mikio Yamamoto, Joe Chiba, Jun-Ichi Mimaya, Kazuhisa Yoshimura, Shuzo Matsushita, Mitsuo Honda, Akihiko Yoshimura, Tatsuya Sawasaki, Ichiro Aoki, Yuko Morikawa, Naoki Yamamoto
    PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 105 (1) 294 - 299 0027-8424 2008/01 [Refereed][Not invited]
     
    Human immunodeficiency virus type 1 (HIV-1) utilizes the macromolecular machinery of the infected host cell to produce progeny virus. The discovery of cellular factors that participate in HIV-1 replication pathways has provided further insight into the molecular basis of virus-host cell interactions. Here, we report that the suppressor of cytokine signaling 1 (SOCS1) is an inducible host factor during HIV-1 infection and regulates the late stages of the HIV-1 replication pathway. SOCS1 can directly bind to the matrix and nucleocapsid regions of the HIV-1 p55 Gag polyprotein and enhance its stability and trafficking, resulting in the efficient production of HIV-1 particles via an IFN signaling-independent mechanism. The depletion of SOCS1 by siRNA reduces both the targeted trafficking and assembly of HIV-1 Gag, resulting in its accumulation as perinuclear solid aggregates that are eventually subjected to lysosomal degradation. These results together indicate that SOCS1 is a crucial host factor that regulates the intracellular dynamism of HIV-1 Gag and could therefore be a potential new therapeutic target for AIDS and its related disorders.
  • Tomohiro Tanaka, Hiroshi Tsutsumi, Wataru Nomura, Yasuaki Tanabe, Nami Ohashi, Ai Esaka, Chihiro Ochiai, Jun Sato, Kyoko Itotani, Tsutomu Murakami, Kenji Ohba, Naoki Yamamoto, Nobutaka Fujii, Hirokazu Tamamura
    ORGANIC & BIOMOLECULAR CHEMISTRY 6 (23) 4374 - 4377 1477-0520 2008 [Refereed][Not invited]
     
    A highly potent CXCR4 antagonist 2 [cyclo (-D-Tyr(1)-Arg(2)-Arg(3)-Nal(4)-Gly(5)-)] has previously been identified by screening cyclic pentapeptide libraries that were designed based on pharmacophore residues of a 14-residue peptidic CXCR4 antagonist 1. In the present study, D-Tyr and Arg in peptide 2 were replaced by a bicyclic aromatic amino acid and a cationic amino acid, respectively, and their binding activity for CXCR4 was evaluated for identification of the novel pharmacophore.
  • Xiaohua Qi, Yoshihiro Koya, Tatsuya Saitoh, Yasunori Saitoh, Saki Shimizu, Kenji Ohba, Norio Yamamoto, Shoji Yamaoka, Naoki Yamamoto
    VIROLOGY 361 (2) 325 - 334 0042-6822 2007/05 [Refereed][Not invited]
     
    Reservoir cells latently infected with HIV-1 pose one of the major obstacles that hamper ultimate eradication of HIV-1 from infected patients. In this report, we showed that direct contact with MOLT-4 T cells induced HIV-1 replication ill J(22)-HL-60 latently infected cells without any additional stimulus. Neutralization experiments revealed that pro-inflammatory cytokines, whose production was increased following cell-cell contact, were unlikely to be primarily involved in the induced HIV-1 replication. Cell-cell contact, but not soluble components in the culture supernatant, caused a rapid phosphorylation and degradation of I kappa B alpha, which led to elevated NF-kappa B DNA binding activity in J(22)-HL-60 cells. Furthermore, forced expression of a super-repressor form Of I kappa B alpha or pretreatment with ritonavir efficiently blocked the activation of NF-kappa B and HIV-1 replication in J(22)-HL-60 cells co-cultured with MOLT-4 T cells. Moreover, either resting or PHA stimulated primary CD4(+) T cells induced HIV-1 replication ill J(22)-HL-60 cells in a similar way with that of MOLT-4 cells. These results indicated that direct contact with CD4(+) T cells induced HIV-1 replication in latently infected cells and provide insight into the molecular mechanism of virus release from myeloid progenitor cells latently infected with HIV-1. (c) 2006 Elsevier Inc All rights reserved.
  • Kenji Ohba, Shinsuke Yoshida, Md. Zahidunnabi Dewan, Hiromi Shimura, Nozomi Sakamaki, Fumihiko Takeshita, Naoki Yamamoto, Keniji Okuda
    VACCINE 25 (21) 4291 - 4300 0264-410X 2007/05 [Refereed][Not invited]
     
    Many influenza vaccines targeted to hemagglutinin (HA) show efficient immunogenicity for protecting subjects against influenza virus infection. Major antigenic changes to HA molecules can help influenza virus to develop resistance against HA-targeted vaccines. DNA vaccines encoding conserved antigens protect animals against diverse subtypes, but their potency requires further improvement. We generated a DNA-based nucleoprotein (NP)-targeted vaccine using an N-terminal mutant of NP (NPm) that efficiently localized in the cytoplasm, and examined the immune responses in mice immunized with NPm or wild-type (WT) NP DNA vaccine. Importantly, the NPm vaccine showed 1.5-2-fold higher immunogenicity than the WT NP vaccine in mice. Furthermore, NPm vaccination efficiently protected the mice against lethal challenge with influenza viruses and showed cross-reactivity toward heterologous viruses. Therefore, DNA-based vaccination with NPm may contribute to the development of protective immunity against diverse influenza virus through its ability to stimulate cellular immunity. (c) 2007 Elsevier Ltd. All rights reserved.
  • Sukumar Saha, Shinsuke Yoshida, Kenji Ohba, Kiyohiko Matsui, Tomoko Matsuda, Fumihiko Takeshita, Kazunori Umeda, Yuichi Tamura, Kentaro Okuda, Dennis Klinman, Ke-Qin Xin, Kenji Okuda
    VIROLOGY 354 (1) 48 - 57 0042-6822 2006/10 [Refereed][Not invited]
     
    We evaluated the immunogenicity and protective activity of plasmid DNA vaccines encoding the influenza virus NP gene (pNP) alone or in combination with the herpes simplex virus type 1 protein 22 gene (pVP22). Optimal immune responses were observed in BALB/c mice immunized with the combination of pVP22 plus pNP, as assessed by enzyme-linked immunosorbent assay (ELISA), enzyme-linked immunospot (ELISPOT) and intracellular cytokine staining (ICCS). These mice also showed maximal resistance following challenge with the A/PR/8/34 (H1N1) and A/Udron/72 (H3N2) strains of influenza virus. The susceptibility of immunized mice to virus infection was significantly increased following depletion of either CD4(+) or CD8(+) T cells. These results indicate that a plasmid DNA vaccine encoding pVP22 plus NP induces a high level of cross-protective immunity against influenza virus subtypes. (c) 2006 Elsevier Inc. All rights reserved.
  • M. Z. Dewan, S. Ahmed, Y. Iwasaki, K. Ohba, M. Toi, N. Yamamoto
    BIOMEDICINE & PHARMACOTHERAPY 60 (6) 273 - 276 0753-3322 2006/07 [Refereed][Not invited]
     
    Stromal cell-derived factor-1 (SDF-1)/CXCR4 interaction is critical for the trafficking of lymphocytes, homing and retention of hematopoietic stem cells within the bone marrow and is essential in fetal hematopoiesis. Binding of SDF-1 to CXCR4 activates a variety of intracellular signal transduction pathways and effector molecules that regulate cell survival, proliferation, chemotaxis, migration and adhesion. Recently, intensive research has demonstrated that SDF-1/CXCR4 interaction also regulates several key events in wide variety, of cancers. Serum-depleted media in the presence of SDF-1 protected the breast cancer cells from apoptosis. CXCR4-low-expressing MCF-7 formed small tumor at inoculated site in SCID mice 8-9 weeks after inoculation while completely failed to metastasis into various organs. In contrast, CXCR4-high-expressing MDA-231 cells were most efficient in the formation of a large tumor and organ-metastasis within 3 weeks in SCID mice. This review briefly focuses on the role of SDF-1/CXCR4 interaction in tumor growth and metastasis of breast cancer cell both in vitro and in vivo. (c) 2006 Elsevier SAS. All rights reserved.
  • MOLT-4細胞との共培養後のJ22-HL-60細胞におけるHIV-1導入の機序(Mechanism of HIV-1 induction in J22-HL-60 cells after co-culture with MOLT-4 cells)
    斉 曉華, 小屋 美博, 斉藤 達哉, 清水 佐紀, 斉藤 愛記, 大庭 賢二, 山岡 昇司, 山本 直樹
    日本エイズ学会誌 7 (4) 372 - 372 1344-9478 2005/11
  • MZ Dewan, H Terunuma, S Ahmed, K Ohba, M Takada, Y Tanaka, M Toi, N Yamamoto
    BIOMEDICINE & PHARMACOTHERAPY 59 S375 - S379 0753-3322 2005/10 [Refereed][Not invited]
     
    Natural killer (NK) cell is an important component of the innate immune system and plays a central role in host defense against tumor and virus-infected cells. This review briefly summarizes the role of murine NK cells in tumor growth and metastasis of breast cancer cells in severe combined immunodeficiency (SCID) mice. Conventional SCID and NOD-SCID strains have been used to study for xenotransplantion of human tumors. SCID mice models of cancer mimic human diseases and have provided valuable information. However, these mice strains have some residual immunity such as NK cells that somewhat limit post-transplantation growth and metastasis of human xenografts. In contrast, NOD/SCID/gamma c(null) (NOG) mice without common gamma-chain inoculated with breast cancer cells were most efficient in the formation of a large tumor and metastasis. NOG mouse strain without NK activity appears to be more promising as tool for xenotransplantion of human cancer. This new xenotransplant model is relevant and can be recommended for use in clarifying the mechanism of growth of cancer cells as well as for developing new therapeutic strategies against cancer. (c) 2005 Elsevier SAS. All rights reserved.
  • MZ Dewan, K Terashima, S Ahmed, K Ohba, M Taruishi, N Yamamoto
    MEDICAL MICROBIOLOGY AND IMMUNOLOGY 194 (4) 175 - 180 0300-8584 2005/08 [Refereed][Not invited]
     
    Human cells have developed innate immunity, exploiting several means to block virus infection, and viruses have evolved diverse strategies to resist these. We show here that the human immunodeficiency virus I (HIV-1) could neither progressively infect engrafted human leukemic T cells nor repress their growth in NOG mice. However, ED-40515(-) cells infected with HIV-1 before inoculation were found to significantly delay the onset of tumor growth and increased the survival period of NOG mice. ED-40515(-) tumor cells showed resistance to HIV-1 which was apparently correlated with the down-regulation of CD4 and CXCR4 molecules in NOG mice. Serum from three different mouse strains, including NOG, retained a suppressive effect on the CD4 molecule of ED-40515(-) cells in vitro. ED-40515(-) cells obtained from mice re-expressed CD4 and CXCR4 molecules upon in vitro culture and were again successfully infected with HIV-1. These findings indicate that HIV-1 may initially successfully delay or regress tumor growth in NOG mice, but eventually fails to do so because of the evolution of HIV-resistant cells due to a rapid down-modulation of CD4 and CXCR4. Our data also demonstrated that some unknown soluble factor(s) present in mouse serum was responsible for conferring resistance to HIV infection to human T cells.
  • KQ Xin, Y Hoshino, Y Toda, S Igimi, Y Kojima, N Jounai, K Ohba, A Kushiro, M Kiwaki, K Hamajima, D Klinman, K Okuda
    BLOOD 102 (1) 223 - 228 0006-4971 2003/07 [Refereed][Not invited]
     
    This study investigates whether genetically modified orally administered Lactococcus lactis (L lactis) could be used as an HIV vaccine. L lactis is immunogenic and extremely safe when delivered orally. We created a recombinant L lactis vector expressing the envelope protein of HIV on its cell surface. Oral immunization with this vector induced high levels of HIV-specific serum IgG and fecal IgA antibodies. Cell-mediated immune responses also were generated in both the regional lymph nodes and the spleen. Dendritic cells are readily infected by L lactis and appear to play a potential role in mediating the development of these immune responses. The protective efficacy of this vaccine strategy was demonstrated by challenging mice intraperitoneally with an HIV Env-expressing vaccinia virus. Their viral loads were 350-fold lower than those of control mice. These findings support the further development of L lactis-based HIV vaccines. (C) 2003 by The American Society of Hematology.
  • N Jounai, K Okuda, Y Kojima, Y Toda, K Hamajima, K Ohba, D Klinman, KQ Xin
    JOURNAL OF GENE MEDICINE 5 (7) 609 - 617 1099-498X 2003/07 [Refereed][Not invited]
     
    Background The Rev protein of HIV plays a critical role in the export of viral mRNA from the nucleus to the cytoplasm of infected cells. This work examines the effect of introducing rev into a DNA vaccine encoding the Env protein of HIV, and compares the activity of env genes regulated by CMV versus CAG promoters. Methods The HIV Env gp160 encoding gene with or without the rev gene was subcloned into a CMV promoter or a CAG promoter-driven expression plasmid. The Env protein expression of the plasmids was examined in vitro and the HIV-specific immunity was explored in BALB/c mice by an intramuscular route. The immune mice were intraperitoneally challenged with an HIV Env-expression vaccinia virus. Results Results indicate that the CAG promoter induces significantly higher levels of Env expression, and better immune responses, than the CMV promoter. Incorporating the rev gene into these plasmids further boosts antigen expression and immunogenicity. Indeed, vaccination with the pCAGrev/env or pCMVrev/env plasmid resulted in 1000-fold lower viral load than that with pCMVenv when the mice were challenged with an Env-expressing vaccinia virus. Conclusions Incorporating rev into a DNA vaccine significantly increases the level of expression and immunogenicity of a co-expressed env gene, and that protective efficacy is further improved by utilizing a pCAG promoter. Copyright (C) 2003 John Wiley Sons, Ltd.
  • KQ Xin, T Ooki, N Jounai, H Mizukami, K Hamajima, Y Kojima, K Ohba, Y Toda, SI Hirai, DM Klinman, K Ozawa, K Okuda
    JOURNAL OF GENE MEDICINE 5 (5) 438 - 445 1099-498X 2003/05 [Refereed][Not invited]
     
    Background DNA vaccines have been used to induce both humoral and cellular immune responses against infectious microorganisms. This study explores whether DNA vaccine immunogenicity can be improved by introducing inverted terminal repeats (ITRs) from adeno-associated virus (AAV) into the regulatory region of the DNA plasmid. Methods CMV promoter-driven HIV Env expressing plasmid (pCMV-HIV) and the pCMV-HIV plasmid introduced ITRs (pITR/CMV-HIV) were transfected in HEK293 cells with LipofectAmine. The HIV Env expression was quantified with Western blot. Fifty mug of pCMV-HIV or pITR/CMV-HIV plasmid with RIBI adjuvant were immunized to BALB/c mice on days 0, 14 and 28 by intramuscular route, and HIV-specific serum IgG titer was detected 2, 6, 10, 14 and 18 weeks after the first immunization. HIV-specific tetramer assay and HIV-specific IFN-gamma ELIspot assay were performed 1 week after the last immunization. The immune mice were intravenously challenged with a vaccinia virus expressing the HIV env gene 1 week after the last immunization. Results Significantly higher level of HIV Env expression was achieved by pITR/CMV-HIV plasmid. BALB/c mice immunized with pITR/CMV-HIV plasmid generated significantly higher HIV-specific antibody, higher cellular immune responses and lower viral loading than animals immunized with pCMV-HIV plasmid. Conclusions AAV ITRs enhance CMV-dependent up-regulation of transgene expression and immunogenicity of DNA vaccine. Copyright (C) 2002 John Wiley Sons, Ltd.

Books etc

  • HIV感染症における治療と研究
    大庭 賢二, 山本 直樹, 山岡 昇司 (Joint work最新医学60巻3月増刊号 特集 免疫と疾患(前篇)-自然・獲得免疫と疾患 p.651-660)
    最新医学 2005

Conference Activities & Talks

MISC

Industrial Property Rights

  • 特表WO 2014/092647A1:A Method For Diagnosis Of Hpv-related Non-genital Cancers Using PCR  
    Ohba Kenji, Yajima Misako, Yamamoto N, Nikaido Masaru, Gemma Nobuhiro  Univ. Singapore, Toshiba Corp (Canon Medical Systems)

Research Grants & Projects

  • 異常細胞のMHC-Iシグナルにより惹起される上皮細胞の免疫細胞様機能
    Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2021/04 -2024/03 
    Author : 丸山 剛, 大庭 賢二, 河野 恵子, 藤枝 俊宜
  • アデノ随伴ウイルスベクターの粒子形成と感染機構の解析
    Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2020/04 -2023/03 
    Author : 大庭 賢二
  • Collaboration for production of AAV vectors
    Takara Bio:Collaboration
    Date (from‐to) : 2020/05 -2022/04 
    Author : Kenji Ohba
  • AMED seeds-A A168
    日本医療研究機構 (AMED):橋渡し研究戦略推進プログラム 革新的医療技術創出拠点プロジェクト 東京大学拠点
    Date (from‐to) : 2021/04 -2022/03 
    Author : Kenji Ohba
  • AMED
    日本医療研究機構 (AMED):橋渡し研究戦略推進プログラム 革新的医療技術創出拠点プロジェクト 東京大学拠点
    Date (from‐to) : 2020/04 -2021/03 
    Author : Kenji Ohba
  • Analysis for new elimination mechanism against virus-induced cancer cells through the cell competition with normal cells.
    Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    Date (from‐to) : 2017/04 -2020/03 
    Author : Kenji Ohba
     
    研究計画に基づいて研究を遂行し、以下に示す進捗・結果が得られた。 細胞競合条件下でテトラサイクリン誘導性HPV E6発現細胞に誘導されるアポトーシスを介した排除機構の解析を行うために、テトラサイクリン刺激から16時間後の細胞群をEGFP-E6の蛍光を利用したCell sortingによって、E6発現細胞を細胞競合条件下から分離した。その後、次世代シークエンスによりRNAシークエンス解析を行ったところ、約100種の遺伝子に発現上昇が、約80種の遺伝子に発現減少が生じていることが分かった。その中で、約10遺伝子がアポトーシスと何らかの関連がある遺伝子であった。 さらに、アポトーシスとの関連が強い3因子の関与を解析するために、E6発現細胞にそれぞれの遺伝子特異的なshRNAを導入し、細胞競合特異的なE6発現細胞の細胞死への影響を観察した。すると、それぞれの因子に対するshRNAの導入によってある程度アポトーシスが減少していることが分かった。アポトーシスの減少度が大きかった1種の遺伝子は生体防御反応時に放出される因子によって惹起される遺伝子であった。 そこで、生体防御反応で放出される因子が刺激するプロモーター活性をルシフェラーゼレポーターを用いて解析したところ、正常細胞やE6発現細胞の単独培養ではあまり活性化しておらず、細胞競合条件下特異的にE6発現細胞内においてプロモーター活性が上昇していることが分かった。 分子機構の解析に加えて、HPVに対する細胞競合をin vivoで解析するためのモデルマウスの構築を行った。Rosa26にCre酵素特異的に組換えを誘導できるEGFP, E6, E7, E6/E7遺伝子を発現できるベクターを構築し、マウスES細胞を樹立した。その後にそれらのES細胞を用いて第一世代のマウスの構築を行っている。


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