Iwasaki Lab/International Research Center for Infectious Diseases  Laboratory of Emerging Viral Diseases

Mammarenaviruses include highly pathogenic agents such as Lassa (West Africa) and Junin (South America) viruses, which cause viral hemorrhagic fever in humans and pose important public health problems within their regions of endemicity. In addition, the worldwide-distributed, prototypic mammarenavirus, lymphocytic choriomeningitis virus (LCMV) is a neglected human pathogen of clinical significance. Despite their substantial impact on human health, current therapeutic options for mammarenaviruses are very limited. Our research focuses on investigating the molecular and cellular biology of mammarenaviruses to facilitate the development of novel antivirals and vaccines.



Mammarenaviruses are simple enveloped viruses with a bi-segmented ambisense RNA genome encoding four genes (Figure Al. Each ANA segment, small (S) and large (L), directs the synthesis of two viral proteins from two open reading frames, which are separated by a non-coding intergenic region (IGR). Despite this simple genome organization, we know very little about the mechanisms by which these viruses multiply and cause disease in infected hosts. To better understand the complex biology of mammarenaviruses and to develop antiviral strategies that can combat these viruses, we use reverse genetics systems to generate recombinant mammarenaviruses, which contain pre-determined mutations and/or additional foreign genes such as enhanced green fluorescent protein (eGFP), from cloned cDNAs. We used these technologies to generate a recombinant LCMV harboring a synthetic LCMV S-IGR-like IGR instead of the L-IGR [rLCMV(IGR/S-Ssyn)] (Figure B). rLCMV(IGR/S-Ssyn) was severely attenuated in vivo but elicited protective immunity against a lethal challenge with wild-type LCMV. This strategy can be used to generate live-attenuated vaccines for currently known and potentially newly emerging hemorrhagic fever-causing mammarenaviruses without the need to incorporate amino acid changes. In addition, we generated recombinant LCMVs expressing eGFP or an affinity-tagged viral protein to facilitate genetic and pharmacological screenings and proteomic analyses with the aim of identifying virus-host interactions required for efficient multiplication of mammarenaviruses that can be exploited as druggable targets.

  • Fig 1.
    (A) Schematic diagram of mammarenavirus genome organization. (B) Predicted RNA secondary structures of the LCMV S-IGR (left) and synthetic LCMV S-IGR-like IGR (right).
    (Iwasaki M. et al., J Virol. (2016) 90(6):3187-97)

  • Fig 2.
    Summary of our findings on each step of the viral life cycle.


  • SA Assoc. Prof.: Masaharu Iwasaki
  • Postdoc.: Mei Hashizume



  • (1)A small stem-loop-forming region within the 3′-UTR of a non-polyadenylated LCMV mRNA promotes translation. Hashizume M. et al., J Biol Chem. (2022) 298(2):101576.doi: 10.1016/j.jbc.2022.101576.
    (2)A Lassa Virus Live-Attenuated Vaccine Candidate Based on Rearrangement of the Intergenic Region.Cai Y. et al., mBio (2020) 11(2):e00186-20.
    (3) Interactome analysis of the lymphocytic choriomeningitis virus nucleoprotein in infected cells reveals ATPase Na+/K+ transporting subunit Alpha 1 and prohibitin as host-cell factors involved in the life cycle of mammarenaviruses. Iwasaki M. et al., PLoS Pathog. (2018) 20;14(2):e1006892.
    (4) Resistance of human plasmacytoid dendritic CAL-1 cells to infection with lymphocytic choriomeningitis virus (LCMV) is caused by restricted virus cell entry, which is overcome by contact of CAL-1 cells with LCMV-infected cells. Iwasaki M. et al., Virology. (2017) 511:106-113.
    (5) Residues K465 and G467 Within The Cytoplasmic Domain of GP2 Critically Contribute To LCMV Persistence In Mice. Iwasaki M. et al., J Virol. (2016) 28;90(22):10102-10112.
    (6) The High Degree of Sequence Plasticity of the Arenavirus Noncoding Intergenic Region (IGR) Enables the Use of a Nonviral Universal Synthetic IGR To Attenuate Arenaviruses. Iwasaki M. et al., J Virol. (2016) 90(6):3187-97.
    (7) General Molecular Strategy for Development of Arenavirus Live-Attenuated Vaccines. Iwasaki M. et al., J Virol. (2015) 89(23):12166-77.
    (8) Efficient Interaction between Arenavirus Nucleoprotein (NP) and RNA-Dependent RNA Polymerase (L) Is Mediated by the Virus Nucleocapsid (NP-RNA) Template. Iwasaki M. et al., J Virol. (2015) 89(10):5734-8.
    (9) Cell Entry of Lymphocytic Choriomeningitis Virus Is Restricted In Myotubes. Iwasaki M. et al., Virology. (2014) 458-459:22-32.
    (10) Sodium Hydrogen Exchangers Contribute to Arenavirus Cell Entry. Iwasaki M. et al., J Virol. (2014) 88(1):643-54.