Applied research on human pathogenic arenaviruses

Development of novel inhibitors of cell entry of pathogenic arenaviruses

Dominique Burri, Dr. Antonella Pasquato

A hallmark of fatal arenavirus hemorrhagic fevers is rapid multiplication of the virus that overwhelms the patient’s immune system resulting in uncontrolled virus infection associated with hemorrhagic fever, shock and death. Those who survive develop a vigorous anti-viral immune response during the second week of disease, control the infection, and ultimately clear the virus. A highly predictive factor for disease outcome is concentration of the virus in the patient’s blood early in disease indicating a close competition between viral spread and the patient’s immune system. Since entry into the host cell is the first step of every virus infection it represents an important target for blocking virus infection, and entry inhibitors have emerged as a new class of anti-viral drugs.
Considering the limited public health infrastructure in endemic regions, we aimed at the development of novel synthetic inhibitors of cell entry of human pathogenic arenaviruses that can be produced at low cost, delivered orally, and stored in tropical climates. To achieve this goal, we performed high-throughput screening of collections of synthetic small molecules using a LASV reporter virus in a cell-based infection assay. Our screening resulted in the discovery of a series of novel and potent candidate inhibitors of LASV cell entry. Remarkably, our most potent candidate inhibitors were also active against the genetically more distant South American hemorrhagic arenaviruses Junin, Machupo, and Guanarito. We found that our inhibitors block the final step of arenavirus entry, the fusion of the viral envelope with the membrane of the host cell. We are currently optimizing our drug candidates and evaluate their anti-viral activity in vitro and in vivo towards the development of a drug candidate for first pre-clinical studies. We will further use these novel inhibitors as molecular probes in our basic virology research to investigate the molecular mechanism of cell entry and membrane fusion of arenaviruses.

Collaborators: Dr. Andrew M. Lee*, Prof. Michael B.A. Oldstone and Prof. Dale L. Boger, *Scripps Research Institute, La Jolla, CA, USA.

Targeting the biosynthesis of arenavirus glycoproteins as an antiviral strategy

Dominique Burri, Dr. Antonella Pasquato

A crucial step in the life cycle of arenaviruses is the biosynthesis of the fusion-active viral envelope glycoprotein (GP) that is required for cell-to-cell propagation of infection and the production of infectious virus.

1. The biosynthesis of functional arenavirus GP critically depends on the proteolytic processing of the GP precursor (GPC) by the cellular proprotein convertase subtilisin kexin isozyme-1/site-1 protease (SKI-1/S1P). This step is crucial for the production of infectious virus and viral spread and represents a promising target for therapeutic intervention. In our efforts to develop novel specific anti-arenaviral drugs, we characterize the molecular interaction between the SKI-1/S1P protease and its viral GPC substrate with the goal to design peptide-based inhibitors of arenavirus GPC processing. This approach is complemented by the development of small molecule inhibitors specific for SKI-1/S1P-mediated processing of arenavirus GPCs. Candidate inhibitors are evaluated for their anti-viral potential in vitro and in vivo.
2. The cellular trafficking of arenavirus GP and its incorporation into virion particles are complex processes that depend on the physical interaction of GP with the matrix protein Z and cellular factors. A crucial step in the formation of progeny virions form infected cells is the targeting of the GP-Z complex to specific microdomains of the plasma membrane that form budding zones in which virus assembly takes place. In contrast to other enveloped viruses, arenaviruses selectively incorporate processed GP into virions. To investigate the role of GPC processing for virus assembly and budding, we characterize the molecular interaction between cleaved/uncleaved GPC and matrix protein Z, examining the cellular trafficking of these proteins and the association with specific membrane domains from where budding occurs.

Collaborators: Prof. Nabil G. Seidah, Laboratory of Biochemical Neuroendocrinology, Montreal, Canada, Dr. Laura Cendron and Prof. Giuseppe Zanotti, University of Padua, Italy.

Development of a Novel Recombinant Lassa Vaccine Using a Nanoparticle Platform

Ana-Rita Gonçalves, Dr. Sachiko Hirsoue*

*Institute of Bioengineering, Ecole Polytéchnique Fédérale Lausanne (EPFL).  

Considering the number of people affected by Lassa virus and the restricted therapeutic options, a safe and efficacious Lassa vaccine is urgently needed. To achieve this goal, we have launched a collaborative project with the laboratories of Prof. Melody A. Swartz and Prof. Jeffrey A. Hubbell from the Institute of Bioengineering, EPFL. Our project aims at the development of a novel recombinant Lassa vaccine based on a nanoparticle platform developed in the laboratories of Prof. Swartz and Prof. Hubbell and its evaluation in a small animal model. During the first phase of the project we designed and produced suitable vaccine antigens that will be delivered by our nanoparticles to elicit a protective T cell response as well as neutralizing antibodies. A particular challenge is the generation of neutralizing antibodies directed to the surface glycoprotein (GP) of LASV. To this end, we have generated a novel type of nanoparticle that allows the presentation of these antigens in their native conformation, allowing the display of the conformational epitopes, enhancing our chances to elicit a neutralizing antibody response. Our approach combines the powerful technology of nanoparticles with an unmet biological problem and may pave the way for the development of a recombinant vaccine for an important emerging human infectious disease.  

Collaborators: Prof. Melody Swartz and Prof. Jeffrey A. Hubbell, Institute of Bioengineering, Ecole Polytéchnique Fédérale Lausanne (EPFL).