BackgroundThe 2014–2016 Ebola virus (EBOV) outbreak in West Africa highlighted the need for improved therapeutic options against this virus. Approaches targeting host factors/pathways essential for the virus are advantageous because they can potentially target a wide range of viruses, including newly emerging ones and because the development of resistance is less likely than when targeting the virus directly. However, systematic approaches for screening host factors important for EBOV have been hampered by the necessity to work with this virus at biosafety level 4 (BSL4).MethodsIn order to identify host factors involved in the EBOV life cycle, we performed a genome-wide siRNA screen comprising 64,755 individual siRNAs against 21,566 human genes to assess their activity in EBOV genome replication and transcription. As a screening platform, we used reverse genetics-based life cycle modelling systems that recapitulate these processes without the need for a BSL4 laboratory.ResultsAmong others, we identified the de novo pyrimidine synthesis pathway as an essential host pathway for EBOV genome replication and transcription, and confirmed this using infectious EBOV under BSL4 conditions. An FDA-approved drug targeting this pathway showed antiviral activity against infectious EBOV, as well as other non-segmented negative-sense RNA viruses.ConclusionsThis study provides a minable data set for every human gene regarding its role in EBOV genome replication and transcription, shows that an FDA-approved drug targeting one of the identified pathways is highly efficacious in vitro, and demonstrates the power of life cycle modelling systems for conducting genome-wide host factor screens for BSL4 viruses.Electronic supplementary materialThe online version of this article (10.1186/s13073-018-0570-1) contains supplementary material, which is available to authorized users.

No abstract

Tacaribe virus (TCRV) is the prototype of the New World arenaviruses (also known as TCRV serocomplex viruses). While TCRV is not itself a human pathogen, many closely related members of this group cause hemorrhagic fever, and thus TCRV has long served as an important BSL2 system for research into diverse areas of arenavirus biology. Due to its widespread use, a coding-complete sequence for both the S and L segments of the bipartite genome has been publically available for almost 30 years. However, more recently, this sequence has been found to contain significant discrepancies compared to other samples of the same original strain (i.e., TRVL-11573). Further, it is incomplete with respect to the genome ends, which contain critical regulatory elements for RNA synthesis. In order to rectify these issues we now present the first complete genome sequence for this important prototype arenavirus. In addition to completing the S segment 5’ end, we identified an apparent error in the L segment 3’ end as well as substantial discrepancies in the S segment intergenic region likely to affect folding. Comparison of this sequence with existing partial sequences confirmed a 12-amino-acid deletion in GP, including putative glycosylation sites, and a 4-amino-acid exchange flanking the exonuclease domain of NP. Accounting for these corrections, the TRVL-11573 strain appears to be nearly identical to that isolated in Florida in 2012. The availability of this information provides a solid basis for future molecular and genetic work on this important prototype arenavirus.

No abstract

New World arenaviruses are rodent-transmitted viruses and include a number of pathogens that are responsible for causing severe human disease. This includes Junín virus (JUNV), which is the causative agent of Argentine hemorrhagic fever. The wild nature and mobility of the rodent reservoir host makes it difficult to control the disease, and currently passive immunization with high-titer neutralizing antibody-containing plasma from convalescent patients is the only specific therapy. However, dwindling supplies of naturally available convalescent plasma, and challenges in developing similar resources for other closely related viruses, have made the development of alternative antibody-based therapeutic approaches of critical importance. In this study, we sought to induce a neutralizing antibody response in rabbits against the receptor-binding subunit of the viral glycoprotein, GP1, and the specific peptide sequences in GP1 involved in cellular receptor contacts. While these specific receptor-interacting peptides did not efficiently induce the production of neutralizing antibodies when delivered as a particulate antigen (as part of hepatitis B virus core-like particles), we showed that recombinant JUNV GP1 purified from transfected mammalian cells induced virus-neutralizing antibodies at high titers in rabbits. Further, neutralization was observed across a range of unrelated JUNV strains, a feature that is critical for effectiveness in the field. These results underscore the potential of GP1 alone to induce a potent neutralizing antibody response and highlight the importance of epitope presentation. In addition, effective virus neutralization by rabbit antibodies supports the potential applicability of this species for the future development of immunotherapeutics (e.g., based on humanized monoclonal antibodies). Such information can be applied in the design of vaccines and immunogens for both prevention and specific therapies against this and likely also other closely related pathogenic New World arenaviruses.