Generation of Recombinant Ebola Viruses Using Reverse Genetics

Reverse genetics systems encompass a wide array of tools aimed at recapitulating some or all of the virus life cycle. In their most complete form, full-length clone systems allow us to use plasmid-encoded versions of the ribonucleoprotein (RNP) components to initiate the transcription and replication of a plasmid-encoded version of the complete viral genome, thereby initiating the complete virus life cycle and resulting in infectious virus. As such this approach is ideal for the generation of tailor-made recombinant filoviruses, which can be used to study virus biology. In addition, the generation of tagged and particularly fluorescent or luminescent viruses can be applied as tools for both diagnostic applications and for screening to identify novel countermeasures. Here we describe the generation and basic characterization of recombinant Ebola viruses rescued from cloned cDNA using a T7-driven system.

Rapid one-step construction of a Middle East Respiratory Syndrome (MERS-CoV) infectious clone system by homologous recombination

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This work describes a minimalist approach to the construction and validation of a coronavirus reverse genetics system utilizing homologous recombination for vector construction and a variety of molecular techniques for virus detection.

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Homologous recombination in S. cerevisiae proves an efficient and fast method of constructing the large and complex genome of MERS-CoV, this strategy will be helpful for future construction of other virus genomes.

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Detection of rescued virus by molecular assay (i.e.: RT-PCR) is a strong alternative to the more traditional immunological detection assays.

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Rescued MERS-CoV was genomically and phenotypically similar to the original isolate MERS-CoV/EMC-2012.

Background

Viral Infectious clone systems serve as robust platforms to study viral gene or replicative function by reverse genetics, formulate vaccines and adapt a wild type-virus to an animal host. Since the development of the first viral infectious clone system for the poliovirus, novel strategies of viral genome construction have allowed for the assembly of viral genomes across the identified viral families. However, the molecular profiles of some viruses make their genome more difficult to construct than others. Two factors that affect the difficulty of infectious clone construction are genome length and genome complexity.

Results

This work examines the available strategies for overcoming the obstacles of assembling the long and complex RNA genomes of coronaviruses and reports one-step construction of an infectious clone system for the Middle East Respiratory Syndrome coronavirus (MERS-CoV) by homologous recombination in S. cerevisiae.

Conclusions

Future use of this methodology will shorten the time between emergence of a novel viral pathogen and construction of an infectious clone system. Completion of a viral infectious clone system facilitates further study of a virus’s biology, improvement of diagnostic tests, vaccine production and the screening of antiviral compounds.