This work was funded by Grant Number 5 U54 AI057156-07 through Western Regional Center of Excellence (WRCE), 1 R01 AI08764301-A1 from National Institute of Allergy and Infectious Diseases, and an internal funding from Sealy Center for Vaccine Development at the University of Texas Medical Branch.

<ol>
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G., Tang, W., Ravindranath, A. K., Clark, W. A., Croze, E., Fuchs, S. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SCF(HOS)+ubiquitin+ligase+mediates+the+ligand-induced+down-regulation+of+the+interferon-alpha+receptor.">SCF(HOS) ubiquitin ligase mediates the ligand-induced down-regulation of the interferon-alpha receptor.</a> EMBO J. 22, 5480-5490 (2003).</li><li>Kakach, L. T., Suzich, J. A., Collett, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rift+Valley+fever+virus+M+segment:+phlebovirus+expression+strategy+and+protein+glycosylation.+Virology.">Rift Valley fever virus M segment: phlebovirus expression strategy and protein glycosylation. Virology.</a> 170, 505-510 (1989).</li><li>Kakach, L. T., Wasmoen, T. L., Collett, M. 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We have nothing to disclose.

Reverse genetics systems for RVFV have been developed by several groups by utilizing T7 promoter2,4,5 or mouse3 or human4 pol-I promoter. In this manuscript, we describe a protocol to generate recombinant RVFV MP-12 strains by using BHK/T7-9 cells15 that stably express T7 RNA polymerase. The efficiency of viral recovery varied depending on the condition of BHK/T7-9 cells, the amount of plasmids, the number of transfected cells and so on. We always amplify the P0 virus in ...

<table border="1">
<tr>
<td>Name of the reagent</td>
<td>Company</td>
<td>Catalogue number</td>
<td>Comments (optional)</td>
</tr>
<tr>
<td>Minimum Essential Medium (MEM)-alpha </td>
<td>Invitrogen</td>
<td>32561037 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Dulbecco&rsquo;s modified minimum essential medium </td>
<td>Invitrogen</td>
<td>11965092 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Modified Eagle Medium (MEM 2x) </td>
<td>Invitrogen</td>
<td>11935046 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Penicillin-Streptomycin </td>
<td>Invitrogen</td>
<td>15140122 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Hygromycin B </td>
<td>Cellgro</td>
<td>30-240-CR </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Tryptose phosphate broth </td>
<td>MP biomedicals</td>
<td>1682149 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Noble agar </td>
<td>VWR </td>
<td>101170-362 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>TransIT-LT1 </td>
<td>Mirus</td>
<td>MIR2300 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Opti-MEM </td>
<td>Invitrogen</td>
<td>31985070 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Aerosol tight lid </td>
<td>Eppendorf </td>
<td>C-2223-25 </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>0.33% neutral red solution </td>
<td>Sigma Aldrich </td>
<td>N2889-100ML </td>
<td>&nbsp;</td>
</tr>
<tr>
<td>C57/WT MEF cells</td>
<td>InvivoGen</td>
<td>mef-c57wt</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Blasticidin S</td>
<td>InvivoGen</td>
<td>Ant-bl-1</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Zeocin</td>
<td>InvivoGen</td>
<td>ant-zn-1</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>QUANTI-Blue</td>
<td>InvivoGen</td>
<td>rep-qb1</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>BHK/T7-9 cells15 </td>
<td>Gifu university, Japan</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
<tr>
<td>Vero E6 cells</td>
<td>ATCC</td>
<td>CRL-1586</td>
<td>&nbsp;</td>
</tr>
</table>

using reverse genetics to manipulate the nss gene of the rift valley fever virus mp-12 strain to improve vaccine safety and efficacy

Rift Valley fever virus (RVFV), which causes hemorrhagic fever, neurological disorders or blindness in humans, and a high rate abortion and fetal malformation in ruminants1, has been classified as a HHS/USDA overlap select agent and a risk group 3 pathogen. It belongs to the genus Phlebovirus in the family Bunyaviridae and is one of the most virulent members of this family. Several reverse genetics systems for the RVFV MP-12 vaccine strain2,3 as well as wild-type RVFV strains 4-6, including ZH548 and ZH501, have been developed since 2006. The MP-12 strain (which is a risk group 2 pathogen and a non-select agent) is highly attenuated by several mutations in its M- and L-segments, but still carries virulent S-segment RNA3, which encodes a functional virulence factor, NSs. The rMP12-C13type (C13type) carrying 69% in-frame deletion of NSs ORF lacks all the known NSs functions, while it replicates as efficient as does MP-12 in VeroE6 cells lacking type-I IFN. NSs induces a shut-off of host transcription including interferon (IFN)-beta mRNA7,8 and promotes degradation of double-stranded RNA-dependent protein kinase (PKR) at the post-translational level.9,10 IFN-beta is transcriptionally upregulated by interferon regulatory factor 3 (IRF-3), NF-kB and activator protein-1 (AP-1), and the binding of IFN-beta to IFN-alpha/beta receptor (IFNAR) stimulates the transcription of IFN-alpha genes or other interferon stimulated genes (ISGs)11, which induces host antiviral activities, whereas host transcription suppression including IFN-beta gene by NSs prevents the gene upregulations of those ISGs in response to viral replication although IRF-3, NF-kB and activator protein-1 (AP-1) can be activated by RVFV7. . Thus, NSs is an excellent target to further attenuate MP-12, and to enhance host innate immune responses by abolishing the IFN-beta suppression function. Here, we describe a protocol for generating a recombinant MP-12 encoding mutated NSs, and provide an example of a screening method to identify NSs mutants lacking the function to suppress IFN-beta mRNA synthesis. In addition to its essential role in innate immunity, type-I IFN is important for the maturation of dendritic cells and the induction of an adaptive immune response12-14. Thus, NSs mutants inducing type-I IFN are further attenuated, but at the same time are more efficient at stimulating host immune responses than wild-type MP-12, which makes them ideal candidates for vaccination approaches.

Watch this Scientific Journal Video about Using Reverse Genetics to Manipulate the NSs Gene of the Rift Valley Fever Virus MP-12 Strain to Improve Vaccine Safety and Efficacy at JoVE.com

Using Reverse Genetics to Manipulate the NSs Gene of the Rift Valley Fever Virus MP-12 Strain to Improve Vaccine Safety and Efficacy

The reverse genetics system for the Rift Valley fever virus MP-12 vaccine strain is a useful tool for creating additional MP-12 mutants with increased attenuation and immunogenicity. We describe the protocol to generate and characterize NSs mutant strains.

Rift Valley fever virus (RVFV), which causes hemorrhagic fever, neurological disorders or blindness in humans, and a high rate abortion and fetal ...

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Immunology and Infection

17.2K Views.  University of Texas Medical Branch. The reverse genetics system for the Rift Valley fever virus MP-12 vaccine strain is a useful tool for creating additional MP-12 mutants with increased attenuation and immunogenicity. We describe the protocol to generate and characterize NSs mutant strains.