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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Virol. 80, 2933-2940 (2006).</li><li>Billecocq, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+polymerase+I-mediated+expression+of+viral+RNA+for+the+rescue+of+infectious+virulent+and+avirulent+Rift+Valley+fever+viruses.">RNA polymerase I-mediated expression of viral RNA for the rescue of infectious virulent and avirulent Rift Valley fever viruses.</a> Virology. 378, 377-384 (2008).</li><li>Habjan, M., Penski, N., Spiegel, M., Weber, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=T7+RNA+polymerase-dependent+and+-independent+systems+for+cDNA-based+rescue+of+Rift+Valley+fever+virus.">T7 RNA polymerase-dependent and -independent systems for cDNA-based rescue of Rift Valley fever virus.</a> J. Gen. Virol. 89, 2157-2166 (2008).</li><li>Gerrard, S. R., Bird, B. H., Albarino, C. G., Nichol, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+NSm+proteins+of+Rift+Valley+fever+virus+are+dispensable+for+maturation,+replication+and+infection.">The NSm proteins of Rift Valley fever virus are dispensable for maturation, replication and infection.</a> Virology. 359, 459-465 (2007).</li><li>Billecocq, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NSs+protein+of+Rift+Valley+fever+virus+blocks+interferon+production+by+inhibiting+host+gene+transcription.">NSs protein of Rift Valley fever virus blocks interferon production by inhibiting host gene transcription.</a> J. Virol. 78, 9798-9806 (2004).</li><li>May, N. L. e. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TFIIH+transcription+factor,+a+target+for+the+Rift+Valley+hemorrhagic+fever+virus.">TFIIH transcription factor, a target for the Rift Valley hemorrhagic fever virus.</a> Cell. 116, 541-550 (2004).</li><li>Ikegami, T. <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+NSs+protein+promotes+post-transcriptional+downregulation+of+protein+kinase+PKR+and+inhibits+eIF2alpha+phosphorylation.">Rift Valley fever virus NSs protein promotes post-transcriptional downregulation of protein kinase PKR and inhibits eIF2alpha phosphorylation.</a> PLoS Pathog. 5, e1000287-e1000287 (2009).</li><li>Habjan, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NSs+protein+of+Rift+valley+fever+virus+induces+the+specific+degradation+of+the+double-stranded+RNA-dependent+protein+kinase.">NSs protein of Rift valley fever virus induces the specific degradation of the double-stranded RNA-dependent protein kinase.</a> J. Virol. 83, 4365-4375 (2009).</li><li>Garcia-Sastre, A., Biron, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Type+1+interferons+and+the+virus-host+relationship:+a+lesson+in+detente.">Type 1 interferons and the virus-host relationship: a lesson in detente.</a> Science. 312, 879-882 (2006).</li><li>Bon, A. L. e. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Type+i+interferons+potently+enhance+humoral+immunity+and+can+promote+isotype+switching+by+stimulating+dendritic+cells+in+vivo.">Type i interferons potently enhance humoral immunity and can promote isotype switching by stimulating dendritic cells in vivo.</a> Immunity. 14, 461-470 (2001).</li><li>Le Bon, A., Tough, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Links+between+innate+and+adaptive+immunity+via+type+I+interferon.">Links between innate and adaptive immunity via type I interferon.</a> Curr. Opin. Immunol. 14, 432-436 (2002).</li><li>Tough, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Type+I+interferon+as+a+link+between+innate+and+adaptive+immunity+through+dendritic+cell+stimulation.">Type I interferon as a link between innate and adaptive immunity through dendritic cell stimulation.</a> Leuk. Lymphoma. 45, 257-264 (2004).</li><li>Ito, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+recovery+of+rabies+virus+from+cloned+cDNA+using+a+vaccinia+virus-free+reverse+genetics+system.">Improved recovery of rabies virus from cloned cDNA using a vaccinia virus-free reverse genetics system.</a> Microbiol. Immunol. 47, 613-617 (2003).</li><li>Terasaki, K., Murakami, S., Lokugamage, K. G., Makino, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+tripartite+RNA+genome+packaging+in+Rift+Valley+fever+virus.">Mechanism of tripartite RNA genome packaging in Rift Valley fever virus.</a> Proc. Natl. Acad. Sci. U.S.A. 108, 804-809 (2010).</li><li>Buchholz, U. J., Finke, S., Conzelmann, K. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+bovine+respiratory+syncytial+virus+(BRSV)+from+cDNA:+BRSV+NS2+is+not+essential+for+virus+replication+in+tissue+culture,+and+the+human+RSV+leader+region+acts+as+a+functional+BRSV+genome+promoter.">Generation of bovine respiratory syncytial virus (BRSV) from cDNA: BRSV NS2 is not essential for virus replication in tissue culture, and the human RSV leader region acts as a functional BRSV genome promoter.</a> J. Virol. 73, 251-259 (1999).</li><li>Diaz, M. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Homozygous+deletion+of+the+alpha-+and+beta+1-interferon+genes+in+human+leukemia+and+derived+cell+lines.">Homozygous deletion of the alpha- and beta 1-interferon genes in human leukemia and derived cell lines.</a> Proc. Natl. Acad. Sci. U.S.A. 85, 5259-5263 (1988).</li><li>Mosca, J. D., Pitha, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+and+posttranscriptional+regulation+of+exogenous+human+beta+interferon+gene+in+simian+cells+defective+in+interferon+synthesis.">Transcriptional and posttranscriptional regulation of exogenous human beta interferon gene in simian cells defective in interferon synthesis.</a> Mol. Cell. Biol. 6, 2279-2283 (1986).</li><li>Constantinescu, S. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+and+signaling+specificity+of+the+IFNAR+chain+of+the+type+I+interferon+receptor+complex.">Expression and signaling specificity of the IFNAR chain of the type I interferon receptor complex.</a> Proc. Natl. Acad. Sci. U.S.A. 92, 10487-10491 (1995).</li><li>Kumar, K. 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. 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:+use+of+recombinant+vaccinia+viruses+to+study+Phlebovirus+gene+expression.">Rift Valley fever virus M segment: use of recombinant vaccinia viruses to study Phlebovirus gene expression.</a> J. Virol. 62, 826-833 (1988).</li><li>Niwa, H., Yamamura, K., Miyazaki, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+selection+for+high-expression+transfectants+with+a+novel+eukaryotic+vector.">Efficient selection for high-expression transfectants with a novel eukaryotic vector.</a> Gene. 108, 193-199 (1991).</li><li>Muller, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+clone+13,+a+naturally+attenuated+avirulent+isolate+of+Rift+Valley+fever+virus,+which+is+altered+in+the+small+segment.">Characterization of clone 13, a naturally attenuated avirulent isolate of Rift Valley fever virus, which is altered in the small segment.</a> Am. J. Trop. Med. Hyg. 53, 405-411 (1995).</li><li>Le May, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+SAP30+complex+inhibits+IFN-beta+expression+in+Rift+Valley+fever+virus+infected+cells.">A SAP30 complex inhibits IFN-beta expression in Rift Valley fever virus infected cells.</a> PLoS Pathog. 4, e13-e13 (2008).</li><li>Kalveram, B., Lihoradova, O., Ikegami, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NSs+Protein+of+Rift+Valley+Fever+Virus+Promotes+Post-Translational+Downregulation+of+the+TFIIH+Subunit+p62.">NSs Protein of Rift Valley Fever Virus Promotes Post-Translational Downregulation of the TFIIH Subunit p62.</a> J. Virol. 85, 6234-6243 (2011).</li><li>Taniguchi, T., Ogasawara, K., Takaoka, A., Tanaka, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IRF+family+of+transcription+factors+as+regulators+of+host+defense.">IRF family of transcription factors as regulators of host defense.</a> Annu. Rev. Immunol. 19, 623-655 (2001).</li><li>Marie, I., Durbin, J. E., Levy, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+viral+induction+of+distinct+interferon-alpha+genes+by+positive+feedback+through+interferon+regulatory+factor-7.">Differential viral induction of distinct interferon-alpha genes by positive feedback through interferon regulatory factor-7.</a> EMBO J. 17, 6660-6669 (1998).</li><li>Ikegami, T., Won, S., Peters, C. J., Makino, 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+NSs+mRNA+is+transcribed+from+an+incoming+anti-viral-sense+S+RNA+segment.">Rift Valley fever virus NSs mRNA is transcribed from an incoming anti-viral-sense S RNA segment.</a> J. Virol. 79, 12106-12111 (2005).</li><li>Mims, C. A. <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+in+mice.+I.+General+features+of+the+infection.">Rift Valley Fever virus in mice. I. General features of the infection.</a> Br. J. Exp. Pathol. 37, 99-109 (1956).</li><li>Bouloy, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+evidence+for+an+interferon-antagonistic+function+of+rift+valley+fever+virus+nonstructural+protein+NSs.">Genetic evidence for an interferon-antagonistic function of rift valley fever virus nonstructural protein NSs.</a> J. Virol. 75, 1371-1377 (2001).</li><li>Bird, B. H., Albarino, C. G., Nichol, S. T. <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+lacking+NSm+proteins+retains+high+virulence+in+vivo+and+may+provide+a+model+of+human+delayed+onset+neurologic+disease.">Rift Valley fever virus lacking NSm proteins retains high virulence in vivo and may provide a model of human delayed onset neurologic disease.</a> Virology. 362, 10-15 (2007).</li></ol>

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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Research

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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.

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

Reverse Genetics Mediated Recovery of Infectious Murine Norovirus

Human noroviruses are responsible for most cases of human gastroenteritis (GE) worldwide and are recurrent problem in environments where close person-to-person contact cannot be avoided 1, 2. During the last few years an increase in the incidence of outbreaks in hospitals has been reported, causing significant disruptions to their operational capacity as well as large economic losses. The identification of new antiviral approaches has been limited due to the inability of human noroviruses to complete a productive infection in cell culture 3. The recent isolation of a murine norovirus (MNV), closely related to human norovirus 4 but which can be propagated in cells 5 has opened new avenues for the investigation of these pathogens 6, 7. 
MNV replication results in the synthesis of new positive sense genomic and subgenomic RNA molecules, the latter of which corresponds to the last third of the viral genome (Figure 1). MNV contains four different open reading frames (ORFs), of which ORF1 occupies most of the genome and encodes seven non-structural proteins (NS1-7) released from a polyprotein precursor. ORF2 and ORF3 are contained within the subgenomic RNA region and encode the capsid proteins (VP1 and VP2, respectively) (Figure 1). Recently, we have identified that additional ORF4 overlapping ORF2 but in a different reading frame is functional and encodes for a mitochondrial localised virulence factor (VF1) 8.
Replication for positive sense RNA viruses, including noroviruses, takes place in the cytoplasm resulting in the synthesis of new uncapped RNA genomes. To promote viral translation, viruses exploit different strategies aimed at recruiting the cellular protein synthesis machinery 9-11. Interestingly, norovirus translation is driven by the multifunctional viral protein-primer VPg covalently linked to the 5' end of both genomic and subgenomic RNAs 12-14. This sophisticated mechanism of translation is likely to be a major factor in the limited efficiency of viral recovery by conventional reverse genetics approaches. 
Here we report two different strategies based on the generation of murine norovirus-1 (referred to as MNV herewith) transcripts capped at the 5' end. One of the methods involves both in vitro synthesis and capping of viral RNA, whereas the second approach entails the transcription of MNV cDNA in cells expressing T7 RNA polymerase. The availability of these reverse genetics systems for the study of MNV and a small animal model has provided an unprecedented ability to dissect the role of viral sequences in replication and pathogenesis 15-17.

Noroviruses are a major cause of gastroenteritis yet molecular techniques for their characterisation are still relatively new. Here we report two different reverse genetics approaches for the efficient recovery of murine norovirus (MNV), the only member of this genus which can be propagated in cell culture.

Human noroviruses are responsible for most cases of human gastroenteritis (GE) worldwide and are recurrent problem in environments where close ...

Using Click Chemistry to Measure the Effect of Viral Infection on Host-Cell RNA Synthesis

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, it is therefore important to have a quick and reliable way of measuring transcriptional activity in infected cells. Traditionally, transcription has been measured either by incorporation of radioactive nucleosides such as 3H-uridine followed by detection via autoradiography or scintillation counting, or incorporation of halogenated uridine analogs such as 5-bromouridine (BrU) followed by detection via immunostaining. The use of radioactive isotopes, however, requires specialized equipment and is not feasible in a number of laboratory settings, while the detection of BrU can be cumbersome and may suffer from low sensitivity.
The recently developed click chemistry, which involves a copper-catalyzed triazole formation from an azide and an alkyne, now provides a rapid and highly sensitive alternative to these two methods. Click chemistry is a two step process in which nascent RNA is first labeled by incorporation of the uridine analog 5-ethynyluridine (EU), followed by detection of the label with a fluorescent azide. These azides are available as several different fluorophores, allowing for a wide range of options for visualization.
This protocol describes a method to measure transcriptional suppression in cells infected with the Rift Valley fever virus (RVFV) strain MP-12 using click chemistry. Concurrently, expression of viral proteins in these cells is determined by classical intracellular immunostaining. Steps 1 through 4 detail a method to visualize transcriptional suppression via fluorescence microscopy, while steps 5 through 8 detail a method to quantify transcriptional suppression via flow cytometry. This protocol is easily adaptable for use with other viruses.

This method describes the use of click chemistry to measure changes in host cell transcription after infection with the Rift Valley fever virus (RVFV) strain MP-12. Results can be visualized qualitatively via fluorescence microscopy or obtained quantitatively through flow cytometry. This method is adaptable for use with other viruses.

Many RNA viruses have evolved the ability to inhibit host cell transcription as a means to circumvent cellular defenses. For the study of these viruses, ...

Cell-based Flow Cytometry Assay to Measure Cytotoxic Activity

Cytolytic activity of CD8+ T cells is rarely evaluated. We describe here a new cell-based assay to measure the capacity of antigen-specific CD8+ T cells to kill CD4+ T cells loaded with their cognate peptide. Target CD4+ T cells are divided into two populations, labeled with two different concentrations of CFSE. One population is pulsed with the peptide of interest (CFSE-low) while the other remains un-pulsed (CFSE-high). Pulsed and un-pulsed CD4+ T cells are mixed at an equal ratio and incubated with an increasing number of purified CD8+ T cells. The specific killing of autologous target CD4+ T cells is analyzed by flow cytometry after coculture with CD8+ T cells containing the antigen-specific effector CD8+ T cells detected by peptide/MHCI tetramer staining. The specific lysis of target CD4+ T cells measured at different effector versus target ratios, allows for the calculation of lytic units, LU30/106 cells. This simple and straightforward assay allows for the accurate measurement of the intrinsic capacity of CD8+ T cells to kill target CD4+ T cells.

This protocol describes a sensitive, cell-based cytotoxicity assay. By enumerating the decrease in frequency of live target CD4+ T cells in the presence of an increasing number of effector CD8+ T cells, this assay allows for the direct assessment of cytolytic activity of antigen-specific CD8+ T cells.

Cytolytic activity of CD8+ T cells is rarely evaluated. We describe here a new cell-based assay to measure the capacity of antigen-specific CD8+ T cells ...

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in mice. Recently, myeloid differentiation factor 88 (MyD88) signaling was shown to be important for initial T cell priming and memory T cell development during WNV NS4B-P38G mutant infection. In this study, two flow cytometry-based methods &#8211; an in vitro T cell priming assay and an intracellular cytokine staining (ICS) &#8211; were utilized to assess dendritic cells (DCs) and T cell functions. In the T cell priming assay, cell proliferation was analyzed by flow cytometry following co-culture of DCs from both groups of mice with carboxyfluorescein succinimidyl ester (CFSE) - labeled CD4+ T cells of OTII transgenic mice. This approach provided an accurate determination of the percentage of proliferating CD4+ T cells with significantly improved overall sensitivity than the traditional assays with radioactive reagents. A microcentrifuge tube system was used in both cell culture and cytokine staining procedures of the ICS protocol. Compared to the traditional tissue culture plate-based system, this modified procedure was easier to perform at biosafety level (BL) 3 facilities. Moreover, WNV- infected cells were treated with paraformaldehyde in both assays, which enabled further analysis outside BL3 facilities. Overall, these in vitro immunological assays can be used to efficiently assess cell-mediated immune responses during WNV infection.

In Vitro Analysis of Myd88-mediated Cellular Immune Response to West Nile Virus Mutant Strain Infection

Two flow cytometry-based methods &#8211; an in vitro T cell priming assay and intracellular cytokine staining were utilized to measure antigen presenting capacity of dendritic cells and antigen-specific T cell responses to a West Nile virus mutant infection in mice.

An attenuated West Nile virus (WNV), a nonstructural (NS) 4B-P38G mutant, induced higher innate cytokine and T cell responses than the wild-type WNV in ...

Evaluation of the Efficacy And Toxicity of RNAs Targeting HIV-1 Production for Use in Gene or Drug Therapy

Small RNA therapies targeting post-integration steps in the HIV-1 replication cycle are among the top candidates for gene therapy and have the potential to be used as drug therapies for HIV-1 infection. Post-integration inhibitors include ribozymes, short hairpin (sh) RNAs, small interfering (si) RNAs, U1 interference (U1i) RNAs and RNA aptamers. Many of these have been identified using transient co-transfection assays with an HIV-1 expression plasmid and some have advanced to clinical trials. In addition to measures of efficacy, small RNAs have been evaluated for their potential to affect the expression of human RNAs, alter cell growth and/or differentiation, and elicit innate immune responses. In the protocols described here, a set of transient transfection assays designed to evaluate the efficacy and toxicity of RNA molecules targeting post-integration steps in the HIV-1 replication cycle are described. We have used these assays to identify new ribozymes and optimize the format of shRNAs and siRNAs targeting HIV-1 RNA. The methods provide a quick set of assays that are useful for screening new anti-HIV-1 RNAs and could be adapted to screen other post-integration inhibitors of HIV-1 replication.

Methods to evaluate the efficacy and toxicity of RNA molecules targeting post-integration steps of the HIV-1 replication cycle are described. These methods are useful for screening new molecules and optimizing the format of existing ones.

Small RNA therapies targeting post-integration steps in the HIV-1 replication cycle are among the top candidates for gene therapy and have the potential ...

Generation of Escape Variants of Neutralizing Influenza Virus Monoclonal Antibodies

Influenza viruses exhibit a remarkable ability to adapt and evade the host immune response. One way is through antigenic changes that occur on the surface glycoproteins of the virus. The generation of escape variants is a powerful method in elucidating how viruses escape immune detection and in identifying critical residues required for antibody binding. Here, we describe a protocol on how to generate influenza A virus escape variants by utilizing human or murine monoclonal antibodies (mAbs) directed against the viral hemagglutinin (HA). With the use of our technique, we previously characterized critical residues required for the binding of antibodies targeting either the head or stalk of the novel avian H7N9 HA. The protocol can be easily adapted for other virus systems. Analyses of escape variants are important for modeling antigenic drift, determining single nucleotide polymorphisms (SNPs) conferring resistance and virus fitness, and in the designing of vaccines and/or therapeutics.

We describe a method by which we identify critical residues required for the binding of human or murine monoclonal antibodies that target the viral hemagglutinin of influenza A viruses. The protocol can be adapted to other virus surface glycoproteins and their corresponding neutralizing antibodies.

Influenza viruses exhibit a remarkable ability to adapt and evade the host immune response. One way is through antigenic changes that occur on the surface ...

Overexpression and Purification of Human Cis-prenyltransferase in Escherichia coli

Prenyltransferases (PT) are a group of enzymes that catalyze chain elongation of allylic diphosphate using isopentenyl diphosphate (IPP) via multiple condensation reactions. DHDDS (dehydrodolichyl diphosphate synthase) is a eukaryotic long-chain cis-PT (forming cis double bonds from the condensation reaction) that catalyzes chain elongation of farnesyl diphosphate (FPP, an allylic diphosphate) via multiple condensations with isopentenyl diphosphate (IPP). DHDDS is of biomedical importance, as a non-conservative mutation (K42E) in the enzyme results in retinitis pigmentosa, ultimately leading to blindness. Therefore, the present protocol was developed in order to acquire large quantities of purified DHDDS, suitable for mechanistic studies. Here, the usage of protein fusion, optimized culture conditions and codon-optimization were used to allow the overexpression and purification of functionally active human DHDDS in E. coli. The described protocol is simple, cost-effective and time sparing. The homology of cis-PT among different species suggests that this protocol may be applied for other eukaryotic cis-PT as well, such as those involved in natural rubber synthesis.

Overexpression and Purification of Human Cis-prenyltransferase in Escherichia coli

A simple protocol for overexpression and purification of codon-optimized, human cis-prenyltransferase, under non-denaturing conditions, from Escherichia coli, is described, along with an enzymatic activity assay. This protocol can be generalized for production of other cis- prenyltransferase proteins in quantity and quality suitable for mechanistic studies.

Prenyltransferases (PT) are a group of enzymes that catalyze chain elongation of allylic diphosphate using isopentenyl diphosphate (IPP) via multiple ...

Using Phylogenetic Analysis to Investigate Eukaryotic Gene Origin

Phylogenetic analysis uses nucleotide or amino acid sequences or other parameters, such as domain sequences and three-dimensional structure, to construct a tree to show the evolutionary relationship among different taxa (classification units) at the molecular level. Phylogenetic analysis can also be used to investigate domain relationships within an individual taxon, particularly for organisms that have undergone substantial change in morphology and physiology, but for which researchers lack fossil evidence due to the organisms&#39; long evolutionary history or scarcity of fossilization.
In this text, a detailed protocol is described for using the phylogenetic method, including amino acid sequence alignment using Clustal Omega, and subsequent phylogenetic tree construction using both Maximum Likelihood (ML) of Molecular Evolutionary Genetics Analysis (MEGA) and Bayesian Inference via MrBayes. To investigate the origin of eukaryotic Sugars Will Eventually be Exported Transporters (SWEET) genes, 228 SWEETs including 35 SWEET proteins from unicellular eukaryotes and 57 SemiSWEET proteins from prokaryotes were analyzed. Interestingly, SemiSWEETs were found in prokaryotes, but SWEETs were found in eukaryotes. Two phylogenetic trees constructed using theoretically distinct methods have consistently&#160;suggested that the first eukaryotic SWEET gene might stem from the fusion of a bacterial SemiSWEET gene and an archaeal SemiSWEET gene.&#160;It is worth noting that one should be cautious to draw a conclusion based only on phylogenetic analysis, although it is useful to explain the underlying relationship between different taxa, which is difficult or even impossible to discern through experimental means.

A method of constructing a phylogenetic tree based on sequence homology of SWEETs from eukaryotes and SemiSWEETs from prokaryotes is described. Phylogenetic analysis is a useful tool for explaining the evolutionary relatedness between homologous proteins or genes from different organism groups.

Phylogenetic analysis uses nucleotide or amino acid sequences or other parameters, such as domain sequences and three-dimensional structure, to construct ...

Assembly and Purification of Prototype Foamy Virus Intasomes

A defining feature and necessary step of the retrovirus life cycle is the integration of the viral genome into the host genome. All retroviruses encode an integrase (IN) enzyme that catalyzes the covalent joining of viral to host DNA, which is known as strand transfer. Integration may be modeled in vitro with recombinant retroviral IN and DNA oligomers mimicking the ends of the viral genome. In order to more closely recapitulate the integration reaction that occurs in vivo, integration complexes are assembled from recombinant IN and synthetic oligomers by dialysis in a reduced salt concentration buffer. The integration complex, called an intasome, may be purified by size exclusion chromatography. In the case of prototype foamy virus (PFV), the intasome is a tetramer of IN and two DNA oligomers and is readily separated from monomeric IN and free oligomer DNA. The integration efficiency of PFV intasomes may be assayed under a variety of experimental conditions to better understand the dynamics and mechanics of retroviral integration.

Recombinant retroviral integrase and DNA oligomers mimicking viral DNA ends can form an enzymatically active complex known as an intasome. Intasomes may be used for biochemical, structural, and kinetic studies. This protocol details how to assemble and purify prototype foamy virus intasomes.

A defining feature and necessary step of the retrovirus life cycle is the integration of the viral genome into the host genome. All retroviruses encode an ...

Evaluation of Host-Pathogen Responses and Vaccine Efficacy in Mice

Vaccines are a 20th century medical marvel. They have dramatically reduced the morbidity and mortality caused by infectious diseases and contributed to a striking increase in life expectancy around the globe. Nonetheless, determining vaccine efficacy remains a challenge. Emerging evidence suggests that the current acellular vaccine (aPV) for Bordetella pertussis (B. pertussis) induces suboptimal immunity. Therefore, a major challenge is designing a next-generation vaccine that induces protective immunity without the adverse side effects of a whole-cell vaccine (wPV). Here we describe a protocol that we used to test the efficacy of a promising, novel adjuvant that skews immune responses to a protective Th1/Th17 phenotype and promotes a better clearance of a B. pertussis challenge from the murine respiratory tract. This article describes the protocol for mouse immunization, bacterial inoculation, tissue harvesting, and analysis of immune responses. Using this method, within our model, we have successfully elucidated crucial mechanisms elicited by a promising, next-generation acellular pertussis vaccine. This method can be applied to any infectious disease model in order to determine vaccine efficacy.

Here we present an elegant protocol for in vivo evaluation of vaccine effectiveness and host immune responses. This protocol can be adapted for vaccine models that study viral, bacterial, or parasitic pathogens.

Vaccines are a 20th century medical marvel. They have dramatically reduced the morbidity and mortality caused by infectious diseases and contributed to a ...