'''Pseudotyping''' is the process of producing viruses or viral vectors in combination with foreign viral envelope proteins. The result is a pseudotyped virus particle, also called a '''pseudovirus'''.<ref>[http://www99.mh-hannover.de/institute/virologie/section/retro/retro_en.html Example for the development of pseudotype retroviral vectors in a work group of MHH] {{webarchive|url=https://web.archive.org/web/20091108024125/http://www99.mh-hannover.de/institute/virologie/section/retro/retro_en.html |date=2009-11-08 }}</ref> With this method, the foreign viral envelope proteins can be used to alter host tropism or increase or decrease the stability of the virus particles. Pseudotyped particles do not carry the genetic material to produce additional viral envelope proteins, so the phenotypic changes cannot be passed on to progeny viral particles. In some cases, the inability to produce viral envelope proteins renders the pseudovirus replication incompetent. In this way, the properties of dangerous viruses can be studied in a lower risk setting.<ref name=":0">{{Cite journal|last1=Nie|first1=Jianhui|last2=Liu|first2=Lin|last3=Wang|first3=Qing|last4=Chen|first4=Ruifeng|last5=Ning|first5=Tingting|last6=Liu|first6=Qiang|last7=Huang|first7=Weijin|last8=Wang|first8=Youchun|date=2019-02-19|title=Nipah pseudovirus system enables evaluation of vaccines in vitro and in vivo using non-BSL-4 facilities|journal=Emerging Microbes & Infections|volume=8|issue=1|pages=272–281|doi=10.1080/22221751.2019.1571871|issn=2222-1751|pmc=6455126|pmid=30866781}}</ref>
Pseudotyping allows one to control the expression of envelope proteins. A frequently used protein is the glycoprotein G (VSV-G) from the Vesicular stomatitis virus (VSV) which mediates entry via the LDL receptor. Envelope proteins incorporated into the pseudovirus allow the virus to readily enter different cell types with the corresponding host receptor.
== Vaccine development == Pseudotyped virus can be used to vaccinate animals against proteins expressed on the envelope of the virion.<ref name=":1">{{Cite journal|last1=Racine|first1=Trina|author2-link=Gary Kobinger|last2=Kobinger|first2=Gary P.|last3=Arts|first3=Eric J.|date=2017-09-12|title=Development of an HIV vaccine using a vesicular stomatitis virus vector expressing designer HIV-1 envelope glycoproteins to enhance humoral responses|journal=AIDS Research and Therapy|volume=14|issue=1|page=55|doi=10.1186/s12981-017-0179-2|issn=1742-6405|pmc=5594459|pmid=28893277 |doi-access=free }}</ref> This approach has been used to produce vaccine candidates against HIV,<ref name=":1" /> ''Nipah henipavirus'',<ref name=":0" /> ''Rabies lyssavirus'',<ref name=":2">{{Cite journal|last1=Moeschler|first1=Sarah|last2=Locher|first2=Samira|last3=Conzelmann|first3=Karl-Klaus|last4=Krämer|first4=Beate|last5=Zimmer|first5=Gert|date=2016-09-16|title=Quantification of Lyssavirus-Neutralizing Antibodies Using Vesicular Stomatitis Virus Pseudotype Particles|journal=Viruses|volume=8|issue=9|page=254|doi=10.3390/v8090254|issn=1999-4915|pmc=5035968|pmid=27649230|doi-access=free }}</ref> SARS-CoV,<ref>{{Cite journal|last1=Kapadia|first1=Sagar U.|last2=Simon|first2=Ian D.|last3=Rose|first3=John K.|date=2008-06-20|title=SARS vaccine based on a replication-defective recombinant vesicular stomatitis virus is more potent than one based on a replication-competent vector|url= |journal=Virology|language=en|volume=376|issue=1|pages=165–172|doi=10.1016/j.virol.2008.03.002|pmid=18396306|pmc=7103385|issn=0042-6822}}</ref> ''Zaire ebolavirus,'' <ref>{{Cite journal|last1=Salata|first1=Cristiano|last2=Calistri|first2=Arianna|last3=Alvisi|first3=Gualtiero|last4=Celestino|first4=Michele|last5=Parolin|first5=Cristina|last6=Palù|first6=Giorgio|date=2019-03-19|title=Ebola Virus Entry: From Molecular Characterization to Drug Discovery|journal=Viruses|volume=11|issue=3|page=274|doi=10.3390/v11030274|issn=1999-4915|pmc=6466262|pmid=30893774|doi-access=free }}</ref> and SARS-CoV-2.<ref>{{Cite journal|last1=Johnson|first1=Marc C.|last2=Lyddon|first2=Terri D.|last3=Suarez|first3=Reinier|last4=Salcedo|first4=Braxton|last5=LePique|first5=Mary|last6=Graham|first6=Maddie|last7=Ricana|first7=Clifton|last8=Robinson|first8=Carolyn|last9=Ritter|first9=Detlef G.|date=2020-10-14|title=Optimized Pseudotyping Conditions for the SARS-COV-2 Spike Glycoprotein|journal=Journal of Virology|language=en|volume=94|issue=21|doi=10.1128/JVI.01062-20| pmc=7565639|issn=0022-538X|pmid=32788194|doi-access=free}}</ref> Recombinant vesicular stomatitis virus–Zaire Ebola virus (rVSV-ZEBOV) was created by the Public Health Agency of Canada (PHAC) and is currently licensed in the European Union and United States for the prevention of Ebolavirus Disease (EVD) caused by ''Zaire ebolavirus.''
== Serological testing == Pseudotyped viruses, especially pseudotyped viruses carrying a recombinant luciferase gene (rLuc), can be used to test whether a treatment can protect host cells infection.<ref>{{Cite journal|last1=Carnell|first1=George William|last2=Ferrara|first2=Francesca|last3=Grehan|first3=Keith|last4=Thompson|first4=Craig Peter|last5=Temperton|first5=Nigel James|date=2015-04-29|title=Pseudotype-Based Neutralization Assays for Influenza: A Systematic Analysis|journal=Frontiers in Immunology|volume=6|page=161|doi=10.3389/fimmu.2015.00161|issn=1664-3224|pmc=4413832|pmid=25972865|doi-access=free }}</ref> For example, blood is drawn from an animal with serological immunity to a virus. A separate pseudovirus is generated with an envelope protein from the virus that the animal has immunity to. The pseudovirus is further engineered to contain a gene for luciferase. When the blood drawn from the animal is mixed with the pseudovirus, the protective antibodies bind and neutralize the introduced envelope protein. In cell culture, neutralized pseudoviruses will be prevented from infecting cells and producing the luminescent reporter gene product. When analysed, cell culture samples where an effective inhibitor of the virus is present will have reduced luminescence.<ref name=":2" />
== References == {{reflist}}
Category:Virology