Pseudotyping

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.[1] 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.[2]

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.[3] This approach has been used to produce vaccine candidates against HIV,[3] Nipah henipavirus,[2] Rabies lyssavirus,[4] SARS-CoV,[5] and Zaire ebolavirus.[6] 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.[7] For example, blood is drawn from an animal with serological immunity to a virus. A separate pseudotype particle is generated with an envelope protein that the animal has immunity to. When the blood drawn from the animal is mixed with the pseudotype particle, the protective antibodies bind and neutralize the introduced envelope protein. In cell culture, neutralized pseudotyped viruses 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.[4]

References
  1. Example for the development of pseudotype retroviral vectors in a work group of MHH Archived 2009-11-08 at the Wayback Machine
  2. Nie, Jianhui; Liu, Lin; Wang, Qing; Chen, Ruifeng; Ning, Tingting; Liu, Qiang; Huang, Weijin; Wang, Youchun (2019-02-19). "Nipah pseudovirus system enables evaluation of vaccines in vitro and in vivo using non-BSL-4 facilities". Emerging Microbes & Infections. 8 (1): 272–281. doi:10.1080/22221751.2019.1571871. ISSN 2222-1751. PMC 6455126. PMID 30866781.
  3. Racine, Trina; Kobinger, Gary P.; Arts, Eric J. (2017-09-12). "Development of an HIV vaccine using a vesicular stomatitis virus vector expressing designer HIV-1 envelope glycoproteins to enhance humoral responses". AIDS Research and Therapy. 14 (1): 55. doi:10.1186/s12981-017-0179-2. ISSN 1742-6405. PMC 5594459. PMID 28893277.
  4. Moeschler, Sarah; Locher, Samira; Conzelmann, Karl-Klaus; Krämer, Beate; Zimmer, Gert (2016-09-16). "Quantification of Lyssavirus-Neutralizing Antibodies Using Vesicular Stomatitis Virus Pseudotype Particles". Viruses. 8 (9): 254. doi:10.3390/v8090254. ISSN 1999-4915. PMC 5035968. PMID 27649230.
  5. Kapadia, Sagar U.; Simon, Ian D.; Rose, John K. (2008-06-20). "SARS vaccine based on a replication-defective recombinant vesicular stomatitis virus is more potent than one based on a replication-competent vector". Virology. 376 (1): 165–172. doi:10.1016/j.virol.2008.03.002. ISSN 0042-6822. PMC 7103385. PMID 18396306.
  6. Salata, Cristiano; Calistri, Arianna; Alvisi, Gualtiero; Celestino, Michele; Parolin, Cristina; Palù, Giorgio (2019-03-19). "Ebola Virus Entry: From Molecular Characterization to Drug Discovery". Viruses. 11 (3): 274. doi:10.3390/v11030274. ISSN 1999-4915. PMC 6466262. PMID 30893774.
  7. Carnell, George William; Ferrara, Francesca; Grehan, Keith; Thompson, Craig Peter; Temperton, Nigel James (2015-04-29). "Pseudotype-Based Neutralization Assays for Influenza: A Systematic Analysis". Frontiers in Immunology. 6: 161. doi:10.3389/fimmu.2015.00161. ISSN 1664-3224. PMC 4413832. PMID 25972865.
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