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The first step in viral infection is the attachment of the virus onto the host cell. This process is mediated by viral fusion proteins, which are expressed on the surface of the virus(1). Examples of these fusion proteins include gp120 of HIV(2), the hemagglutinin glycoprotein (HA) of the influenza virus(3), and most recently, the spike protein of the SARS-CoV-2 virus(4). All three of these examples belong to the family of class I viral membrane fusion proteins(5). Due to their necessary role in viral infection, these proteins are the targets of many antiviral therapeutic strategies which include small molecules and neutralizing antibodies(6).  
 
Viral fusion proteins have been the subject of past Anatrace newsletters. In April, 2017, we highlighted the crystal structures of the F protein from human respiratory syncytial virus (RSV) bound to single-domain neutralizing antibodies determined by the labs Xavier Saelens at Ghent University and VIB in Belgium and Jason S. McLellan at Dartmouth College (Now at UT Austin)(7). In our April 2019 newsletter, we featured the Cryo-EM structures of the full length influenza HA protein determined by the labs of Steven Gamblin, Peter Rosenthal, and John Skehel at the Francis Crick Institute in London(8). Most recently, last month’s newsletter highlighted the recent structural biology work being done on the SARS-CoV-2 spike protein including the Cryo-EM structures of the trimeric spike glycoprotein by research groups at the University of Texas at Austin and the University of Washington(9,10).

In order to solubilize these viral fusion proteins, detergents are commonly used for viral lysis. Although several detergents can lyse virus particles, the zwitterionic detergent Zwittergent 3-14, is frequently used in assays to isolate viral fusion proteins. Zwittergent is the trademarked name of this detergent(11), but is chemically identical to our Anzergent 3-14 (AZ314) detergent.

As an example, in influenza vaccine development, a standard assay to measure the potency of vaccines is the Single Radial Immunodiffusion (SRID) Assay. In this assay, virus particles are solubilized with Zwittergent 3-14 (or Anzergent 3-14) in order to permit the diffusion of the HA antigen through a gel containing antibodies to the antigen. The radius of diffusion of the antigens is proportional to the amount of antigen in the sample(12). Another example is the VaxArray assay, where virus particles are lysed with Zwittergent 3-14 and antigen content is measured using multiplexed sandwich immunoassay(13).

Since the start of the COVID-19 pandemic, we have seen an increased demand for Anzergent 3-14 detergent. In response, we have invested in infrastructure and operational improvements to significantly increase our production of this detergent. In addition to the production of RNA viral lysis buffer, and sterile viral transport media, this is one of the many ways CalibreScientific companies are working together to provide the tools and reagents needed to aid in the fight against COVID-19.



 References:
  1. Harrison SC. Viral membrane fusion. Virology. 2015 May;479–480:498–507.
  2. Acharya P, Lusvarghi S, Bewley CA, Kwong PD. HIV-1 gp120 as a therapeutic target: navigating a moving labyrinth. Expert Opin Ther Targets. 2015 Jun;19(6):765–83.
  3. Hashem AM. Prospects of HA-based universal influenza vaccine. Biomed Res Int. 2015;2015:414637.
  4. Tay MZ, Poh CM, Rénia L, MacAry PA, Ng LFP. The trinity of COVID-19: immunity, inflammation and intervention. Nat Rev Immunol. 2020 Apr 28;
  5. White JM, Delos SE, Brecher M, Schornberg K. Structures and mechanisms of viral membrane fusion proteins: multiple variations on a common theme. Crit Rev Biochem Mol Biol. 2008 Jun;43(3):189–219.
  6. Vigant F, Santos NC, Lee B. Broad-spectrum antivirals against viral fusion. Nat Rev Microbiol. 2015 Jul;13(7):426–37.
  7. Rossey I, Gilman MSA, Kabeche SC, Sedeyn K, Wrapp D, Kanekiyo M, et al. Potent single-domain antibodies that arrest respiratory syncytial virus fusion protein in its prefusion state. Nat Commun. 2017 13;8:14158.
  8. Benton DJ, Nans A, Calder LJ, Turner J, Neu U, Lin YP, et al. Influenza hemagglutinin membrane anchor. Proc Natl Acad Sci USA. 2018 02;115(40):10112–7.
  9. Wrapp D, Wang N, Corbett KS, Goldsmith JA, Hsieh C-L, Abiona O, et al. Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science. 2020 13;367(6483):1260–3.
  10. Walls AC, Park Y-J, Tortorici MA, Wall A, McGuire AT, Veesler D. Structure, Function, and Antigenicity of the SARS-CoV-2 Spike Glycoprotein. Cell. 2020 16;181(2):281-292.e6.
  11. Zwittergent is a registered trademark of Merck KGAA
  12. Williams MS. Single-radial-immunodiffusion as an in vitro potency assay for human inactivated viral vaccines. Vet Microbiol. 1993 Nov;37(3–4):253–62.
  13. Byrne-Nash RT, Miller DF, Bueter KM, Gillis JH, Kuck LR, Rowlen KL. VaxArray potency assay for rapid assessment of “pandemic” influenza vaccines. NPJ Vaccines. 2018;3:43.