VSV Pseudotyped with Coronavirus S Protein
Viruses enter host cells by first attaching themselves the cell surface. This is achieved via the binding of specific viral receptors to their complementary receptors on host cells. For enveloped viruses such as coronavirus and lentivirus, which have a lipid bilayer membrane as their outer envelope, the viral receptor proteins are anchored in the envelope. For non-enveloped viruses such as adenovirus and AAV, which possess a protein capsid shell rather than a lipid membrane, the viral receptors are an integral part of the capsid.
In the case of coronavirus, the spike (S) protein embedded in the viral envelope is responsible for binding to cell-surface receptors. It also mediates subsequent fusion of viral envelope with host cell membrane that leads to viral entry. The virus is named coronavirus because the S protein forms spiky structures that protrude out of the envelope to give the virus a crown or halo-like appearance.
Coronavirus comprises a large group of related viruses that display different tropisms for different host species. Generally, a given coronavirus species can only efficiently infect one or a few host species. This tropism is due to the binding specificity of the S protein of a given type of virus to its host cell receptor. For example, the coronavirus SARS-CoV-2 and SARS-CoV, which cause COVID-19 and SARS, respectively, infect human respiratory epithelial cells via specific binding to the angiotensin converting enzyme 2 (ACE2) receptor on host cells, whereas the MERS-CoV virus, which causes MERS, binds to the human dipeptidyl peptidase-4 (DPP4) receptor.
Using pseudotyped VSV to study coronavirus cell entry
Studying how coronavirus uses its S protein to enter host cells is important for developing prophylactic and therapeutic regimes. However, the use of live virus is technically challenging in cases of dangerous strains such as SARS-CoV-2, as it requires biosafety level 3 (BSL-3) labs that are not available to most researchers.
An alternative approach is to use recombinant vesicular stomatitis virus (VSV) pseudotyped with the coronavirus S protein in cell entry assays. Similar to coronavirus, VSV is an enveloped virus. During the packaging recombinant VSV, the S protein could be introduced onto the VSV envelope. The resulting pseudotyped VSV can employ the S protein displayed on its surface to gain entry into host cells expressing the appropriate receptor, in a manner that mimics coronavirus cell entry. Recombinant VSV is very safe and can be pseudotyped with either wildtype or mutant S proteins from any type of coronavirus.
VectorBuilder offers a variety of VSV vectors pseudotyped with S proteins from a wide range of coronavirus species. Different vectors can be used to express different reporters such as EGFP or luciferase, allowing the tracking of viral entry into host cells by a variety of assays.
Types of VSV vectors used in pseudotyping
In theory, any VSV vector can be pseudotyped. You can create a custom VSV vector as follows:Click here to send us a vector design request
Types of spike (S) proteins used in pseudotyping
Coronavirus comprises a vast group of viruses that are extremely widespread in nature, infecting virtually all mammals and birds examined. Hundreds of coronavirus species have been characterized thus far. Of these, a few dozen can be deemed important because they infect humans, livestock, pets, or model animals, or they are evolutionarily close related to them. The phylogenetic tree of these import coronavirus species is shown below:
Phylogenetic Tree of Important Coronavirus Species
More detailed information of these important coronavirus species is listed in the table below:
List of important coronavirus species
VectorBuilder offers VSV pseudotyped by S proteins of any of the above coronavirus species. Pseudotyping by other sources of S proteins can also be requested.
For pseudotyping with the SARS-CoV-2 S protein, we provide two options. The default option uses the canonical S protein from the first published SARS-CoV-2 genome sequence (GenBank accession: NC_045512.2). A later study reported that a new S variant containing the D614G mutation (GenBank accession: MT628063.1) can dramatically increase infectivity. Viruses carrying the D614G mutation have spread rapidly in many parts of the world due to a transmission advantage. VectorBuilder also offers VSV pseudotyped with the D614G variant of S, which can transduce ACE2-expressing cells more efficiently than VSV pseudotyped with the canonical S protein.
VectorBuilder also offers bald VSV lacking viral envelope protein, which can be used as negative control.
How do I obtain VSV pseudotyping services?
You can inquire about our VSV pseudotyping services by following the link below:Click here to send us a VSV pseudotyping request