Why the VSV delta G system helps study viruses safely

Kerafast
6 Jan, 2016
Kerafast

The VSV delta G system, like many other expression vectors, is leading the way in how scientists safely learn about a collection of viruses.

Expression vectors are plasmids or viruses used for protein expression in cells. These plasmids or viruses are specifically developed so that they can introduce a certain gene to a target cell. Once the pair are introduced, the vector can control the cell’s functioning so that it has to use the protein encoded in the gene for protein synthesis. It does this through a series of regulatory sequences that use the same transcription and translation mechanisms used by the target cell to cause the pair to link up. Vectors also usually contain promoter regions needed for that gene’s expression.

“One type of vector was used to create the insulin in 1982.”

Getting to know expression vectors
Along with learning about viruses, expression vectors are used for many things. For instance, one type of vector was used to create insulin in 1982 needed to aid diabetes patients. Human recombinant proteins allow people to obtain protein and peptide pharmaceuticals in large amounts. In the past, several of these protein and peptide pharmaceuticals were hard to obtain. When produced in these big amounts, it is harder for contaminants, such as viruses, prions and toxins, to get into the vectors. Prior to vectors, things tended to go wrong. Viral contaminants in clotting factor VIII that was separated from human blood ended up causing hepatitis and AIDS to be transmitted to people. Luckily, vectors don’t use human cell lines, preventing these contaminants from forming.

However, vectors aren’t just used for human viruses. They have also been used for crops and other animals. Vectors have been used to introduce certain genes to plants and animals to create transgenic organisms. For example, an expression vector was used to introduce certain genes needed to create beta carotene to target the cells of rice plants, creating a new strain of the product known as golden rice.

Because of the extreme control scientists and researchers have over the vector, it is used to study viruses. According to Stanford University, there are several different types of viruses that can be studied by expression vectors. Researchers may need to take extra precaution in their facilities depending on the contaminant risk of the vector or the virus in question. Medical scientists often take extra care when dealing with viruses that have genes with growth-regulating products. Some of the viruses that vectors are commonly used for include the Epstein-Barr virus, which is one of the most common human viruses, adenovirus, rabies virus, poxvirus, baculovirus, herpesvirus and retrovirus, including both MMLV and lentivirus. The herpesvirus is the most commonly used vector.

Some viruses can only be studied in specific facilities

The convenience of the VSV delta G system
The VSV delta G system uses the vesticular stomatitis virus, which is one of the most commonly used viruses to study virus entry, replication and assembly. VSV has a considerable range of properties that allows it to duplicate quickly in both animal and insect cells. Initial studies using this virus lead to a development of a recombinant VSV where the glycoprotein was removed. This new recombinant created the VSV delta G system, which has been used to create pseudotypes that have the glycoproteins of heterologous viruses, including ones that are at high risk of contamination. Researchers can use this system and study viruses safely because they only replicate the virus once. As a result, researchers can perform their anaylsis using biosafety level 2, a common procedure method. This means that unlike other viruses, scientists don’t need to take extra precaution or use a specialized facility to study this virus.

This platform gives researchers several options and allows them to study virus mechanisms in depth without having to worry about contamination, which is a big relief.