Herpes simplex virus (HSV) is a neurotropic herpesvirus that can establish lifelong infections in its human host through latent maintenance in the ganglia of sensory neurons. Because of their wide host range, efficient infection, long-term persistence, capacity to accommodate large amounts of foreign DNA, and ability to deliver genes to post-mitotic cell types, HSV has showed considerable promise to establish long-term gene expression in most cells, particularly in neurons where other systems have low efficiency. Helper-free and amplicon HSV vectors have deletions in one or more essential viral genes and can be used to express transgenes by replacing other non-essential viral genes.
Several unique features of HSV-1 make vectors derived from this virus very appealing for preventive or therapeutic gene transfer. These include:
- Delivery of large transgenes to the nucleus of mammalian cells.
- Non-integrating, but can replicate separately from host cell genome.
- The ability to invade and establish lifelong non-toxic latent infections in neurons; can establish stable transgene expression.
- Based on the HSV amplicon packaging method, which yields higher titers and has lower toxicity.
By pairing this technology with our expertise in virus packaging, abm
offers custom HSV-1 Virus subcloning and virus production, allowing high level gene expression in host cells.
What is HSV amplicon packaging?
There are two major technologies for packaging HSV: the amplicon system and the helper-free system. The main differences between the two technologies are: (1) The amplicon method of packaging requires a helper virus, whereas the helper-free method does not; (2) the amplicon technology yields titers that are 3-4 logs higher than the helper-free technology; and (3) amplicon virus preparations show no toxicity, while helper-free preparations can be toxic. The notion that helper-free packaging is “better” than amplicon packaging is not supported in the literature. Contrary to popular belief, the helper virus is not neurotoxic, nor is replication-competent virus produced during the packaging procedure.
Taking the above advantages into account, we employ the amplicon method instead of the helper-free method here at abm.
Is HSV toxic?
It has been reported that the HSV amplicon packaging procedure may produce virus that is neurotoxic. However, the improved purification and concentration steps developed by abm eliminates all potential toxicity from virus preparations. Some transgenes, on the other hand, can be slightly toxic if expressed at high levels. Therefore, it is suggested that the virus preparation be diluted between 1:1 and 1:3- with a solution of PBS, 10% sucrose and 25 mM HEPES at pH 7.3 if such toxicity is encountered.
How do you measure the virus titer?
We perform a plaque assay to determine the quantity of infectious virus.
Is your HSV system icp27 deficient?
Yes, we use a icp27 deficient system.