Transfecting Insect Cells, Pt. 4

Dr. Bees is back with our final insect-themed blog post. This time we will be discussing the use of insect cells for production of viral vectors. Previously, we have discussed the different types of insect cells used in research (Part 1) as well as the various tools Mirus provides for working with insect cells such as the TransIT®-Insect Transfection Reagent, flashBAC™ Baculovirus Expression System (Part 2) and pOET Plasmids (Part 3). We have the tools, but what can we build?

As previously discussed, baculovirus (like other viruses) can be assembled to carry various genes, which will be expressed once cells have been infected with the baculovirus. This means baculovirus can be used to express proteins, including proteins coded on multiple genes and consisting of multiple subunits. Furthermore, baculovirus expression systems use eukaryotic cells, such as the insect cell line Sf9, which are capable of more complex protein folding and post-translational modifications than some traditionally used microbial expression systems. Which brings me to the topic of this post: harnessing baculovirus to produce viruses and virus-like particles (VLPs).

VLPs are essentially composed of virus capsids or proteins without the viral genetic information. Producing proteins and VLPs is probably very familiar to you TransIT-PRO® users, who have been making all kinds of proteins in HEK 293 and CHO cell lines. But, should your lab be having issues that a traditional CHO or HEK 293 production platform cannot overcome, TransIT®-Insect has your back!

Figure 1. Using recombinant baculovirus to make other types of viruses or VLPs

How can we make viral vectors, e.g. adeno-associated virus, and VLPs with baculovirus? “Carrying” instructions for making a virus in a virus (Figure 1)! Contrast this with most AAV production processes used currently: HEK 293 cells are transfected with plasmids carrying a gene of interest, rep/cap genes (encoding replication and capsid proteins) and helper adenovirus genes for producing AAV. Baculovirus obviates the need for plasmids and adenovirus genes; the genes required for AAV production are carried by the baculoviral vector. Also, both the baculoviral vector and baculovirus-produced AAV can be efficiently produced in great quantities in insect cells. Insect cell lines like Sf9 are easier to grow, scale and use for production of high levels of recombinant virus. Use of insect cells also reduces the chance of mammalian pathogens being introduced into the AAV during production.¹ Additionally, baculovirus does not natively replicate in vertebrate hosts.

That about covers it for transfecting our insect pals around these parts. Hopefully the next time you’re looking to make recombinant proteins and viruses, you will keep our Spodopteran sidekicks in mind. 

Happy Trails,

Dr. Bees

PS: HEK 293 your AAV production platform of choice? No worries, Mirus Bio has you covered. Check out our VirusGEN® line of transfection reagents, which are compatible with viral vector production in both suspension and adherent HEK 293 cells from RUO to GMP!