By Nana Dadzie Ghansah
Novavax’s COVID-19 vaccine — NVX-CoV2373 — ,ay be the last US-made vaccine to go for approval, but its platform might be the most elegant…if you ask me.
Unlike those on the market already, it is neither RNA nor DNA-based. It is a protein-based vaccine, and that protein is none other than the notorious spike protein of SARS-CoV-2.
Like using mRNA for therapeutics, the idea behind the technique Novavax uses was also rejected by the scientific world for years. This is the original paper by Gale Smith, the Ph.D. behind it (Smith GE et al. Mol Cell Biol 1983 Dec; 3(12):2156–65).
It is a process that involves the use of DNA, a virus that infects insects, cells from the ovary of the fall armyworm moth, a nanoparticle, and an extract from the Chilean soapbark tree, Quillaja saponaria.
Let’s look at the process in a simplified fashion:
1. The scientists at Novavax used the spike protein’s known genetic sequence to create a strip of DNA that coded for the spike.
2. They then inserted this DNA strip in a virus called the Baculovirus, a virus that can infect insects and insert DNA into their genome.
3. The Baculovirus with the spike protein DNA in its genome was then used to infect cells from the ovary of the fall armyworm moth. These reactions were carried out in 2000 liter bioreactors.
(The moth cell line is called Sf9. Also, Gale Smith showed at Texas A&M in 1983 that these moth ovarian cells could produce any protein if the protein’s genetic sequence is inserted into the cells’ genome.)
4. The moth cells then produced the spike proteins on their cell membranes. These recombinant proteins were then harvested.
5. The harvested recombinant spike proteins are then inserted into a cylinder-shaped nanoparticle made up of proteins, lipids and sugars. Fourteen spikes are inserted into each particle to form a unit and, five mcg of these units are in a dose of the vaccine, NVX-CoV2373. It is given in two doses.
So where does the extract from the Chilean soapbark tree come in?