How tobacco plants and their relatives are helping us win the war against polio and Zika
One of the great 20th century medicine success stories is the near eradication of the scourge of polio. Since the introduction of a vaccine in the 1950s, cases of polio have dropped by 99 percent. Offering hopes of complete eradication of the disease, a team of scientists in the UK has created a synthetic polio vaccine that contains non-infectious virus particles that can be grown quickly and cheaply in a close relative of the tobacco plant.
In order to make a vaccine, large quantities of a virus must first be produced. If we want to completely eradicate a virus from the worldwide population, alternative vaccines need to be developed that don't rely on a live virus as its basis. These alternative vaccine methods generally utilize virus-like particles (VLPs), which are non-infectious particles that look exactly like virus particles on the outside, but are essentially hollow and cannot cause infection.
In the case of the poliovirus, previous vaccines developed using VLPs have proved to be effective, but the big challenge was growing these VLPs quickly, cheaply and on a scale that could produce large quantities of vaccine. The team at the John Innes Centre in Norwich has for the first time successfully grown poliovirus mimics inside the leaves of a close relative of the tobacco plant.
"The beauty of this system of growing non-pathogenic virus mimics in plants, is that it boosts our ability to scale-up the production of vaccine candidates to combat emerging threats to human health," says Professor George Lomonossoff from the John Innes Centre.
After years of being arguably one of the most damaging plants to human health, tobacco is currently being turned to a variety of positive uses in the world of medicine. From drastically accelerating the production of millions of doses of H1N1 vaccine in 2013, to helping produce an anti-inflammatory molecule to assist in treatment of autoimmune diseases, the tobacco plant is certainly paying humanity a strong penance for the years of damage it has done.
The close relative of the tobacco plant often used in scientific contexts is Nicotiana benthamiana, an ancient Australian native. The plant is so useful to the world of science because it was discovered the plant had evolved a gene mutation that turned off its immune system.
The evolution of the plant replaced the general protective function of its immune system by producing over-sized seeds and speeding up its reproduction. This oddly specific genetic characteristic has also offered scientists hints at ways to improve the speed of crop growing in space environments.
A recent study from Arizona State University demonstrated the successful development of a vaccine for the Zika virus based on a VLP that can be produced using the same plant species. This vaccine has shown success in mouse models and is currently being fast-tracked to human trials within the next two years.
Looking at polio VLPs produced in this John Innes Centre study we can find some of the most complex particles generated by this plant-based process to date. Using cryo-electron microscopy, the team positively confirmed the plant-made VLPs were structurally identical to poliovirus particles.
As well as holding the potential to help completely eliminate polio from the planet, the researchers hope to use their techniques to produce a variety of VLP-based vaccines.
The research was published in the journal Nature Communications.
Source: John Innes Centre