Engineering plants to make vaccines

Bibiana Campos-Seijo/Washington, DC, US  

Norovirus outbreaks may become a thing of the past, say US scientists who have used engineered tobacco plants to make the first vaccine for this stomach bug. 

The noroviruses, also known as ’winter vomiting disease’ or the ’cruise ship virus’, spreads very quickly causing severe diarrhoea and nausea in their victims. Pharmaceutical companies have so far been reluctant to develop a vaccine for these viruses because they rapidly mutate, meaning the vaccine may require frequent updating, according to Charles Arntzen, from Arizona State University in Tempe, who presented the work at the recent American Chemical Society’s Fall meeting in Washington, DC. 

His team have created a manufacturing technology more suited for mutating viruses, as it requires a fraction of the time and financial investment of traditional vaccine manufacture methods, and production can be scaled up quickly. ’We think we have a major advantage in using engineered plant viruses to scale-up vaccine manufacture within weeks instead of months,’ says Arntzen. 

Engineering proteins 

To make their vaccine, the team used a unique and fast technique that involves infecting the tobacco plants with a plant virus genetically engineered to produce the protein that makes up the outer shell of noroviruses. And it is this portion that is recognised by the body’s immune system.  

The protein produced in the tobacco plant self-assembles into a little round ball approximately 25nm in diameter, explains Arntzen, which is the same size as the noroviruses. The nanoparticles are empty so they cannot cause any disease but in every other respect they mimic the virus itself, he adds. 

Arntzen acknowledges that while other plant-made vaccines exist, ’what’s been missing is this rapid ability to produce a vaccine and so far no one has got anything that approaches the time frame that we can do it in’.  

Stephen Duke, from the US Department of Agriculture, says that the researchers ’have innovatively blended cutting-edge plant molecular biology and medical science to find a solution to producing vaccines more rapidly and economically than with current production methods’. Additionally, he adds that while lowering the cost will make certain vaccines available to larger numbers of people, ’it may also make it economically feasible to produce vaccines for [rare] diseases’. 

Arntzen has secured financial support to carry out clinical trials in 2010, but before it can be tested in humans the US Food and Drug Administration (FDA) must give its approval. Arntzen is hopeful this will be granted, as plant-made vaccines have previously been approved.