Why scientists say we should grow future vaccines in plants

Most of us aren’t thrilled at the thought of getting pricked with a needle for our yearly flu shot. But what if there was a more delicious way? What if we could eat vaccines?

At first blush, this idea seems as sci-fi as sky highways, Stepford-wife-style robots, and self-contained, floating island orbs. But it’s actually far more realistic than flying cars. In the not-so-distant future, we could be growing our most crucial vaccines in plants and eating them for breakfast.

In an article for Science Perspectives published on Thursday, microbiologist and infectious disease researcher Gary Kobinger and Hugues Fausther-Bovendo make a case for plant-made vaccines. Both are members of the same team, headed up by Kobinger, in the Research Centre on Infectious Diseases at Université Laval in Canada.

Here’s their argument: There are already vaccines out there like this that work — this is not as new an idea as it sounds — and plant-made vaccines offer several advantages over and above how most vaccines are made today.

How vaccines are made

Before we get too deep in this theory, it’s worth knowing that many vaccines are already made in self-contained organic systems. In fact, more than 80 percent of flu vaccines are developed inside chicken eggs. Others can be made inside cell cultures taken from insects or other mammals.

In an egg-based vaccine, makers inject what is called “candidate vaccine viruses,” or a version of a virus, into the eggs and allow it to multiply. Then, the virus-dense fluid is extracted from the egg and the vaccine maker essentially renders the virus inactive.

After that, the material is purified and processed to produce the mixture that a nurse eventually injects into your arm.

In mammalian cell-based vaccines, the process is similar, only with cell incubators in place of eggs. This approach allows large amounts of a vaccine to be made at once, as you can have thousands of cell cultures cooking at one time.

Here’s how plant-based vaccines work — In a process known as “molecular farming,” engineers put DNA that codes for certain proteins inside a plant cell — for example, proteins that help the immune system fight a particular virus. Then, the engineers let the plant grow and take material from it to make an extract. After that, they purify the extract to isolate the proteins so that they can be injected into our flesh — just like a standard vaccine.

But what if you just ate the plant before all the processing? Well, in that case, Kobinger and Fausther-Bovendo say, you wouldn’t need to do anything else — you would ingest the proteins.

There is an example of this working in real-life: In 2012 the FDA approved a plant-made drug to treat a condition known as Gaucher disease. It is a rare genetic condition that leads to enlarged livers and spleens. The drug was an injectable form of an enzyme that treats the problem, and is made in carrot cell cultures as opposed to whole carrots.

Fausther-Bovendo and Kobinger propose developing more of these kinds of drugs and vaccines, but they also propose doing away with the last extraction step altogether. Rather than make batches of drugs, why not develop whole plants with disease-fighting properties that can imbue the eater with health benefits?

Why it matters — Fausther-Bovendo and Kobinger argue that, from a technical standpoint, we’re better equipped than ever to make plant-based vaccines and that they have serious advantages over traditional vaccinations.

There’s even a plant-made coronavirus vaccine in Phase III clinical trials involving more than 30,000 participant, they say. This vaccine is being developed in an Australian weed that’s a relative of tobacco and it would still need to be injected. However it will also be the first “therapeutic protein” for human use that is grown in a whole plant, Fausther-Bovendo and Kobinger say.

There are five central reasons why Fausther-Bovendo and Kobinger think plant-based vaccines may supplant traditional vaccines:

• It’s less resource-intensive to grow plants than animals — this may become a growing concern with climate change intensifying pressure on existing energy, food, and water resources.
• It’s less expensive — the manufacturing hardware doesn’t cost as much money as traditional vaccines.

“Procurement of greenhouses is cheaper than bioreactor suites, which are required for bacterial, mammalian, and insect cell culture systems, making molecular farming particularly attractive for developing countries,” the authors write.

• Plants are protected — Pathogens that infect animals and humans, the authors point out, can’t infect plants and contaminate them.

• It’s a stronger immune response — Plant-produced proteins give a stronger immune response in many cases.
• It’s more vaccine by weight — Plant-produced proteins yield higher ratios of vaccine to fresh plant weight than traditional vaccine development.
• It’s easier to do — Plant matter can be dehydrated, stored easily, and processed into an edible form.

It wasn’t all roses a few decades ago. In earlier trials with drugs like these beginning in the 1990s through the early 2000s, the researchers write, the “proportion of immunized individuals who generated an immune response against the desired target was disappointingly lower than in clinical trials involving standard vaccines.”

But now, the yield of vaccinating proteins has increased substantially, making this a realistic option.

What’s next — Beyond proving the success of plant-made vaccines with current trials and better, higher yields, the researchers point out a number of other hurdles to be cleared before we launch into an era of edible vaccines.

Governments must provide better guidelines and regulations for vaccines and their manufacture and distribution in the first place. And there needs to be a concerted effort to build the facilities to grow and process the plants across the globe. Right now, that is an expensive endeavor some may be unwilling to take for what is still a novel idea.

The future of dehydrated plant vaccines may be close, but until the incentives to make them increase, it’s still a futuristic dream for now.