Eating your veggies isn’t only good for you — it may someday protect you against COVID-19.
That’s the hope of a plant biologist at the University of Ottawa who’s working to create an edible vaccine for the novel coronavirus.
Allyson MacLean’s research involves injecting tomato, potato and lettuce plants with a tiny particle of viral DNA swimming in a bacterial solution.
“We take a syringe that does not have a needle point. You press it up against the large leaf … and you basically push … the bacteria into the plant tissues,” said MacLean, 41, an assistant professor of plant biology.
The bacteria piggyback that DNA into the plant, which triggers the production of viral proteins. Eating the plant allows these proteins to pass through the digestive system, where they’re taken up by special cells in the gut, stimulating a type of immunity.
It’s called “mucosal immunity,” and it’s of particular interest to the scientists currently joined in battle with COVID-19 because the virus that causes the disease, SARS-CoV-2, enters the body via the mucosal surface of the respiratory system.
Rooted in nature
MacLean has spent a decade researching symbiosis in nature, specifically how microbes and plants co-exist. One of the most common microbes is Agrobacterium tumefaciens, which lives in soil and naturally latches onto plants.
“It finds a wound in the plant and it gets in there. It takes part of its DNA and injects it into a plant cell. It basically makes the plant cells grow tumours … that the bacteria can then use as a food source,” MacLean explained.
“People realized a few decades ago that this was going on in nature,” she said. “Somebody had the brilliant idea: OK, can we harness this as a way of making genetically modified organisms?”
In her current research to create an edible vaccine for COVID-19, MacLean is using “parts of the virus that other researchers believe will elicit a strong protective antibody response.” They’re catching a ride into the plant tissue on the back of her old friend Agrobacterium.
At this point in the research, MacLean is using a close relative of tobacco to determine the best way to make a plant express the viral proteins. Next stop, lettuce.
The pandemic hasn’t made MacLean’s research easy. When COVID-19 struck in March, she struggled to move her hands-on laboratory course online, and began alternating work days with her husband so they could care for their two children, ages one and four.
“It was having to simultaneously balance unprecedented challenges in terms of research, in terms of teaching and in terms of myself as a parent,” MacLean said. “It was really hard.”
She was especially worried about her “precious transgenic mutant plants” that were left behind in the lab when the U of O campus was shut down due to COVID-19.
“You can’t just stop caring for them or you will lose them,” said MacLean, who arranged permission to feed and fertilize the plants three times a week.
MacLean had an early fascination with biology and ecology. As a child, she set up a dragon fly hospital in her bedroom, catching flies for her patients’ dinner. She harboured a garter snake in her closet one winter. She remembers dabbing a drop of liquid paper on toads in her backyard to see if she could trace their movements.
“I always very much loved living organisms. They just got smaller,” she said.
There are a few conventional COVID-19 vaccines already at the human trial stage, but “it’s premature to stop exploring other avenues,” said MacLean — especially if the outcome is a more efficient route to global immunity.
“Plant-based vaccines are better for the developing world. They’re cheaper to produce. They don’t need … to be refrigerated for long periods of time.”
Plus, she believes people would rather eat their medicine than get a shot.
“People are more willing to ingest a vaccine than they are to get a needle.”
MacLean’s work will be tested on mice in collaboration with John Bell of the Ottawa Health Research Institute.
“This project is pairing up a cancer researcher who uses viruses to tackle cancer and a plant biologist who normally studies the way microorganisms interact with plants,” MacLean said. “We’re both stretching out of our comfort zones.”