Can we immunize our food supply the same way we combat deadly diseases with vaccines?

image t z

In 16th century China, physicians found that inoculating healthy individuals with pus or dried scabs from someone infected with smallpox, a process known as variolation, usually led to a less severe illness. Physician and biologist Edward Jenner took the idea of variolation one step further in 1796, observing that humans could be vaccinated against diseases without first being infected by them.

Just as fire drills teach us how to respond should an actual fire break out, vaccines expose the immune system to a harmless infectious agent, typically components of a pathogen or a severely weakened pathogen, that trick it into building antibodies that can recognize a real threat.

This strategy of tricking our immune system has been effective against 26 different diseases in humans and eradicated smallpox altogether. We have also helped our furry family members with vaccines against diseases like canine parvovirus in dogs and panleukopenia in cats. Presently, developing a vaccine for COVID-19 is our best hope for ending the ongoing pandemic that has already claimed thousands of lives.

Related article:  99% of tested food samples 'well below' EPA pesticide safety limits, new USDA report shows

The scramble to develop a vaccine for this novel coronavirus offers us an opportunity to ask an equally important question: Given the effectiveness of vaccines for humans and animals, can we make plant vaccines that protect our food supply from destructive pests?

This is a complicated question, but the short answer is yes. Vaccine-like technologies have already been developed to protect plants from deadly infections. Not only can these tools help reduce billions of dollars worth of crop damage, they pose little risk to human health and could help cut the use of synthetic pesticides.

A primer on plant immune response

fe b e
Credit: Bill Ravlin/Michigan State University

Let’s examine those aforementioned complications. Plant vaccines work a bit differently than those designed to protect humans and our pets, primarily because plants possess an innate immune system that functions differently from the adaptive immune system present in humans and other animals.

The plant immune system is made up of two parts: receptors on the outside of cells that identify pathogens or byproducts of infected cells, and proteins within cells that recognize infection-promoting molecules released by pathogens. Activation of either of these mechanisms during an infection results in a strengthening of cell walls, producing enzymes to counter damaging pathogenic enzymes and antimicrobial compounds called defensins and phytoalexins. This process also triggers something known as a “hypersensitive response” that leads to strategic cell death as a way to stymie progress of the infection.

Put simply, the difference between plant and animal immune systems is that instead of organizing a directed assault against a specific pathogen, plants sound a general call to arms. Furthermore, unlike antibodies, the receptors and proteins in plants that recognize signs of infection are genetically coded so that new receptors cannot be produced within a generation to deal with a new pathogen. This is why the plant immune system is innate and animal immune systems are adaptive.

Can vaccinating plants be an effective strategy?

Given these differences in immune systems, plant vaccines would induce a general strengthening of immunity (instead of preparing the plant to deal with a specific threat) by tricking its immune system to activate with a fake infection.

Through a mechanism called defense priming, compounds that bind to immune receptors or proteins in uninfected/unharmed areas of the plant stimulate the accumulation of molecules that amplify cellular signals, increase the number of immune receptors produced, and facilitate changes in DNA packaging to allow for faster access to defense-related genes.

px apple tree with fire blight
Apple tree with fire blight. Credit: Paethon, Wikipedia

In this heightened defensive state, the cells are able to respond faster and more forcefully to a pathogen. There are already several products available that function in this manner. While not called plant vaccines, these products use pathogen-derived molecules to stimulate defense priming in plants, often as a supplement to normal pesticide and fungicide applications.

One example is the Messenger pesticide, which uses a protein called Harpin from Erwinia amylovora, a pathogen that causes fire blight in apples and pears. Another product uses chitosan: a derivative of chitin, which is found in fungal cell walls and insect exoskeletons. Research shows that pre-treatment of plants with chitosan before fungal infection improved resistance by as much as 68 percent when applied 72 hours before infection. Even when co-treated with the fungus, plants had improved immunity, though the effectiveness of these plant vaccines will vary based on the plant species and pathogen causing infection.

Follow the latest news and policy debates on agricultural biotech and biomedicine? Subscribe to our newsletter.

Boosting plant immune systems with these vaccine-like compounds could be a novel way to reduce overall use of pesticides. With many in the public disapproving of synthetic chemical pesticides, plant vaccines could serve as a natural replacement or amendment to current crop protection strategies. At the first sign of infection a farmer could apply a vaccine to the whole field to reduce the spread, while applying pesticides only to the affected area. Notably, many naturally derived plant vaccines are known for their non-toxicity to humans and the environment. Chitosan has even been used in different drug delivery systems for pharmaceutical applications.

While plant vaccines may not completely replace synthetic chemical pesticides, they are another important tool in the arsenal to keep crops happy and healthy, and by extension to ensure our access to a sustainable food supply. As farmers know all too well, pests and pathogens can quickly learn how to defeat individual crop protection tools. Plant vaccines can therefore help us stay one step ahead in the evolutionary arms race against insects and microbes that want to eat our food.

Tautvydas Shuipys is a PhD candidate in the Genetics and Genomics Graduate Program at the University of Florida. Follow him on Twitter @tshuipys

Outbreak Daily Digest
Biotech Facts & Fallacies
Talking Biotech
Genetics Unzipped

Video: We can ‘finally’ grow GMOs—Nigerian farmer explains why developing countries need biotech crops

Nigerian farmer Patience Koku discusses the GMO crop trials she is conducting on her farm, and why growers can "rise ...
mag insects image superjumbo v

Disaster interrupted: Which farming system better preserves insect populations: Organic or conventional?

A three-year run of fragmentary Armageddon-like studies had primed the journalism pumps and settled the media framing about the future ...
dead bee desolate city

Are we facing an ‘Insect Apocalypse’ caused by ‘intensive, industrial’ farming and agricultural chemicals? The media say yes; Science says ‘no’

The media call it the “Insect Apocalypse”. In the past three years, the phrase has become an accepted truth of ...
breastfeeding bed x facebook x

Infographic: We know breastfeeding helps children. Now we know it helps mothers too

When a woman becomes pregnant, her risk of type 2 diabetes increases for the rest of her life, perhaps because ...
organic hillside sweet corn x

Organic v conventional using GMOs: Which is the more sustainable farming?

Many consumers spend more for organic food to avoid genetically modified products in part because they believe that “industrial agriculture” ...
benjamin franklin x

Are most GMO safety studies funded by industry?

The assertion that biotech companies do the research and the government just signs off on it is false ...
gmo corn field x

Do GMO Bt (insect-resistant) crops pose a threat to human health or the environment?

Bt is a bacterium found organically in the soil. It is extremely effective in repelling or killing target insects but ...

Environmental Working Group: EWG challenges safety of GMOs, food pesticide residues

Known by some as the "Environmental Worrying Group," EWG lobbies for tighter GMO legislation and famously puts out annual "dirty dozen" list of fruits and ...
m hansen

Michael Hansen: Architect of Consumers Union ongoing anti-GMO campaign

Michael K. Hansen (born 1956) is thought by critics to be the prime mover behind the ongoing campaign against agricultural biotechnology at Consumer Reports. He is an ...
News on human & agricultural genetics and biotechnology delivered to your inbox.
Optional. Mail on special occasions.
Send this to a friend