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A new influenza vaccine grown on plants has been tested in two large-scale clinical trials, a first for vaccine research.
The vaccine contained virus-like particles that resembled circulating flu strains, extracted from native Australian tobacco parents who had been given genetic instructions to produce the viral proteins.
The two trials combined involved nearly 23,000 people and the results suggest that the plant-derived vaccine is not only safe, but comparable to current influenza vaccines.
“To our knowledge, these studies and the clinical development program that preceded them are the greatest demonstration to date of the potential of a herbal platform to produce a human vaccine that can be safe, immunogenic and effective. , ”The research team wrote.
Every year, the vaccines that protect us from the flu have to be reformulated for the next flu season, which is a colossal undertaking.
The flu virus is sort of a chameleon, constantly changing the protein molecules it displays on its outer surface, prompting researchers to feverishly search for ways to improve our current vaccine technology.
Most influenza vaccines are currently made from virus particles grown and harvested from chicken eggs or cells grown in the lab, which takes months even after scientists determine which influenza strains (and surface proteins ) they must target.
Plants, which can be engineered to produce selected proteins and grown on a large scale, could be an alternative, helping to strengthen our ability to produce seasonal influenza vaccines.
The technique could also help overcome complications in the way current influenza vaccines are made, which sometimes make vaccines less effective.
In this system, the researchers used an Australian relative of the tobacco plant, Nicotiana benthamiana, designed to produce only the outer shell of influenza viruses. These viral particles are then extracted and purified under strict conditions to make an influenza vaccine.
The researchers tested their plant-derived vaccine in two clinical trials, funded by the Canadian biotechnology company that developed the technique, and no major safety issues were reported.
Phase III safety and efficacy trials of this type are usually one of the last hurdles that vaccines must overcome before they can be approved for widespread use.
But keep in mind that even if an influenza vaccine is approved as safe and effective, any manufacturer must be able to produce millions of doses each year, which could be a challenge for vaccine production plants.
The first trial involved more than 10,100 adults from Asia, Europe and North America, aged 18 to 64, and it was designed to show that the vaccine could prevent 70% of people participating in the trying to develop influenza-like respiratory illnesses or other respiratory illnesses in an influenza season.
Although this high benchmark was not reached in the trial, the vaccine protected about a third of people against strains of influenza circulating during the winter of 2017-18 in the Northern Hemisphere that matched the virus particles. of this vaccine.
This result may seem low, but the effectiveness of commercial influenza vaccines often varies from year to year depending on the suitability of a vaccine for the different strains of influenza circulating that winter.
The researchers concluded, based on data collected during the period 2017-2018, that their plant-derived vaccine offered a level of protection “broadly similar” to that of the commercial vaccines used during this particularly long influenza season. , which is a good result.
The second study recruited another 12,700 people aged 65 and over. This is quite important because the immune system of older people tends to weaken with age, making them more vulnerable to infections.
“Like other influenza vaccines, antibody responses [plant-derived] the vaccine also declined with age, ”the researchers said.
The plant-based vaccine had less of an antibody response in the elderly, a somewhat expected result, but it activated a substantial increase in immune cells ready to respond to influenza-like infections.
Promisingly, the protection the vaccine afforded people against influenza-like illnesses during the 2018-2019 influenza season was still on par with a commercially available influenza vaccine in use this season.
“The field of plant-based vaccines has grown significantly over the past 28 years, since it was first demonstrated [in 1992] that viral proteins could be expressed in plants, ”said John Tregoning, an infectious disease researcher at Imperial College London. a comment on the latest test results.
“This is the first time that a plant vaccine has been tested in a [human] clinical trial, “Tregoning added.” This is a milestone for this technology and is sowing the seeds for other vaccines and herbal therapies. “
If all goes well, this research could one day give us another way to make seasonal flu shots that could also be scaled up in the event of another flu pandemic.
In their paper, the researchers claim that their herbal system can produce the first doses of a newly designed influenza vaccine within two months of identifying an emerging influenza strain.
But there’s probably still a long way to go to get regulatory approvals for this vaccine, so watch this space.
The research was published in The Lancet.
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