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Almost every year, virologists and immunologists have to adapt flu vaccines to monitor the emergence of new viral strains and the inherent tendency of the virus to mutate extremely frequently. To do this, they have to go through a relatively lengthy process of cell culture in the laboratory in order to produce the right viral particles to target. Recently, a team of researchers found an alternative: to develop a vaccine from surface viral proteins produced by plants. Results from Phase III clinical trials have demonstrated a reliable, effective and safe vaccine for humans.
A new flu vaccine developed from plants has been tested in two large-scale clinical trials, the first for vaccine research. The vaccine contained viral particles that resembled circulating flu strains, extracted from Australian tobacco mother plants that had been genetically responsible for producing the viral proteins. The study was published in the journal The Lancet.
The two studies combined involved nearly 23,000 people and the results suggest that the plant-based vaccine is not only safe, but comparable to current flu vaccines in terms of effectiveness. ” To our knowledge, these studies and the clinical development program that preceded them are the largest demonstration to date of the potential of a herbal platform to produce a human vaccine that can be safe, immunogenic and effective. “, Write the researchers.
Annual adaptation of influenza vaccines: a long and complex process
Every year the vaccines that protect us from the flu need to be reformulated for the next flu season, which is a colossal undertaking. The influenza virus is a kind of chameleon, constantly changing the protein molecules it produces on its outer surface, prompting scientists to look for ways to improve our current vaccine technology.
Most flu vaccines currently consist of viral particles grown and harvested from chicken eggs or cells grown in the lab, which takes months even after scientists determine which flu strains (and surface proteins) they need to target. Plants, which can be engineered to produce select proteins and grown on a large scale, could be an alternative, helping to strengthen our ability to produce seasonal flu vaccines.
Tobacco plants to produce viral proteins
The technique could also help overcome complications in the way current flu vaccines are produced, 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 virus-like particles are then extracted and purified under rigorous conditions to produce a flu 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 kind are usually one of the last hurdles vaccines need to overcome before they can be approved for widespread use.
A plant-based vaccine comparable to current standard vaccines
The first study involved more than 10,100 adults from Asia, Europe and North America, aged 18-64, and was designed to show that the vaccine could prevent 70% of people trying to develop respiratory diseases similar to flu or other respiratory diseases during the flu season. Although this high parameter was not achieved in the study, the vaccine protected about a third of people against influenza strains circulating during winter 2017-18 in the Northern Hemisphere that matched the virus particles. of this vaccine.
This result may seem low, but the effectiveness of commercial flu vaccines often varies from year to year depending on the suitability of a vaccine for the different flu strains circulating that winter. The researchers concluded, based on data collected during the 2017-2018 period, that their plant-based vaccine offered a “broadly similar” level of protection to that of commercial vaccines used during this particularly long flu season. , which is a good result.
The second study recruited an additional 12,700 people aged 65 and over. This is very important because older people’s immune systems tend to weaken with age, making them more vulnerable to infection. ” Like other influenza vaccines, antibody responses to plant-derived vaccine also decline with age. », The authors write. The plant-based vaccine had a lower antibody response in the elderly, a somewhat expected result, but it triggered a substantial increase in immune cells ready to respond to flu-like infections.
Towards a general trend towards plant-based vaccines?
” The field of plant-based vaccines has grown significantly over the past 28 years, since it was first shown in 1992 that viral proteins could be expressed in plants. This is the first time that a herbal vaccine has been tested in a human clinical study Says John Tregoning, an infectious disease researcher at Imperial College London.
” This is a milestone for this technology and sets the stage for other vaccines and herbal therapies Hopefully, this research could someday give us another way to make seasonal flu vaccines. Production that could be ramped up globally in the event of a new flu pandemic.
In their article, the researchers state that their herbal system can produce the first doses of a newly developed flu vaccine within two months of identifying an emerging flu strain.
Sources: The Lancet
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