Molecular Pharming: Using plants to make vaccines

Vaccines have long been a crucial tool in public health and disease management, since Jenner invented the smallpox vaccination in the late 1700s. Diseases like polio, tetanus, mumps, measles, and rubella, which used to be major health risks, have become much less prevalent in first world countries because of vaccinations. More recently, the Covid-19 pandemic at the start of the 2020s has been yet another stark reminder of the importance of vaccines, and how paramount speedy production and accessible distribution is for public health responses.

At the Department of Plant Sciences at the University of Oxford, pioneering research into Molecular Pharming is exploring how to maximise the efficiency of plant-based vaccines. Led by Professor Renier van der Hoorn, researchers are looking into how best to use plant cells in leaves to carry proteins that can be used both as vaccines, as well as neutralising antibodies to inactivate viruses.

Traditionally, vaccines have been made using animal cells – for example, the flu vaccine is made using embryonic chicken eggs. However, this comes with several drawbacks. Most notably, it takes around 3 months for the vaccine to be produced in animal expression systems, meaning that when responding to new public health threats such as Covid-19, it takes a lot of time for vaccines to be mass produced. Additionally, there are risks to those making the vaccine because of the use of live viruses in production, as well as risks of reproducing other animal pathogens during the production process.

When using plant-based vaccines, however, it only takes around 5 days for the vaccine to be expressed in their host cells, which is much faster. This has obvious advantages in public health responses, as well as in managing the resources it takes to create these vaccines, making them cheaper to produce and thus more widely accessible. There are also less safety concerns, as there’s low risk of pathogens that would be harmful to humans being present.

Researchers at Oxford are focused on the molecular and sub-molecular gene editing, typically in Nicotiana benthamiana, a tobacco relative that originates from Australia and has become a favourite plant for plant scientists. The researchers aim to increase the efficiency of these plants to decrease protein degradation and make the cells in the leaves more stable producers of vaccines and virus-neutralising antibodies. Making these plants more stable hosts for protein production will make these products more widely accessible.

Future research is going to focus on increasing the stability of antibodies that can neutralise viruses in the human body. Currently, these treatments, whilst they do exist, are very expensive and inaccessible to most. By using plants to create them more cheaply and quickly, these cures will be more accessible and save lives.