Developing Plant-Based Vaccines and Therapeutics for COVID-19 and Beyond
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In an interview with Technology Networks, Dr. Kathleen Hefferon, a microbiologist from Cornell University, highlighted how and why plant-derived vaccines are being designed to prevent diseases including Ebola, Middle East respiratory syndrome (MERS) and coronavirus disease (COVID-19).
“Traditional vaccines can be very expensive and in short supply,” Dr. Hefferon pointed out.
In contrast to traditional vaccines, plant-based vaccines do not require needles, syringes or specialized training for their administration. Quite often, they can be stored ambiently, reducing the need for expensive cold storage systems. As such, they can help to remove some of the roadblocks associated with large-scale vaccination programs in developing countries.
Hefferon highlighted how “plants can be used to enhance the availability of inexpensive pharmaceuticals to even the most remote of places”. With only 10.6% of people in low-income countries having received at least their first dose of a COVID-19 vaccine (as of February 2022), initiating vaccine rollout to remote locations is crucial.
“Plant-made vaccines and other pharmaceuticals can provide a unique opportunity to make an impact on global health,” – Dr. Kathleen Hefferon.
Hefferon’s latest work involves producing the SARS-CoV-2 spike protein in plants for use as a vaccine or as a diagnostic. The spike protein is the “major antigen capable of producing a robust immune response” against the virus.1 The team modified the spike protein to ensure its stability when expressed in plants and to enable it to be purified. “We’ve added some prolines into a furin domain, which helps stabilize the [spike protein] trimer,” she explains. “We replaced [the transmembrane domain] with a KDEL motif, which is an endoplasmic reticulum retainer.”
The spike protein open reading frame was then inserted into a geminivirus, which is used to infect plants and causes transient expression of the virus transgene.
The spike protein produced by the plants can then be used to “make a cheap vaccine for people around the world”.
At the time of writing, two biopharma companies have entered plant-based COVID-19 vaccines into clinical trials.
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During Technology Networks’ 2021 Advances in Drug Discovery & Development online symposium, Hefferon discussed her recent work focused on designing plant virus nanoparticles to target cancer cells and highlighted how plant viruses can be used as expression vectors to produce pharmaceuticals. You can watch her presentation below.
Ebola virus disease (EVD) in humans can be caused by four different viruses from the Ebolavirus genus. The majority of Ebola outbreaks and cases have been in Africa. The largest outbreaks occurred in 2014 and 2018 in West Africa and the eastern Democratic Republic of the Congo, respectively. The virus spreads through direct contact with blood or bodily fluids of a person who is sick with or has died from EVD. There are currently two monoclonal antibody-based treatments available, Inmazeb and Ebanga. Both treatments are designed for use in patients with Zaire ebolavirus infection. Ebanga is a single monoclonal antibody that prevents virus binding to the cell receptor. Inmazeb is a combination of three monoclonal antibodies that simultaneously bind to the virus glycoprotein. A vaccine that protects against the most lethal species of ebolavirus has been approved for use in the US.
Middle East respiratory syndrome (MERS) is caused by a coronavirus infection and was first reported in Saudi Arabia in 2012. Since then, cases have been reported in 27 countries across the Arabian Peninsula.2 The largest outbreak outside of the Peninsula occurred in the Republic of Korea, in 2015. Transmission is through close contact with an infected person. There are currently no specific treatments for MERS, and vaccines are in clinical trials.
Coronavirus disease (COVID-19) is caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first cases of COVID-19 were reported in China in 2019 and the virus has since spread worldwide. Numerous vaccines have been developed and administered, with WHO emphasizing the importance of vaccine equity.
References:
- Venkataraman S, Hefferon K, Makhzoum A, Abouhaidar M. Combating human viral diseases: Will plant-based vaccines be the answer? Vaccines. 2021;9(7):761. doi: 10.3390/vaccines9070761
- Xu J, Jia W, Wang P, et al. Antibodies and vaccines against Middle East respiratory syndrome coronavirus. Emerg Microbes Infect. 2019;8(1):841-856. doi: 10.1080/22221751.2019.1624482
