VLP vaccines: How harmless molecules disguised as viruses prevent disease

Shawna Hiley
28 July 2015

Above: Illustration of Ebola virus (© istockphoto.com/Ralwel)

Did you know? The idea of vaccination was first developed in 1796 by Edward Jenner. He was an English doctor who noticed that children exposed to the cowpox virus were protected from deadly smallpox.Between March 2014 and June 2015, an Ebola outbreak centered in West Africa killed over 11,000 people. Airports and hospitals around the world were put on high alert, as some of the more than 27,000 cases were diagnosed as far away as the United States and Europe. So what was behind all this death and panic? The Ebola virus is actually nothing more than a microscopic bundle of viral nucleic acid packed in a protein capsule.

It’s amazing something so small can cause so much trouble! But by studying the structure of viruses like Ebola, scientists are also discovering ways to make people healthier. In particular, they are using virus-like particles (VLPs) to make new and more effective vaccines.

To understand how VLP vaccines work, you need to remember that viruses can’t reproduce on their own. In order to survive, they need to take over host cells before making copies of themselvesmar. Meanwhile, the host cells can’t operate normally and the organism they belong to becomes sick. Depending on the type of virus, the illness can be fairly routine. For example, rhinoviruses (the cause of the common cold) and many strains of seasonal influenza aren’t very dangerous to humans. However, viruses like Ebola, pandemic flus (including H1N1 and H5N1), Ebola, and some types of cancer can be deadly.

Did you know? Many common vaccines are produced using fertilized chicken eggs.VLPs are like molecules at a virus costume party. They look like viruses on the outside, but they are very different on the inside: they don’t contain viral nucleic acid. This means they can’t infect a host cell, reproduce, or cause any of the harm that a virus can. However, VLPs are covered with virus structural proteins, which means they have roughly the same shape of a virus. It also means they can fool your immune system into thinking that they pose a threat.

This con-artist routine could revolutionize vaccinations. Traditional vaccines are made from viruses that have been modified to minimize the risk of causing harm to the person being vaccinated. As soon as the nurse jabs your arm, your body senses a threat and activates your immune system. Once the immune response is complete, you are left with antibodies and killer cells ready to defeat a future invasion by a real virus. But what if VLPs could do an even better job than these modified viruses at preparing your body to fight disease?

While traditional vaccines can be credited with wiping out devastating diseases like polio and smallpox, the technology is not without its problems. One major drawback is that it takes months to prepare a new vaccine. In the meantime, an aggressive new disease can continue to infect and kill large numbers of people. For instance, an H1N1 outbreak started in Mexico in March 2009, but a vaccine wasn’t available until November. That was long after the worst of the pandemic had passed. Also, most flu vaccines are produced by growing viruses in fertilized chicken eggs. So on top of the delays, they can’t be given to anyone with an allergy to eggs.

Did you know? Both attenuated (alive, but weakened) and inactivated (dead) viruses are commonly used in vaccines.VLP vaccine manufacturers, like Canadian biotechnology company Medicago, claim they can make vaccines more quickly, at lower cost, and without the allergy problem. Although many of the details are secret, Medicago’s system involves three main steps:

The laboratory creates a DNA sequence corresponding to the viral surface protein needed to trick the immune system. The leaves of mature tobacco plants are dipped in a solution containing the DNA sequence. The solution also contains Agrobacteria, which are microbes that help the viral DNA transfer to the plant cells. In just a couple of minutes, the sequences are absorbed by leaves, where the VLPs are expressed. After the leaves grow some more, they are picked and the VLPs are extracted and purified. At this point, they are ready to be tested as vaccines.

All this can happen within just four weeks of receiving a new virus's nucleic acid sequence.

Did you know? Virus-like particle (VLP) vaccines for hepatitis B and human papillomavirus are already widely used. VLP vaccines for HIV, anthrax, and RSV are currently being developed.Critics argue that VLP vaccines are expensive to make and may not be as effective or long-lasting as traditional vaccines. However, Medicago claims that their VLP vaccines are actually more effective than traditional vaccines and provide longer-lasting immunity. The company also says that VLP vaccines require a lower dosage, which would mean lower costs and a lower risk of side effects.

Canada has been playing a leading role in vaccine development for more than a century. Currently, Medicago is focusing its efforts on VLP vaccines against seasonal and pandemic influenza, as well as the devastating Ebola virus. If you’re interested in saving lives one cutting-edge vaccine at a time, you should consider a career in molecular virology. You can help carry Canada’s legacy as a leader in vaccine technology!

Learn more!

Viral Diseases (2013)

Vaccines in Canada White Paper Series (2010)

General information on viral diseases, vaccines, and immunity.

Virus-like particle (VLP)-based vaccines for pandemic influenza: performance of a VLP vaccine during the 2009 influenza pandemic (2012)
Constantino López-Macias, Human Vaccines & Immunotherapeutics 8

Virus-like particles in vaccine development (2010)
A. Roldão, M. C. M. Mellado, L. R. Castilho, M. J. T. Carrondo & P M. Alves, Expert

Scientific articles on VLP vaccine research.

Virus-Like Particles: Vaccines of Tomorrow? (2011)
Elizabeth Fischer, pharmaceutical-technology.com

Influenza virus-like particle vaccine (2009)
Vincent Racaniello, Virology Blog

News articles on VLP vaccine research.

Shawna Hiley

Shawna first fell in love with science when she won her grade 7 science fair with a project on Solutions, earned a trip to the regional fair and met lots of smart kids fired-up about all kinds of cool projects. The science bug stuck and she went on to complete a B.Sc. in Biochemistry and a Ph.D. in Molecular Genetics. She eventually shifted her focus from research to teaching, and more recently has branched out again with writing. She finds all kinds of science fascinating and loves to share that passion with anyone who will listen!

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