3Rs Stimulus Fund: using a peptide as a virus detector

1 month ago

Xander de Haan is an associate professor of molecular virology in the faculty of Veterinary Medicine’s Virology department. He primarily studies influenza (flu) viruses and other viruses that affect the airways. He has developed a synthetic alternative to ‘growing’ antibodies in animals.

How are animals normally used in virus research?
“The conventional way is to immunise animals on a large scale. Each animal makes antibodies, then we take them out and use them in our research as a way of detecting viruses. This works very well, since antibodies bind to very specific targets with high affinity. Put simply, affinity means that you need very little of an antibody to get binding. So in order to demonstrate that a cell is virus-infected, we often use antibodies, which mostly come from mice, rabbits and llamas. And of course we also use antibodies in a purified form to treat viral infections, with the most famous example today being SARS-CoV-2.”

How did the idea to develop an alternative to antibodies come up?
“Seino Jongkeer, a chemist at the Vrije Universiteit and a partner in this project, introduced a method that he’d learned in Japan. We’re using this method to develop macrocyclic peptides. A peptide is a shorter variant of a protein. Both consist of a chain of amino acids, like beads strung in a necklace. In a peptide the chain is short and not folded stably. By making a peptide macrocyclic – that means that we close up the chain – its form becomes more robust and more stable, which considerably increases its ability to bind selectively. These peptides are made in a test tube by simulating the ‘translation’ that takes place in the cell nucleus: transmitting the genetic code through what’s called messenger RNA. We have a huge library available of messenger RNA forms that can make peptides. By using clever selection methods we can select a small number (about 100) of strong binders and test their binding further.” 

Before the average reader’s eyes glaze over, can you tell us more concretely what this results in?
“Every flu virus contains an N protein and an H protein. For example, there are two flu viruses which can infect humans: H3N2 and H1N1. There are also several bird-flu viruses, like H5N1. In this project, we’ve developed peptides that can bind to both H1 and H5 proteins. This makes it possible for us to study whether they can be used instead of antibodies as virus detectors, and also as virus inhibitors. Parallel to this 3Rs project we also developed peptides for the SARS virus. So there are many more applications possible in the future. At the moment using them in practice for detection is still problematic, since our peptides turned out to be too ‘sticky’ as it were, in other words, they would also bind non-specifically to some plastics that we use in the research.”

Have you published your research results?
“We presented the results of this method at two international congresses. We also were able to get them published in a renowned international scientific journal. How well an article like this is received will be clear in a few years from the number of citations. Based on that, you can then make a cautious estimate as to whether this alternative to using animals is catching on elsewhere.”

What did the 3Rs Stimulus Fund support mean for this project?
“Given the total research cost, the 3Rs funding was mainly a helping hand. Our kind of research is time-consuming, which makes it expensive. At the same time it was also a catalyst for thinking more outside the box: without that encouragement, we probably would have confined our research to the virus-inhibiting function, and not looked at the detection function as an alternative to antibodies.”

How much importance to you attach to that alternative?
“I sat on the Animal Ethics Committee (Dierexperimentencommissie) for a while. I think that if you’re going to use animals for research, then the way you do it has to be very well thought out. And the benefits have to clearly outweigh the amount of suffering the animals will undergo. At the same time, I’m not fundamentally opposed to using animals in experiments, because I think that a lot of good can come out of it. What’s interesting and attractive about our method is that we can tinker and experiment in the test tube a lot more easily than we can, and are allowed to, with animals. Additional research can give us much more effective binders and inhibitors of viruses.”