Fighting bird flu with genetically engineered bacteria

Over the last few years, bird flu has become endemic in large parts of Europe. Wild birds spread the very contagious flu virus that is infecting more and more birds at poultry farms. If bird flu is discovered on a farm, all birds on that farm must be killed. The economic costs are high and vaccination is now considered a possible solution. Students from the University of Groningen have come up with a novel way of protecting birds: by genetically engineering a bacterium that is naturally present in the lungs of poultry. The project is their entry for the annual iGEM competition.

The International Genetically Engineered Machine competition (iGEM) challenges students to solve a real-world problem by genetically engineering a microorganism. Each year, teams from all over the world enter in what used to be a ‘summer school project’ but that is now often a year-long project at many universities. The University of Groningen team started early this year. ‘The team was formed in February 2022 and we selected our project in early spring’, explains Bindert Algra of ‘Team Nanobuddy’.

Strategies

The team’s name reflects the technology that they are using. ‘We work with nanobodies, which are small fragments of antibodies,’, explains team member Mink Sieders. Antibodies are produced by the immune system and bind to pathogens. Antibodies are huge proteins, but the part that actually binds is much smaller. That is the ‘nanobody’ the team is working with.

Sieders: ‘We looked at novel strategies to protect poultry against bird flu. First, we aimed for an edible vaccine, for example engineered lettuce. Then, one of our team members came across these nanobodies.’ The genetic code for these small proteins is relatively easy to manipulate. So, the idea was to put it into a bacterium that is already present in the lungs of poultry birds.

This led them to Lactobacillus reuteri, a strain of bacteria that is known as ‘probiotic’, which means beneficial to its host. Algra: ‘We want to administer it directly to the lungs, where it can produce and secrete the nanobodies. Our idea is that these nanobodies will bind to the virus and neutralize it in the lungs.’

Workhorse

To this end, they first needed a gene that codes for such a nanobody. ‘We found a paper that described a nanobody that broadly neutralized regular highly pathogenic influenza,’ says Algra. ‘So, we asked the authors if we could use their genetic construct for this nanobody. They were happy to share it with us.’ The genetic construct was modified inside E. coli bacteria, the standard laboratory workhorse. It then had to be transferred to L. reuteri. Sieders: ‘This required some modifications, as the way in which this bacterium translates the genetic code is slightly different from the way in which E. coli does this.’

The laboratory work is almost finished and the team is now working on showing that their nanobody binds to the bird flu virus. A standard nebulizer can be used to spray a solution with the modified bacteria into a poultry shed. ‘These portable units are widely used in the agricultural sector,’ says Sieders. When poultry birds inhale the aerosols, the bacteria end up in their lungs, where they will produce and secrete the nanobodies. Algra: ‘Our strategy could support normal vaccines by providing extra protection inside the lungs. But if the manipulated bacteria are able to thrive inside the lungs, they will continue to produce the nanobodies and that would be more like a full vaccination.’

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Of course, the idea of spraying genetically modified bacteria into a poultry shed might raise some eyebrows. That is why the team is working on fitting it with a ‘kill switch’. Sieders: ‘This could be activated by temperature. The body temperature of a chicken is 41 °C and the switch would kill the bacteria at temperatures below 40 °C.’

Some of their ideas have already been tried and tested. Others are at present only theoretical, but supported by the scientific literature. The idea behind the iGEM competition is to do as much work as possible; however, a tried and tested product is not required. ‘We have until 12 October to submit material to our competition website. On that day, it will be frozen. From 26 to 28 October, the international jamboree, where all participants present their work and prizes are awarded, will take place in Paris,’ says Algra. The team will go to Paris early–not to visit the Moulin Rouge, but to hopefully participate in an international conference on bird flu, which will be held there on 25 October. Sieders: ‘We do hope that we can share our approach there over a coffee. It is a great opportunity to showcase our methods.’