Thursday, June 20, 2019
Home Tech A "vaccine" against a bacteria that kills bees

A "vaccine" against a bacteria that kills bees

Two researchers at the University of Helsinki have developed a vaccine, PrimeBee, to protect bees against American foulbrood, a bacteria that attacks bees.

In theory, this technique could immunize chicken and fish farms, replace antibiotics, and thus reduce the antimicrobial resistance.

In the world, the honeybee (Apis mellifera) contributes to the pollination of 90% of the main crops. But in recent years, these precious animals have been decimated by the "Collapse syndrome of bee colonies", an evil still very poorly known. Possible causes include mites (the famous Varroa destructor), bacteria (American foulbrood), viruses (acute paralysis, deformed wings), fungi (Nosema), pesticides (neocotinoids, some of which are banned in France), and most likely a combination of these factors.

A scientific breakthrough

The bee is not naturally endowed with antibodies, these proteins made by white blood cells (lymphocytes) which specifically recognize foreign agents (antigens), and constitute one of the main mechanisms of immune defense similar to that of humans. These antibodies are the basis of "immune memory" and the principle of vaccination. Nobody believed that one day they could "vaccinate" insects.

However, two biologists from the University of Helsinki, Dalial Freitak, an immunologist, and Heli Salmela, a molecular biologist, have succeeded in developing a "vaccine" that allows bees to resist American foulbrood, Paenibacillus larvae, the most widespread and most destructive bacterial brood disease.

An idea that has sprung up following a judicious observation

In 2014, Dalial Freitak, a specialist in insect immunology, noticed that butterflies or flies fed with certain bacteria produced offspring that were more resistant to these bacteria. "They could transmit something they had ingested, but I did not know what the mechanism was", she says.

For her part, her colleague Heli Salmela was working on vitellogenin, a lipid antioxidant protein, acting as a fat reserve during embryonic development, much like egg yolk in hens.

Bees used to spot mines

The queen transmits a kind of immunity to her offspring

This is how she hypothesized that vitellogenin could be the molecule that transmitted a signal from one generation to the next. In 2015, with Finnish and American colleagues, the Finns published the discovery of a new principle of "vaccination", based on the transfer of a food, much like women transfer their antibodies in the first milk, colostrum ( 1). Here, the queen, fed with pollen containing spores of the bacterium, digests them and stores them in her fat reserves made up of vitellogenin. Fragments of bacteria will then bind to vitellogenin. It would be she who would carry the immune response. When the larvae are born, they are naturally "vaccinated" against the disease.

In practice, "vaccination" consists of giving a piece of sugar soaked with fragments of bacteria to the queen, like children who are vaccinated against polio by swallowing a piece of sugar soaked in vaccine solution.

A potential alternative to antibiotics

A patent was filed in January 2018 and the university received funding from Business Finland to launch the development of the "vaccine". The researchers hope to extend this technique to other infections, such as European foulbrood and fungi. " In the long run, we think we can vaccinate bees against any microbe Says Dalial Freitak.

But above all, this invention would pave the way for a possible revolution in vaccination: this mechanism concerns all species that lay eggs containing vitellogenin, such as insects, fish, amphibians, reptiles and birds. An inexpensive and natural alternative to antibiotics for chicken farms and aquaculture.

However "There are still many regulatory hurdles. Four to five years to access the market is an optimistic estimate "she continues.

In France, bee biologists remain cautious. " Vitellogenin is known to strengthen natural defenses and be associated with the longevity of workers, reminds Axel Decourtye, head of the bee protection unit (INRA-ITSAP) in Avignon. But transmitting immunity seems to me more complicated than the technique implemented in PrimeBee, which is not a vaccine in the classic sense of the word. This could be a complementary method to increase the bee's defenses. But in the meantime, it is better to improve access to food resources, so to the natural environment, with flowers, nectar and pollen of quality, that is to say, not polluted. "

Bees are still dying

Denis Sergent



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