An international group of researchers – led by Dr Dalial Freitak from the University of Helsinki, Finland – has found that a bee blood protein called vitellogenin plays a critical role in providing bee babies protection against disease.
How bees vaccinate their babies and why understanding this is important to humans. Image credit: Sabine Deviche.
In a honey bee (Apis mellifera) colony, the queen rarely leaves the nest, so worker bees must bring food to her. Forager bees can pick up pathogens in the environment while gathering pollen and nectar. Back in the hive, worker bees use this same pollen to create ‘royal jelly,’ a food made just for the queen that incidentally contains bacteria from the outside environment.
After eating these bacteria, the pathogens are digested in the gut and transferred to the body cavity; there they are stored in the queen’s ‘fat body’ – an organ similar to a liver.
Pieces of the bacteria are then bound to vitellogenin and carried via blood to the developing eggs.
Because of this, bee babies are vaccinated and their immune systems better prepared to fight diseases found in their environment once they are born.
Vitellogenin is the carrier of these immune-priming signals, something scientists did not know until now.
“The process by which bees transfer immunity to their babies was a big mystery until now. What we found is that it’s as simple as eating,” said Prof Gro Amdam from the Norwegian University of Life Sciences in Aas, Norway, a team member and a co-author of a paper published in the journal PLoS Pathogens.
“Our amazing discovery was made possible because of 15 years of basic research on vitellogenin. This exemplifies how long-term investments in basic research pay off.”
In their study, the scientists demonstrated that vitellogenin binds to bacteria, both Paenibacillus larvae – the gram-positive bacterium causing American foulbrood disease – and to Escherichia coli that represents gram-negative bacteria. They also verified that vitellogenin binds to pathogen-associated molecular patterns.
“We document that vitellogenin is required for transport of cell-wall pieces of Escherichia coli into eggs by imaging tissue sections. These experiments identify vitellogenin, which is distributed widely in oviparous species, as the carrier of immune-priming signals,” they wrote in the paper.
While bees immunize their offspring against some diseases, many pathogens are deadly and the insects are unable to fight them.
“We are patenting a way to produce a harmless vaccine, as well as how to cultivate the vaccines and introduce them to bee hives through a cocktail the bees would eat. They would then be able to stave off disease,” Dr Freitak said.
The discovery could have far-reaching benefits for other species, as well as substantial, positive impacts on food production. All egg-laying species including fish, poultry, reptiles, amphibians and insects have vitellogenin in their bodies.
The food industry could implement the use of natural vaccines that would not only be inexpensive to produce, they could easily be used in developing countries.
“Because this vaccination process is naturally occurring, this process would be cheap and ultimately simple to implement. It has the potential to both improve and secure food production for humans,” Prof Amdam explained.
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Salmela H et al. 2015. Transfer of Immunity from Mother to Offspring Is Mediated via Egg-Yolk Protein Vitellogenin. PLoS Pathog 11 (7): e1005015; doi: 10.1371/journal.ppat.1005015
