Use of SUlfated POlysaccharides for the treatment of BEE nosemosis – SUPOBEE

The detection of anti- parasitic activity of sulfated polysaccharides (PS) , from marine micro - and / or macro-algae , is performed using an in vitro cell culture screening firstly, and secondly an in vivo system. The in vitro screening is a cytotoxicity test, used to retain the PS without toxic potential , followed by a test on cells infected with Encephalitozoon cuniculi (a parasite belonging to the same family as N. ceranae) due to the lack of in vitro system for maintaining N. ceranae in culture. PS showing an inhibition of the parasite growth are then tested in vivo in the laboratory on experimentally infected bees. The PS showing a strong decrease of the parasite load and of the bee mortality will then be evaluated in the field, on experimentally infected hives in confined conditions under tunnels.

The results obtained from experimentally N. ceranae-infected bees in the laboratory have allowed to select two sulfated polysaccharides. These lead to a significant decrease in the amount of parasite load and bee mortality. These two polysaccharidess will be tested, in 2014, on experimentally infected hives (in tunnels) to test their safety on the hive and their protective role against Nosema. The valuation of these results will be carried out through the creation of a start-up.

The next step will allow to validate the use of sulfated polysaccharides in the treatment of nosemosis. The products with a strong protective effect against Nosema will be tested in apiaries selected on the basis of the presence of naturally Nosema-infected hives. This validation step will be conducted in collaboration with the group of bee health defense (GDSA63) of the Puy-de-Dome location.

A French patent application was filed in november 2012 (FR1260941), the instruction and extension procedures at the international level are underway. A manuscript is being prepared for publication in an international journal for peer review.

Bee colony losses have been reported worldwide at alarming rates. While the causes remain unclear, they are likely to be multifactorial and to involve pesticides, predators, and honeybee pests, which include bacteria, viruses, and parasites. The coordinating partner of the SUPOBEE project has recently reported a synergy between an emerging microsporidian parasite, Nosema ceranae responsible of nosemosis, and insecticides. It also has been shown that N. ceranae reduces the efficiency of acaricide treatment against Varroa destructor, a serious threat for beekeeping. To date, no therapeutic or prophylactic treatment is available to fight bee nosemosis. Indeed, due to regulation reasons, fumagillin which inhibits the development of both species, has been withdrawn. The absence of maximum residue limit (MRL) determination for honey has conditioned this decision, the use of fumagillin is therefore forbidden in France and in the majority of EU member states. SUPOBEE is dedicated to fill this gap, as partners of this project have identified some polysaccharides that have antimicrosporidian activities. The aim of this proposal is to provide the proof of concept of using sulfated polysaccharides to treat nosemosis. Here, we propose to validate new prophylactic treatment against nosemosis by ensuring the feasibility as regards production and quality of polysaccharides of interest. These products will be confirmed as anti-microsporidian agents both in vitro and in vivo on different available insect models (the fly, Drosophila melanogaster and the honeybee, Apis mellifera). The ultimate step will be to prove in hives infected by N. ceranae the prophylactic effects of sulfated polysaccharides. This will be validated by ensuring the absence of perturbation of the colony homeostatis by testing polysaccharides on healthy colonies.
SUPOBEE is thus characterized by extensive interactions and cross-talk between several partners that are all acknowledged specialists in their domains. Namely, Partner 1, a team of eukaryotic microbiologists, has been investigating nosemosis in honeybees and researching new treatments for several years. Partner 2 is a team of polysaccharide specialists that has a strong expertise in extraction, purification processes applied to poly- and oligosaccharides from micro- and macro-algae and in their structural characterization. Partner 3 is an expert intended to develop the technology transfer from academic research towards socio-economic world. A patent, involving partners 1 and 2, is pending to be filled concerning the use of polysaccharides as anti-Nosema agent. SUPOBEE will ultimately allow us to validate the proof of concept of our strategy to use sulfated polysaccharides as anti-microsporidian treatment.