Protecting bees from viruses

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Honey bees are crucial for pollination of food crops and production of hive products such as honey. In the past two decades, honey bees have suffered from declines across Europe and North America. This is due to a number of incursions of non-native pests and pathogens which damage honey bees, but also due to a change in the prevalence and virulence in viruses posited to be induced by the introduced parasitic mite, Varroa destructor. There are no controls for these viruses and management of Varroa is challenging due to widespread resistance to chemical pesticides and few new products available for this market.Wolbachia are intracellular bacteria which live inside the cells of a large number of insect species, including species of wasps, bees and a small number of honey bees, and even some spider and worm species. Wolbachia are widespread in the UK. Some strains of this bacteria can make their host resistant to certain pathogenic viruses. This has been exploited by researchers working with the mosquitoes that transmit Dengue, Zika and Chikungunya viruses; in laboratory and field trials, the bacteria made the mosquitoes resistant to these viruses. Importantly, some strains of Wolbachia that make their hosts resistant to viruses do not appear to cause a serious fitness penalty to their insect host.Our central hypothesis, based on these clear data from other insect species, is that infection with appropriate strains of Wolbachia will make honey bees resistant to important honey bee viruses; these are related to viruses known to be inhibited by Wolbachia. We will test this hypothesis in cultured bee cells, which allows more rapid testing of Wolbachia-virus combinations than using bees. We will also explore effects on the microsporidian parasite, Nosema, as there is some evidence that Wolbachia can also inhibit cellular pathogens. In addition to testing Wolbachia in honey bee cell lines, we can perform direct studies on individual honey bees in laboratory cages. In mosquitoes, adults can be injected with a purified strain of Wolbachia, which will disseminate through the tissues, this is called a 'transient' infection. These insects can then be challenged with viruses to get an indication of the effects of Wolbachia infection. Adult honey bees will be challenged in the same way in a contained environment, as a complementary approach for the potential anti-viral or anti-microsporidian activity of Wolbachia. We propose to investigate the feasibility of using Wolbachia to inhibit positive sense RNA viruses, using a honey bee cell line as initial proof of concept. We will deliver this through four linked objectives:Obj1:Set up cell culture and establish Wolbachia infected and Wolbachia-free derivatives Obj2:Set up viral and Nosema cultures in cell linesObj3:Test pathogen infection on Wolbachia infected and Wolbachia free cell linesObj4:Validate and test transient Wolbachia infections of worker honey beesThere is a clear need for new methods for control of viral and cellular pathogens in bees. This project aims to explore the potential of a Wolbachia-based, non-chemical approach that, if realised, would potentially fit well into an enhanced, sustainable integrated bee health programme. If Wolbachia can inhibit viruses and/or Nosema spp. in honey bees, this would provide an exciting new approach to control of bee diseases; this project will test the feasibility of this approach. Wolbachia is transmitted through the female germline, so Wolbachia infected queen bees could be used to generate disease resistant colonies. This Wolbachia-based approach does not involve the use of recombinant DNA methods and the resulting strains are not considered to be genetically modified organisms (GMOs), providing lower barriers to any eventual field use than some other potential genetic approaches to pathogen resistance.