Deformed Wing Virus infection induces immunosuppression and gut dysbiosis in honey bees

Background: The global decline of honey bee health, driven by multiple stressors impairing immunity, threatens both natural and managed ecosystems. Deformed Wing Virus (DWV) is often found at high loads in collapsing colonies, associated with an immunosuppressive syndrome still poorly understood. This study investigates gut microbiota community patterns associated with different levels of DWV infection, an overlooked aspect which can contribute to the reduction of immunocompetence in infected honey bees. Results We quantified DWV in nurse bees from the field and compared gut microbiota in individuals with high vs. low viral loads. We also examined microbiota changes in bees experimentally infected with DWV. In both cases, highly infected bees showed a decreased transcription level of dorsal 1-A, a consolidated molecular proxy of reduced immunocompetence in honey bees. Host immunosuppression was associated with a consistent gut dysbiosis, marked by a reduced relative abundance of beneficial genera such as Fructobacillus, Lactobacillus, and Apilactobacillus (Firmicutes, Bacilli), and a relative enrichment of Bartonella (Proteobacteria). Conclusions These findings shed new light on host-pathogen interactions and will allow a targeted manipulation of honey bee gut microbiota to limit DWV infections, which strongly contribute to colony losses.