• Acute bee paralysis virus infection and mortality can be reduced by RNA interference oral administration in adult Honey bees Apis mellifera

FERRUFINO CECILIA; SCANNAPIECO ALEJANDRA; RUSSO ROMINA; GONZALEZ FERNANDA; SALVADOR RICARDO; DUS SANTOS MARIA JOSE

Congreso; 48th International Apicultural Congress Apimondia; 2023

Bee viruses cause significant losses of honeybee colonies and hence impact on honey and living material production. In previous studies, we detected different viruses in Argentinean queen rearing apiaries. As a promising strategy, RNA interference has been evaluated to control honeybee virus infection. The aim of this study was to evaluate the effect of RNAi technology mediated by double stranded RNA (dsRNA) to reduce Acute bee paralysis virus (ABPV) infection in adult honey bees. ABPV gene fragments were used for dsRNA synthesis by in-vitro transcription. To prepare infective virus stock, ABPV was injected in bee pupae and purified by sucrose gradients and ultracentrifugation. Viral presence and abundance was assessed by quantitative real-time PCR. Adult bees experiment was performed by oral administration of dsRNA. It was designed with five treatments, control (A), specific dsRNA + Virus (B), Virus (C), specific dsRNA (D) and non-specific dsRNA + virus (E), 4 replicates per treatment, and 50 bees per replicate. The viral quantity used was 1 ml 104 genomic copies/replicate, and dsRNA quantity per bee was 1 μg. The experiment lasted 10 days; bee survival was recorded and samples were processed for viral quantification.In the experiment, at day 6, there was a significant reduction in the average viral loads in treatment B, compared to treatments C and E. Oral administration of dsRNA, reduced the viral replication curve, producing higher bee survival levels in treatment B. On day 5 (2 days post-infection) significant differences were observed in the mean number of live bees between treatment B and treatment E, and from day 6 (3 dpi) between treatment B and treatments C and E. Moreover, treatment B showed no significant differences with controls, regarding bee survival, until day 7. The effect produced by dsRNA administration was that for each μg of dsRNA administered, there was a decrease in average viral loads from 2.48 to 3.48 log cg/μl at time 6 (3 dpi). This is the first report of ABPV infection reduction in honey bees by dsRNA. The results of this work support the feasibility of using this methodology to control honey bee virus infection.