RNA interference technology reduced Acute bee paralysis virus and Black queen cell virus infection in Honey bees (Apis mellifera)

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

Congreso; 47th Apimondia Apiculture Congress; 2022

Bee viruses cause significant losses in honey production around the world. In previous studies, different viruses were detected in Argentinean honey producer apiaries and queen rearing apiaries, causing significant losses. 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) and Black queen cell virus (BQCV) infection in adult honey bees. The dsRNA was produced by in-vitro transcription; two dsRNA formulations were evaluated: Mixture I targeted viral polyprotein and helicase genes from BQCV and Mixture II targeted viral polyprotein and replicase genes from ABPV. For the preparation of infective virus stocks, BQCV and ABPV were inoculated in bee pupae by injection and purified by sucrose gradients and ultracentrifugation. The presence and quantification of the virus were assessed by quantitative real-time PCRTwo experiments (one for each bee virus) were performed on adult worker bees by oral administration of dsRNA or dsRNA plus virus. Each experiment was designed with five treatments (control, specific dsRNA, specific dsRNA + Virus, Virus, and non-specific dsRNA + virus), 4 replicates of each treatment, and 50 bees per replicate. The viral quantity used per bee were 20 x 106 genomic copies for BQCV and 20 x 104 genomic copies for ABPV, and the quantity of dsRNA per bee was 1 ug. On each treatment, bee mortality was also recorded. Each experiment lasted 16 days on a bench with 65% humidity and a temperature of 35°C.In the ABPV experiment, bee mortality was significantly reduced in the group of bees treated with the specific dsRNA + ABPV in comparison with the groups that received ABPV or non-specific dsRNA + ABPV. In the BQCV experiment, mortality was slightly lower in the dsRNA + BQCV group than in the BQCV group. Quantification of the viral loads was consistent with the bee mortality observed.Post-transcriptional gene silencing by oral administration of dsRNA in honey bees has been previously informed, however, this is the first report of reduction of Acute bee paralysis virus and Black queen cell virus infection in honey bees.