Large-scale field application of RNAi technology reducing Israeli Acute Paralysis Virus Disease in honey bees (Apis mellifera, Hymenoptera; Apidae)

Authors: Hunter, Wayne; ELLIS, J - University Of Florida; VANENGLESDORP, D - Pennsylvania State University; HAYES, J - Florida Department Of Agriculture; WESTERVELT, D - Florida Department Of Agriculture; GLICK, E - Beeologics, Llc; WILLIAMS, M - Pennsylvania State University; SELA, I - Hebrew University; MAORI, E - Hebrew University; Pettis, Jeffery; COX-FOSTER, D - Pennsylvania State University; PALDI, N - Beeologics, Llc

Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2010
Publication Date: 12/23/2010
Citation: Hunter, W.B., Ellis, J.D., vanEnglesdorp, D., Hayes, J., Westervelt, D., Glick, E., Williams, M., Sela, I., Maori, E., Pettis, J., Cox-Foster, D., Paldi, N. 2010. Large-scale field application of RNAi technology reducing Israeli Acute Paralysis Virus disease in honey bees (Apis mellifera, Hymenoptera: Apidae). PLoS Pathogens. 6(12):e1001160.

Interpretive Summary: A new medicine, based on RNA interference, was developed which increased honey bee health under the constraints of colony collapse disorder, CCD. High rates of honey bee mortality continue to threaten food security and apicultural industries worldwide. At least some of these losses are likely the result of viral infections. The importance of honey bees as pollinators of crops to the global economy far surpasses their contributions in terms of honey production. In all, 52 of the world’s 115 leading agricultural crops rely on honey bee pollination for food production to some extent. These crops represent approximately 35% of the human diet. Insect pollination, which is provided predominately by honey bees, is estimated to have a value of US$ 212 billion. Application of RNAi technologies in the treatment and management of disease promises new solutions to disease problems through the naturally occurring biological processes of living organisms. We applied a novel dsRNA product developed specifically with the aim of improving honey bee health. The results demonstrate the successful application of RNAi strategies to improve disease tolerance. Honey bees were fed this natural product, a dsRNA called Remebee™, in the presence of the Israeli Acute Paralysis Virus, IAPV. Treatment resulted in increased bee survival, thus larger colony populations, and subsequently resulted in a four-fold increase in honey production. We show that IAPV specific homologous dsRNA successfully curbed the negative effects of IAPV infection in 160 honey bee hives in two discrete climates, seasons and geographical locations (Florida and Pennsylvania). We provide the first successful demonstration of the use of RNAi as a preventative treatment for an insect disease under field conditions over a large, real-world scale.

Technical Abstract: We present the first successful use of RNAi under a large-scale real-world application for disease control. Israeli acute paralysis virus, IAPV, has been linked as a contributing factor in coolly collapse, CCD, of honey bees. IAPV specific homologous dsRNA were designed to reduce impacts from IAPV infection across 160 honey bee hives in two discrete climates, seasons and geographical locations (Florida and Pennsylvania). These results demonstrate the first successful use of RNAi as a preventative treatment for an insect disease, thus improving the health of important pollinators such as the honey bee, Apis mellifera (Hymenoptera). The importance of honey bees as pollinators of crops to the global economy far surpasses their contributions in terms of honey production. In all, 52 of the world’s 115 leading agricultural crops rely on honey bee pollination to some extent. These crops represent approximately 35% of the human diet. Insect pollination, which is provided predominately by honey bees, is estimated to have a value of US$ 212 billion. Honey bee populations have been decreasing globally in recent years. Since fall 2006, honey bees overwintering in the U.S.A. have faced unusually high rates of mortality, in part because of a phenomenon now known as Colony Collapse Disorder (CCD). Several hypotheses have been offered to explain CCD and existing and emerging pathogens have been implicated either directly or indirectly. Colonies affected by CCD are infected with larger numbers of pathogenic organisms than control colonies, yet no single pathogen was found associated with all affected colonies. However, researchers did find that single-stranded RNA viruses, specifically picorna-like viruses, occurred at elevated levels in CCD colonies. These elevated levels of viruses appear to interfere with gene transcription, thus reducing immune response competence and pesticide detoxification capabilities, subsequently leading to premature death of infected bees. Honey bees are susceptible to a host of picorna-like viruses, including the closely related Acute Bee Paralysis Virus (ABPV), Kashmir Bee Virus (KBV), and Israeli Acute Paralysis Virus (IAPV). The latter of these three viruses, IAPV, was identified as a good marker for CCD occurrence, especially when found in association with the microsporidia Nosema. While IAPV is probably not the sole cause of CCD [7], its ability to cause increased mortality in honey bees has been established. The process of post-transcriptional gene silencing is thought to be an evolutionarily-conserved cellular defense mechanism used to prevent the expression of foreign genes and is commonly shared by diverse flora and phyla. The presence of long double-stranded RNAs in cells stimulates the activity of a ribonuclease III, Dicer, which is involved in the processing of the double stranded RNA (dsRNA) into short interfering RNAs (siRNAs). The RNAi response also features an endonuclease complex, commonly referred to as an RNA-induced silencing complex (RISC), which mediates cleavage of target ssRNA having sequence complementary to the antisense strand of the siRNA duplex. In a variety of organisms, exogenously applied dsRNA or their siRNA derivatives, can be used to arrest, retard or even prevent a variety of pathogens. In some of these organisms, such as plants and the nematode C. elegans, an amplification stage follows the initiation stage of gene silencing, involving an RNA dependent RNA Polymerase (RdRp), which may lead subsequently to degradation of RNAs outside the initial dsRNA region of homology. RNAi can spread from the initial site of dsRNA delivery, producing interference phenotypes throughout the treated animal. To serve as a preventive or curative strategy, amplification and systemic spread of the silencing signal are both paramount. In some invertebrates, including honey bees, a systemic in