Chinese sacbrood virus infection in Asian honey bees (Apis cerana cerana) and host immune responses to the virus infection

Authors: LIU, SHAN - Chinese Academy Of Agricultural Sciences; WANG, LIUHAO - Chinese Academy Of Agricultural Sciences; GUO, JUN - Kunming University Of Science And Technology; TANG, YUJIE - Chinese Academy Of Agricultural Sciences; Chen, Yanping - Judy; WU, JIE - Chinese Academy Of Agricultural Sciences; LI, JILIAN - Chinese Academy Of Agricultural Sciences

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2017
Publication Date: 9/12/2017
Citation: Liu, S., Wang, L., Guo, J., Tang, Y., Chen, Y., Wu, J., Li, J. 2017. Chinese sacbrood virus infection in Asian honey bees (Apis cerana cerana) and host immune responses to the virus infection. Journal of Invertebrate Pathology. 150:63-69. https://doi.org/10.1016/j.jip.2017.09.006.
DOI: https://doi.org/10.1016/j.jip.2017.09.006

Interpretive Summary: Sacbrood virus (SBV) is the most destructive virus in the Asian honeybee. Using molecular methods, we conducted a study to investigate the transmission pathways of SBV in Asian honey bee colonies. We also examined honeybee host immune responses to the virus infection. we have detected viruses in various tissues of honey bee queens, indicating a vertical route of virus transmission, We detected the virus in colony brood food and queen feces, suggesting that queens of bee colonies could be infected through virus-contaminated food. We also detected the virus in queen reproductive tissues as well as eggs of the colonies, suggesting that offspring could obtain the virus from their infected mother queen. This study indicates that SBV can be can spread in bee colonies even in the absence of the vector, parasitic Varroa mites. It also alerts federal agencies that regulate the importation of honey bee queens into the Unites States that these queens may be the source of the virus. The results of our study should be of interest to the researchers, regulatory policy officers, graduate students, apiary inspectors, and beekeepers worldwide.

Technical Abstract: Chinese Sacbrood virus (CSBV) is a common honey bee virus that infects both the European honey bee (A. mellifera) and the Asian honey bee (A. cerana). However, CSBV has much more devastating effects on Asian honey bees than on European honey bees, posing a serious threat to the agricultural and natural ecosystems that rely on A. cerana for crop pollination and honey production. Using quantitative RT-PCR method, we conducted studies to examine the CSBV infection in Asian honey bee colonies and immune responses of individual bees in response to CSBV infection. Our study showed that CSBV could cause infection in different developmental stages of workers including eggs, larvae, pupae, newly emerged workers, and foraging workers. In addition, evaluating the tissue tropism and pathogenesis of CSBV showed that CSBV was detected in the ovaries, spermatheca, and feces of queens as well as semen of drones of the same colonies, suggesting the existence of vertical transmission of CSBV in Asian honey bees. Further, the detection of CSBV in brood food suggests that brood and queen bees could be infected by the CSBV through virus-contaminated food, and therefore, the possible existence of a food-borne transmission pathway of CSBV in Asian bee colonies. The expression analysis of immune transcripts (defensin,abaecin,apidaecin, and hymenoptaecin) showed that CSBV infection could induce significant host immune responses in infected bees, however, the immune responses to CSBV infection varied among different development stages with eggs exhibiting the lowest level of immune expression and forager workers exhibiting the highest level of immune gene expression. The results obtained in the study provide important insights into the mechanisms underlying disease pathogenesis of CSBV infections in Asian honey bees.