Antiviral Activities of a Medicinal Plant Extract Against Sacbrood Virus in Honeybees

Shufa Xu,Jin Xu,Xueqi Zhang,Liping Sun,Chunsheng Hou,Yanping Chen,Dongxiang Zhao

doi:10.1186/s12985-021-01550-y

Abstract

BackgroundSacbrood is an infectious disease of the honey bee caused by Scbrood virus (SBV) which belongs to the family Iflaviridae and is especially lethal for Asian honeybee Apis cerana. Chinese Sacbrood virus (CSBV) is a geographic strain of SBV. Currently, there is a lack of an effective antiviral agent for controlling CSBV infection in honey bees.MethodsHere, we explored the antiviral effect of a Chinese medicinal herb Radix isatidis on CSBV infection in A. cerana by inoculating the 3rd instar larvae with purified CSBV and treating the infected bee larvae with R. isatidis extract at the same time. The growth, development, and survival of larvae between the control and treatment groups were compared. The CSBV copy number at the 4th instar, 5th instar, and 6th instar larvae was measured by the absolute quantification PCR method.ResultsBioassays revealed that R. isatidis extract significantly inhibited the replication of CSBV, mitigated the impacts of CSBV on larval growth and development, reduced the mortality of CSBV-infected A. cerana larvae, and modulated the expression of immune transcripts in infected bees.ConclusionAlthough the mechanism underlying the inhibition of CSBV replication by the medicine plant will require further investigation, this study demonstrated the antiviral activity of R. isatidis extract and provides a potential strategy for controlling SBV infection in honey bees.

Highlights

The Eastern honeybee (Apis cerana) is an important pollinator for crops and wild plants in Southeast Asia [31]
We provide evidence that R. isatidis extract could effectively inhibit the replication of Chinese Sacbrood virus (CSBV) in A. ceranae larvae, improve the immune response and extend the lifespan of CSBV infection larvae, clearly demonstrating an effective medicine for protecting honeybees from Scbrood virus (SBV) infection
R. isatidis extract could reverse the effects of CSBV on larval growth and development The comparison of the morphology of larvae across three different groups showed that CSBV could severely impact the growth and development of A. cerana larvae and that R. isatidis extract was able to reverse the negative effects of CSBV on larval growth and development

Summary

Introduction

The Eastern honeybee (Apis cerana) is an important pollinator for crops and wild plants in Southeast Asia [31]. SBV has evolved into multiple strains based on different geographical distribution. Chinese Sacbrood virus (CSBV) is a geographic strain of SBV infecting Chinese honeybee A. cerana [24]. CSBV was first found in A. cerana of Guangdong province in 1972 in China, and spread rapidly to other regions of China and Southeast Asia and has been regarded as a major threat to A. cerana colonies [24]. Sacbrood is an infectious disease of the honey bee caused by Scbrood virus (SBV) which belongs to the family Iflaviridae and is especially lethal for Asian honeybee Apis cerana. Chinese Sacbrood virus (CSBV) is a geographic strain of SBV. There is a lack of an effective antiviral agent for controlling CSBV infection in honey bees

Methods

Results

Discussion

Conclusion