Characterisation of Structural Proteins from Chronic Bee Paralysis Virus (CBPV) Using Mass Spectrometry.

Chronic bee paralysis virus (CBPV) is the etiological agent of chronic paralysis, an infectious and contagious disease in adult honeybees. CBPV is a positive single-stranded RNA virus which contains two major viral RNA fragments. RNA 1 (3674 nt) and RNA 2 (2305 nt) encode three and four putative open reading frames (ORFs), respectively. RNA 1 is thought to encode the viral RNA-dependent RNA polymerase (RdRp) since the amino acid sequence derived from ORF 3 shares similarities with the RdRP of families Nodaviridae and Tombusviridae. The genomic organization of CBPV and in silico analyses have suggested that RNA 1 encodes non-structural proteins, while RNA 2 encodes structural proteins, which are probably encoded by ORFs 2 and 3. In this study, purified CBPV particles were used to characterize virion proteins by mass spectrometry. Several polypeptides corresponding to proteins encoded by ORF 2 and 3 on RNA 2 were detected. Their role in the formation of the viral capsid is discussed.

Experimental infection of the honeybee (Apis mellifera L.) with the chronic bee paralysis virus (CBPV): infectivity of naked CBPV RNAs.

Chronic paralysis is an infectious and contagious disease of the honeybee (Apis mellifera L.) and is caused by the chronic bee paralysis virus (CBPV). This disease leads to death in adult bees and is therefore a serious threat for colony health. CBPV is a positive single-stranded RNA virus and its genome is composed of two RNA segments, RNA 1 and RNA 2, 3674 nt and 2305 nt, respectively. Although CBPV shares some characteristics with viruses classified into families Nodaviridae and Tombusviridae, it has not been assigned to any viral taxa yet. The characterisation of CBPV proteins and their functions are needed to better understand the mechanisms of CBPV infection. However, since honeybee cell lines are not yet available, experimental infection of adult bees is the only method currently available to propagate the virus. With the objective of studying CBPV proteins using the viral genome, we used experimental infection in adult bees to evaluate the infectivity of naked CBPV RNAs by direct inoculation. Our results demonstrated that an injection of naked RNAs, ranging from 10(9) to 10(10) CBPV copies, caused chronic paralysis. Bees inoculated with naked RNA showed chronic paralysis signs 5 days after inoculation. Moreover, injected RNAs replicated and generated viral particles. We therefore provide an in vivo experimental model that will be useful tool for further studies by using a reverse genetics system.