A comparison of biological characteristics of three strains of Chinese sacbrood virus in Apis cerana

We selected and sequenced the entire genomes of three strains of Chinese sacbrood virus (CSBV): LNQY-2008 (isolated in Qingyuan, Liaoning Province), SXYL-2015 (isolated in Yulin, Shanxi Province), and JLCBS-2014 (isolated in Changbaishan, Jilin Province), by VP1 amino acid (aa) analysis. These strains are endemic in China and infect Apis cerana. Nucleotide sequences, deduced amino acid sequences, genetic backgrounds, and other molecular biological characteristics were analysed. We also examined sensitivity of these virus strains to temperature, pH, and organic solvents, as well as to other physicochemical properties. On the basis of these observations, we compared pathogenicity and tested cross-immunogenicity and protective immunity, using antisera raised against each of the three strains. Our results showed that compared with SXYL-2015, LNQY-2008 has a 10-aa deletion and 3-aa deletion (positions 282-291 and 299-301, respectively), whereas JLCBS-2014 has a 17-aa deletion (positions 284-300). However, the three strains showed no obvious differences in physicochemical properties or pathogenicity. Moreover, there was immune cross-reactivity among the antisera raised against the different strains, implying good protective effects of such antisera. The present study should significantly advance the understanding of the pathogenesis of Chinese sacbrood disease, and offers insights into comprehensive prevention and treatment of, as well as possible protection from, the disease by means of an antiserum.