Codon optimization, expression in , and immunogenicity analysis of deformed wing virus (DWV) structural protein.

Background: Deformed wing virus (DWV) is a serious threat to honey bees () and is considered a major cause of elevated losses of honey bee colonies. However, lack of information on the immunogenicity of DWV structural proteins has hindered the development of effective biocontrol drugs.

Methods: We optimized the , and codons of DWV surface capsid protein genes on the basis of an codon bias, and the optimized genes of , and were separately expressed in and purified. Next, the three recombinant proteins of , and were intramuscularly injected into BALB/c and the immunogenicity was evaluated by the levels of specific IgG and cytokines. Furthermore, anti--antisera ( or or ) from the immunized mice was incubated with DWV for injecting healthy white-eyed pupae for the viral challenge test, respectively.

Results: The optimized genes , and achieved the expression in using SDS-PAGE and Western blotting. Post-immunization, and exhibited higher immunogenicity than and stimulated a stronger humoral immune response in the mice, which showed that the recombinant proteins of and induced a specific immune response in the mice. In the challenge test, data regarding quantitative real-time RT-PCR (qRT-PCR) from challenged pupae showed that the level of virus copies in the recombinant protein groups was significantly lower than that of the virus-only group at 96 h post-inoculation ( < 0.05). Among them, the degree of neutralization using antibodies raised to the recombinant proteins are between approximately 2-fold and 4-fold and the virus copies of the group are the lowest in the three recombinant protein groups, which indicated that specific antibodies against recombinant proteins , and of DWV could neutralize DWV to reduce the virus titer in the pupae. Collectively, these results demonstrated that the surface capsid protein of DWV acted as candidates for the development of therapeutic antibodies against the virus.