Immunogenicity of a cell culture-derived inactivated vaccine against a common virulent isolate of grass carp reovirus

• Inactivated HuNan1307 vaccine could elicit a strong humoral antibody response.
• Inactivated HuNan1307 vaccine produced GCRV-specific neutralizing antibody.
• Inactivated vaccine conferred significant protection against GCRV infection.
• The duration of protection of the inactivated vaccine last for one year.

Grass carp (Ctenopharyngodon idella) hemorrhagic disease, caused by grass carp reovirus (GCRV), is emerging as a serious problem in grass carp aquaculture. There is no available antiviral therapy and vaccination is the primary method of disease control. In the present study, the immunological effects and protective efficacy of an inactivated HuNan1307 vaccine in grass carp were evaluated. The GCRV isolate HuNan1307 was produced by replication onto the grass carp PSF cell line, and inactivated with 1% β-propiolactone for 60 h at 4 °C. Grass carp were injected with inactivated GCRV vaccine, followed by challenge with the isolate HuNan1307. The results showed that the minimum dosage of the inactivated vaccine was 105.5 TCID50/0.2 mL to induce immune protection. All grass carp immunized with the inactivated vaccine produced a high titer of serum antibodies and GCRV-specific neutralizing antibody. Moreover, the inactivated vaccine injection increased the expression of 6 immune-related genes in the spleen and head kidney, which indicated that a immune response was induced by the HuNan1307 vaccine. In addition, grass carp immunized with the inactivated vaccine showed a survival rate above 80% after the viral challenge, equal to that of grass carp immunized with a commercial attenuated vaccine, and the protection lasted at least for one year. The data in this study suggested that the inactivated HuNan1307 vaccine may represent an efficient method to induce immunity against GCRV infection and the induced disease in grass carp.