Single-walled carbon nanotubes as candidate recombinant subunit vaccine carrier for immunization of grass carp against grass carp reovirus

• VP7 can be a potent subunit vaccine in fish against infection by GCRV.
• Humoral and cellular immune responses were induced by SWCNTs-VP7.
• Immune protective effect is observed in smaller size grass carp (0.2 g).
• Immunization with SWCNTs-VP7 provides nearly 100% protections against GCRV.
• SWCNTs can be a potent bath vaccine carrier against viral pathogens of fish.

Grass carp reovirus (GCRV), the most pathogenic aquareovirus, can cause fatal hemorrhagic disease in fingerling and yearling grass carp. Vaccination by injection is by far the most effective method of combating disease. However it is labor intensive, costly and not feasible to vaccinate large numbers of the fish. Thus, an efficient and economic strategy for the prevention of GCRV infection becomes urgent. Here, functionalized single-walled carbon nanotubes (SWCNTs) as carrier were used to manufacture SWCNTs-VP7 subunit vaccine with chemical modification. Different developmental stages of grass carps were immunized by VP7/SWCNTs-VP7 subunit vaccine against GCRV by intramuscular injection and bath immunization. The results indicate that better immune responses of grass carp immunized with the SWCNTs-VP7 subunit vaccine were induced in comparison with VP7 subunit vaccine alone. Immunization doses/concentrations are significantly reduced (about 5–8 times) to prevent GCRV infection in different developmental stages of grass carp with injection or bath treatment when SWCNTs carrier was used. A good immune protective effect (relative percentage survival greater than 95%) is observed in smaller size fish (0.2 g) with SWCNTs-VP7 bath immunization. In addition, serum respiratory burst activity, complement activity, lysozyme activity, superoxide dismutase activity, alkaline phosphatase activity, immune-related genes and antibody levels were significantly enhanced in fish immunized with vaccine. This study suggested that functionalized SWCNTs was the promising carrier for recombinant subunit vaccine and might be used to vaccinate fish by bath approach.