The immunoprotective effect of whole-cell lysed inactivated vaccine with SWCNT as a carrier against Aeromonas hydrophila infection in grass carp

Aeromonas hydrophila is a strong gram-negative bacterium that can cause a mass death of grass carp, and result in the huge economic loss. Development of practical vaccines is the best way to control the outbreak of this bacterial disease. In this study, a whole-cell inactivated vaccine was obtained via sonication, and then single-walled carbon nanotubes (SWCNTs) was used to link to the bacterial lysate (BL) for a novel vaccine (SWCNTs-BL). A total of 400 fish were vaccinated with BL and SWCNTs-BL via immersion (5, 10 mg L) or injection (5, 10 μg/fish) before challenge with live A. hydrophila at the 28 days post immunization (d.p.i.). The results showed that the antibody titer, enzymatic activity, expression of some immune-related genes (especially IgM and TNF-α) and RPS of fish in the injection groups were significantly increased compared to the control group after 28 d.p.i. For the immersion groups, immunological parameters were increased compared to the control group. Furthermore, the immuno-protective effects of SWCNTs-BL were better than BL. The above results indicated that BL of A. hydrophila can effectively induce specific immune response of grass carp, and BL linked with functionalized SWCNTs could enhance the protective effect of immersion immunization. Our results may provide a practical vaccine, with a simple production, to fight against bacterial diseases in aquaculture industry.