An immersion subunit vaccine loaded by single-walled carbon nanotube protects pearl gentian grouper from viral nervous necrosis virus

Grouper is an important cultured fish in China. However, a large number of larval and juvenile groupers dead from the infection of nervous necrosis virus every year, which calls for an effective prevention and control measure. In this study, recombinant major capsid protein (MCP) of nervous necrosis virus (NNV) was produced through a prokaryotic expression vector as a subunit vaccine. We processed single walled carbon nanotube (SWCNTs) by conc H2SO4 and conc. HNO3 to make it a carrier for the vaccine. The fish were inoculated by immersion immunization for 6 h and three concentrations included 5, 10, 20 mg/L were set. Antibody levels, immunization related enzyme activities of acid phosphatase, superoxide dismutase, and alkaline phosphatase in serum as well as the transcription of immune genes (IgM, Mx1, IL1-beta, TNF alpha, CD4, CD8. MHC I, and MHC II) were tested. According to the results, the data of vaccine with the carrier had a significant increase compared with that without. After the virus challenge test, the vaccines carried by SWCNTs with concentrate of 5, 10, 20 mg/L of provided the relative survival rates of 28.57%, 50.62%, 70.76% respectively, while 16.67%, 25.93%, 33.33% were provided by the vaccines without SWCNTs. Besides, the body length and weight of a fish were measured every week, the data showed that there was no significant difference among the groups. The research showed the immersion subunit vaccine loaded by SWCNTs can protect pearl gentian grouper from NNV.