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To reduce the economic losses caused by diseases in aquaculture industry, more efficient and economic prophylactic measures should be urgently investigated. In this research, the effects of a novel functionalized single-walled carbon nanotubes (SWCNTs) applied as a delivery vehicle for DNA vaccine administration in juvenile grass carp against Aeromonas hydrophila were studied. Our results showed that SWCNTs loaded with DNA vaccine induced a better protection to juvenile grass carp against A. hydrophila . Moreover, SWCNTs conjugated with DNA vaccine provided significantly protective immunity compared with free DNA vaccine. Thereby, SWCNTs may be considered as a potential efficient DNA vaccine carrier to enhance the immunological activity. [ABSTRACT FROM AUTHOR]

To reduce the lethal hemorrhagic disease caused by grass carp reovirus (GCRV) and improve the production of grass carp, efficient and economic prophylactic measure against GCRV is the most pressing desired for the grass carp farming industry. In this work, a novel SWCNTs-pEGFP- vp5 DNA vaccine linked vp5 recombinant in the form of plasmid pEGFP- vp5 and ammonium-functionalized SWCNTs by a chemical modification method was prepared to enhance the efficacy of a vp5 DNA vaccine against GCRV in juvenile grass carp. After intramuscular injection (1, 2.5 and 5 μg) and bath administration (1, 10, and 20 mg/L), the ability of the different immune treatments to induce transgene expression was analyzed. The results showed that higher levels of transcription and expression of vp5 gene could be detected in muscle tissues of grass carp in SWCNTs-pEGFP- vp5 treatment groups compare with naked pEGFP- vp5 treatment groups. Moreover, antibody levels, immune-related genes, and relative percentage survival were significantly enhanced in fish immunized with SWCNTs-pEGFP- vp5 vaccine. In addition, we found that a good immune protective effect was observed in bath immunization group; which at a concentration of 20 mg/L could reach the similar relative percentage survival (approximately 100%) in injection group at a dose of 5 μg. All these results indicated that ammonium-functionalized SWCNTs could provide extensive application prospect to aquatic vaccine and might be used to vaccinate fish by intramuscular injection or bath administration method. [ABSTRACT FROM AUTHOR]

Grass carp hemorrhagic disease has widely received great attention for Chinese freshwater aquaculture due to its strong infectiousness and high fatality rate. The pathogen is grass carp reovirus (GCRV). DNA vaccination is a high efficient approach for disease control. Although some encouraging progress have been made, developing a highly-efficient DNA vaccine with genetic type II GCRV predominant antigen epitope is less successful and still require further research. However, the DNA vaccine has made it challenging to avoid the problem of easily metabolized and degraded in vivo. In an effort to overcome this challenge, we constructed the DNA vaccine using single-walled carbon nanotubes (SWCNTs) as delivery vector (SWCNTs-pcDNA- vp4-3) and immunized grass carp (1.2 ± 0.2 g) by intramuscular injection. Experiments are grouped as follows: control group, pcDNA- vp4-3 immune group (10 μg per fish) and SWCNTs-pcDNA- vp4-3 immune groups (2.5, 5 and 10 μg per fish, respectively). The immune effect of DNA vaccine is evaluated comprehensively by testing immune-related parameters (the persistence and expression of DNA vaccine, serum antibody level, immune-related physiological indexes, immune-related genes expression and relative percentage survival). The results showed that serum antibody levels of grass carp were elevated significantly after immunization with DNA vaccines. And the serum antibody levels in SWCNTs-pcDNA- vp4-3 immune groups were higher than pcDNA- vp4-3 immune group. Likewise, the immune-related physiological indexes and immune-related genes expression were elevated significantly after immunization. The IgM gene expression in the SWCNTs-pcDNA- vp4-3 immune group (5 μg per fish) was 3.14 times as much as control group. The relative percentage survival in SWCNTs-pcDNA- vp4-3 immune group (5 μg per fish) reached the peak, protected 74% of grass carp from type II GCRV. Conclusively, the vp4-3 -centric DNA vaccine can induce efficient immune response by injection. Single-walled carbon nanotubes extend the retention time of DNA vaccine in the body and improve its expression intensity. SWCNTs-loaded DNA vaccine induce stronger immune response and enhance the resistance to grass carp haemorrhagic disease. • We introduced a DNA vaccine (pcDNA-vp4-3) based on the GCRV II predominant antigen epitope VP4-3. • SWCNT-loaded DNA vaccine based on predominant antigen epitope widely applied to prevent and control grass carp hemorrhagic diseases in the future. • SWCNTs is promising suitable candidate for improving the delivery efficiency of DNA vaccine in fish. [ABSTRACT FROM AUTHOR]

Grass carp reovirus (GCRV), causative agent of grass carp hemorrhagic disease, causes high mortality of grass carp and results in huge economic losses in grass carp farming. Vaccination is considered the most effective way of preventing GCRV infection and losses of grass carp. In the study, recombination pcDNA3.1-vp4 and pcDNA3.1-vp4-3 plasmids were constructed and respectively transformed into E. coli DH5α. The pcDNA3.1-vp4 and pcDNA3.1-vp4-3 plasmids were used to vaccinate grass carp via intramuscular injection and we evaluated the immune responses induced by different forms of the DNA vaccine and investigated the efficacy in vaccinated fish. The results indicate that better immune responses of grass carp immunized with the pcDNA3.1-vp4 (10 μg/fish) compared with the pcDNA3.1-vp4-3 (10 μg/fish) DNA vaccine. Immune genes were expressed at higher levels in pcDNA3.1-vp4-3 treatment group compared to pcDNA3.1-vp4. The survival post vaccination and challenge of pcDNA3.1-vp4-3 vaccinated fish was 57.89% compared to 36.84% for pcDNA3.1-vp4 group and at 100% mortality in control groups. These results indicated that the segment of vp4-3 could be a plausible candidate for preventing GCRV-JX02 infection among grass carp. • Grass carp injected with pcDNA3.1-vp4 and pcDNA3.1-vp4-3 confers strong immunity against GCRV-JX02. • The DNA vaccine was manufactured by the core of dominant antigen epitope of GCRV-JX02, and its protective effects on grass carp against GCRV-JX02 infection by injection were assessment. • pcDNA3.1-vp4-3 could be a potential therapeutic vaccine against GCRV-JX02. [ABSTRACT FROM AUTHOR]