Fei Ling

Protective immunity of grass carp immunized with DNA vaccine encoding the vp7 gene of grass carp reovirus using carbon nanotubes as a carrier molecule

The uses of single walled carbon nanotubes (SWCNTs) as carriers for DNA delivery have received considerable attention in cell studies. DNA vaccination of fish has been shown to elicit durable transgene expression, but no reports exist on intramuscular administration of SWCNTs-DNA vaccine electrostatic complexes which prepared through non-covalent conjugation. In this study, we injected grass carp intramuscularly with a plasmid vector containing a major capsid protein gene (vp7) of grass carp reovirus as a) naked pcDNA-vp7, b) SWCNTs-pcDNA-vp7, c) empty plasmid vector, or phosphate buffered saline. After intramuscular administration, the ability of the different immune treatments to induce transgene expression was analyzed. The results indicated that higher levels of transcription and expression of the vp7 gene could be detected in muscle tissues of grass carp 28 days intramuscular injection in SWCNTs-pcDNA-vp7 treatment groups compare with naked pcDNA-vp7 treatment groups. Moreover, the serum respiratory burst activity, complement activity, lysozyme activity, superoxide dismutase activity, immune-related genes, antibody levels and relative percentage survival were significantly enhanced in fish immunized with SWCNTs-pcDNA-vp7 vaccine. The data in this study suggested that SWCNTs were promising carriers for plasmid DNA vaccine and might be used to vaccinate fish by intramuscular approach.

Effect of a new recombinant Aeromonas hydrophila vaccine on the grass carp intestinal microbiota and correlations with immunological responses

Intestinal microbiota has become an integral component of the fish, and plays a key role in host metabolism, immunity and health maintenance. However, information on the immune responses after vaccine administration in relation to the intestinal microbiota is absent in fish. The present study focused on the effect of a new recombinant Aeromonas hydrophila vaccine (Aera) by using a novel functionalized, single-walled carbon nanotubes (SWCNTs) as a delivery vehicle on the intestinal microbiota of grass carp (Ctenopharyngodon idella) through the bath immunization, and further explored the immunological responses in intestine, kidney and spleen. By performing deep sequencing, a total of 81,979 valid reads and 609 OTUs obtained from 4 intestine samples were analyzed. We detected 141 genuses, most of which belonged to Firmicutes, Fusobacteria and Proteobacteria. Of note, the quantity of Aeromonas in library Aera (after 6 h Aera vaccine pretreatment, fish were transferred to tanks without SWCNTs-Aera for 28 d) and Aera-GD (6 h Aera vaccine pretreated prior to the group injected by A. hydrophila) was declined 6.5% and 14.6% compared with the control, respectively. Moreover, the expression of seven immune-related genes (IFN-I, TNF-α, CRP, IL-8, IgM, MHC I and CD8α) in the intestine, kidney and spleen of Aera treated fish was significantly enhanced, which indicated that a better tissue immune response in grass carp was induced by the SWCNTs-Aera vaccine. Therefore, a new recombinant SWCNT-Aera vaccine may represent potentially efficient and immunological role in grass carp intestine to resist A. hydrophila infection.

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

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.

Toxicological effects of multi-walled carbon nanotubes on Saccharomyces cerevisiae: The uptake kinetics and mechanisms and the toxic responses.

Using Saccharomyces cerevisiae as an experimental model, the potential toxicological effects of oxidized multi-walled carbon nanotubes (MWCNTs) were investigated following exposure to 0-600mg/L for 24h. Results indicated that MWCNTs (>100mg/L) had adverse effects on the cell proliferation. MWCNTs were clearly visible in lysosome, vacuole, endosome, mitochondria, multivesicular body and localization in the perinuclear region. The uptake kinetics data demonstrated that the maximum MWCNTs content (209.61mg/g) was reached at 3h, and a steady state was reached after 18h. Based on the combined results of transmission electron microscope, endocytosis inhibition experiments and endocytosis-related genes (END3, END6, Sla2 and Rsp5) expression analysis, we elucidated MWCNTs uptake mechanism: (i) via a direct penetration of single MWCNTs; (ii) via endocytosis of single MWCNTs; and (iii) via endocytosis of MWCNTs aggregates. The percentage of apoptosis was significant increased at 600mg/L. The decrease of mitochondrial transmembrane potential and the leakage of cytochrome c shown dose-dependent manners. Interestingly, there was no significant increase of reactive oxygen species (ROS). The apoptosis-related genes (SOD1, SOD2, Yca1, Nma111 and Nuc1) were significant changed. These results obtained in our study demonstrated that oxidized MWCNTs induce Saccharomyces cerevisiae apoptosis via mitochondrial impairment pathway.

In vitro and in vivo assessment of the effect of antiprotozoal compounds isolated from Psoralea corylifolia against Ichthyophthirius multifiliis in fish.

Highlights • Two antiprotozoal compounds from P. corylifolia were isolated and identified.• In vitro antiprotozoal efficacies of isopsoralen and psoralidin were evaluated.• Psoralidin had a detrimental effect on I. multifiliis trophont in situ.• The action mechanism against I. multifiliis trophont in situ was investigated.

Development toxicity of functionalized single-walled carbon nanotubes on rare minnow embryos and larvae.

Abstract Carbon nanotubes (CNTs) are widely used in industrial and commercial applications, but few studies systematically evaluate their developmental toxicity on aquatic organism. Using rare minnow (Gobiocypris rarus) at early life stages as experimental models, developmental toxicity of functionalized single-walled CNTs (SWCNTs) was investigated following exposure to 0–320 mg/L for 144 h. Results revealed that significantly increased in mortality and malformation was only observed after hatching. Decreased body length, heart rate and swimming speed provide a concentration-dependent manner on larvae; values of 144 h LC50 and EC50 were 140.8 and 109.8 mg/L, respectively. Antioxidant enzyme activities (superoxide dismutase, catalase and glutathione S-transferase) and antioxidant enzyme related mRNA expressions were significant changed; cell apoptosis activities (caspase-3, -8, -9) and cell apoptosis related mRNA expressions were significant up-regulated; reactive oxygen species and DNA damage were significantly induced when the concentration of SWCNTs above 100 mg/L. Fluorescence and electron microscopy sliced observation show that SWCNTs were well dispersed in larvae within 0.5 h, eventually cleared from the larvae at 144 h. This is the first study to define uptake kinetics and to focus on behavioral consequences, physiological changes and mRNA expression following SWCNTs exposure in the early life stages of fish. The results obtained in the present study demonstrated that functionalized SWCNTs have the potential to affect aquatic life when released into the aquatic environment and reached high concentration. In the increasing economical context of SWCNTs, complementary studies must be undertaken, especially including mechanistic and environmental investigations.

Assessment of trifloxystrobin uptake kinetics, developmental toxicity and mRNA expression in rare minnow embryos.

Trifloxystrobin (TFS) is the widely used strobilurin fungicide. However, little information is so far available regarding the uptake kinetics and developmental toxicity of TFS to fish. The present study was conducted to investigate the uptake kinetics, potential environment risk and toxicity of TFS on Gobiocypris rarus embryos. Results revealed that increased malformation, decreased body length and heart rate, affected spontaneous movement and swimming speed provide a gradual concentration-dependent manner; values of 144 h LC50 (median lethal concentration) and EC50 (median effective concentration) were 1.11 and 0.86 μg L(-1). Continuous exposure to TFS resulted in a steady accumulation with no evidence of elimination. Enzyme activities were significantly changed; reactive oxygen species and DNA damage were significantly induced after TFS treatment. Certain genes related to cell apoptosis (p53), metabolism (cyp1a), stress response (hsp70) and blood vessels (vezf1) development were all significantly up-regulated. This is the first study to define uptake kinetics and to focus on behavioral consequences, physiological changes and mRNA expression following TFS exposure in the early life stages of fish. Our results suggest that TFS is highly toxic to fish embryos.

Expression of immune-related genes in goldfish gills induced by Dactylogyrus intermedius infections.

Dactylogyrus intermedius, an oviparous monogenean parasite, is regarded as a devastating pathogen in freshwater aquaculture and ornamental fish trade, and accounts for significant economic losses worldwide. The study was undertaken to determine the differential expression of immune-related genes TNFα1, TNFα2, IL-1β2, TGFβ, iNOSa and iNOSb in goldfish gills during D. intermedius infection by real-time quantitative PCR. The results show that the expression of the pro-inflammatory cytokines (IL-1β2, TNFα1 and TNFα2) and the anti-inflammatory cytokine (TGFβ) were up-regulated at day 7 p.i. (post infection). The mRNA levels of these cytokines returned to normal levels or were down-regulated at day 21 p.i. In the cases of iNOSa and iNOSb, a significant up-regulation in iNOSa transcription levels were seen at day 14 p.i. while the expression of iNOSb gene showed a distinct up-regulation at day 7 p.i. Additionally, this study was conducted to investigate the expression of immune-related genes in different degrees of goldfish experimentally infected with the monogenean D. intermedius. The results indicated that D. intermedius infection might regulate the fish immunity by showing differential expression levels of immune-related gene. The study confirms goldfish gill acts as an important source of inflammatory molecules, as well as an active modulator of local inflammation after initially infected with D. intermedius. Moreover, the results obtained in this study could be useful towards understanding the susceptibility of goldfish to D. intermedius and mechanisms involved in protection of goldfish to ectoparasitic infections.

In vitro immunocompetence of two compounds isolated from Polygala tenuifolia and development of resistance against grass carp reovirus (GCRV) and Dactylogyrus intermedius in respective host

The present study was undertaken to isolate some compounds from methanol extract of Polygala tenuifolia and evaluate their immunostimulatory properties and antiviral activity using grass carp Ctenopharyngodon idella kidney (CIK) cells and GCRV. By applying insecticidal bioassay-guided, chromatography techniques and successive recrystallization, two purified compounds were obtained. The changes of expression of selected immune genes (Mx1, IL-1β, TNFα, MyD88 and IgM) in C. idella kidney cell lines were evaluated after exposure to these isolated compounds. The results showed that compound 1 and 2 up-regulated to varying degrees of Mx1, IL-1β, TNFα, and MyD88 in C. idella kidney cells. WST-8 kit assay verified the two compounds has no toxic effects on CIK cell, and furthermore, have in vitro antivirus activity. Especially, that there is keeping 79% cell viability when exposure to compound 2 (100 mg L(-1)). According to in vivo insecticidal assays against Dactylogyrus intermedius, compound 2 exhibited higher efficacy than compound 1, which was found to be 87.2% effective at the concentrations of 5 mg L(-1) and safe to goldfish (Carassius auratus). Besides, the purified compounds were identified by spectral data as: (1) 1,5-Anhydro-D-glucitol and (2) 3,4,5-trimethoxy cinnamic acid. Overall, the results indicate that bath administration of these compounds modulates the immune related genes in C. idella kidney cells and to some extent, eliminate the virus and parasitic infections.

Protective immunity of grass carp induced by DNA vaccine encoding capsid protein gene (vp7) of grass carp reovirus using bacterial ghost as delivery vehicles

ABSTRACT Grass carp reovirus (GCRV) is one of the most pathogenic aquareovirus and can cause lethal hemorrhagic disease in grass carp (Ctenopharyngodon idella). However, management of GCRV infection remains a challenge. Therefore, it is necessary to find effective means for the control of its infection. The uses of bacterial ghost (BG, non‐living bacteria) as carriers for DNA delivery have received considerable attentions in veterinary and human vaccines studies. Nevertheless, there is still no report about intramuscular administration of bacterial ghost‐based DNA vaccines in fish. In the current study, a novel vaccine based on Escherichia coli DH5&agr; bacterial ghost (DH5&agr;‐BG), delivering a major capsid protein gene (vp7) of grass carp reovirus encoded DNA vaccine was developed to enhance the efficacy of a vp7 DNA vaccine against GCRV in grass carp. The grass carp was injected intramuscularly by different treatments ‐i) naked pcDNA‐vp7 (containing plasmid 1, 2.5 and 5 &mgr;g, respectively), ii) DH5&agr;‐BG/pcDNA‐vp7 (containing plasmid 1, 2.5 and 5 &mgr;g, respectively) and iii) naked pcDNA, DH5&agr;‐BG or phosphate buffered saline. The immune responses and disease resistance of grass carp were assessed in different groups, and results indicated that the antibody levels, serum total antioxidant capacity (T‐AOC), superoxide dismutase (SOD) activity, acid phosphatase (ACP) activity and alkaline phosphatase (AKP) activity and immune‐related genes were significantly enhanced in fish immunized with DH5&agr;‐BG/pcDNA‐vp7 vaccine (DNA dose ranged from 2.5 to 5 &mgr;g). In addition, the relative percentage survival were significantly enhanced in fish immunized with DH5&agr;‐BG/pcDNA‐vp7 vaccine and the relative percentage survival reached to 90% in DH5&agr;‐BG/pcDNA‐vp7 group than that of naked pcDNA‐vp7 (42.22%) at the highest DNA dose (5 &mgr;g) after 14 days of post infection. Moreover, the level of pcDNA‐vp7 plasmid was higher in DH5&agr;‐BG/pcDNA‐vp7 groups than naked pcDNA‐vp7 groups in muscle and kidneys tissues after 21 days. Overall, those results suggested that DH5&agr; bacterial ghost based DNA vaccine might be used as a promising vaccine for aquatic animals to fight against GCRV infection. HIGHLIGHTSE. coli DH5&agr; ghost was used as carrier to prepare a novel DNA vaccine in grass carp.Immunization with DH5&agr;/pcDNAvp7 induced stronger immune response than naked pcDNAvp7.Immunization with DH5&agr;/pcDNAvp7 enhanced disease resistance against GCRV in fish.Bacterial ghost based DNA vaccine had prospects for application to aquatic vaccine.