Vaccine Molecule Design Based on Phage Display and Computational Modeling against Rhabdovirus.

Rhabdoviruses with rich species lead a variety of high lethality and rapid transmission diseases to plants and animals around the globe. Vaccination is one of the most effective approaches to prevent and control virus disease. However, the key antigenic epitopes of glycoprotein being used for vaccine development are unclear. In this study, fish-derived Abs are employed for a Micropterus salmoides rhabdovirus (MSRV) vaccine design by phage display and bioinformatics analysis. We constructed an anti-MSRV phage Ab library to screen Abs for glycoprotein segment 2 (G2) (G129-266). Four M13-phage-displayed Abs (Ab-5, Ab-7, Ab-8 and Ab-30) exhibited strong specificity to target Ag, and Ab-7 had the highest affinity with MSRV. Ab-7 (300 µg/ml) significantly increased grass carp ovary cell viability to 83.40% and significantly decreased the titer of MSRV. Molecular docking results showed that the key region of Ag-Ab interaction was located in 10ESQEFTTLTSH20 of G2. G2Ser11 and G2Gln12 were replaced with alanine, respectively, and molecular docking results showed that the Ag-Ab was nonbinding (ΔG > 0). Then, the peptide vaccine KLH-G210-20 was immunized to M. salmoides via i.p. injection. ELISA result showed that the serum Ab potency level increased significantly (p < 0.01). More importantly, the challenge test demonstrated that the peptide vaccine elicited robust protection against MSRV invasion, and the relative percentage survival reached 62.07%. Overall, this study proposed an approach for screening key epitope by combining phage display technology and bioinformatics tools to provide a reliable theoretical reference for the prevention and control of viral diseases.

Mannose modified targeted immersion vaccine delivery system improves protective immunity against Infectious spleen and kidney necrosis virus in mandarin fish (Siniperca chuatsi).

Vaccination is an effective method to prevent viral diseases. However, the biological barrier prevents the immersion vaccine from achieving the best effect without adding adjuvants and carriers. Researches on the targeted presentation technology of vaccines with nanocarriers are helpful to develop immersion vaccines for fish that can break through biological barriers and play an effective role in fish defense. In our study, functionally modified single-walled carbon nanotubes (SWCNTs) were used as carriers to construct a targeted immersion vaccine (SWCNTs-M-MCP) with mannose modified major capsid protein (MCP) to target antigen-presenting cells (APCs), against iridovirus diseases. After bath immunization, our results showed that SWCNTs-M-MCP induced the presentation process and uptake of APCs, triggering a powerful immune response. Moreover, the highest relative percent survival (RPS) was 81.3% in SWCNTs-M-MCP group, which was only 41.5% in SWCNTs-MCP group. Altogether, this study indicates that the SWCNTs-based targeted immersion vaccine induces strong immune response and provided an effective protection against iridovirus diseases.

Drug delivery system based on metal-organic framework improved 5-Fluorouracil against spring viremia of carp virus.

Spring viremia of carp virus (SVCV), as a high pathogenicity pathogen, has seriously restricts the healthy and sustainable development of cyprinid farming industry. In this study, we selected 5-Fluorouracil (5-Fu) as the drug model based on zeolitic imidazolate framework-8 (ZIF-8) to construct a drug delivery system (5-Fu@ZIF-8), and the anti-SVCV activity was detected in vitro and in vivo. The results showed 5-Fu@ZIF-8 was uniform cubic particle with truncated angle and smooth surface, and the particle size was 90 nm. The anti-SVCV activity in vitro results showed that the highest inhibition rate of 5-Fu was 77.93% at 40 mg/L and the inhibitory concentration at half-maximal activity (IC50) was 20.86 mg/L. For 5-Fu@ZIF-8, the highest inhibition rate was 91.36% at 16 mg/L, and the IC50 value was 5.85 mg/L. In addition, the cell viability was increased by 18.1% after 5-Fu treatment. Similarly, after 5-Fu@ZIF-8 treatment, the cell viability increased by 27.3%. Correspondingly, in vivo experimental results showed the viral loads reduced by 18.1% on the days 7 and the survival rate increased to 19.4% at 80 mg/L after 5-Fu treatment. For 5-Fu@ZIF-8, the viral loads reduced by 41.2% and the survival rate increased to 54.8%. Mechanistically, 5-Fu inhibits viral replication by regulating p53 expression and promoting early apoptosis in infected cells. All results indicated that 5-Fu@ZIF-8 improved the anti-SVCV activity; it may be a potential strategy to construct a drug-loaded system with ZIF-8 as a carrier for the prevention and treatment of aquatic diseases.