Immunogenicity and efficacy of two DNA vaccines encoding antigenic PspA and TerD against Nocardia seriolae in hybrid snakehead

• Published in: Fish & shellfish immunology 2020-11, Vol.106, p.742-754
• Main Authors: Chen, Jianlin, Li, Bei, Huang, Biyan, Yang, Guangjia, Mo, Fangling, Weng, Tingting, Chen, Guoquan, Xia, Liqun, Lu, Yishan
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Bacterial - blood; Antigens, Bacterial - chemistry; Antigens, Bacterial - genetics; Antigens, Bacterial - immunology; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - immunology; Bacterial Vaccines; DNA vaccine; Fish Diseases - prevention & control; Fishes - immunology; Heat-Shock Proteins - chemistry; Heat-Shock Proteins - genetics; Heat-Shock Proteins - immunology; Hybrid snakehead; Immunoglobulin M - blood; Nocardia - immunology; Nocardia Infections - prevention & control; Nocardia Infections - veterinary; Nocardia seriolae; Phage shock protein A (PspA); Tellurium resistance protein D (TerD); Vaccines, DNA; Virulence Factors - chemistry; Virulence Factors - genetics; Virulence Factors - immunology
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2020.08.013

Fish nocardiosis is a widespread chronic granulomatous disease in aquatic environment, which was particularly caused by Nocardia seriolae. The phage shock protein A (PspA) and tellurium resistance protein D (TerD) were identified to be the immunodominant antigens of the wild-type N. seriolae strain ZJ0503 in our previous study. In an attempt to develop effective DNA vaccines against this pathogen, PspA and TerD were used as candidates to ligate with pcDNA3.1-Flag plasmids, respectively. In addition, the abilities of these two DNA vaccines to elicit various immune responses in hybrid snakehead and supply protective efficacy against artificial challenge with N. seriolae were determined in the present study. The results showed that intramuscular injection with pcDNA-PspA and pcDNA-TerD did not exhibit cytotoxic activities in hybrid snakehead via histopathological examination. Besides, hybrid snakehead immunization with pcDNA-PspA and pcDNA-TerD could increase several non-specific immune paraments in serum, including LYZ, POD, ACP, AKP and SOD activities. Meanwhile, the pcDNA-TerD DNA vaccine could induce strongly specific antibody (IgM) titer in hybrid snakehead with a relative percent of survival (RPS) value of 83.14% against N. seriolae, while that of pcDNA-PspA DNA vaccine was displayed comparably low IgM titer with RPS value of 57.83%. Furthermore, quantitative real-time PCR assays presented that the expression of immune-related genes (MHCIα, MHCIIα, CD4, CD8α, IL-1β and TNFα) were up-regulated to various degrees after vaccination with pcDNA-PspA or pcDNA-TerD, indicating that these two DNA vaccines were able to boost humoral and cell-mediated immune responses in hybrid snakehead. Taken together, both the pcDNA-PspA and pcDNA-TerD DNA vaccines were proved to be safe, immunogenic and effective in protecting hybrid snakehead against N. seriolae infection, which can promote the development and application of DNA vaccines to control fish nocardiosis in aquaculture. •Two DNA vaccines were prepared by utilizing the ribosomal proteins (PspA and TerD) as antigens for treatment of fish nocardiosis.•Both DNA vaccines not only did not exhibit cytotoxic activities but also could boost the innate, humoral and cellular immune response in hybrid snakehead.•Two DNA vaccines show highly protective efficacy against N. seriolae infection in hybrid snakehead with relative percentage survival (RPS) of 57.83% and 83.14%, respectively.