Cloning, expression, and immunogenicity of Flavobacterium columnare heat shock protein dnaJ

Protective efficacy of four heat-shock proteins as recombinant vaccines against photobacteriosis in Asian seabass (Lates calcarifer)

Photobacterium damselae subsp. piscicida (Phdp) is the causative agent of photobacteriosis in marine fish and is responsible for huge losses to marine aquaculture worldwide. Efforts have been made to develop a vaccine against this disease. Heat-shock proteins (HSPs) are a family of proteins that are ubiquitous in cellular life. Bacteria produce elevated levels of HSPs as a survival strategy when exposed to stressful environments in a host during infection. This group of proteins are also important antigens that can induce both humoral and cellular immune responses. In this study, four HSPs of Phdp, HSP90, HSP33, HSP70, and DnaJ, were selected for cloning and recombinant expression. Western blotting with rabbit anti-Phdp helped identify rHSP70 and rHSP33 as immunogenic proteins. Asian seabass (Lates calcarifer) immunised with rHSP90, rHSP33, rHSP70, and rDnaJ showed 48.28%, 62.07%, 51.72%, and 31.03% relative percent survival, respectively, after being challenged with Phdp strain AOD105021. High expression levels of immune-related genes and high antibody titres were observed in the rHSP33 group, and the sera of this group also exhibited a high level of bactericidal activity against Phdp. Collectively, our results suggest that HSP33 is a potential candidate for vaccine development against Phdp infection.

Development of fish vaccine in Southeast Asia: A challenge for the sustainability of SE Asia aquaculture

Southeast (SE) Asia plays an important role in global food security as this region has been regarded as one of the major producers of aquaculture product and, to date, freshwater fish accounted for one-third of the total aquaculture in SE Asia. The intensification of freshwater farming corresponding to increase of consumer demands has inevitably led to the emergence and re-emergence of diseases causing tremendous economic loss in the region. Nile tilapia (Oreochromis niloticus) and striped catfish (Pangasianodon hypophthalmus), the major freshwater fish species of SE Asia, have been reported susceptible to several bacterial pathogens, e.g. Streptococcus agalactiae, Edwardsiella ictalurid and Flavobacterium columnare. Since only a limited number of vaccines being registered and marketed, these pathogenic organisms still represent a severe threat to aquaculture industry in SE Asia. However, there is profound advancement in the understanding of disease epidemiology, pathogenic mechanisms, teleost mucosal immunity and vaccine delivery system over the last few years. This review aimed to summarize those recent findings which hopefully can provide novel insight into the future development of suitable vaccine and vaccination regime against bacterial infection in SE Asia region.

Identification of immunogenic proteins of Flavobacterium columnare by two-dimensional electrophoresis immunoblotting with antibacterial sera from grass carp, Ctenopharyngodon idella (Valenciennes)

Flavobacterium columnare is a Gram-negative bacterium causing columnaris disease of freshwater fish worldwide, and development of efficacious vaccines has been a continuous challenge in aquaculture. In this study, 14 proteins were identified from cellular components of F. columnare using an immunoblotting approach in two-dimensional electrophoresis map gels with antibacterial sera from grass carp, Ctenopharyngodon idella (Valenciennes), and then anti-grass carp-recombinant Ig (rIg) polyclonal antibodies. These proteins were characterized conclusively by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF/TOF MS). The 14 proteins are immunogenic molecules of F. columnare, including chaperonins DnaK, GroEL and trigger factor, and translation elongation factor G, translation elongation factor Tu, 30S ribosomal subunit protein S1, dihydrolipoamide succinyltransferase, succinyl-CoA synthetase, SpoOJ regulator protein, alcohol dehydrogenase, fructose-bisphosphate aldolase, 3-hydroxybutyryl-CoA dehydrogenase and two conserved hypothetical proteins. These identified immunogenic proteins may provide candidate molecules for the development of vaccines against columnaris disease.

Use of vaccination against enteric septicemia of catfish and columnaris disease by the U.S. catfish industry

Vaccination is an effective strategy used for the protection of food animals against infectious diseases. A 2010 U.S. Department of Agriculture questionnaire examined U.S. catfish industry use (in 2009) of two commercial vaccines that provide protection against enteric septicemia of catfish (ESC) and columnaris disease, catfish producers' opinions regarding the percentage of vaccinated fish they expect to be protected, and producers' general expectations regarding survival of vaccinated fish compared with unvaccinated fish. During 2009, 9.7% of the total fingerling operations used one or both vaccines; 12.3% of the total industry fry production was vaccinated against ESC, and 17.0% was vaccinated against columnaris disease. Of the producers who grew food-sized catfish to harvest, 6.7% used vaccinated catfish. The farms that did not use vaccinated fish for grow out had a mean size of 63.4 water surface hectares (156.6 water surface acres). The operations that used vaccinated fish were larger (mean size = 206.6 water surface hectares, or 510.6 water surface acres). The producers that stocked ESC-vaccinated fish for grow out represented 19.0% of the total water surface area of food fish production; producers that stocked columnaris-vaccinated fish represented 16.6% of the total area. Of the producers that stocked ESC-vaccinated catfish, 41.9% thought that survival was better in vaccinated fish than in unvaccinated fish; of the producers that stocked columnaris-vaccinated catfish, 46.2% thought that vaccinated fish displayed better survival. However, 37.5% of producers that used the ESC vaccine and 39.7% of producers that used the columnaris vaccine did not know whether vaccination improved survival rates. When all producers were asked about their expectations regarding the percentage of vaccinated fish that would be protected from disease, 52.4% responded that they expected 100% of their fish to be protected. More producer information about reasonable expectations regarding vaccine efficacy, the conditions under which immunosuppression and vaccine failure can occur, and assessment of vaccine performance may result in increased use of vaccination as a tool for the catfish industry.

Edwardsiella tarda DnaJ is a virulence-associated molecular chaperone with immunoprotective potential

Members of the DnaJ/Hsp40 family play an important role in protein homeostasis by regulating the activity of DnaK/Hsp70. In this study, we examined the activity and function of the DnaJ from Edwardsiella tarda, a serious fish pathogen that can also infect humans and birds. In silico analysis indicated that E. tarda DnaJ contains structural features, i.e. the J domain, the glycine/phenylalanine-rich region, and the zinc-finger domain, that are conserved among Type I Hsp40. Purified recombinant DnaJ was able to stimulate the ATPase activity of DnaK. Pull-down assay indicated that DnaJ could interact specifically with DnaK. Mutation of the conserved HPD site in the J domain completely abolished the DnaK-stimulating effect of DnaJ. To examine the functional importance of DnaJ, a dnaJ-defective mutant was constructed. Compared to the wild type, the dnaJ mutant (i) was retarded in growth and more sensitive to H₂O₂-induced oxidative damage, (ii) dramatically reduced in general bacterial virulence and in blood dissemination capacity, and (iii) significantly weakened in the ability to block macrophage activation and to survive within macrophages. Furthermore, when used as a subunit vaccine, purified recombinant DnaJ induced protective immunity in Japanese flounder (Paralichthys olivaceus). Taken together, these results indicate that DnaJ plays an important role in the pathogenesis of E. tarda probably by functioning as a DnaK partner and that DnaJ, with its immunoprotective property, may be useful in the control of E. tarda infection in aquaculture.