Abstract
Channel catfish farming dominates the aquaculture industry in the United States. However, epidemic outbreaks of motile Aeromonas septicemia (MAS), caused by virulent Aeromonas hydrophila (vAh), have become a prominent problem in the catfish industry. Although vaccination is an effective preventive method, there is no vaccine available against MAS. Recombinant proteins could induce protective immunity. Thus, in this work, vAh ATPase protein was expressed, and its protective capability was evaluated in catfish. The purified recombinant ATPase protein was injected into catfish, followed by experimental infection with A. hydrophila strain ML09-119 after 21 days. Results showed catfish immunized with ATPase exhibited 89.16% relative percent survival after challenge with A. hydrophila strain ML09-119. Bacterial concentrations in liver, spleen, and anterior kidney were significantly lower in vaccinated fish compared with the non-vaccinated sham group at 48 h post-infection (p < 0.05). Catfish immunized with ATPase showed a significant (p < 0.05) higher antibody response compared to the non-vaccinated groups. Overall, ATPase recombinant protein has demonstrated potential to stimulate protective immunity in catfish against virulent A. hydrophila infection.
Highlights
Aquaculture is an approximately $1.2 billion industry, and catfish production is a mainstay of the U.S aquaculture industry, accounting for $386 million in 2016 [1]
Catfish fingerlings immunized with recombinant ATPase protein showed 4.72% mortality (89.16% relative percent survival (RPS)), which was significantly lower (p < 0.01) than both non-vaccinated groups: PBSadjuvant (29.55% mortality) and phosphate buffered saline (PBS)-only (43.51% mortality) groups (Figure 2)
There was no significant difference (p > 0.05) in antibody response between recombinant ATPase vaccinated and nonvaccinated catfish when enzyme-linked immunosorbent assay (ELISA) plates were coated with whole bacteria lysate (Figure 4A)
Summary
Aquaculture is an approximately $1.2 billion industry, and catfish production is a mainstay of the U.S aquaculture industry, accounting for $386 million in 2016 [1]. The three bacterial species responsible for most of these losses are Edwardsiella ictaluri, Flavobacterium columnare, and Aeromonas hydrophila. These pathogens are the causative agents of enteric septicemia of catfish (ESC), columnaris disease, and motile Aeromonas septicemia (MAS), respectively [4, 5]. Since 2009, a clonal group of A. hydrophila strains (referred to as virulent A. hydrophila or vAh) has become a major pathogen of farm-raised channel catfish, causing motile Aeromonas septicemia (MAS) outbreaks [6]. Estimated losses in ponds with disease outbreaks of vAh infection ranged from 4,000 to 10,000 pounds lost (about 8,000–15,000 fish), Recombinant vAh ATPase Vaccine for Catfish and pond mortality rates can be very high (close to 100%). In the last decade, $60–70 million in losses to the U.S aquaculture industry have been attributed to MAS outbreaks due to mortalities, lost feeding days, and costs associated with antimicrobial therapy [9]
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