Passive transfer of serum from tilapia vaccinated with a Vibrio vulnificus vaccine provides protection from specific pathogen challenge

Authors: Lafrentz, Benjamin; Shoemaker, Craig

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2015
Publication Date: 3/5/2015
Publication URL: http://handle.nal.usda.gov/10113/60514
Citation: Lafrentz, B.R., Shoemaker, C.A. 2015. Passive transfer of serum from tilapia vaccinated with a Vibrio vulnificus vaccine provides protection from specific pathogen challenge. Aquaculture. 442:16-20.

Interpretive Summary: Vibrio vulnificus is an opportunistic human pathogen that can also cause disease and mortality in some important aquaculture fish species, such as tilapia. Our laboratory previously characterized a virulent strain of V. vulnificus that was recovered from sick tilapia and developed a vaccine that was effective in reducing mortality due to this pathogen in the laboratory. In that research, vaccinated tilapia generated specific antibodies against the bacterium and it was suggested that these immune components were likely involved in the protection provided by the vaccine. In this study, experiments were performed to determine whether the specific antibodies elicited by vaccination with the V. vulnificus vaccine were involved in the protection observed. Two studies were conducted in which naïve tilapia were injected with serum from vaccinated tilapia that contained antibodies specific for the pathogen. Then, these fish were infected with V. vulnificus. The results showed that naïve tilapia that received antibodies from the vaccinated fish were protected from mortality caused by V. vulnificus. These results confirmed that antibodies specific for V. vulnificus play an important role in protective immunity and suggested that detection of specific antibody in vaccinated fish may be a useful metric for predicting vaccine efficacy in the field.

Technical Abstract: Vibrio vulnificus is a Gram-negative bacterium that has been associated with disease losses in some aquaculture reared fish species. Vaccination has proven effective for reducing the impact of this disease and research has suggested that specific antibodies are important for protective immunity. The present study determined the role of antibodies specific for V. vulnificus in protection by passive immunization and identified components of the bacterium the antibodies specifically recognize. Antiserum was generated by vaccinating hybrid tilapia with a formalin killed V. vulnificus ARS-1-Br-09 bacterin. Two passive immunization experiments were conducted, with and without heat inactivation of the antiserum. In both experiments, hybrid tilapia (mean weight, 6.5 g) were passively immunized by intraperitoneal injection of antiserum or control serum and then challenged with homologous V. vulnificus 24 h post immunization. Following challenge, relative percent survival values of 86 and 90 were obtained for tilapia passively immunized with non-heated and heat inactivated antiserum, respectively. Cell lysates and lipopolysaccharide preparations from V. vulnificus ARS-1-Br-09 and a heterologous isolate (CECT 4601) were probed with the antiserum and control serum by western blot analyses to determine the specificity of the antibodies. The antibodies exhibited specificity to proteins of both isolates and to the lipopolysaccharide of only the homologous isolate. The results supported a role of specific antibodies in protection of tilapia against V. vulnificus, and suggested that shared immunogenic antigens were involved in protection previously described against heterologous isolates.