|Streptococcus agalactiae vaccination in fish
Streptococcus agalactiae is a well-known bacterium in mammals. But it is also a major pathogen in a diversity of fish species, leading to serious economic losses in many species of freshwater, marine and estuarine fish worldwide. Is the new vaccine the right choice?|
|A highly efficacious S. agalactiae vaccine was developed using extracellular products (ECP) and formalin-killed whole cells of S. agalactiae. The vaccine efficacy following storage of S. agalactiae ECP and formalin-killed S. agalactiae cells at 4 Â°C for 1 year was determined.
The stored ECP containing S. agalactiae formalin-killed cells failed to prevent morbidity and mortality among the vaccinated fish, and the relative percentage survival was 29.
Serum antibody responses of the stored ECP and freshly prepared ECP against soluble whole cell extract of S. agalactiae indicated that significantly less antibody was produced in fish immunized with stored ECP and S. agalactiae cells than in those fish immunized with freshly prepared ECP and S. agalactiae cells at day 31 post-vaccination.
Silver staining of sodium dodecyl sulphate-polyacrylamide gels and immunostaining of Western blots with tilapia antiserum to S. agalactiae revealed that predominant 54 and 55 kDa bands were present in the freshly prepared ECP fraction.
The 55 kDa band was absent from the stored ECP and new bands below 54 kDa appeared on the Western blot.
The results of this study on S. agalactiae ECP provide evidence for a correlation between protection and antibody production to ECP and for the importance of the 55 kDa ECP antigen for vaccine efficacy.
Source: Pasnik, D J, Evans, J J, Panangala, V S, Klesius, P H, Shelby, R A & Shoemaker, C A (2005):
Antigenicity of Streptococcus agalactiae extracellular products and vaccine efficacy. In:
Journal of Fish Diseases 28 (4), 205-212.
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