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United States Department of Agriculture

Agricultural Research Service

Title: Protective Antibody Responses Following Vaccination with Streptococcus Agalactiae in Nile Tilapia, Oreochromis Niloticus

item Pasnik, David
item Evans, Joyce
item Klesius, Phillip
item Panangala, Victor
item Shoemaker, Craig
item Shelby, Richard

Submitted to: International Aquatic Animal Health Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 2006
Publication Date: September 2, 2006
Citation: Pasnik, D.J., Evans, J.J., Klesius, P.H., Panangala, V.S., Shoemaker, C.A., Shelby, R.A. 2006. Protective antibody responses following vaccination with Streptococcus agalactiae in Nile tilapia, Oreochromis niloticus. 5th International Symposium on Aquatic Animal Health Proceedings. San Francisco, CA. September 2-6, 2006. p 210.

Technical Abstract: Experiments using Nile tilapia, Oreochromis niloticus, were conducted to further characterize a highly efficacious Streptococcus agalactiae vaccine containing extracellular products [ECP] and formalin-killed whole cells. One study assessed the efficacy of stored reconstituted S. agalactiae vaccine, which failed to significantly (p = 0.19) prevent mortality among vaccinates. Significantly lower (p < 0.0001) anti-S. agalactiae antibody levels were produced among fish administered stored ECP than fresh ECP. Western blot immunostaining revealed bands around 55 kDa in freshly-prepared ECP fractions but not in the stored fractions. The duration of protection and its correlation to S. agalactiae-specific antibodies was also evaluated. Fish were injected with fresh vaccine and challenged with S. agalactiae 47, 90, or 180 days post-vaccination (DPV), and mortalities among vaccinates were significantly lower (p < 0.05) than for controls at each time point. Specific antibody levels among vaccinates were significantly higher (p < 0.05) than among controls, with significant correlation (r2 = 0.5712 to 0.8828 though 180 DPV) between increased antibody levels and protection. Fingerling tilapia were also administered serum from S. agalactiae-immune fish and challenged with S. agalactiae. Passively-immunized fish had significantly higher (p < 0.0001) pre-challenge antibody levels than controls and significantly less (p < 0.0001) mortalities post-challenge. A highly significant (r2 = 0.5892; p < 0.0001) correlation between increased pre-challenge specific serum antibody OD levels and survival post-challenge was demonstrated. The results of these studies illustrate a strong correlation between protection and ECP-specific antibody production and also the immunogenicity of the 55 kDa ECP antigen.

Last Modified: 4/20/2015
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