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Title: Protection against heterologous Streptococcus iniae isolates using a modified bacterin vaccine in Nile tilapia, Oreochromis niloticus (L.)

Author
item SHOEMAKER, CRAIG - US Department Of Agriculture (USDA)
item Lafrentz, Benjamin
item Klesius, Phillip
item Evans, Joyce

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2010
Publication Date: 6/1/2010
Citation: Shoemaker, C.A., Lafrentz, B.R., Klesius, P.H., Evans, J.J. 2010. Protection against heterologous Streptococcus iniae isolates using a modified bacterin vaccine in Nile tilapia, Oreochromis niloticus (L.). Journal of Fish Diseases. 33: 537-544.

Interpretive Summary: According to the Food and Agriculture Organization of the United Nations (FAO; 2009), in the last decade the production of tilapia (Oreochromis spp.) had increased worldwide to about 250,000 tons in 2006. Streptococcus iniae, a Gram positive bacterium, is a significant pathogen causing millions of dollars in loss to tilapia and other aquaculture production worldwide. The objectives of this study were to determine if a developed modified S. iniae bacterin vaccine was protective in Nile tilapia (Oreochromis niloticus L.) challenged with different S. iniae isolates from diverse geographic locations. The results demonstrated significant protection against all challenge isolates, and relative percent survivals ranged from 79 to 100 %. Electrophoretic analysis (SDS-PAGE) of whole-cell proteins from the S. iniae isolates demonstrated similar protein profiles between 10 and 31 kDa (molecular mass) and variation in profiles between 35 and 100 kDa. Western blot analysis using antiserum from vaccinated fish demonstrated shared immunogenic proteins among all isolates in the molecular mass range of 22-35 kDa and high molecular mass material > 150 kDa. The results suggest that the ARS developed S. iniae vaccine has broad ranging protection and should provide protection against most S. iniae isolates that infect fish.

Technical Abstract: Streptococcus iniae is a significant pathogen impacting aquaculture production worldwide. The objectives of this study were to determine if a developed modified S. iniae (ARS-98-60) bacterin vaccine is efficacious in Nile tilapia (Oreochromis niloticus L.) against challenge with heterologous isolates from diverse geographic locations and to evaluate protein and antigenic variability among the isolates tested. Two groups of tilapia (~ 5 g) were intraperitoneally (IP) vaccinated with 100 µl of the vaccine or sham-vaccinated with 100 µL of sterile tryptic soy broth and held for 28 d. Fish were challenged with each isolate by IP injection of about 20 million CFU / fish using a calcein cohabitation challenge system. The results demonstrated significant protection against all challenge isolates, and relative percent survivals ranged from 79 to 100 %. SDS-PAGE analysis of whole-cell lysate proteins from the S. iniae isolates demonstrated similar protein profiles between 10 and 31 kDa and variation in profiles between 35 and 100 kDa. Western blot analysis using antiserum from vaccinated fish (ARS-98-60) demonstrated shared immunogenic proteins among all isolates in the molecular mass range of 22-35 kDa and high molecular mass material > 150 kDa. The results suggest that the developed S. iniae vaccine has broad ranging protection among isolates exhibiting different protein profiles.