Protective immunity in juvenile coho salmon Oncorhynchus kisutch following immunization with Vibrio ordalii lipopolysaccharide or from exposure to live V. ordalii cells

Naive, juvenile coho salmon Oncorhynchus kisutch were protected against an experimental challenge with the fish pathogen Vibrio ordalii following vaccination with V. ordalii lipopolysaccharide (LPS) administered by either the intraperitoneal or immersion route. Purified LPS extracted from V. ordalii cell walls (CW-LPS) and semi-purified extracellular LPS from the broth used for growing V. ordalii cells (EC-LPS) resulted in protection by each of these routes. Amounts of CW-LPS as low as 100 pg via the intraperitoneal route and 500 ng/ml via the immersion route were effective in protecting 4.8 g coho salmon against V. ordalii . Naive, juvenile coho salmon surviving bath exposure to live cells of V. ordalii also developed immunity to the pathogen. Exposure for 15 min to numbers of V. ordalii cells low enough not to cause vibriosis (2.8 x 10 super(1) to 1.1 x 10 super(6)) resulted in measurable immunity to V. ordalii).