DAO 36:37-44 (1999)  -  doi:10.3354/dao036037

Evaluation of a whole cell, p57- vaccine against Renibacterium salmoninarum

Jon D. Piganelli1,*, Gregory D. Wiens1,**, Jia Allen Zhang2, John M. Christensen2, Stephen L. Kaattari1,***

1Department of Microbiology and Center for Salmon Disease Research, Oregon State University, Corvallis, Oregon 97331, USA
2Department of Pharmacy, Oregon State University, Corvallis, Oregon 97331, USA
Present addresses: *Barbara Davis Center for Childhood Diabetes and Department of Immunology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. E-mail:
**Department of Molecular Microbiology and Immunology, Oregon Health Sciences Center, Portland, Oregon 97219, USA
***School of Marine Science, Virginia Institute of Marine Science, The College of William & Mary, Gloucester Point, Virginia 23062, USA

ABSTRACT: A whole cell Renibacterium salmoninarum vaccine was developed using 37°C heat treated cells that were subsequently formalin fixed; this treatment reduced bacterial hydrophobicity and cell associated p57. Coho salmon Oncorhynchus kisutch were immunized with the p57- vaccine by either a combination of intraperitoneal (ip) and intramuscular (im) injections or per os. In the first experiment, ip/im vaccination of coho salmon with p57- cells in Freund's Incomplete Adjuvant (FIA) conferred a statistically significant increase in mean time to death after the salmon were ip challenged with 4.1 x 106 colony forming units (cfu) of R. salmoninarum. There was no significant difference in response between fish immunized with R. salmoninarum cell surface extract in FIA and those immunized with extracellular protein (ECP) concentrated from culture supernatant in FIA. The ip challenge dose resulted in complete mortality of all fish by Day 43. In a second experiment, fish were orally vaccinated with p57- R. salmoninarum cells encased in a pH protected, enteric-coated antigen microsphere (ECAM). Fish were bath challenged with 4.2 x 106 cfu ml-1 on Day 0 and sampled at time points of 0 (pre-challenge), 50, 90, or 150 d immersion challenge. Vaccine efficacy was determined by monitoring the elaboration of p57 in the kidneys of vaccinated and control fish. Fish vaccinated orally demonstrated a significantly lower concentration of p57 (p < 0.01) at Day 150 post challenge compared to fish receiving ECAMs alone. Fish receiving p57- cells without ECAM coating also showed a significantly lower p57 level (p < 0.03) versus control. In contrast, fish injected intraperitoneally with the p57- cells or fish fed p57+ R. salmoninarum cells in ECAMs demonstrated no significant difference (p > 0.05) versus controls. In summary, these studies suggest the preliminary efficacy of 37°C treatment of R. salmoninarum cells as an oral bacterial kidney disease vaccine.

KEY WORDS: Bacterial kidney disease · Renibacterium salmoninarum · p57 · Oral vaccine

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