M.L. Landolt D.B. Powell J. R. Winton M.N. Barnes 1998 <p><i>Piscirickettsia salmonis</i><span> is the etiological agent of salmonid rickettsial septicemia, an economically significant disease affecting the salmon aquaculture industry. As with other rickettsial pathogens, antigenic analysis of </span><i>P. salmonis</i><span> has been limited by the inherent difficulties of purifying an intracellular organism away from host cell material. In this report, we describe the use of diatrizoate meglumine and diatrizoate sodium (DMDS) density gradient centrifugation to purify </span><i>P. salmonis</i><span> grown in chinook salmon embryo (CHSE-214) cells. Plaque assay titers and total protein assays confirmed that viable </span><i>P. salmonis </i><span>was consistently concentrated in a visible band within the DMDS density gradient at a density of 1.15 to 1.16 g ml</span>^-1<span>. Recovery of purified, viable organisms from DMDS density gradients varied from 0.6 to 3%. Preparations of uninfected CHSE-214 cells, CHSE-214 cells infected with </span><i>P. salmonis</i><span>, and gradient-purified </span><i>P. salmonis</i><span> were compared using sodium dodecyl sulfate polyacrylamide gel electrophoresis to assess the degree of purification and to identify </span><i>P. salmonis</i><span>-specific proteins. Although gradient-purified </span><i>P. salmonis</i><span> preparations were not completely free of host cell material, 8 bacterial proteins were identified. Polyclonal rabbit antiserum was used in an immunoblot of proteins from purified </span><i>P. salmonis</i><span> to identify 3 major and 5 minor antigens. The major antigens of 56, 30 and 20 kDa were potential candidates for experimental vaccines and development of novel diagnostic assays.</span></p> application/pdf 10.3354/dao033033 en Inter-Research Science Center Purification of <i>Piscirickettsia salmonis</i> and partial characterisation of antigens article