Effectiveness of immunization with single and multi-component vaccines prepared from a common antigen (OEP), protease and elastase toxoids of Pseudomonas aeruginosa on protection against hemorrhagic pneumonia in mink due to P. aeruginosa

Abstract

Toxoids of protease and elastase of Pseudomonas aeruginosa were successfully prepared by treatment with 8% formalin plus 0.2 m lysine and by 4% formalin respectively. The two toxoids proved sufficiently potent to elicit high antibody titers as estimated by both the enzyme-neutralizing and passive hemagglutination tests. The effectiveness of immunizing minks with a single component-vaccine consisting of the common antigen (OEP) of P. aeruginosa or the protease toxoid (PT) or the elastase toxoid (ET) and with the two (PT and ET) or the three (OEP, PT and ET) component-mixed vaccines, on hemorrhagic pneumonia in minks due to the bacteria was investigated. Female Sapphire minks, 3.5 months old, were used in two experiments performed in 1975 and 1976. Minks were immunized three times in one month with a total of 1 mg of each of the three antigens in the case of a single component vaccine and with a total of 2 or 3 mg (equal amounts of each component) in the case of the two or three component vaccines. Two or three weeks after the last immunization, challenge exposure with strain No. 5 was carried out by intranasally inoculating an inoculum containing serial dilutions of 10(3) -10(10) of live bacteria. Summarizing the results of the two experiments, in the case of controls, nonimmunized minks and minks immunized with potassium aluminum sulfate (potash alum) alone, the LD50 values were approximately 10(3) -10(4) with no significant difference between the two. In the case of OEP-vaccinated minks, the LD50 value was about 10(6) and thus clearly differed from those of the controls. In minks immunized with the three-component-vaccine, however, the LD50 value was about 10(8) -10(9), which indicated that the three-component-mixed vaccine was remarkably more effective than the single OEP vaccine component. In minks immunized with either PT or ET or both, the LD50 values were about 10(8) -10(9). The effectiveness of the vaccine made with ET or PT alone is discussed in the text. The pathological findings of the minks which died or survived are described.