In vitro interactions between rabbit alveolar macrophages and Pasteurella tularensis. J. Bacteriol. 92:645-651. 1966.-Rabbit alveolar macrophages were successfully employed in a study of host cell-Pasteurella tularensis interactions in vitro. Under cell culture conditions in which inhibitory antibiotics were not employed and small infection ratios were used, the relative in vivo virulence of two strains of P. tularensis was duplicated. As a consequence of intracellular multiplication, normal macrophages were killed in relation to the virulence of the strain employed. Alveolar macrophages were also collected from une rabbits, and macrophage mortality and bacterial growth were significantly suppressed below levels observed with normal macrophage preparations. The effect of iune serum could only be ascribed a minor role in the observed reactions. A marked intravenous toxicity of P. tularensis for the rabbit was observed with both virulent and attenuated strains. The toxicity was possessed only by viable preparations and could be elicited in animals immune to virulent challenge.

Ether-water (EW) extraction of Pasteurella tularensis produced better antigens than five other chemical procedures. EW extracts produced from stationary-phase, liquid-grown, saline suspensions of strain SCHU S4 cells regularly induced agglutinin and precipitin formation in rabbits. Mice, guinea pigs, and monkeys also responded to EW extracts but with lower antibody levels. The use of strains of lower virulence, acetone-dried cells, organisms grown on a solid medium, and abbreviated extraction conditions all resulted in extracts with a diminished antigenicity, but logarithmicphase and stationary-phase cells yielded equivalent EW extracts. The use of adjuvant, hyperimmunization, and large doses of antigen increased the precipitin responses of rabbits without appreciably altering the agglutinin response. By the appropriate combination of centrifugal fractionation of EW extracts, use of adjuvant, and vaccination schedule, rabbit antisera with either predominantly agglutinating or precipitating activities were obtained.

The response of the rabbit to viable or killed whole-cell Pasteurella tularensis vaccines was studied. The most practical preparation for the production of anti-P. tularensis antibodies was viable organisms of the live vaccine strain (LVS). The intravenous route of administration proved superior to either the subcutaneous or intradermal routes, and incorporation of LVS into Freund's adjuvants did not result in increased levels of antibody. Short-term hyperimmunization, three injections at weekly intervals, constituted the most efficient method for increasing levels of the antibodies.

No abstract

The response of the rabbit to viable or killed whole-cell Pasteurella tularensis vaccines was studied. The most practical preparation for the production of anti- P. tularensis antibodies was viable organisms of the live vaccine strain (LVS). The intravenous route of administration proved superior to either the subcutaneous or intradermal routes, and incorporation of LVS into Freund's adjuvants did not result in increased levels of antibody. Short-term hyperimmunization, three injections at weekly intervals, constituted the most efficient method for increasing levels of the antibodies.

No abstract

To delineate dfifrenL:es in the resistanca of irradiated and nonirradLatod animals to live tularemia vAccines, the chronological appearance and growth rate of LVS in the lung, liver, spleen, and blood of guinea pigs were studied. Nonlcradlaced controls and guinea pigs having received 140 R three days previoualy were exposed via the rizp'rttory route to.: 1.0 cells of LVS and sacrificed at Intervals from one to 21 days, No major difference* were noted in the time of spprarance, growth rate, zaximust organissm content, or time o: clearance of LVS from the tissues of Irradiated and nonirradis•td animals;

A schedule was developed for the simultaneous production of a Pasteurella tularensis-Brucella abortus antiserum in rabbits. Three doses of 101 viable P. tularensis LVS organisms were given intravenously at weekly intervals. One day prior to the final dose of P. tularensis, the rabbits received 109 viable cells of B. abortus strain 19 intravenously. The use of live vaccines, administered in this sequence, resulted in high agglutinin titers within 3 weeks. The maximal agglutinin titer to either organism was observed 1 week after the final injection. A single antiserum capable of reacting with more than one bacterium could facilitate serological testing and studies by serving as a screening reagent. A procedure was developed for the production of anti-Pasteurella tularensis antisera in rabbits by using the attenuated vaccine strain LVS (4). The purpose of the present study was to determine the feasibility of producing a bivalent antiserum by combined vaccination of rabbits with viable Brucella abortus strain 19 and P. tularensis LVS. MATERIALS AND METHODS Animals. New Zealand white rabbits weighing between 1.8 and 2.5 kg were used. Except where noted, all experimental groups contained five animals. Vaccines. The production and administration of viable tularemia vaccine have been reported (4). Desiccated B. abortus strain 19 vaccine was obtained