Certain immunological responses of wild rodents and laboratory animals following challenge with Pasteurella tularensis.

Five species of wild rodents native to the Great Salt Lake Basin have been found to produce a characteristic cutaneous response to intradermal injection of various Past. tularensis preparations, following challenge with viable Past. tularensis organisms. An area of in duration was produced which reached maximal size at 48 hours following intradermal injection of the Past. tularensis preparations. Histologically this reaction appeared to be a typical acute inflammatory process. Cutaneous sensitivity as a result of intradermal injection of heat killed Past. tularensis cells into challenged deer mice, Ord kangaroo rats, and desert wood rats persisted for up to 53, 40 and 25 weeks respectively. Deer mice challenged with Br. suis did not react to intradermal injection of heat killed Schu A strain cells whereas reactors were observed among deer mice challenged the Br. neotomae. White mice, guinea pigs and albino rabbits challenged with Past. tularensis were also observed to develop characteristic responses following intradermal injection of various Past. tularensis preparations. The cutaneous response of the challenged white mice was similar to that of the challenged wild rodents. In challenged guinea pigs the cutaneous response was one of edema and erythema which was maximal 24 hours after skin test. The response of rabbits to intradermal injection of Past. tularensis preparation was an erythematous area attaining a maximum size 48 hours after skin tests. The occurrence and development of cutaneous sensitivity in guinea pigs following challenge with Past. tularensis, strain Jap4, was studies. It was observed that cutaneous sensitivity may develop 4 to 5 days following challenge. Passive transfer studies with peritoneal exudate cells indicated a lack of detectable delayed hypersensitivity during the first week following challenge. However, delayed hypersensitivity was demonstrated in guinea pigs two, three and four weeks following challenge with the Jap4 strain Past. tularensis. A method of quantitative determination of Past. tularensis antibody precipitated by polysaccharide was established and used to determine the antibody nitrogen necessary to evoke local cutaneous sensitivity to Past. tularensis skin test antigens in normal rabbits and guinea pigs. Experimental evidence demonstrated that the cutaneous response of Past. tularensis challenged guinea pigs to intradermal injection of polysaccharide was similar to the Arthus type of reaction. It was also demonstrated that the cutaneous response of challenged guinea pigs to intradermal injections of heat killed Past. tularensis Schu A organisms was a combination of the Arthus type and the delayed type of hypersensitivity response. The persistence of Past. tularensis complement fixing and agglutinating antibodies in Past. tularensis Jap4 challenged deer mice, Ord kangaroo rats and wood rats was studied. The deer mice complement fixing antibody persisted for 31 weeks and agglutinating antibody for 25 weeks. Antibody detected by both tests persisted in Ord kangaroo rats for at least 40 weeks, although the agglutinin titers were much higher than the complement fixing titers. In challenged wood rats, both tests were positive in some animals 25 weeks following challenge. The relative values of the skin tests, agglutination test, and complement fixation test to detect Past. tularensis infection in rodents were discussed.