Protective capacity of L-form Salmonella typhimurium against murine typhoid in C3H/HeJ mice.
L forms of Salmonella typhimurium LT2 conferred strong protection to a lethal challenge with its parental bacterium on innately hypersusceptible C3H/HeJ mice, and its minimal protective dose was approximately 150 L-forming units. Although L-form S. typhimurium was avirulent for C3H/HeJ mice, it multiplied slowly in both the liver and spleen with the maximal growth 2-3 weeks after immunization and thereafter it persisted in the liver until 24 weeks. Protective immunity began to work between 4 and 6 weeks after immunization, and it remained active as long as the L forms colonized the liver (until 24 weeks after immunization). Vaccination with the L form induced a population of T cells responding to L-form whole-cell lysate (WCL), while delayed-type hypersensitivity (DTH) to the extract of S. typhimurium was induced after the establishment of solid immunity. Moreover, neither T-cell responses nor DTH to heat-killed S. typhimurium was generated. In addition, antibody responses were elicited to WCL but not to heat-killed S. typhimurium. These results indicate that protection conferred by the L forms is attributable to the persistent colonization of the L forms rather than the presence of DTH, and also that Salmonella cytoplasmic antigens are involved in induction of immunological responses by vaccination with the L forms.
Nishikawa
F
F
Department of Bacteriology, Nara Medical University, Japan.
Kita
E
E
Yamada
H
H
Nakano
A
A
Kashiba
S
S
D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis; D000942:Antigens, Bacterial; D004195:Disease Models, Animal; D005260:Female; D006968:Hypersensitivity, Delayed; D007114:Immunization; D051379:Mice; D008809:Mice, Inbred C3H; D012486:Salmonella typhimurium / Q000254:growth & development / Q000276:immunology*; D013154:Spleen / Q000276:immunology / Q000382:microbiology; D013601:T-Lymphocytes / Q000276:immunology; D013997:Time Factors; D014435:Typhoid Fever / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D014436:Typhoid-Paratyphoid Vaccines / Q000494:pharmacology
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D014436:Typhoid-Paratyphoid Vaccines