title: Mechanism of the protective immunity against murine typhoid: persistence of Salmonella L forms in the liver after immunization with live-cell vaccines.
abstract: Live-cell vaccines of Salmonella typhimurium, either a sub-lethal dose of a wild-type (strain LT2) or a high dose of its two-heptose Rd1 mutant (strain SL1004), induced acquired resistance to murine typhoid, which remained 180 days after immunization. Growth of S. typhimurium as a bacillary form ceased between days 30 and 60 of immunization, but L forms of this bacterium colonized the liver (the mean number of L forms in the liver: 600 L-forming units) even at 180 days post-immunization. In contrast, a high inoculum of either a Ra mutant (strain TV148) of strain LT2 or S. schottmülleri 8006 sharing the same O antigenic components with those of S. typhimurium induced only a short-lived protection in proportion to the number of L forms in the liver, and the protective immunity was lost before day 180. However, there was no significant difference in the salmonella-specific T-cell responses among groups of immunized mice on day 180 of immunization. A lethal infection with strain LT2 in mice which had been immunized 75 days previously with living cells of strain SL1004 resulted in a rapid clearance of the challenge inoculum, together with a rapid elevation of anti-S. typhimurium antibody responses. Thus, the present data suggest that the long-lived immunity conferred upon live S. typhimurium vaccines is attributable to the colonization of this bacterium in the liver as L forms and the ability to colonize the liver as L forms is independent of the chain length of salmonella O-antigens.
authors.affiliation: Department of Bacteriology, Nara Medical University, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Kita
authors.forename: F
authors.initials: F
authors.lastname: Nishikawa
authors.forename: N
authors.initials: N
authors.lastname: Kamikaidou
authors.forename: D
authors.initials: D
authors.lastname: Oku
authors.forename: K
authors.initials: K
authors.lastname: Yasui
authors.forename: S
authors.initials: S
authors.lastname: Kashiba
mesh_terms: D000818:Animals; D005260:Female; D007740:L Forms / Q000254:growth & development / Q000276:immunology*; D008099:Liver / Q000382:microbiology*; D051379:Mice; D012484:Salmonella paratyphi B / Q000254:growth & development / Q000276:immunology / Q000302:isolation & purification; D012485:Salmonella typhi / Q000254:growth & development / Q000276:immunology* / Q000302:isolation & purification; D013047:Specific Pathogen-Free Organisms; D013601:T-Lymphocytes / Q000276:immunology; D014435:Typhoid Fever / Q000517:prevention & control*; D014436:Typhoid-Paratyphoid Vaccines / Q000276:immunology*; D014611:Vaccination
chemical_list: D014436:Typhoid-Paratyphoid Vaccines