Mechanism of the protective immunity against murine typhoid: persistence of salmonella L forms in the liver after immunization with live-cell vaccines |
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Authors: | Eiji Kita Fumiko Nishikawa Noriaki Kamikaidou Daisuke Oku Kiyoshi Yasui Shuzo Kashiba |
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Institution: | Department of Bacteriology, Nara Medical University, Kashihara, Nara, Japan |
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Abstract: | 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 immunozation. 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 brain length of salmonella O-antigens. |
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Keywords: | Murine typhoid L form Salmonella typhimurium Salmonella schottmülleri |
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