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Host defenses in experimental scrub typhus: histopathological correlates
Infection and Immunity
|March 1, 1976
Summary
Mice infected with Rickettsia tsutsugamushi survived lethal scrub typhus when their immune response in the peritoneal cavity was strong. This response involved rickettsiacidal macrophages that suppressed the infection.
Area of Science:
- Immunology
- Pathology
- Microbiology
Background:
- Intraperitoneal (i.p.) infection with Rickettsia tsutsugamushi can be lethal in mice.
- Pathological alterations in lethal infections are typically confined to the peritoneal cavity, including macrophage proliferation, hepatic granulomas, splenomegaly, and peritonitis.
Purpose of the Study:
- To investigate the factors influencing survival in Rickettsia tsutsugamushi infections.
- To understand the immune mechanisms involved in controlling scrub typhus within the peritoneal cavity.
Main Methods:
- BALB/c mice were infected intraperitoneally with different strains and doses of Rickettsia tsutsugamushi.
- Mice were also infected after immunization with a different strain to assess protective immunity.
- Pathological alterations and rickettsial proliferation were examined in infected and immunized mice.
Main Results:
- Lethal Karp strain infections showed continuous rickettsial proliferation and severe pathology.
- Non-lethal infections, including those with the Gilliam strain or in immunized mice, exhibited minimal rickettsial proliferation and reduced pathology.
- Splenomegaly due to lymphoid proliferation was prominent in non-lethal and immunized infections.
Conclusions:
- Survival from intraperitoneal scrub typhus depends on a robust peritoneal immune response.
- The development of rickettsiacidal macrophages is crucial for suppressing Rickettsia tsutsugamushi infection.
- Immune protection can be achieved through specific strain infections or prior immunization.