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A murine model of infection with Rickettsia prowazekii: implications for pathogenesis of epidemic typhus
Yassina Bechah1, Christian Capo, Georges E Grau
1Unité des Rickettsies, CNRS UMR 6020, Université de la Méditerranée, Faculté de Médecine, 27 Bld. J. Moulin, 13385 Marseille Cedex 05, France.
Abstract:
Epidemic typhus remains a major disease threat, furthermore, its etiologic agent, Rickettsia prowazekii, is classified as a bioterrorism agent. We describe here a murine model of epidemic typhus that reproduced some features of the human disease. When BALB/c mice were inoculated intravenously with R. prowazekii (Breinl strain), they survived but did not clear R. prowazekii infection. Immunohistological analysis of tissues and quantitative PCR showed that R. prowazekii was present in blood, liver, lungs and brain 1 day after infection and persisted for at least 9 days. Importantly, infected mice developed interstitial pneumonia, with consolidation of the alveoli, hemorrhages in lungs, multifocal granulomas in liver, and hemorrhages in brain, as seen in humans. Circulating antibodies directed against R. prowazekii were detected at day 4 post-infection and steadily increased for up to 21 days, demonstrating that R. prowazekii lesions were independent of humoral immune response. R. prowazekii-induced lesions were associated with inflammatory response, as demonstrated by elevated levels of inflammatory cytokines including interferon-gamma, tumor necrosis factor and the CC chemokine RANTES in the lesions. We concluded that the BALB/c mouse strain provides a useful model for studying the pathogenic mechanisms of epidemic typhus and its control by the immune system.
Insights
A new mouse model mimics human epidemic typhus, caused by Rickettsia prowazekii. This model aids in understanding disease mechanisms and immune responses to this bioterrorism agent.
Area of Science:
- Infectious Diseases
- Immunology
- Microbiology
Background:
- Epidemic typhus, caused by Rickettsia prowazekii, is a significant public health concern and a bioterrorism agent.
- Existing models do not fully recapitulate human disease features, hindering research into pathogenesis and control.
Purpose of the Study:
- To develop and characterize a murine model of epidemic typhus.
- To investigate the early pathological and immunological responses to Rickettsia prowazekii infection in mice.
Main Methods:
- Intravenous inoculation of BALB/c mice with Rickettsia prowazekii (Breinl strain).
- Immunohistological analysis and quantitative PCR to track bacterial presence and distribution.
- Assessment of pathological lesions in various organs (lungs, liver, brain).
- Measurement of circulating antibodies and inflammatory cytokine levels (interferon-gamma, TNF-alpha, RANTES).
Main Results:
- Infected mice survived but did not clear the R. prowazekii infection, with bacteria detected for at least 9 days post-infection.
- Mice developed human-like pathology, including interstitial pneumonia, lung consolidation, liver granulomas, and brain hemorrhages.
- Lesions occurred independently of the early humoral immune response, with antibodies detected from day 4.
- Elevated levels of inflammatory cytokines were observed in infected tissues.
Conclusions:
- The BALB/c mouse model effectively reproduces key features of human epidemic typhus.
- This model is valuable for studying Rickettsia prowazekii pathogenesis and evaluating immune system control mechanisms.
- Further research using this model can inform strategies for managing epidemic typhus and bioterrorism threats.
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