Persisting Rickettsia typhi Causes Fatal Central Nervous System Inflammation

Area of Science:

• Infectious Diseases
• Neuroscience
• Immunology

Background:

• Rickettsioses are emerging febrile diseases caused by Rickettsiaceae bacteria.
• Rickettsia typhi causes endemic typhus, a potentially fatal disease.
• The long-term effects and persistence of R. typhi are not fully understood.

Purpose of the Study:

• To investigate the course of R. typhi infection in immunocompromised mice.
• To determine if R. typhi can persist in the central nervous system.
• To examine the host immune response to persistent R. typhi infection.

Main Methods:

• Infection of C57BL/6 RAG1(-/-) mice with R. typhi.
• Monitoring of disease progression and survival.
• Analysis of bacterial load, immune cell infiltration, and neuropathology in the brain.
• Recultivation of R. typhi from tissues of infected mice.

Main Results:

• Immunocompromised mice survived initial R. typhi infection but developed lethal neurological disorders months later.
• High R. typhi loads were found in the brain, associated with microglia expansion, neuronal death, and infiltrating inflammatory macrophages.
• R. typhi was successfully recultivated from multiple tissues, including the brain, up to one year post-infection in both immunocompromised and wild-type mice.

Conclusions:

• Rickettsia typhi can persist long-term, primarily in the central nervous system, of immunocompromised mice.
• Persistent R. typhi infection can lead to severe neurological disease and death.
• This study highlights the potential for R. typhi persistence and delayed pathology in the host.