Mycobacterium avium-complex infections in normal and immunodeficient mice

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Mycobacterium avium-complex (MAC) infections pose a significant threat, particularly to individuals with Acquired Immune Deficiency Syndrome (AIDS).
• Understanding the host-pathogen interactions and immune responses is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the susceptibility of different mouse strains to MAC infection via various routes.
• To elucidate the role of T-cells in controlling MAC infections.

Main Methods:

• Aerogenic and oral challenges of specific pathogen-free mice (B6D2 F1, Balb/c, C57Bl/6, A/J) with virulent and avirulent MAC strains.
• Assessment of lung and spleen infections over several months.
• Evaluation of MAC infection in T-cell depleted (nude or Thxb) Balb/c mice.

Main Results:

• Virulent M. avium and M. intracellulare showed more extensive growth in susceptible mice (Balb/c, C57Bl/6) compared to resistant strains (A/J, B6D2).
• Oral challenge with virulent MAC caused substantial infection in gut-associated lymphoid tissues, lungs, and spleen, while avirulent strains did not establish infection.
• T-cell depletion in Balb/c mice markedly enhanced lung and spleen infections with virulent M. avium, but not with avirulent MAC strains.

Conclusions:

• T-cells play a critical role in controlling systemic infections caused by virulent M. avium-complex strains.
• The findings highlight the importance of T-cell-mediated immunity in preventing severe MAC disease, with implications for understanding MAC infections in immunocompromised individuals, such as those with AIDS.