Resistance to infection with Nocardia asteroides

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Nocardia asteroides is an opportunistic pathogen causing nocardiosis.
• Understanding host resistance mechanisms is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the mechanisms of host resistance against Nocardia asteroides in a murine model.
• To determine if humoral or cellular immunity plays a primary role in Nocardia asteroides resistance.

Main Methods:

• Mice were immunized with viable Nocardia asteroides via intraperitoneal or intravenous routes.
• Immunized and control mice were challenged with Nocardia asteroides.
• Resistance transfer experiments were conducted using serum and spleen cells.
• Macrophage activation was assessed using an in vitro L-cell inhibition assay.
• Cross-resistance to Listeria monocytogenes and Toxoplasma gondii was evaluated.

Main Results:

• Mice immunized with Nocardia asteroides exhibited significant resistance to subsequent challenge.
• Resistance could not be transferred via serum or spleen cells, indicating a non-antibody mediated mechanism.
• Peritoneal macrophages from immunized mice showed activation.
• Mice infected with Listeria monocytogenes or Toxoplasma gondii, which induce macrophage activation, were resistant to Nocardia asteroides challenge.

Conclusions:

• Host resistance to Nocardia asteroides in mice is primarily mediated by activated macrophages.
• Cellular immunity, rather than humoral immunity, is key in controlling Nocardia asteroides infections.
• Macrophage-activating infections confer resistance to Nocardia asteroides.