Acute cavitary histoplasmosis in Rhesus monkeys: influence of immunological status

Area of Science:

• Mycology
• Immunology
• Infectious Diseases

Background:

• Histoplasma capsulatum is a fungal pathogen causing histoplasmosis.
• Understanding host immune responses is crucial for managing H. capsulatum infections.

Purpose of the Study:

• To investigate the relationship between immune responses and disease manifestations in a nonhuman primate model of histoplasmosis.
• To determine the roles of delayed hypersensitivity and circulating antibodies in H. capsulatum infection outcomes.

Main Methods:

• Male rhesus monkeys were immunized with H. capsulatum antigens and intratracheally infected.
• Weekly monitoring included complement fixation antibody titers, skin tests, and chest X-rays.
• Autopsy involved spleen cultures and organ dissection to assess fungal dissemination.

Main Results:

• Pulmonary cavities developed in 33% and extrapulmonary dissemination occurred in 85% of infected monkeys.
• Early delayed hypersensitivity correlated with reduced fungal dissemination.
• A delayed onset of circulating antibodies was associated with pulmonary cavity formation.

Conclusions:

• Immune responses, specifically the timing of delayed hypersensitivity, significantly influence H. capsulatum dissemination.
• The development of pulmonary cavities in histoplasmosis may be linked to delayed antibody production.