Interferon-gamma mediates long-term persistent Chlamydia psittaci infection in vitro

Area of Science:

• Veterinary Medicine
• Immunology
• Microbiology

Background:

• Chlamydia psittaci is an important veterinary pathogen.
• Interferon gamma is a key cytokine in immune responses.
• Understanding long-term effects of treatments is crucial for disease control.

Purpose of the Study:

• To investigate the long-term anti-chlamydial effects of recombinant ovine interferon gamma (rOvIFN-gamma).
• To determine the minimum effective concentration and duration of rOvIFN-gamma treatment against Chlamydia psittaci.

Main Methods:

• Ovine ST-6 fibroblasts were infected with Chlamydia psittaci.
• Recombinant ovine interferon gamma (rOvIFN-gamma) was applied at various concentrations.
• Chlamydial multiplication was assessed using ELISA, IFU titrations, and inclusion body enumeration.

Main Results:

• rOvIFN-gamma at 250 and 1000 U/ml exhibited microbistatic effects, becoming microbicidal after 14 days.
• Lower concentrations (25 and 100 U/ml) inhibited growth but allowed chlamydiae re-emergence upon removal.
• Re-emergence was faster at 25 U/ml compared to 100 U/ml, leading to fibroblast death.

Conclusions:

• Sustained high-dose rOvIFN-gamma can achieve microbicidal activity against Chlamydia psittaci.
• Intermittent or low-dose rOvIFN-gamma may not provide complete eradication and risks pathogen re-emergence.
• Further research into optimal dosing and duration for effective Chlamydia psittaci treatment is warranted.