Phagocytosis and algicidal activity of human polymorphonuclear neutrophils against Prototheca wickerhamii

Area of Science:

• Medical Mycology
• Immunology
• Infectious Diseases

Background:

• Protothecosis is a rare infection caused by Prototheca wickerhamii.
• A recent case demonstrated successful treatment of cutaneous protothecosis in a patient with impaired polymorphonuclear neutrophil (PMN) function.
• This suggests a potential role for PMNs in combating this infection.

Purpose of the Study:

• To evaluate the role of PMNs and serum opsonins in host defense against Prototheca wickerhamii.
• To understand the mechanisms of PMN-mediated killing of P. wickerhamii.
• To identify factors essential for effective phagocytosis and clearance of the organism.

Main Methods:

• In vitro assays assessing human PMN phagocytosis and killing of P. wickerhamii.
• Ultrastructural studies using electron microscopy to visualize PMN-organism interactions.
• Experiments to determine the necessity of specific antibodies and complement components for optimal PMN function.

Main Results:

• Human PMNs demonstrated the capacity to ingest and effectively kill P. wickerhamii.
• Ultrastructural analysis confirmed the digestion of P. wickerhamii by PMNs within 60 minutes post-ingestion.
• Optimal phagocytosis and killing were dependent on the presence of both specific IgG antibodies and heat-labile opsonins.

Conclusions:

• Polymorphonuclear neutrophils are crucial in the host defense against Prototheca wickerhamii.
• Specific IgG antibodies and heat-labile opsonins are essential for efficient PMN-mediated clearance of P. wickerhamii.
• These findings elucidate key components of the immune response required to control protothecosis.