Surfactant protein D facilitates Cryptococcus neoformans infection

Area of Science:

• Immunology
• Microbiology
• Pulmonary Medicine

Background:

• Cryptococcal infections are a growing global health concern, particularly in AIDS patients, and Cryptococcus neoformans is increasingly causing disease in healthy individuals.
• While C. neoformans virulence factors are studied, host immune responses in the lungs during early infection stages remain less understood.
• Previous in vitro studies indicated pulmonary surfactant protein D (SP-D) protects C. neoformans from macrophage defenses.

Purpose of the Study:

• To investigate the role of SP-D in host response to C. neoformans infection in vivo.
• To test the hypothesis that SP-D facilitates fungal infection by protecting C. neoformans from host immune mechanisms.

Main Methods:

• Utilized SP-D deficient (SP-D⁻/⁻) mice to assess host response to C. neoformans infection.
• Administered exogenous SP-D to SP-D⁻/⁻ mice to observe reversal of protective effects.
• Evaluated SP-D binding to yeast cells and its effect on macrophage-mediated defenses and oxidative stress in vitro and in vivo.

Main Results:

• SP-D⁻/⁻ mice exhibited partial protection against C. neoformans infection, showing increased survival time and reduced fungal burden compared to wild-type mice.
• Administration of exogenous SP-D reversed the protective effect in SP-D⁻/⁻ mice.
• SP-D was found to bind to C. neoformans, shielding it from macrophage defenses and hydrogen peroxide-induced oxidative stress.

Conclusions:

• Cryptococcus neoformans can exploit host SP-D to enhance susceptibility to infection.
• SP-D plays a critical role in host susceptibility to C. neoformans, contrary to initial hypotheses based on in vitro data.
• These findings offer new insights into cryptococcosis pathogenesis and potential therapeutic targets.