This study examined whether three human plasma proteins—albumin, fibrinogen, and transferrin—bind to Candida species using immunofluorescence assays. The researchers found that all three proteins bound with high avidity exclusively to germ-tubes of Candida albicans, not to blastospores (yeast form) of C. albicans or other Candida species. Fibrinogen showed the strongest binding affinity, followed by transferrin and albumin. Protein binding to germ-tubes varied depending on the growth medium used and showed cell-to-cell variation in intensity. When whole human serum or plasma was used instead of purified proteins, binding patterns differed significantly, with proteins appearing on both germ-tubes and parent blastospores. Treatment with azole antifungal drugs did not affect protein binding ability. Notably, a C. albicans strain with reduced virulence in mice bound plasma proteins more avidly than most other strains, suggesting that plasma protein binding may not directly correlate with fungal virulence in vivo.

Key findings

• All three purified plasma proteins bound exclusively to C. albicans germ-tubes, not to blastospores or other Candida species, with fibrinogen showing highest binding affinity
• Protein binding to germ-tubes varied significantly with growth medium, with EMEM and NAG media supporting higher binding than AAS or MSAB
• Whole human serum and plasma produced different binding patterns than purified proteins, with fluorescence detected on both germ-tubes and blastospores, suggesting nonspecific interactions
• A C. albicans strain with attenuated virulence for mice showed the highest plasma protein binding capacity, indicating plasma protein binding may not be essential for virulence