Recognition of Fungal Components by the Host Immune System.

By being the first point of contact of the fungus with the host, the cell wall plays an important role in the pathogenesis, having many molecules that participate as antigens that are recognized by immune cells, and also that help the fungus to establish infection. The main molecules reported to trigger an immune response are chitin, glucans, oligosaccharides, proteins, melanin, phospholipids, and others, being present in the principal pathogenic fungi with clinical importance worldwide, such as Histoplasma capsulatum, Paracoccidioides brasiliensis, Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Blastomyces dermatitidis, and Sporothrix schenckii. Knowledge and understanding of how the immune system recognizes and responds to fungal antigens are relevant for the future research and development of new diagnostic tools and treatments for the control of mycosis caused by these fungi.

Anti-Candidaalbicans germ tube antibodies reduce in vitro growth and biofilm formation of C. albicans.

BACKGROUND: Invasive candidiasis by Candida albicans is associated with high morbidity and mortality, due in part to the late implementation of an appropriate antifungal therapy hindered by the lack of an early diagnosis. AIMS: We aimed to evaluate the in vitro antifungal activity of the antibodies against C. albicans germ tubes (CAGTA) raised in a rabbit model of candidemia. METHODS: We measured the effect of CAGTA activity by colorimetric XTT and crystal violet assays, and colony forming units count, both on C. albicans planktonic cells and during the course of biofilm formation and maturation. Viability and cell morphology were assessed by optical, fluorescent or scanning electron microscopy. RESULTS: CAGTA ≥50µg/ml caused a strong inhibition of C. albicans blastospores growth, and DiBAC fluorescent staining evidenced a fungicidal activity. Moreover, electron microscopy images revealed that CAGTA induced morphological alterations of the surface of C. albicans germ tubes grown free as well as in biofilm. Interestingly, CAGTA ≥80µg/ml reduced the amount of C. albicans biofilm, and this effect started at the initial adhesion stage of the biofilm formation, during the first 90min. CONCLUSIONS: This is the first report showing that CAGTA reduce C. albicans growth, and impair its metabolic activity and ability to form biofilm in vitro. The antigens recognized by CAGTA could be the basis for the development of immunization protocols that might protect against Candida infections.