Melanin fromFonsecaea pedrosoiInduces Production of Human Antifungal Antibodies and Enhances the Antimicrobial Efficacy of Phagocytes

Abstract

Fonsecaea pedrosoi is a fungal pathogen that produces melanin. The functions of melanin and its possible influence in the protective immunological response during infection by F. pedrosoi are not known. In this work, treatment of F. pedrosoi mycelia with proteases and glycosidases followed by a denaturing agent and hot concentrated acid left a black residue. Scanning electron microscopy demonstrated that this processed melanized residue resembled very closely the intact mycelium in shape and size. Melanin particles were also isolated from culture fluids of conidia or sclerotic forms of F. pedrosoi. Secreted melanins were reactive with sera from infected human patients, suggesting that F. pedrosoi synthesizes melanin in vivo. The antibodies against melanin were purified from patients' sera and analyzed by indirect immunofluorescence. They reacted with sclerotic cells from patients' lesions as well as with sclerotic bodies cultivated in vitro, conidia, mycelia, and digested residues. Treatment of F. pedrosoi with purified antibodies against melanin inhibited fungal growth in vitro. The interaction of F. pedrosoi with phagocytes in the presence of melanin resulted in higher levels of fungal internalization and destruction by host cells, which was accompanied by greater degrees of oxidative burst. Taken together, these results indicate that melanin from F. pedrosoi is an immunologically active fungal structure that activates humoral and cellular responses that could help the control of chromoblastomycosis by host defenses.

Miltefosine is active against Sporothrix brasiliensis isolates with in vitro low susceptibility to amphotericin B or itraconazole

“…Untreated and miltefosine-treated S. brasiliensis ATCC MYA 4823 yeast cells (treated with subinhibitory concentration (1/2 MIC) for 24 h at 35 uC) were washed in PBS, fixed in 4 % of formaldehyde in PBS, incubated with 1 % BSA for 30 min and then labelled with anti-melanin antibodies (0.1 mg ml 21 , for 30 min at room temperature) purified from sera obtained from chromoblastomycosis patients (Alviano et al, 2004). Then, samples were incubated with FITC-labelled anti-human IgG (Molecular Probes) for 30 min at room temperature and analysed in a BD Accuri C6 flow cytometer (10 000 events/sample).…”

Ab binding alters gene expression in Cryptococcus neoformans and directly modulates fungal metabolism

“…For example, specific IgM is microbicidal for Borrelia burgdorferi (1); Abs to fungal cell wall components, such as melanin (2,3) and glucosylceramide (4), are fungistatic; and a genetically recombinant mAb against cell wall HSP90 of Candida albicans is fungicidal against different species of fungi in vitro (5) and increases the fungicidal effect of amphotericin B in clinical trials (6). For encapsulated organisms like Streptococcus pneumoniae and Cryptococcus neoformans, the binding of specific Ab to the capsule can produce the phenomenon of capsular reaction ("quellung" reaction), whereby the capsule becomes visible through differential interference contrast microscopy, as a consequence of refractive index change caused by the addition of protein (7).…”

Resistance of melanized yeast cells of Paracoccidioides brasiliensis to antimicrobial oxidants and inhibition of phagocytosis using carbohydrates and monoclonal antibody to CD18

“…The following species were investigated: C. neoformans , Sporothrix schenckii (Romero-Martinez et al 2000), P. brasiliensis (Gomez et al 2001, da Silva et al 2006, Fonsecaea pedrosoi (Alviano et al 2004), Aspergillus fumigatus (Youngchim et al 2004) and C. posadasii (Nosanchuk et al 2007). Generally, a cellular immune response appears to be the most effective defence mechanism against both experimental and human PCM (Calich et al 1994, Marques Mello et al 2002, Batista et al 2005.…”