Cell-mediated and innate immunity are considered the most important mechanisms of host defense against fungus infections. However, recent studies demonstrated that specific antibodies show different degrees of protection against mycosis. In a previous study, antigens secreted by Sporothrix schenckii induced a specific humoral response in infected animals, mainly against the 70-kDa molecule, indicating a possible participation of antibodies to this antigen in infection control. In the present study, an IgG1 mAb was produced against a 70-kDa glycoprotein of S. schenckii in order to better understand the effect of passive immunization of mice infected with S. schenckii. Results showed a significant reduction in the number of CFU in organs of mice when the mAb was injected before and during S. schenckii infection. Similar results were observed when T-cell-deficient mice were used. Moreover, in a second schedule treatment, the mAb was injected after infection was established, and again we observed a significant reduction in CFU associated with an increase of IFN-cproduction. Also, the 70-kDa antigen is shown to be a putative adhesin present on the surface of this fungus. In conclusion, we report for the first time the protective effect of a specific antibody against S. schenckii.Key words: Adhesins . Mab . Passive immunization . Sporothrix schenckii . Sporotrichosis IntroductionSporotrichosis is a chronic subcutaneous mycosis that occurs worldwide. However, this disease is commonly seen in tropical and subtropical regions [1]. It is caused by traumatic inoculation of the dimorphic fungus Sporothrix schenckii, which is an ubiquitous environmental saprophyte that can be isolated from soil and plant debris [2]. In the past, infections were limited to the cutaneous forms of the disease.Recently, occurrences of more severe clinical forms of this mycosis were described, especially among immunocompromised individuals [3,4].The immunological mechanisms involved in prevention and control of sporotrichosis suggest that cell-mediated immunity plays an important role in protecting The host against S. schenckii [5]. In experimental infections, athymic nude mice are more susceptible to sporotrichosis, and acquired immunity against S. schenckii is mainly mediated by T-cell-activated macrophages [6,7].In contrast, the role of the humoral immune response in protection against this fungus has not been studied in detail. In a previous study, we showed that antigens secreted by S. 3080induce a specific humoral response in infected animals, mainly against the 70-kDa molecule, indicating a possible participation of specific antibodies to this molecule in infection control [8].Cell-mediated and innate immunity are considered the most important mechanisms of host defense against fungus infections. However, recent studies demonstrated that antibodies with defined specificity show different degrees of protection against mycosis [9]. Administration of mAb-mediated protection against Paracoccidioides brasiliensis and Candida albicans and modif...

We performed a serological study with sera from 92 patients with confirmed sporotrichosis registered between 1999 and 2004 in two hospitals in Rio de Janeiro State, Brazil. The clinical presentation of sporotrichosis was distributed as follows: lymphocutaneous, 67%; fixed cutaneous, 23%; disseminated cutaneous, 8%; and extracutaneous, 2%. Sera were assayed by ELISA against a cell wall antigen of Sporothrix schenckii, SsCBF, that we have previously described. The cross-reactivity was determined with 77 heterologous sera. The serological test showed a sensitivity of 90% and a global efficiency of 86%. A group of 55 patients with several clinical presentations of sporotrichosis was clinically and serologically followed-up for at least 6 months. We observed by ELISA data a decrease in the antibody serum titers which correlated with the progress in healing. An HIV-positive patient with meningeal sporotrichosis was serologically followed-up for over 2 years. Serum and cerebrospinal fluid specimens were examined and significant antibodies levels against the antigen SsCBF were detected. Our results strongly suggest that this serological test is valuable for the differential diagnosis and follow-up of all clinical forms of sporotrichosis.

The virulence of four Sporothrix schenckii isolates was compared in a murine model of sporotrichosis, together with the protein pattern of the yeast cell surface and the capacity to bind the extracellular matrix protein fibronectin. Virulence was determined by the mortality rate, fungal burden and histopathology. Two clinical isolates were more virulent for C57BL/6 mice, but no direct correlation was seen between virulence and the clinical or environmental origin of the isolates. The lowest virulence was observed for an isolate recovered from a patient with meningeal sporotrichosis. Although all isolates could effectively disseminate, the dissemination patterns were not similar. Using flow cytometry analysis, we investigated the interaction of all the strains with fibronectin, and showed that the binding capacity correlated with virulence. Western blot analysis of S. schenckii cell wall extracts revealed positive bands for fibronectin in the range of 37-92 kDa. The 70 kDa adhesin was also recognized by a protective monoclonal antibody raised against a gp70 antigen of S. schenckii (mAb P6E7). Confocal microscopy confirmed the colocalization of fibronectin and mAb P6E7 on the yeast cell surface. To our knowledge, this is the first report identifying adhesins for fibronectin on the surface of this human pathogen.

Melanin is a complex polymer widely distributed in nature and has been described as an important virulence factor in several pathogenic fungi, including Sporothrix schenckii. The aim of the present work was to investigate the presence of melanin on the surface of S. schenckii yeast cells which showed differences in their virulence depending on the culture conditions under which they were grown. Yeast cells were cultivated in brain heart infusion (BHI) broth from Difco and Oxoid. BHI from these two vendors are different in their brain and heart infusion contents. Yeasts cultivated in the medium containing the higher brain infusion content were highly virulent as ascertained by the mice mortality rate, CFU and histopathology. Transmission electron microscopy revealed a higher expression of electron dense granules on the fungal cell wall of the most virulent yeast cells. Flow cytometry analysis, with anti-melanin antibodies, confirmed that this pigment was melanin. Furthermore, spectrophotometric analysis showed a higher concentration of this polymer on NaOH and cell wall extracts of the most virulent yeast cells. These results suggest that differences in the relative content of brain and heart infusion in the culture medium modulated melanin expression on the surface of S. schenckii yeast cells and, as a consequence, virulence. A new pathway of melanin biosynthesis in S. schenckii is proposed which involves the use of phenolic compounds from rich brain medium as melanin substrate.

Candida albicans public proteomic data sets, though growing steadily in the last few years, still have a very limited presence in online repositories. We report here the creation of a C. albicans PeptideAtlas comprising near 22000 distinct peptides at a 0.24 % False Discovery Rate (FDR) that account for over 2500 canonical proteins at a 1.2% FDR. Based on data from 16 experiments, we attained coverage of 41% of the C.albicans open reading frame sequences (ORFs) in the database used for the searches. This PeptideAtlas provides several useful features, including comprehensive protein and peptide-centered search capabilities and visualization tools that establish a solid basis for the study of basic biological mechanisms key to virulence and pathogenesis such as dimorphism, adherence, and apoptosis. Further, it is a valuable resource for the selection of candidate proteotypic peptides for targeted proteomic experiments via selected reaction monitoring (SRM) or SWATH-MS.