Proteomics-Based Characterization of the Humoral Immune Response in Sporotrichosis: Toward Discovery of Potential Diagnostic and Vaccine Antigens.

BACKGROUND: Sporothrix schenckii and associated species are agents of human and animal sporotrichosis that cause large sapronoses and zoonoses worldwide. Epidemiological surveillance has highlighted an overwhelming occurrence of the highly pathogenic fungus Sporothrix brasiliensis during feline outbreaks, leading to massive transmissions to humans. Early diagnosis of feline sporotrichosis by demonstrating the presence of a surrogate marker of infection can have a key role for selecting appropriate disease control measures and minimizing zoonotic transmission to humans. METHODOLOGY: We explored the presence and diversity of serum antibodies (IgG) specific against Sporothrix antigens in cats with sporotrichosis and evaluated the utility of these antibodies for serodiagnosis. Antigen profiling included protein extracts from the closest known relatives S. brasiliensis and S. schenckii. Enzyme-linked immunosorbent assays and immunoblotting enabled us to characterize the major antigens of feline sporotrichosis from sera from cats with sporotrichosis (n = 49), healthy cats (n = 19), and cats with other diseases (n = 20). PRINCIPAL FINDINGS: Enzyme-linked immunosorbent assay-based quantitation of anti-Sporothrix IgG exhibited high sensitivity and specificity in cats with sporotrichosis (area under the curve, 1.0; 95% confidence interval, 0.94-1; P<0.0001) versus controls. The two sets of Sporothrix antigens were remarkably cross-reactive, supporting the hypothesis that antigenic epitopes may be conserved among closely related agents. One-dimensional immunoblotting indicated that 3-carboxymuconate cyclase (a 60-kDa protein in S. brasiliensis and a 70-kDa protein in S. schenckii) is the immunodominant antigen in feline sporotrichosis. Two-dimensional immunoblotting revealed six IgG-reactive isoforms of gp60 in the S. brasiliensis proteome, similar to the humoral response found in human sporotrichosis. CONCLUSIONS: A convergent IgG-response in various hosts (mice, cats, and humans) has important implications for our understanding of the coevolution of Sporothrix and its warm-blooded hosts. We propose that 3-carboxymuconate cyclase has potential for the serological diagnosis of sporotrichosis and as target for the development of an effective multi-species vaccine against sporotrichosis in animals and humans.

Immunodiagnosis of paracoccidioidomycosis due to Paracoccidioides brasiliensis using a latex test: detection of specific antibody anti-gp43 and specific antigen gp43.

BACKGROUND: Paracoccidioidomycosis (PCM) is a life-threatening systemic disease and is a neglected public health problem in many endemic regions of Latin America. Though several diagnostic methods are available, almost all of them present with some limitations. METHOD/PRINCIPLE FINDINGS: A latex immunoassay using sensitized latex particles (SLPs) with gp43 antigen, the immunodominant antigen of Paracoccidioides brasiliensis, or the monoclonal antibody mAb17c (anti-gp43) was evaluated for antibody or antigen detection in sera, cerebrospinal fluid (CSF), and bronchoalveolar lavage (BAL) from patients with PCM due to P. brasiliensis. The gp43-SLPs performed optimally to detect specific antibodies with high levels of sensitivity (98.46%, 95% CI 91.7-100.0), specificity (93.94%, 95% CI 87.3-97.7), and positive (91.4%) and negative (98.9%) predictive values. In addition, we propose the use of mAb17c-SLPs to detect circulating gp43, which would be particularly important in patients with immune deficiencies who fail to produce normal levels of immunoglobulins, achieving good levels of sensitivity (96.92%, 95% CI 89.3-99.6), specificity (88.89%, 95% CI 81.0-94.3), and positive (85.1%) and negative (97.8%) predictive values. Very good agreement between latex tests and double immune diffusion was observed for gp43-SLPs (k = 0.924) and mAb17c-SLPs (k = 0.850), which reinforces the usefulness of our tests for the rapid diagnosis of PCM in less than 10 minutes. Minor cross-reactivity occurred with sera from patients with other fungal infections. We successfully detected antigens and antibodies from CSF and BAL samples. In addition, the latex test was useful for monitoring PCM patients receiving therapy. CONCLUSIONS/SIGNIFICANCE: The high diagnostic accuracy, low cost, reduced assay time, and simplicity of this new latex test offer the potential to be commercialized and makes it an attractive diagnostic assay for use not only in clinics and medical mycology laboratories, but mainly in remote locations with limited laboratory infrastructure and/or minimally trained community health workers.

Characterization of virulence profile, protein secretion and immunogenicity of different Sporothrix schenckii sensu stricto isolates compared with S. globosa and S. brasiliensis species.

A comparative study about protein secretion, immunogenicity and virulence was performed in order to characterize and to compare eight Sporothrix schenckii sensu stricto isolates. For virulence characterization, a murine model, based on survival assay and CFU counting was used. S. brasiliensis and S. globosa, a highly virulent and a non-virulent isolates, respectively were used as external controls. Exoantigen profiles showed different secreted molecules; the 46- and 60-kDa molecules were commonly secreted by all three species. The S. schenckii s. str. isolates could be classified as non-virulent or presenting low, medium or high virulence, based on survival times after infection and recovery of viable fungi. The humoral response profiles of mice infected with S. schenckii s. str., S. globosa and S. brasiliensis were heterogeneous; five virulent isolates (S. schenckii s. str., n = 4 and S. brasiliensis, n = 1) had in common the recognition of the 60-kDa molecule by their respective antisera, suggesting that this antigen may be involved in virulence. Furthermore, the 110-kDa molecule was secreted and recognized by antisera from four virulent isolates (S. schenckii s. str., n = 3 and S. brasiliensis, n = 1), so there is a possibility that this molecule is also related to virulence. Our findings reveal different degrees of virulence in S. schenckii s. str. isolates and suggest the correlation of protein secretion and immunogenicity with virulence of S. schenckii complex. These findings provide new insights into the pathogenesis of S. schenckii s. str. and improve the knowledge about immunogenicity and protein profiles in S. schenckii complex.

Characteristics of environmental Paracoccidioides brasiliensis isolates.

The ecological niche or exact habitat of the fungus Paracoccidioides brasiliensis is not known, and few isolates have been obtained from the environment. In this study, ten isolates were analyzed with respect to antigenic composition, serology, pathogenicity, and molecular aspects. Gp43 is considered to be the molecular basis for the serodiagnosis of paracoccidioidomycosis; however, in this study only six of the environmental isolates secreted this molecule (four in great amounts and two in small amounts). Other molecules were also produced. When exoantigens from these isolates were tested using immunodiffusion, only four preparations were positive by ID tests. However, when these exoantigens were tested by ELISA, all of them except one were able to detect anti-P. brasiliensis antibodies. In Western blot assays, these exoantigens showed different reactivities. Isolates that secreted gp43 presented positive reactions for this molecule, and isolates that did not secrete gp43 gave positive reactions for other minor molecules. RAPD analysis revealed that there is great genetic variation between these environmental isolates. These isolates were non-pathogenic: no mortality was observed among the inoculated mice during an 18-month follow-up period.