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

PLoS Negl Trop Dis. 2015 Aug 25;9(8):e0004016. doi: 10.1371/journal.pntd.0004016. eCollection 2015.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Fungal / blood
  • Antibodies, Fungal / immunology*
  • Antigens, Fungal / analysis
  • Antigens, Fungal / immunology
  • Cat Diseases / diagnosis
  • Cat Diseases / immunology*
  • Cat Diseases / microbiology
  • Cats
  • Cross Reactions
  • Electrophoresis, Gel, Two-Dimensional
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Immunity, Humoral*
  • Immunoblotting
  • Immunoglobulin G / immunology*
  • Mice
  • Proteomics
  • Serologic Tests
  • Sporothrix / chemistry
  • Sporothrix / immunology*
  • Sporotrichosis / diagnosis
  • Sporotrichosis / immunology*
  • Sporotrichosis / microbiology
  • Sporotrichosis / veterinary*
  • Zoonoses / diagnosis
  • Zoonoses / immunology
  • Zoonoses / microbiology

Substances

  • Antibodies, Fungal
  • Antigens, Fungal
  • Immunoglobulin G

Grant support

ZPdC acknowledge financial support from the São Paulo Research Foundation (FAPESP 2009/54024-2) and the National Council for Scientific and Technological Development (CNPq). AMR (FAPESP 2011/07350-1) and GFF (FAPESP 2011/01628-8) are São Paulo Research Foundation fellows. SAP thanks Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Young Scientist 2013. LMA, PPDT, LMLB, and TMPS are CNPq fellows. This study was supported in part by grants from São Paulo Research Foundation (http://www.fapesp.br/), the National Council for Scientific and Technological Development (http://www.cnpq.br/), and the Coordination for the improvement of higher education (http://www.capes.gov.br/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.