Paracoccidioides lutzii Plp43 is an active glucanase with partial antigenic identity with P. brasiliensis gp43

PLoS Negl Trop Dis. 2014 Aug 28;8(8):e3111. doi: 10.1371/journal.pntd.0003111. eCollection 2014 Aug.

Abstract

Background: Paracoccidioides brasiliensis and P. lutzii cause paracoccidioidomycosis (PCM). P. brasiliensis main diagnostic antigen is glycoprotein gp43, and its peptide sequence is 81% identical with a P. lutzii ortholog here called Plp43. P. lutzii ("Pb01-like") apparently predominates in Midwestern/Northern Brazil, where high percentages of false-negative reactions using P. brasiliensis antigens have recently been reported. The aim of this work was to produce recombinant Plp43 to study its antigenic identity with gp43.

Methodology: We expressed rPlp43 as a secreted major component in Pichia pastoris and studied its reactivity in immunoblot with PCM patients' sera from Southwestern and Midwestern Brazil.

Principal findings: We showed that rPlp43 is not glycosylated and bears glucanase activity. The protein did not react with anti-gp43 monoclonal antibodies in immunoblot, suggesting absence of the corresponding gp43 epitopes. Nevertheless, common epitope(s) might exist, considering that gp43-positive PCM sera recognized rPlp43 in immunoblot, while gp43-negative sera (33 out of 51) from patients resident in Midwestern Brazil were also rPlp43-negative. Two genotyped P. lutzii were from patients with gp43-negative sera, suggesting that non-reactive sera are from patients infected with this species.

Conclusion: Our data suggest that gp43 and Plp43 bear one or only a few common epitopes and that gp43 cannot be used in diagnosis of PCM patients infected with P. lutzii probably because Plp43 is poorly expressed during infection.

MeSH terms

  • Amino Acid Sequence
  • Antigens, Fungal* / chemistry
  • Antigens, Fungal* / immunology
  • Antigens, Fungal* / metabolism
  • Epitopes
  • Fungal Proteins* / chemistry
  • Fungal Proteins* / immunology
  • Fungal Proteins* / metabolism
  • Glycoproteins* / chemistry
  • Glycoproteins* / immunology
  • Glycoproteins* / metabolism
  • Glycoside Hydrolases* / chemistry
  • Glycoside Hydrolases* / immunology
  • Glycoside Hydrolases* / metabolism
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Paracoccidioides* / chemistry
  • Paracoccidioides* / classification
  • Paracoccidioides* / enzymology
  • Paracoccidioides* / immunology
  • Paracoccidioidomycosis / immunology
  • Paracoccidioidomycosis / microbiology

Substances

  • 43 kDa protein, Paracoccidioides
  • Antigens, Fungal
  • Epitopes
  • Fungal Proteins
  • Glycoproteins
  • Glycoside Hydrolases

Grants and funding

This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo: RP (06/05095-6), NPL (10/03193-6), MCV (05/535555-3) and Conselho Nacional de Desenvolvimento Científico e Tecnológico: RP (PQ303632/2004-6), PMC (PIBIC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.