Paracoccidioides lutzii Plp43 Is an Active Glucanase with Partial Antigenic Identity with P. brasiliensis gp43

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. © 2014 leitão jr.