Abstract
The sensitivity of the double agar gel immunodiffusion test is about 90% in patients with untreated paracoccidioidomycosis (PCM), but it is much lower in cases of relapse. In addition, serum from patients with PCM caused by Paracoccidioides lutzii, frequent in the Midwest region of Brazil, do not react with the classical antigen obtained from Pb B-339. These findings showed the need for alternative diagnostic methods, such as biological markers through proteomics. The aim of this study was to identify biomarkers for the safe identification of PCM relapse and specific proteins that could distinguish infections caused by Paracoccidioides brasiliensis from those produced by Paracoccidioides lutzii. Proteomic analysis was performed in serum from 9 patients with PCM caused by P. brasiliensis, with and without relapse, from 4 patients with PCM produced by P. lutzii, and from 3 healthy controls. The comparative evaluation of the 29 identified plasma proteins suggested that the presence of the immunoglobulin (Ig) alpha-2 chain C region and the absence of Ig heavy chain V-III TIL indicate infection by P. lutzii. In addition, the absence of complement factor B protein might be a predictor of relapse. The evaluation of these proteins in a higher number of patients should be carried out in order to validate these findings.
Highlights
Paracoccidioidomycosis (PCM) is a systemic disease caused by thermodimorphic fungi of the Paracoccidioides brasiliensis complex–P. brasiliensis and P. lutzii [1]
Group 1 (G1): consisted of five patients from the Botucatu region, with PCM caused by P. brasiliensis; these individuals presented a late relapse; Group 2 (G2): consisted of four patients from the Midwest region of Brazil, with PCM caused by P. lutzii; Group 3 (G3): was comprised of four patients from the Botucatu region, with PCM caused by P. brasiliensis; these individuals did not relapse; and
To identify the most abundant, differentially expressed proteins present in the serum of PCM patients caused by P. brasiliensis and P. lutzii, the samples were submitted to shotgun analysis, where all proteins were hydrolysed serially and subjected to the free-label analysis in a system liquid chromatography tandem mass spectrometry (MS) (LC-MSMS)
Summary
Paracoccidioidomycosis (PCM) is a systemic disease caused by thermodimorphic fungi of the Paracoccidioides brasiliensis complex–P. brasiliensis and P. lutzii [1]. The recent identification of PCM caused by P. lutzii explained the low frequency of positive serological tests in these patients when the Pb B-339 antigen, a P. brasiliensis fungus, was used. Serological proteomic biomarkers to identify Paracoccidioides species finding demonstrated the difficulty of performing both the serological diagnosis of PCM by P. lutzii and the serological follow-up during its treatment [4,5,6]. Despite the effective treatment of PCM caused by P. brasiliensis, quiescent fungi can lead to relapse, usually about five years after discontinuation of the treatment, in both acute/subacute and chronic forms [7]. The recent identification of P. lutzii has required studies to identify PCM caused by every species. That study revealed that the sensitivity of the double immunodiffusion agar gel reaction (DID) was only 45% at relapse, and that the enzyme-linked immunosorbent assay (ELISA) was slightly better (65%), but with a sensitivity level much lower than that observed in treatment-naive patients [7]
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