Research Article: Proteomic analysis of Paracoccidioides brasiliensis complex isolates: Correlation of the levels of differentially expressed proteins with in vivo virulence

Date Published: July 2, 2019

Publisher: Public Library of Science

Author(s): Cristiane Candida do Amaral, Geisa Ferreira Fernandes, Anderson Messias Rodrigues, Eva Burger, Zoilo Pires de Camargo, Monde Ntwasa.


Paracoccidioidomycosis (PCM) is a systemic mycosis commonly found in Latin America that is caused by distinct species of Paracoccidioides genus: Paracoccidioides brasiliensis complex (S1, PS2, PS3 and PS4) and Paracoccidioides lutzii. Its pathobiology has been recently explored by different approaches to clarify the mechanisms of host-pathogen interactions underpinning PCM. The diversity of clinical forms of this disease has been attributed to both host- and fungus-related factors.

For better understanding of the molecular underpinnings of host-fungus interactions, we evaluated in vivo virulence of nine Paracoccidioides brasiliensis complex isolates and correlated it to protein expression profiles obtained by two-dimensional gel electrophoresis. Based on the recovery of viable fungi from mouse organs, the isolates were classified as those having low, moderate, or high virulence. Highly virulent isolates overexpressed proteins related to adhesion process and stress response, probably indicating important roles of those fungal proteins in regulating the colonization capacity, survival, and ability to escape host immune system reaction. Moreover, highly virulent isolates exhibited enhanced expression of glycolytic pathway enzymes concomitantly with repressed expression of succinyl-CoA ligase beta chain, a protein related to the tricarboxylic acid cycle.

Our findings may point to the mechanisms used by highly virulent P. brasiliensis isolates to withstand host immune reactions and to adapt to transient iron availability as strategies to survive and overcome stress conditions inside the host.

Partial Text

Paracoccidioidomycosis (PCM) is the most frequent endemic systemic mycosis in Latin America with high incidence in Brazil, Argentina, Colombia, and Venezuela [1, 2]. It is caused by the thermally dimorphic species of the genus Paracoccidioides. Until recently, Paracoccidioides was considered a monotypic taxon typified by Paracoccidioides brasiliensis [3]. However, the introduction of molecular phylogenetics shed light on the taxonomy of Paracoccidioides, leading to the description of new cryptic entities. To date, four phylogenetic species are recognized inside the P. brasiliensis complex: S1, PS2, PS3 and PS4 [4, 5]. P. brasiliensis sensu stricto (s. str.), formerly known as S1, is the most widely distributed agent of PCM, occurring in Brazil, Argentina, Paraguay, Uruguay, Peru and Venezuela [6]. Paracoccidioides americana (formerly known as PS2) occurs in Venezuela and Brazil, in sympatry with P. brasiliensis s. str. [6]. Paracoccidioides restrepiensis (PS3) and P. venezuelensis (PS4) are geographically restricted to Colombia and Venezuela, respectively [6]. Finally, P. lutzii, an ancient divergent of the P. brasiliensis complex occurs in Brazil with its epicenter in the Central-West region [7, 8]. A recent speciation event is assumed for species embedded in the P. brasiliensis complex (especially PS3 and PS4), whereas it seems that P. brasiliensis sensu lato (s.l.) and P. lutzii are reproductively isolated in nature [6].

In this study, we used a proteomic approach to identify proteins differentially expressed by P. brasiliensis complex isolates that exhibited different levels of virulence. Our main objective was to correlate biological roles of these proteins to respective virulence level. A total of eight up-regulated proteins were successfully identified by LC-MS/MS in highly virulent isolates. One up-regulated protein was identified in a moderately virulent isolate, and two—in isolates of low virulence. Unfortunately, other proteins with differential abundance levels could not be identified, probably because their amounts were too low to produce a good spectrum, or because the confidence levels of the database search were insufficient to yield unambiguous results.