Differentially expressed proteins in the interaction of Paracoccidioides lutzii with human monocytes.

Background: Fungi of the genus Paracoccidioides are the etiological agents of paracoccidioidomycosis, a highly prevalent mycosis in Latin America. Infection in humans occurs by the inhalation of conidia, which later revert to the form of yeast. In this context, macrophages are positioned as an important line of defense, assisting in the recognition and presentation of antigens, as well as producing reactive oxygen species that inhibit fungal spreading.

Aims: The objective of this study was to identify differentially expressed proteins during the interaction between Paracoccidioides lutzii Pb01 strain and human U937 monocytes.

Methods: Two-dimensional electrophoresis, combined with mass spectrometry, was used to evaluate the differential proteomic profiles of the fungus P. lutzii (Pb01) interacting with U937 monocytes.

Results: It was possible to identify 25 proteins differentially expressed by Pb01 alone and after interacting with U937 monocytes. Most of these proteins are directly associated with fungal metabolism for energy generation, such as glyceraldehyde-3-phosphate dehydrogenase, and intracellular adaptation to monocytes. Antioxidant proteins involved in the response to oxidative stress, such as peroxiredoxin, cytochrome, and peroxidase, were expressed in greater quantity in the interaction with monocytes, suggesting their association with survival mechanisms inside phagocytic cells. We also identified 12 proteins differentially expressed in monocytes before and after the interaction with the fungus; proteins involved in the reorganization of the cytoskeleton, such as vimentin, and proteins involved in the response to oxidative stress, such as glioxalase 1, were identified.

Conclusions: The results of this proteomic study of a P. lutzii isolate are novel, mimicking in vitro what occurs in human infections. In addition, the proteins identified may aid to understand fungal-monocyte interactions and the pathogenesis of paracoccidioidomycosis.