Paracoccidioides brasiliensis interferes on dendritic cells maturation by inhibiting PGE2 production.

Paracoccidioidomycosis (PCM) is a systemic mycosis, endemic in most Latin American countries, especially in Brazil, whose etiologic agent is the thermodimorphic fungus of the genus Paracoccidioides, comprising cryptic species of Paracoccidioides brasiliensis, S1, PS2, PS3 and Paracoccidioides lutzii. The mechanisms involved in the initial interaction of the fungus with cells of the innate immune response, as dendritic cells (DCs), deserve to be studied. Prostaglandins (PGs) are eicosanoids that play an important role in modulating functions of immune cells including DCs. Here we found that human immature DCs derived from the differentiation of monocytes cultured with GM-CSF and IL-4 release substantial concentrations of PGE2, which, however, were significantly inhibited after challenge with P. brasiliensis. In vitro blocking of pattern recognition receptors (PRRs) by monoclonal antibodies showed the involvement of mannose receptor (MR) in PGE2 inhibition by the fungus. In addition, phenotyping assays showed that after challenge with the fungus, DCs do not change their phenotype of immature cells to mature ones, as well as do not produce IL-12 p70 or adequate concentrations of TNF-α. Assays using exogenous PGE2 confirmed an association between PGE2 inhibition and failure of cells to phenotypically mature in response to P. brasiliensis. We conclude that a P. brasiliensis evasion mechanism exists associated to a dysregulation on DC maturation. These findings may provide novel information for the understanding of the complex interplay between the host and this fungus.

Human neutrophils produce IL-12, IL-10, PGE2 and LTB4 in response to Paracoccidioides brasiliensis. Involvement of TLR2, mannose receptor and dectin-1.

The functions of phagocytic cells against pathogens are initiated by the interaction between membrane receptors and molecular structures which compose the cell wall of these microorganisms. Thus our study aimed to identify the neutrophil receptors involved in the recognition of different strains of Paracoccidioides brasiliensis and the consequent modulation of immune response through the production of cytokines and inflammatory mediators. Neutrophils did not produce TNF-alfa in response to both strains. However, these cells produce IL-12, mainly in response to Pb 265, with participation of TLR2 and dectin-1. These cells also produce L-10, whose levels were higher for Pb 18 with involvement of TLR2 and MR and only TLR2 for Pb 265. The production of PGE2 and LTB4 was detected similarly for the two strains. For PGE2, MR and dectin-1 were involved, while in relation to LTB4, none of them. In summary, we demonstrated that neutrophils have a dynamic role during host immune response to P. brasiliensis, since in addition to their role as effector cells of innate immunity; they have the capacity to modulate innate and adaptative immune response against this fungus by producing cytokines and lipidic mediators. This modulation may be toward a pró- or anti-inflammatory pattern in a dependence of P. brasiliensis strains and PRR involved in fungus recognition by these cells.