Neutrophil-suppressive activity over T-cell proliferation and fungal clearance in a murine model of Fonsecaea pedrosoi infection.

Neutrophils are essential to control several fungal infections. These cells are commonly known for their pro-inflammatory activities. However, some studies have demonstrated the anti-inflammatory properties of neutrophils during certain infectious diseases, culminating in the inhibition of T cell proliferation. Chromoblastomycosis (CBM) is a deep and progressive mycosis that affects thousands of people worldwide. Although neutrophil infiltrates are observed in the lesion histopathology, the fungus can overtake the immune system response and destroy the host-infected tissue. The present study demonstrated that neutropenic animals had an increase in the IL-6 production in the spleen and liver, followed by a lower fungal burden in these organs up to 14 days of infection. Neutropenic animals also showed a lower F. pedrosoi-specific antibody production 14-days post infection and higher T-cell proliferation in the in vitro experiments after stimulation with F. pedrosoi-purified proteins. Taken together, our results suggest that the presence of regulatory neutrophils in the mouse model of F. pedrosoi infection could act favoring the spread of the fungus and the chronicity of the infection. These findings shed light on the CBM treatment, which might target neutrophil polarization as a new therapy approach to treat CBM lesions.

Fonsecaeapedrosoi Conidia and Hyphae Activate Neutrophils Distinctly: Requirement of TLR-2 and TLR-4 in Neutrophil Effector Functions.

Chromoblastomycosis is a chronic and progressive subcutaneous mycosis caused mainly by the fungus Fonsecaea pedrosoi. The infection is characterized by erythematous papules and histological sections demonstrating an external layer of fibrous tissue and an internal layer of thick granulomatous inflammatory tissue containing mainly macrophages and neutrophils. Several groups are studying the roles of the innate and adaptive immune systems in F. pedrosoi infection; however, few studies have focused on the role of neutrophils in this infection. In the current study, we verify the importance of murine neutrophils in the killing of F. pedrosoi conidia and hyphae. We demonstrate that phagocytosis and reactive oxygen species during infection with conidia are TLR-2- and TLR-4-dependent and are essential for conidial killing. Meanwhile, hyphal killing occurs by NET formation in a TLR-2-, TLR-4-, and ROS-independent manner. In vivo experiments show that TLR-2 and TLR-4 are also important in chromoblastomycosis infection. TLR-2KO and TLR-4KO animals had lower levels of CCL3 and CXCL1 chemokines and impaired neutrophil migration to the infected site. These animals also had higher fungal loads during infection with F. pedrosoi conidia, confirming that TLR-2 and TLR-4 are essential receptors for F. pedrosoi recognition and immune system activation. Therefore, this study demonstrates for the first time that neutrophil activation during F. pedrosoi is conidial or hyphal-specific with TLR-2 and TLR-4 being essential during conidial infection but unnecessary for hyphal killing by neutrophils.

Effect of Fonsecaea monophora on the Polarization of THP-1 Cells to Macrophages.

BACKGROUND: Chromoblastomycosis is a chronic, progressive fungal disease of the skin and subcutaneous tissue caused by a unique group of dematiaceous fungi. Fonsecaea monophora, a new species distinct from Fonsecaea pedrosoi strains, is the main pathogen responsible for chromoblastomycosis in south China. Macrophages can be polarized into two categories: classically activated and alternatively activated. OBJECTIVES: Little is known about the relationship between F. monophora and macrophage polarization. This study aimed to study the effect of F. monophora on the polarization of THP-1 cells to macrophages. METHODS: We established coculture systems of F. monophora and THP-1-derived macrophages in different activation states. RESULTS: F. monophora enhanced the phagocytosis by macrophages in the initially activated state and weakened the phagocytosis by classically activated macrophages without affecting that by alternatively activated macrophages. Classically activated macrophages had the strongest killing effect on F. monophora, while the initially activated macrophages had the weakest. The pathogen could not be rapidly cleared by any type of macrophage. F. monophora promoted the expression of proinflammatory cytokines and inhibited that of anti-inflammatory cytokines. CONCLUSIONS: F. monophora promoted the polarization of THP-1 cells to classically activated macrophages and inhibited that of THP-1 cells to alternatively activated macrophages.

Fonsecaea pedrosoi Conidia Induces Activation of Dendritic Cells and Increases CD11c+ Cells in Regional Lymph Nodes During Experimental Chromoblastomycosis.

The chromoblastomycosis is a subcutaneous mycosis with a high morbidity rate, Fonsecaea pedrosoi being the largest etiologic agent of this mycosis, usually confined to the skin and subcutaneous tissues. Rarely people get the cure, because the therapies shown to be deficient and few studies report the host-parasite relationship. Dendritic cells (DCs) are specialized in presenting antigens to naïve T lymphocytes inducing primary immune responses. Therefore, we propose to study the migratory capacity of DCs after infection with conidia of F. pedrosoi. The phenotype of DCs was evaluated using cells obtained from footpad and lymph nodes of BALB/c mice after 12, 24 and 72 h of infection. After 24 and 72 h of infection, we found a significant decrease in DCs in footpad and a significant increase in the lymph nodes after 72 h. The expression of surface markers and co-stimulatory molecules were reduced in cells obtained from footpad. To better assess the migratory capacity of DCs migration from footpad, CFSE-stained conidia were injected subcutaneously. We found that after 12 and 72 h, CD11c+ cells were increased in regional lymph nodes, leading us to believe that DCs (CD11c+) were able to phagocytic conidia present in footpad and migrated to regional lymph nodes.