Fonsecaea pedrosoiconidia and hyphae activate neutrophils distinctly: Requirement of TLR-2 and TLR-4 in neutrophil effector functions
Authors: Breda Leandro Carvalho Dantas , de Souza Breda Cristiane Naffah , de Almeida José Roberto Fogaça , Paulo Larissa Neves Monteiro , Jannuzzi Grasielle Pereira , de Godoy Menezes Isabela , Albuquerque Renata Chaves , Câmara Niels Olsen Saraiva , Ferreira Karen Spadari , de Almeida Sandro Rogério 
Published: January 2020

Chromoblastomycosis is a chronic and progressive subcutaneous mycosis caused mainly by the fungusFonsecaea pedrosoi. The infection is characterized by erythaematous papules and the 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 have been studying the roles of the innate and adaptive immune systems inF. pedrosoiinfection; however, few studies have focused on the role of neutrophils in this infection. In the current study, we verified the importance of murine neutrophils in the killing ofF. pedrosoiconidia and hyphae. We demonstrate that phagocytosis and reactive oxygen species during infection with conidia are TLR-2 and TLR-4-dependent and are essentials for conidial killing. Meanwhile, hyphal killing occurs by NETs formation, in a TLR-2, TLR-4 and ROS-independent manner. In vivo experiments showed that TLR-2 and TLR-4 are also important in Chromoblastomycosis infection. TLR-2KO and TLR-4KO animals had lower levels of MIP-2 and KC chemokines and impaired neutrophil migration to the infected site. These animals also had higher fungal loads during infection withF. pedrosoiconidia, confirming that TLR-2 and TLR-4 are essential receptors forF. pedrosoirecognition and immune system activation. Therefore, this study demonstrated for the first time that neutrophils activation duringF. pedrosoiis conidial or hyphal-specific, with TLR-2 and TLR-4 being essential during conidial infection but unnecessary for hyphal killing by neutrophils

Author Summary

Chromoblastomycosis (CBM) is a chronic and progressive subcutaneous mycosis that affects mainly low-income individuals, such as farm workers. CBM have been diagnosed all over the world, but the majority of cases were diagnosed in tropical and subtropical climate countries. The treatment is difficult and involves the combination of antifungal prescriptions, cryo/heat-therapy and, in some cases, surgery to remove all the infected tissue. The treatment is long (at least 6 months) and expensive, leading to a high rate of treatment dropout and disease relapse. However, the understanding of pathogen-host interaction is far from being elucitaded. Our understanding is that this pathogen-host interaction in CBM needs to be uncovered so a different and more effective treatment could be proposed to help those patients that are struggling against this chronic infection. Therefore, our study shed a light in neutrophils and innate immune response against this fungal infection, showing the neutrophils capacity to killFonsecaea pedrosoiconidia and hifa, showing the importance of toll-like receptors 2 and 4 in the neutrophil fungicidal capacity againstF. pedrosoiconidia but not hyphae. Therefore this work help to the better understanding of how our organism fights back in the CBM infection.