title: Therapeutic administration of recombinant Paracoccin confers protection against paracoccidioides brasiliensis infection: involvement of TLRs.
abstract: BACKGROUND
  Paracoccin (PCN) is an N-acetylglucosamine-binding lectin from the human pathogenic fungus Paracoccidioides brasiliensis. Recombinant PCN (rPCN) induces a T helper (Th) 1 immune response when prophylactically administered to BALB/c mice, protecting them against subsequent challenge with P. brasiliensis. In this study, we investigated the therapeutic effect of rPCN in experimental paracoccidioidomycosis (PCM) and the mechanism accounting for its beneficial action.
  
  
  RESULTS
  Four distinct regimens of rPCN administration were assayed to identify which was the most protective, relative to vehicle administration. In all rPCN-treated mice, pulmonary granulomas were less numerous and more compact. Moreover, fewer colony-forming units were recovered from the lungs of rPCN-treated mice. Although all therapeutic regimens of rPCN were protective, maximal efficacy was obtained with two subcutaneous injections of 0.5 µg rPCN at 3 and 10 days after infection. The rPCN treatment was also associated with higher pulmonary levels of IL-12, IFN-γ, TNF-α, nitric oxide (NO), and IL-10, without IL-4 augmentation. Encouraged by the pulmonary cytokine profile of treated mice and by the fact that in vitro rPCN-stimulated macrophages released high levels of IL-12, we investigated the interaction of rPCN with Toll-like receptors (TLRs). Using a reporter assay in transfected HEK293T cells, we verified that rPCN activated TLR2 and TLR4. The activation occurred independently of TLR2 heterodimerization with TLR1 or TLR6 and did not require the presence of the CD14 or CD36 co-receptors. The interaction between rPCN and TLR2 depended on carbohydrate recognition because it was affected by mutation of the receptor's N-glycosylation sites. The fourth TLR2 N-glycan was especially critical for the rPCN-TLR2 interaction.
  
  
  CONCLUSIONS
  Based on our results, we propose that PCN acts as a TLR agonist. PCN binds to N-glycans on TLRs, triggers regulated Th1 immunity, and exerts a therapeutic effect against P. brasiliensis infection.
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brasil.
authors.forename: Ana Claudia Paiva
authors.initials: AC
authors.lastname: Alegre-Maller
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brasil.
authors.forename: Flávia Costa
authors.initials: FC
authors.lastname: Mendonça
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brasil.
authors.forename: Thiago Aparecido
authors.initials: TA
authors.lastname: da Silva
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brasil.
authors.forename: Aline Ferreira
authors.initials: AF
authors.lastname: Oliveira
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brasil.
authors.forename: Mateus Silveira
authors.initials: MS
authors.lastname: Freitas
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brasil.
authors.forename: Ebert Seixas
authors.initials: ES
authors.lastname: Hanna
authors.affiliation: Border Biomedical Research Center (BBRC), Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas, United States of America.
authors.forename: Igor C
authors.initials: IC
authors.lastname: Almeida
authors.affiliation: Department of Biochemistry, Cambridge University, Cambridge, United Kingdom.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Gay
authors.affiliation: Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brasil.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Roque-Barreira
mesh_terms: D000818:Animals; D005656:Fungal Proteins / Q000008:administration & dosage* / Q000276:immunology; D057809:HEK293 Cells; D006801:Humans; D037102:Lectins / Q000008:administration & dosage* / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010229:Paracoccidioidomycosis / Q000188:drug therapy / Q000276:immunology / Q000517:prevention & control*; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000276:immunology; D051193:Toll-Like Receptors / Q000276:immunology*
chemical_list: D005656:Fungal Proteins; D037102:Lectins; D011994:Recombinant Proteins; D051193:Toll-Like Receptors; C548066:paracoccin, Paracoccidioides brasiliensis