Therapeutic Administration of Recombinant Paracoccin Confers Protection against Paracoccidioides brasiliensis Infection: Involvement of TLRs.

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. METHODOLOGY/PRINCIPAL FINDINGS: 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 microg rPCN at 3 and 10 days after infection. The rPCN treatment was also associated with higher pulmonary levels of IL-12, IFN-gamma, TNF-alpha, 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\u27s N-glycosylation sites. The fourth TLR2 N-glycan was especially critical for the rPCN-TLR2 interaction. CONCLUSIONS/SIGNIFICANCE: 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

Role of Mast Cells and C-Sensory Fibers in Concanavalin A-Induced Paw Edema in Two Rat Strains

This study investigated a putative contribution of mast cells and C-sensory fibers to differences in the development of inflammatory edema following the injection of concanavalin A (Con A) into the hind paws of Dark Agouti (DA) and Albino Oxford (AO) rats. The treatment of adult rats with mast cell-depletor compound 48/80 and neonatal depletion of C-sensory fibers independently revealed that leukocyte composition of the inflamed paws and lymph nodes during local inflammatory response to Con A was generally regulated in a similar way in DA and AO rat strains. However, in DA and AO rats, the decrease and the increase of Con A-induced plasma extravasation were associated with mast cell depletion and activation, respectively, whereas neonatal capsaicin treatment activated dermal mast cells and potentiated inflammatory plasma extravasation only in adult rats of DA strain. Hence, strain differences in Emphasis Type="Strikethrough" the development of the inflammatory response to Con A are probably controlled by the differences in the interplay between mast cells and C-sensory fibers in DA and AO rats