Lack of Galectin-3 Drives Response to Paracoccidioides brasiliensis toward a Th2-Biased Immunity Luciana Pereira Ruas 1 , Emerson Soares Bernardes 1 , Marise Lopes Fermino 1 , Leandro Licursi de Oliveira 2 , Daniel K. Hsu 3 , Fu-Tong Liu 3 , Roger Chammas 4 , Maria-Cristina Roque-Barreira 1 * 1 Departamento de Biologia Celular e Molecular e Bioagentes Patoge ˆnicos, Faculdade de Medicina de Ribeira ˜o Preto, Universidade de Sa ˜o Paulo, Ribeira ˜o Preto, Brasil, 2 Departamento de Biologia Geral, Universidade Federal de Vic ¸osa, Vic ¸osa, Brasil, 3 Department of Dermatology, School of Medicine, University of California Davis, Sacramento, California, United States of America, 4 Laborato ´ rio de Oncologia Experimental, Faculdade de Medicina, Universidade de Sa ˜o Paulo, Sa ˜o Paulo, Brasil Abstract There is recent evidence that galectin-3 participates in immunity to infections, mostly by tuning cytokine production. We studied the balance of Th1/Th2 responses to P. brasiliensis experimental infection in the absence of galectin-3. The intermediate resistance to the fungal infection presented by C57BL/6 mice, associated with the development of a mixed type of immunity, was replaced with susceptibility to infection and a Th2-polarized immune response, in galectin-3-deficient (gal3 2/2 ) mice. Such a response was associated with defective inflammatory and delayed type hypersensitivity (DTH) reactions, high IL-4 and GATA-3 expression and low nitric oxide production in the organs of infected animals. Gal3 2/2 macrophages exhibited higher TLR2 transcript levels and IL-10 production compared to wild-type macrophages after stimulation with P. brasiliensis antigens. We hypothesize that, during an in vivo P. brasiliensis infection, galectin-3 exerts its tuning role on immunity by interfering with the generation of regulatory macrophages, thus hindering the consequent Th2- polarized type of response. Citation: Ruas LP, Bernardes ES, Fermino ML, de Oliveira LL, Hsu DK, et al. (2009) Lack of Galectin-3 Drives Response to Paracoccidioides brasiliensis toward a Th2- Biased Immunity. PLoS ONE 4(2): e4519. doi:10.1371/journal.pone.0004519 Editor: Marta Feldmesser, Albert Einstein College of Medicine, United States of America Received December 19, 2008; Accepted January 16, 2009; Published February 20, 2009 Copyright: ß 2009 Ruas et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) and Conselho Nacional de Pesquisa Cientı ´fica e Tecnologica (CNPq). L.P.R. is a PhD student with a scholarship from FAPESP. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: mcrbarre@fmrp.usp.br Introduction Paracoccidioides brasiliensis, a thermally dimorphic fungus, is the etiological agent of human paracoccidioidomycosis, one of the most frequent systemic mycosis in Central and South America [1,2]. The main host defense against P. brasiliensis is the cell- mediated immune response [3–5]. Macrophage activation and granuloma formation characterize the inflammatory response induced by the fungus, and protect the host against parasite dissemination [6]. Macrophages and lymphocytes are generally considered the major effector cells controlling the disease in vivo [7,8] through TNF-a and IFN-c production [9,10]. In the past few years, the immunity to several infections has been demonstrated to be influenced by galectin-3, the most studied member of the galectin family. These investigations were performed by comparing the course of experimental infections in mice that were genetically deficient, or not, in galectin-3 [11– 13]. The studies of infection with the intracellular bacteria Rhodococcus equi have demonstrated that galectin-3 may regulate the innate immune response by diminishing IL-1b production by macrophages [13]. On the other hand, during Toxoplasma gondii and Schistosoma mansonii infection, the absence of galectin-3 drives the development of a heightened Th1-type immune response, suggesting that the lectin exerts a profound effect on the development of the adaptive immune response against pathogens [11,12]. Together with results obtained from a murine model of asthma [14], the studies provide consistent evidences that gal3 2/2 mice develop a lower Th2 response but a higher Th1 response compared with gal3 +/+ mice. In consequence, galectin-3 emerges as a fine regulator of Th1/Th2 balance. Since protection against P. brasiliensis infection depends on adequate inflammation, cellular immune response and cytokine production, and because galectin-3 is important in the regulation of the Th1/Th2 balance, the aim of this study was to analyze the immunological aspects of P. brasiliensis infection in galectin-3- deficient (gal3 2/2 ) mice. We demonstrate that gal3 2/2 mice present increased susceptibility to P. brasiliensis infection, associated with the inability to mount an adequate inflammatory response, the impairment of DTH response, high serum levels of specific antibodies, and the development of a Th2-polarized immune response. Such a picture is possibly due to the fact that, following contact with P. brasiliensis antigens, macrophages from gal3 2/2 mice have higher TLR2 transcript levels and produce higher levels of the deactivating cytokine IL-10. Our results indicate that galectin-3 exerts a protective and immunoregulatory role in the host response to P. brasiliensis infection. Materials and Methods Experimental Animals Galectin-3-deficient mice (gal3 2/2 ) were generated as previ- ously described and backcrossed to C57BL/6 mice for nine generations [15]. Age-matched wild-type mice C57BL/6 (gal3 +/+ ) were used as controls in all the experiments. Mice were housed PLoS ONE | www.plosone.org 1 February 2009 | Volume 4 | Issue 2 | e4519