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KM+is a mannose-binding lectin from Artocarpus integrifoliathat induces interleukin (IL)-12 production by macrophages and protective T helper 1 immune response against Leishmania majorinfection. In this study, we performed experiments to evaluate the therapeutic activity of jackfruit KM+(jfKM+) and its recombinant counterpart (rKM+) in experimental paracoccidioidomycosis. To this end, jfKM+or rKM+was administered to BALB/c mice 10 days after infection with Paracoccidiodes brasiliensis. Thirty days postinfection, lungs from the KM+-treated mice contained significantly fewer colony-forming units and little to no organized granulomas compared to the controls. In addition, lung homogenates from the KM+-treated mice presented higher levels of nitric oxide, IL-12, interferon-γ, and tumor necrosis factor-α, whereas higher levels of IL-4 and IL-10 were detected in the control group. With mice deficient in IL-12, Toll-like receptor (TLR) 2, TLR4, or TLR adaptor molecule MyD88, we demonstrated that KM+led to protection against P. brasiliensisinfection through IL-12 production, which was dependent on TLR2. These results demonstrated a beneficial effect of KM+on the severity of P. brasiliensisinfection and may expand its potential use as a novel immunotherapeutic molecule.

The outcome and severity of some diseases correlate with the dominance of either the T helper 1 (Th1) or Th2 immune response, which is stimulated by IL-12 or IL-4, respectively. In the present study we demonstrate that gamma interferon (IFN-γ) secretion by murine spleen cells stimulated with KM+, a mannose-binding lectin from Artocarpus integrifolia, is due to IL-12 induction, because (1) macrophages from several sources (including cell lines) produced IL-12 p40 in response to KM+, and (2) lectin-free supernatants from J774 cell line cultures stimulated with KM+ induced the secretion of IFN-γ by spleen cell cultures, an effect blocked by the supernatant pretreatment with anti-IL-12 antibody. The known pattern of susceptibility of BALB/c mice to infection with Leishmania major, attributed to high levels of IL-4 production leading to a Th2 nonprotective immune response, was modified by administration of KM+. Draining lymph node cells from these immunized BALB/c mice (in contrast to cells from animals immunized only with soluble leishmanial antigen [SLA]) secreted high levels of IFN-γ and low levels of IL-4, which characterized a Th1 rather than a Th2 response pattern. The footpad thickness of BALB/c mice immunized with SLA plus KM+ and challenged with L. major was similar to that of uninfected mice. This beneficial effect against leishmanial infection was blocked by pretreatment of these mice with anti-IL-12 antibody. These observations indicate that KM+ induces IL-12 p40 in vivo and has a protective effect against L. major infection.

Host cell invasion by Toxoplasma gondii is a multistep process with one of the first steps being the apical release of micronemal proteins that interact with host receptors. We demonstrate here that micronemal protein 1 (MIC1) is a lactose-binding lectin. MIC1 and MIC4 were recovered in the lactose-eluted (Lac+) fraction on affinity chromatography on immobilized lactose of the soluble antigen fraction from tachyzoites of the virulent RH strain. MIC1 and MIC4 were both identified by N-terminal microsequencing. MIC4 was also identified by sequencing cDNA clones isolated from an expression library following screening with mouse polyclonal anti-60/70 kDa (Lac+ proteins) serum. This antiserum localized the Lac+ proteins on the apical region of T. gondii tachyzoites by confocal microscopy. The Lac+ fraction induced hemagglutination (mainly type A human erythrocytes), which was inhibited by β-galactosides (3 mM lactose and 12 mM galactose) but not by up to 100 mM melibiose (α-galactoside), fucose, mannose, or glucose or 0.2 mg/ml heparin. The lectin activity of the Lac+ preparation was attributed to MIC1, because blotted MIC1, but not native MIC4, bound human erythrocyte type A and fetuin. The copurification of MIC1 and MIC4 may have been due to their association, as reported by others. These data suggest that MIC1 may act through its lectin activity during T. gondii infection.