ACandida albicansMannoprotein Deprived of Its Mannan Moiety Is Efficiently Taken Up and Processed by Human Dendritic Cells and Induces T-Cell Activation without Stimulating Proinflammatory Cytokine Production

Abstract

Mannoproteins are cell wall components of pathogenic fungi and play major virulence and immunogenic roles with both their mannan and protein moieties. The 65-kDa mannoprotein (MP65) of Candida albicans is a ␤-glucanase adhesin recognized as a major target of the human immune response against this fungus, and its recombinant product (rMP65; devoid of the mannan moiety) is presently under consideration as a vaccine candidate. Here we investigated cellular and molecular aspects of the interaction of rMP65 with human antigen-presenting cells. We also assessed the ability of rMP65 to initiate a T-cell response. Both the native mannosylated MP65 (nMP65) and the recombinant product were efficiently bound and taken up by macrophages and dendritic cells. However, contrarily to nMP65, rMP65 did not induce tumor necrosis factor alpha and interleukin-6 release from these cells. On the other hand, rMP65 was rapidly endocytosed by both macrophages and dendritic cells, in a process involving both clathrin-dependent and clathrin-independent mechanisms. Moreover, the RGD sequence inhibited rMP65 uptake to some extent. After internalization, rMP65 partially colocalized with lysosomal membrane-associated glycoproteins 1 and 2. This possibly resulted in efficient protein degradation and presentation to CD4 ؉ T cells, which proliferated and produced gamma interferon. Collectively, these results demonstrate that the absence of the mannan moiety does not deprive MP65 of the capacity to initiate the pattern of cellular and molecular events leading to antigen presentation and T-cell activation, which are essential features for further consideration of MP65 as a potential vaccine candidate.

A Novel Th Cell Epitope of Candida albicans Mediates Protection from Fungal Infection

“…In addition to the Als proteins, the 65-kDa mannoprotein MP65 from Candida also act as a Th cell Ag as previously reported (18,19) and confirmed in this study, although the latter only activates a minor proportion of Candida-specific T cells, and the precise range of amino acids binding to MHCII have not been determined in case of MP65. Nevertheless, the common feature of these two Candida-derived T cell Ags is their localization to the fungal cell wall.…”

“…3). In the same experiments, we also included a peptide pool of MP65, which was previously reported to act as a fungus-derived Ag (18,19), and an Aspergillus fumigatus-derived peptide (p41) that has been proposed to cross-stimulate Candida-specific T cells (15). Similar to pATG, MP65 induced IL-17A production from Candida-specific T cells after secondary infection, but the response was much lower than the one induced by pALS (Fig.…”

Secreted aspartic proteases of Candida albicans activate the NLRP3 inflammasome

“…The uptake of Sap2 and Sap6 by human monocytes was analyzed by flow cytometry as previously described [58]. Monocytes (2.5 × 10 5 ) were treated with or without 45 μM of chlorpromazine for 30 min at 37 • C, incubated with 20 μg/mL of FITClabeled Sap2, Sap6, LPS, or CTLA-4 F(ab) 2 for 30, 60, and 120 min at 37 • C in the presence of 5% CO 2 .…”

“…The generation of DCs and MDMs from monocytes was performed as previously described, with minor modifications [58]. Immature DCs were obtained by treating monocytes with 50 ng/mL of human recombinant GM-CSF (Biosource) and 30 ng/mL of human recombinant IL-4 (Biosource) for 5-6 days.…”

Identification of Immunogenic Antigens from Aspergillus fumigatus by Direct Multiparameter Characterization of Specific Conventional and Regulatory CD4+ T Cells

“…2). The C. albicans protein MP65 was described to be a major Ag target of human T cell responses (34,35) and served as a positive control.…”