C-type lectin receptor DCIR modulates immunity to tuberculosis by sustaining type I interferon signaling in dendritic cells

A. Troegeler, I. Mercier, C. Cougoule, D. Pietretti, A. Colom, C. Duval, T.P. Vu Manh, F. Capilla, R. Poincloux, K. Pingris, J. Nigou, J. Rademann, M. Dalod, F.A. Verreck, T. Al Saati, G. Lugo-Villarino, B. Lepenies, D. Hudrisier, O. Neyrolles
Immune response against pathogens is a tightly regulated process that must ensure microbial control while preserving integrity of the infected organs. Tuberculosis (TB) is a paramount example of a chronic infection in which antimicrobial immunity is protective in the vast majority of infected individuals but can become detrimental if not finely tuned. Here, we report that C-type lectin dendritic cell (DC) immunoreceptor (DCIR), a key component in DC homeostasis, is required to modulate lung inflammation and bacterial burden in TB. DCIR is abundantly expressed in pulmonary lesions in Mycobacterium tuberculosis-infected nonhuman primates during both latent and active disease. In mice, we found that DCIR deficiency impairs STAT1-mediated type I IFN signaling in DCs, leading to increased production of IL-12 and increased differentiation of T lymphocytes toward Th1 during infection. As a consequence, DCIR-deficient mice control M. tuberculosis better than WT animals but also develop more inflammation characterized by an increased production of TNF and inducible NOS (iNOS) in the lungs. Altogether, our results reveal a pathway by which a C-type lectin modulates the equilibrium between infection-driven inflammation and pathogen’s control through sustaining type I IFN signaling in DCs. Proc Natl Acad Sci U S A. 2017 Jan 24;114(4):E540-E549. doi: 10.1073/pnas.1613254114. Epub 2017 Jan 9.

Understanding carbohydrate-protein interactions using homologous supramolecular chiral Ru(ii)-glyconanoclusters

H. Bavireddi, R.V. Murthy, M. Gade, S. Sangabathuni, P.M. Chaudhari, C. Alex, B. Lepenies, R. Kikkeri
Multivalent glycodendrimers make promising tools to tackle the basic and translational research in the field of carbohydrate-mediated interactions. Despite advances in glycodendrimers and glycopolymers, the multivalent probes available to date are still far from being ideal biological mimics. This work demonstrates the inherent chirality of glycodendrimers to be one of the promising factors to generate different spatial carbohydrate micro-environments to modulate specific carbohydrate-protein interactions. By exploiting the host-guest strategy, chiral Ru(ii) complexes (Δ and Λ) and mannose capped β-cyclodextrin (β-CD), we generated a library of homologous metallo-glycodendrimers (MGDs) with sizes of 50-70 nm. These nanoclusters can enantioselectively bind to specific C-type lectins and displayed selectivity in cellular uptake. We also discovered their potential clathrin-mediated endocytotic pathway in DC-SIGN and SIGNR3-transfected cell lines. Finally, in vivo biodistribution and sequestration of MGDs was determined to understand the role of chirality mediated spatial arrangement in carbohydrate-mediated interactions. Nanoscale. 2016 Dec 1;8(47):19696-19702.

Influence of Core β-1,2-Xylosylation on Glycoprotein Recognition by Murine C-type Lectin Receptors and Its Impact on Dendritic Cell Targeting

K. Brzezicka, U. Vogel, S. Serna, T. Johannssen, B. Lepenies*, N.-C. Reichardt
Targeting antigens to dendritic cell subsets is a promising strategy to enhance the efficacy of vaccines. C-type lectin receptors (CLRs) expressed by dendritic cells are particularly attractive candidates since CLR engagement may promote cell uptake and may further stimulate antigen presentation and subsequent T cell activation. While most previous approaches have involved antibody-mediated CLR-targeting, glycan-based CLR targeting has become more and more attractive in recent years. In the present study, we show that small structural glycan modifications may markedly influence CLR recognition, dendritic cell targeting, and subsequent T cell activation. A biantennary N-glycan (G0) and its analogous O-2 core xylosylated N-glycan (XG0) were synthesized, covalently conjugated to the model antigen ovalbumin, and analyzed for binding to a set of murine CLR-Fc fusion proteins using lectin microarray. To evaluate whether the differential binding of G0 and XG0 to CLRs impacted dendritic cell targeting, uptake studies using murine dendritic cells were performed. Finally, effects of the ovalbumin glycoconjugates on T cell activation were measured in a dendritic cell/T cell cocultivation assay. Our results highlight the utility of glycan-based dendritic cell targeting and demonstrate that small structural differences may have a major impact on dendritic cell targeting efficacy. ACS Chem. Biol., 2016, 11 (8), pp 2347–2356

Evaluation of a Commercial Real-Time PCR Kit for the Detection of Mycobacterium avium subspecies paratuberculosis in Milk.

Alajmi A, Klein G, Grabowski NT, Fohler S, Akineden Ö, Abdulmawjood A.
There are several commercial test kits for Mycobacterium avium subspecies paratuberculosis (MAP) detection, each with different advantages, disadvantages, and applications. In the present study, a real-time PCR kit targeting the unique transposon sequence ISMAP02 was evaluated. The analytical sensitivity was determined using the type strain ATCC 19698, and the specificity was validated by testing fifteen MAP isolates, thirteen non-MAP Mycobacterium isolates, and eight non-Mycobacterium isolates. Six spiking experiments were performed using raw milk and reconstituted infant milk artificially contaminated with dilutions containing 100-105 MAP cells mL-1. Sensitivity and specificity were at 100 %. The detection probabilities in raw milk and reconstituted infant milk for the samples (containing 1.4 × 101 and 1.7 × 101 MAP cell 50 mL-1) were 16.6 and 91.6 %, respectively. Thus, the tested kit yielded satisfying results to detect MAP in milk. Curr Microbiol. 2016 Aug 9. [Epub ahead of print] PMID:27502065

Trehalose diester glycolipids are superior to the monoesters in binding to Mincle, activation of macrophages in vitro and adjuvant activity in vivo.

A. Huber, R.S. Kallerup, H. Franzyk, K.S. Korsholm, B. Lepenies, D. Christensen, C. Foged, R. Lang
The T-cell adjuvanticity of mycobacterial cord factor trehalose 6,6′-dimycolate (TDM) is well established. The identification of the C-type lectin Mincle on innate immune cells as the receptor for TDM and its synthetic analogue trehalose 6,6′-dibehenate (TDB) has raised interest in development of synthetic Mincle ligands as novel adjuvants. Trehalose mono- (TMXs) and diesters (TDXs) with symmetrically shortened acyl chains [denoted by X: arachidate (A), stearate (S), palmitate (P), and myristate (M)] were tested. Upon stimulation of murine macrophages, G-CSF secretion and NO production were strongly augmented by all TDXs tested, in a wide concentration range. In contrast, the TMXs triggered macrophage activation only at high concentrations. Macrophage activation by all TDXs required Mincle, but was independent of MyD88. The superior capacity of TDXs for activating macrophages was paralleled by direct binding of TDXs, but not of TMXs, to a Mincle-Fc fusion protein. Insertion of a short polyethylene glycol between the sugar and acyl chain in TDS reduced Mincle-binding and macrophage activation. Immunization of mice with cationic liposomes containing the analogues demonstrated the superior adjuvant activity of trehalose diesters. Overall, immune activation in vitro and in vivo by trehalose esters of simple fatty acids requires two acyl chains of length and involves Mincle. Innate Immun. 2016 Aug;22(6):405-18. doi: 10.1177/1753425916651132. Epub 2016 Jun 1.