Dectin-1 is essential for reverse transcytosis of glycosylated SIgA-antigen complexes by intestinal M cells.

Intestinal microfold (M) cells possess a high transcytosis capacity and are able to transport a broad range of materials including particulate antigens, soluble macromolecules, and pathogens from the intestinal lumen to inductive sites of the mucosal immune system. M cells are also the primary pathway for delivery of secretory IgA (SIgA) to the gut-associated lymphoid tissue. However, although the consequences of SIgA uptake by M cells are now well known and described, the mechanisms whereby SIgA is selectively bound and taken up remain poorly understood. Here we first demonstrate that both the Cα1 region and glycosylation, more particularly sialic acid residues, are involved in M cell-mediated reverse transcytosis. Second, we found that SIgA is taken up by M cells via the Dectin-1 receptor, with the possible involvement of Siglec-5 acting as a co-receptor. Third, we establish that transcytosed SIgA is taken up by mucosal CX3CR1⁺ dendritic cells (DCs) via the DC-SIGN receptor. Fourth, we show that mucosal and systemic antibody responses against the HIV p24-SIgA complexes administered orally is strictly dependent on the expression of Dectin-1. Having deciphered the mechanisms leading to specific targeting of SIgA-based Ag complexes paves the way to the use of such a vehicle for mucosal vaccination against various infectious diseases

Polarized Entry of Uropathogenic Afa/Dr Diffusely Adhering Escherichia coli Strain IH11128 into Human Epithelial Cells: Evidence for α(5)β(1) Integrin Recognition and Subsequent Internalization through a Pathway Involving Caveolae and Dynamic Unstable Microtubules

Afa/Dr diffusely adhering Escherichia coli strain IH11128 bacteria basolaterally entered polarized epithelial cells by a CD55- and CD66e-independent mechanism through interaction with the α(5)β(1) integrin and a pathway involving caveolae and dynamic microtubules (MTs). IH11128 invasion within HeLa cells was dramatically decreased after the cells were treated with the cholesterol-extracting drug methyl-β-cyclodextrin or the caveola-disrupting drug filipin. Disassembly of the dynamically unstable MT network by the compound 201-F resulted in a total abolition of IH11128 entry. In apically infected polarized fully differentiated Caco-2/TC7 cells, no IH11128 entry was observed. The entry of bacteria into apically IH11128-infected fully differentiated Caco-2/TC7 cells was greatly enhanced by treating cells with Ca(2+)-free medium supplemented with EGTA, a procedure that disrupts intercellular junctions and thus exposes the basolateral surface to bacteria. Basally infected fully differentiated polarized Caco-2/TC7 cells grown on inverted inserts mounted in chamber culture showed a highly significant level of intracellular IH11128 bacteria compared with cells subjected to the apical route of infection. No expression of CD55 and CD66e, the receptors for the Afa/Dr adhesins, was found at the basolateral domains of these cells. Consistent with the hypothesis that a cell-to-cell adhesion molecule acts as a receptor for polarized IH11128 entry, an antibody blockade using anti-α(5)β(1) integrin polyclonal antibody completely abolished bacterial entry. Experiments conducted with the laboratory strain E. coli K-12 EC901 carrying the recombinant plasmid pBJN406, which expresses Dr hemagglutinin, demonstrated that the dra operon is involved in polarized entry of IH11128 bacteria. Examined as a function of cell differentiation, the number of internalized bacteria decreased dramatically beyond cell confluency. Surviving intracellular IH11128 bacteria residing intracellularly had no effect on the functional differentiation of Caco-2/TC7 cells

Antibiotic treatment of infections caused by carbapenem-resistant Gram-negative bacilli: an international ESCMID cross-sectional survey among infectious diseases specialists practicing in large hospitals

Objectives: To explore contemporary antibiotic management of infections caused by carbapenem-resistant Gram-negative bacteria in hospitals. Methods: Cross-sectional, internet-based questionnaire survey. We contacted representatives of all hospitals with more than 800 acute-care hospital beds in France, Greece, Israel, Italy, Kosovo, Slovenia, Spain and selected hospitals in the USA. We asked respondents to describe the most common actual practice at their hospital regarding management of carbapenem-resistant Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa through close-ended questions. Results: Between January and June 2017, 115 of 141 eligible hospitals participated (overall response rate 81.6%, country-specific rates 66.7%–100%). Most were tertiary-care (99/114, 86.8%), university-affiliated (110/115, 89.1%) hospitals and most representatives were infectious disease specialists (99/115, 86.1%). Combination therapy was prescribed in 114/115 (99.1%) hospitals at least occasionally. Respondents were more likely to consider combination therapy when treating bacteraemia, pneumonia and central nervous system infections and for Enterobacteriaceae, P. aeruginosa and A. baumannii similarly. Combination of a polymyxin with a carbapenem was used in most cases, whereas combinations of a polymyxin with tigecycline, an aminoglycoside, fosfomycin or rifampicin were also common. Monotherapy was used for treatment of complicated urinary tract infections, usually with an aminoglycoside or a polymyxin. The intended goal of combination therapy was to improve the effectiveness of the treatment and to prevent development of resistance. In general, respondents shared the misconception that combination therapy is supported by strong scientific evidence. Conclusions: Combination therapy was the preferred treatment strategy for infections caused by carbapenem-resistant Gram-negative bacteria among hospital representatives, even though high-quality evidence for carbapenem-based combination therapy is lacking. © 2018 European Society of Clinical Microbiology and Infectious Disease