2013. and PA), and four viral envelope proteins (hemagglutinin [HA], neuraminidase [NA], M1 matrix protein, and M2 ion channel protein). Type A influenza viruses have been further classified into 18 HA (H1 to H18) and 11 NA (N1 to N11) serotypes on the basis of the antigenic characteristics of their HA and NA glycoproteins (2,C4). The HA glycoprotein, which is the major target of BTZ043 infection-blocking antibodies, exhibits continuous changes in antigenic properties under immune selective pressure (5). Considered the most potent professional antigen-presenting cells, dendritic cells (DCs) link innate and adaptive immunity (6). When they encounter microbial pathogens, endogenous danger signals, or inflammatory mediators, DCs elicit quick and short-lived innate immune responses before migrating to secondary lymphoid organs and enhancing adaptive immunity (7). DCs are also capable of inducing immunotolerance under certain conditions (8). Two major DC subsets are found in mice and humans: (i) myeloid DCs (mDCs; also called standard DCs) that participate directly in antigen presentation and naive T-cell activation and (ii) plasmacytoid DCs (pDCs) that produce type I interferons (IFNs) in response to viral infections (9, 10). Because of their important role in immune regulation, DCs have been used as immunotherapeutic brokers in the development of prophylactic and therapeutic vaccines for malignancy and both infectious and immune-related BTZ043 diseases (11, 12). Considered essential for controlling innate and adaptive immune responses against influenza computer virus infections (13), DCs trigger proinflammatory and adaptive immune responses in hosts (14). Both mDCs and pDCs Rabbit Polyclonal to USP32 can be activated by vaccinations with trivalent inactivated or live-attenuated viruses, mainly via Toll-like receptor 7 (TLR7)/type I IFN pathways (15). mDCs and pDCs also comprise different heterologous subsets with unique phenotypes and functions. It has been reported that migratory lung-derived and lymph node-derived DCs can be infected by H2N2 (16), pH1N1 (17), and H5N1 influenza viruses (18, 19). The pH1N1 computer virus induces lower levels of antiviral IFN and proinflammatory tumor necrosis factor alpha (TNF-) cytokine expression; it reportedly replicates as efficiently as other seasonal H1N1 and H3N2 viruses in human mDCs (17). Highly pathogenic avian H5N1 viruses can induce productive infections in human mDCs and mouse main lung DCs (18), whereas H7N9 viruses only result in impaired IFN production in infected human mDCs (20). We previously reported that recombinant HA proteins from H5N1 and pH1N1 influenza viruses are capable of triggering mouse mDC activation and maturation (21). For this study, we used Chinese hamster ovary (CHO) cell expression to obtain rH1HA, rH5HA, and rH7HA proteins consisting of (i) terminally sialylated complex-type N-glycans, BTZ043 (ii) high-mannose-type N-glycans, and (iii) single-O111:B4; Sigma), and 10 or 50 g/ml rHA (H1, H5, or H7) or KIF-rHA BTZ043 (H1, H5, or H7) with or without endo H for 6 h. Brefeldin A (10 g/ml; BioLegend) was added for the final 4 h. Cells were fixed, permeabilized, stained with a mouse anti-TNF- monoclonal antibody (BioLegend), and analyzed with a circulation cytometer and Accuri C6 software (BD Biosciences). To determine human mDC cytokine secretion levels, DC culture supernatants were collected following treatment with PBS, LPS, or rHA for 48 h (IL-12 p40, IL-12 p70, IL-10). Detection was performed with enzyme-linked immunosorbent assay (ELISA) packages (R&D) according to the manufacturer’s instructions. Surface marker expression analyses. Murine mDC maturation was decided in terms of IAb, CD40, and CD86 expression as explained in reference 21. Human mDC maturation was examined in terms of HLA-DR, CD40, CD83, and CD86 expression (24). Immature mouse mDCs derived from C57BL/6 mouse bone marrow were treated with PBS, 100 ng/ml LPS, and 50 g/ml wild-type rHA or KIF-treated rHA (H1, H5, or H7) for 18 h, stained with mouse anti-CD11c, -IAb, -CD40, or -CD86 antibodies (BioLegend), and analyzed by circulation cytometry (Accuri C6 software). Immature BTZ043 human mDCs derived from PBMCs collected from healthy donors were treated with PBS, 100 ng/ml LPS, and 10 g/ml wild-type rHA or KIF-treated rHA (H1, H5, or H7) for 48 h, stained with anti-human anti-CD11c, -HLA-DR, -CD40, -CD83, or -CD86 antibodies (eBioscience), and analyzed by circulation cytometry (FACSCalibur). mDC endocytotic analyses using dextran-FITC uptake. Stimulated human mDCs were suspended in staining buffer (1% FBS plus 0.01% NaN3 dissolved in PBS) with 200 g/ml dextran-fluorescein isothiocyanate (FITC; Sigma) and incubated in darkness at 4 or 37C for 1 h, after which cells were washed with chilly PBS and analyzed with a FACSCalibur circulation cytometer. Antibody blocking assays. Mouse mDCs were treated with 1 g/ml anti-mannose receptor (anti-MR) antibodies (ab64693; Abcam) or anti-Dectin-1 antibodies (mabg-mdect; InvivoGen) at 37C overnight to block MRs or Dectin-1 C-type lectin receptors prior to rHA, rHA (KIF), or rHA (KIF+E) (10 g/ml) protein activation. Intracellular TNF- production was determined by using Accuri C6 circulation cytometry and analyzed by Accuri C6 software (BD Biosciences). Percentages of TNF-+ mDCs were decided. Statistical analyses..