Galectin-1 induces immune response and antiviral ability in Cherry Valley ducks after duck plague virus infection

Cherry Valley Duck Galectin-2 Plays an Essential Role in Avian Pathogenic Escherichia coli Infection-Induced Innate Immune Response

Galectins play important roles in the host's innate immunity as pattern recognition receptors. In this study, the coding sequences of galectin-2 were identified from Cherry Valley ducks. Tissue distribution of duck galectin-2 (duGal-2) in healthy ducks and ducks infected with avian pathogenic Escherichia coli (APEC) was studied, respectively. The results showed that duGal-2 expression was higher in the gut, kidney, and liver tissue, and weakly expressed in the lung and brain, in healthy ducks; however, the expression level of duGal-2 was detected as being up-regulated after infection with APEC. In addition, knockdown or overexpression of duGal-2 in DEFs was achieved by small interference RNA (siRNA) transfection and plasmid transduction, respectively. The knockdown of duGal-2 led to a decrease in the expression of some inflammatory cytokines such as IL-1β, IL-6, and IL-8, while the expression levels of anti-inflammatory factor IL-10 were up-regulated. At the same time, the bacterial load of APEC was increased after knockdown of duGal-2 in vitro. However, the opposite results were obtained in the duGal-2 overexpression group. Taken together, duGal-2 plays an important role in the host against APEC infection.

Isolation and Selection of Duck Primary Cells as Pathogenic and Innate Immunologic Cell Models for Duck Plague Virus

Duck plague virus (DPV) is a representative pathogen transmitted among aquatic animals that causes gross lesions and immune inhibition in geese and ducks. The mechanism of organ tropism and innate immune evasion of DPV has not been completely deciphered due to a lack of cell models to study the innate immune manipulation and pathogenicity of aquatic viruses. In the present study, we isolated five types of duck primary cells [duck embryo fibroblasts (DEFs), neurons, astrocytes, peripheral blood mononuclear cells (PBMCs), and monocytes/macrophages] to identify appropriate cell models for DPV, using tropism infection and innate immunologic assays. Cells responded differently to stimulation with DNA viruses or RNA virus analogs. DPV infection exhibited broad tropism, as the recombinant virulent strain (CHv-GFP) infected DEFs, neurons, astrocytes, and monocytes/macrophages, but not the PBMCs, as the expression of EGFP was negligible. The basal levels of innate immunity molecules were highest in monocytes/macrophages and lower in DEFs and astrocytes. Conversely, the titer and genomic copy number of the attenuated virus strain was higher in DEFs and astrocytes than in neurons and monocytes/macrophages. The titer and genomic copy number of the attenuated virus strain were higher compared with the virulent strain in DEFs, neurons, and astrocytes. The innate immune response was not significantly induced by either DPV strain in DEFs, neurons, or astrocytes. The virulent strain persistently infected monocytes/macrophages, but the attenuated strain did so abortively, and this was accompanied by the phenomenon of innate immune inhibition and activation by the virulent and attenuated strains, respectively. Blockage of IFNAR signaling promoted replication of the attenuated strain. Pre-activation of IFNAR signaling inhibited infection by the virulent strain. The selection assay results indicated that induction of innate immunity plays an essential role in controlling DPV infection, and monocytes/macrophages are an important cell model for further investigations. Our study provided practical methods for isolating and culturing duck primary cells, and our results will facilitate further investigations of organ tropism, innate immune responses, latent infection, and the effectiveness of antiviral drugs for treating DPV and potentially other aerial bird pathogens.