Poly (I: C) inhibits reticuloendothelial virus replication in chicken macrophage-like cells through the activation of toll-like receptor-3 signaling

Reticuloendothelial virus (REV) is widely found in many domestic poultry areas and results in severe immunosuppression of infected chickens. This increases the susceptibility to other pathogens, which causes economic losses to the poultry industry. The aim of our study was to determine whether polyinosinic-polycytidylic acid [Poly (I: C)] treatment could inhibit REV replication in chicken macrophage-like cell line, HD11. We found that Poly (I: C) treatment could markedly inhibit REV replication in HD11 from 24 to 48 h post infection (hpi). Additionally, Poly (I: C) treatment could switch HD11 from an inactive type into M1-like polarization from 24 to 48 hpi. Furthermore, Poly (I: C) treatment promoted interferon-β secretion from HD11 post REV infection. Moreover, Toll-like receptor-3 (TLR-3) mRNA and protein levels in HD11 treated with Poly (I: C) were markedly increased compared to those of HD11 not treated with Poly (I: C). The above results suggested that Poly (I: C) treatment switches HD11 into M1-like polarization to secret more interferon-β and activate TLR-3 signaling, which contributes to block REV replication. Our findings provide a theoretical reference for further studying the underlying pathogenic mechanism of REV and Poly (I: C) as a potential therapeutic intervention against REV infection.

Effect of Listeria monocytogenes on intestinal stem cells in the co-culture model of small intestinal organoids

Listeria monocytogenes is a foodborne pathogen that causes systemic infections by crossing the intestinal barrier. However, in vitro analysis of the interaction of L. monocytogenes and small intestinal epithelium has yet to be fully elucidated. To study host responses from intestinal epithelium during L. monocytogenes infection, we used the co-culture model of small intestinal organoids and L. monocytogenes. Results showed that L. monocytogenes mediated damage to intestinal epithelium, especially intestinal stem cells. L. monocytogenes was found to reduce budding rate and increase mortality of organoids. Moreover, it affected the proliferation of epithelial cells and numbers of secretory cells. In addition, it was demonstrated that L. monocytogenes stimulated a reduction in the number of Lgr5+ stem cells. Furthermore, L. monocytogenes affected the expression of Hes1, Math1 and Sox9 to interfere with the differentiation of intestinal stem cells. Collectively, our findings reveal the effects of L. monocytogenes infection on intestinal stem cells and demonstrate that small intestinal organoid is a suitable experimental model for studying intestinal epithelium-pathogen interactions.

A method to differentiate chicken monocytes into macrophages with proinflammatory properties

Macrophages are part of the first line of defense against invading pathogens. In mammals, the in vitro culture of macrophages from blood monocytes or bone marrow cells is well established, including culturing conditions to differentiate them towards M1 or M2-like macrophages. In chicken, monocyte-derived macrophages have been used in several studies, but there is no uniform protocol or actual characterization of these cells. Therefore, to generate proinflammatory M1-like macrophages, in this study blood monocytes were differentiated using GM-CSF for 4 days and characterized based on cell morphology, surface marker expression and cytokine expression response to TLRs stimulation at each (daily) time point. Cell morphology showed that one-day-cultured cells contained a mixture of cell populations, while the homogenous population of cells on day 3 and day 4 were flat and had a 'fried-egg' like shape, similar to human M1 macrophages. In addition, cell surface marker staining showed that 3 and 4- days-cultured cells expressed a high level of MRC1L-B (KUL01) and MHC-II. Furthermore, LPS stimulation of the cultured cells induced gene expression of the proinflammatory cytokines IL-1β, IL-6 and IL-8 after 3 days of culture. Finally, it was shown that day 3 macrophages were able to phagocytose avian pathogenic E. coli (APEC) and respond by nitric oxide production. Overall, our systematic characterization of the monocyte derived cells from blood showed that a 3-days culture was optimal to obtain pro-inflammatory M1 like macrophages, increasing our knowledge about chicken macrophage polarization and providing useful information for studies on chicken macrophage phenotypes.

The Differential Phosphorylation-Dependent Signaling and Glucose Immunometabolic Responses Induced during Infection by Salmonella Enteritidis and Salmonella Heidelberg in Chicken Macrophage-like cells

Salmonella is a burden to the poultry, health, and food safety industries, resulting in illnesses, food contamination, and recalls. Salmonella enterica subspecies enterica Enteritidis (S. Enteritidis) is one of the most prevalent serotypes isolated from poultry. Salmonella enterica subspecies enterica Heidelberg (S. Heidelberg), which is becoming as prevalent as S. Enteritidis, is one of the five most isolated serotypes. Although S. Enteritidis and S. Heidelberg are almost genetically identical, they both are capable of inducing different immune and metabolic responses in host cells to successfully establish an infection. Therefore, using the kinome peptide array, we demonstrated that S. Enteritidis and S. Heidelberg infections induced differential phosphorylation of peptides on Rho proteins, caspases, toll-like receptors, and other proteins involved in metabolic- and immune-related signaling of HD11 chicken macrophages. Metabolic flux assays measuring extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) demonstrated that S. Enteritidis at 30 min postinfection (p.i.) increased glucose metabolism, while S. Heidelberg at 30 min p.i. decreased glucose metabolism. S. Enteritidis is more invasive than S. Heidelberg. These results show different immunometabolic responses of HD11 macrophages to S. Enteritidis and S. Heidelberg infections.

Avian pathogenic Escherichia coli-induced activation of chicken macrophage HD11 cells

Avian pathogenic Escherichia coli (APEC) can cause severe respiratory diseases in poultry. The initial interaction between APEC and chicken macrophages has not been characterized well and it is unclear how effective chicken macrophages are in neutralizing APEC. Therefore, the effect of APEC on activation of chicken macrophage HD11 cells was studied. Firstly, the effect of temperature (37 vs 41 °C) on phagocytosis of APEC by HD11 cells was determined. The results showed that APEC was more susceptible to being phagocytosed by HD11 cells at 41 °C than 37 °C. Subsequently, the capacity of HD11 cells to kill APEC was shown. In addition, HD11 cells produced nitric oxide (NO) at 18 h post-infection and a strong increase in the mRNA expression of IL-8, IL-6, IL-1β and IL-10 was detected, while IFN-β gene expression remained unaffected. Finally, it was shown that the response of HD11 was partially dependent on viability of APEC since stimulation of HD11 cells with heat-killed APEC resulted in a reduced expression level of these cytokines. In conclusion, APEC induces an effector response in chicken macrophages by enhanced NO production and cytokines gene expression.

Enhanced Replication of Virulent Newcastle Disease Virus in Chicken Macrophages Is due to Polarized Activation of Cells by Inhibition of TLR7

Newcastle disease (ND), caused by infections with virulent strains of Newcastle disease virus (NDV), is one of the most important infectious disease affecting wild, peridomestic, and domestic birds worldwide. Vaccines constructed from live, low-virulence (lentogenic) viruses are the most accepted prevention and control strategies for combating ND in poultry across the globe. Avian macrophages are one of the first cell lines of defense against microbial infection, responding to signals in the microenvironment. Although macrophages are considered to be one of the main target cells for NDV infection in vivo, very little is known about the ability of NDV to infect chicken macrophages, and virulence mechanisms of NDV as well as the polarized activation patterns of macrophages and correlation with viral infection and replication. In the present study, a cell culture model (chicken bone marrow macrophage cell line HD11) and three different virulence and genotypes of NDV (including class II virulent NA-1, class II lentogenic LaSota, and class I lentogenic F55) were used to solve the above underlying questions. Our data indicated that all three NDV strains had similar replication rates during the early stages of infection. Virulent NDV titers were shown to increase compared to the other lentogenic strains, and this growth was associated with a strong upregulation of both pro-inflammatory M1-like markers/cytokines and anti-inflammatory M2-like markers/cytokines in chicken macrophages. Virulent NDV was found to block toll-like receptor (TLR) 7 expression, inducing higher expression of type I interferons in chicken macrophages at the late stage of viral infection. Only virulent NDV replication can be inhibited by pretreatment with TLR7 ligand. Overall, this study demonstrated that virulent NDV activates a M1-/M2-like mixed polarized activation of chicken macrophages by inhibition of TLR7, resulting in enhanced replication compared to lentogenic viruses.

Listeria Occurrence in Poultry Flocks: Detection and Potential Implications

Foodborne pathogens such as Salmonella, Campylobacter, Escherichia coli, and Listeria are a major concern within the food industry due to their pathogenic potential to cause infection. Of these, Listeria monocytogenes, possesses a high mortality rate (approximately 20%) and is considered one of the most dangerous foodborne pathogens. Although the usual reservoirs for Listeria transmission have been extensively studied, little is known about the relationship between Listeria and live poultry production. Sporadic and isolated cases of listeriosis have been attributed to poultry production and Listeria spp. have been isolated from all stages of poultry production and processing. Farm studies suggest that live birds may be an important vector and contributor to contamination of the processing environment and transmission of Listeria to consumers. Therefore, the purpose of this review is to highlight the occurrence, incidence, and potential systemic interactions of Listeria spp. with poultry.