Role of the chicken oligoadenylate synthase-like gene during in vitro Newcastle disease virus infection.

The enzyme 2'-5' oligoadenylate synthase (OAS) is one of the key interferon-induced antiviral factors that act through inhibition of viral replication. In chickens, there is a single well-characterized OAS gene, oligoadenylate synthase-like (OASL) that has been shown to be upregulated after infection with various viruses. However, a deeper understanding of how chicken OASL acts against viral infection is still necessary. In this study, we tested the hypothesis that OASL short interfering RNA (siRNA)-mediated knockdown would decrease the host gene expression response to the Newcastle disease virus (NDV) by impacting antiviral pathways. To assess our hypothesis, a chicken fibroblast cell line (DF-1) was infected with the NDV (LaSota strain) and OASL expression was knocked down using a specific siRNA. The level of NDV viral RNA in the cells and the expression of interferon response- and apoptosis-related genes were evaluated by quantitative PCR at 4, 8, and 24 h postinfection (hpi). Knockdown of OASL increased the level of NDV viral RNA at 4, 8, and 24 hpi (P < 0.05) and eliminated the difference between NDV-infected and noninfected cells for expression of interferon response- and apoptosis-related genes (P > 0.05). The lack of differential expression suggests that knockdown of OASL resulted in a decreased response to NDV infection. Within NDV-infected cells, OASL knockdown reduced expression of signal transducer and activator of transcription 1, interferon alfa receptor subunit 1, eukaryotic translation initiation factor 2 alpha kinase 2, ribonuclease L, caspase 8 (CASP8) and caspase 9 (CASP9) at 4 hpi, CASP9 at 8 hpi, and caspase 3, CASP8, and CASP9 at 24 hpi (P < 0.05). We suggest that the increased NDV viral load in DF-1 cells after OASL knockdown was the result of a complex interaction between OASL and interferon response- and apoptosis-related genes that decreased host response to the NDV. Our results provide comprehensive information on the role played by OASL during NDV infection in vitro. Targeting this mechanism could aid in future prophylactic and therapeutic treatments for Newcastle disease in poultry.

Epigallocatechin Gallate (EGCG) Inhibited the Alv-J-Induced Apoptosis in Df-1 Cells by Inactivation of Nuclear Factor b Pathway

Avian leukosis virus subgroup J (ALV-J), a member of the retroviridae family, can infect both broilers and layers and induce a spectrum of different neoplasms, resulting in serious economic losses in poultry production. Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, has demonstrated remarkable anti-inflammatory and cancer chemopreventive effects in many animal tumor bioassays, cell culture systems and epidemiological studies. To assess the antiviral effects of EGCG on ALV-J-induced cell apoptosis in vitro, DF-1 cells were treated with different EGCG concentrations (0, 5, 10, 20 and 40 µg/mL), and their antiviral effects were examined at different time points (0, 24, 48, 72 and 96 h) using a variety of assays. EGCG alleviated the ALV-J-induced apoptosis in a dose-dependent manner. Because high concentrations (20 and 40 µg/mL) inhibited DF-1 cell growth, and low concentration (5 µg/mL) did not suppress the ALV-J virus, 10 µg/mL was the most appropriate concentration. After 96 h of incubation, 10 µg/mL EGCG improved the ALV-J-triggered suppression of the nuclear transcription factor system by enhancing cytoplasmic NF-B p50/p65 expression and inhibiting nuclear NF-B p50/p65 expression, resulting in decreased cell apoptosis. These results demonstrated that EGCG inhibited ALV-J-induced apoptosis in DF-1 cells in a dose-dependent manner via the NF-B signaling pathway, and that 10 µg/mL EGCG is the optimal concentration, which may be useful for therapeutic drug design.(AU)

Epigallocatechin Gallate (EGCG) Inhibited the Alv-J-Induced Apoptosis in Df-1 Cells by Inactivation of Nuclear Factor b Pathway

Avian leukosis virus subgroup J (ALV-J), a member of the retroviridae family, can infect both broilers and layers and induce a spectrum of different neoplasms, resulting in serious economic losses in poultry production. Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, has demonstrated remarkable anti-inflammatory and cancer chemopreventive effects in many animal tumor bioassays, cell culture systems and epidemiological studies. To assess the antiviral effects of EGCG on ALV-J-induced cell apoptosis in vitro, DF-1 cells were treated with different EGCG concentrations (0, 5, 10, 20 and 40 µg/mL), and their antiviral effects were examined at different time points (0, 24, 48, 72 and 96 h) using a variety of assays. EGCG alleviated the ALV-J-induced apoptosis in a dose-dependent manner. Because high concentrations (20 and 40 µg/mL) inhibited DF-1 cell growth, and low concentration (5 µg/mL) did not suppress the ALV-J virus, 10 µg/mL was the most appropriate concentration. After 96 h of incubation, 10 µg/mL EGCG improved the ALV-J-triggered suppression of the nuclear transcription factor system by enhancing cytoplasmic NF-B p50/p65 expression and inhibiting nuclear NF-B p50/p65 expression, resulting in decreased cell apoptosis. These results demonstrated that EGCG inhibited ALV-J-induced apoptosis in DF-1 cells in a dose-dependent manner via the NF-B signaling pathway, and that 10 µg/mL EGCG is the optimal concentration, which may be useful for therapeutic drug design.