Activation of Toll-like receptor 3 inhibits Marek’s disease virus infection in chicken embryo fibroblast cells

Abstract

Toll-like receptor 3 (TLR3) is a critical component of the innate immune system against viral infection and controls the activation of adaptive immunity. The role of TLR3 in Marek's disease virus (MDV) infection is not clear. In this study, we found that the abundance of TLR3 mRNA was significantly higher in chicken embryo fibroblast cells (CEF) infected with MDV than in a control group. Activated TLR3 signaling via TLR3 ligand stimulation inhibited replication of the RB1B strain of MDV in CEF cells. In contrast, CEF cells transfected with TLR3 siRNA promoted RB1B infection and replication. However, treatment with other TLR ligands, whether stimulatory (LPS, imiquimod and CpG) or inhibitory (TLR2/4 inhibitor and/or MyD88 inhibitor), had little effect on RB1B infection and replication. In addition, we found that the expression trend of TLR3 mRNA in RB1B-infected CEF cells was similar to that of mdv1-mir-M4-5p (a functional ortholog of oncogenic miR-155 encoded by MDV). Inconsistent with this, the TLR3 protein level was sharply reduced in RB1B-infected CEF cells at 96 hpi, while there was an at least 200-fold increase in miR-M4-5p at the same time point. Additionally, CEF cells transfected with an mdv1-mir-M4-5p mimic promoted RB1B infection and replication, while an mdv1-mir-M4-5p inhibitor inhibited RB1B infection and replication. Similar results were observed in CEF cells transfected with a gga-miR-155 mimic or inhibitor. These findings suggest that TLR3 and MDV-encoded miRNAs might be involved in MDV infection.

Environmental pollutants modulate RNA and DNA virus-activated miRNA-155 expression and innate immune system responses: Insights into new immunomodulative mechanisms*

“…The up-regulation of mir-155 after GaHV-2 infection in non-polluted CEF seen here is in agreement with data from the study of Hu et al (2016). The ability of CEF to react to GaHV-2 by inducing miRNA was previously demonstrated by sequence analysis; host miRNA represented the dominant form of miRNA induced in CEF during GaHV-2 infections (81%), whereas only 0.6% contributed to GaHV-2-encoded miRNA (Burnside and Morgan 2007).…”

“…All the immune response genes investigated here were upregulated after 8 h of GaHV-2 infection and showed, except for mir-155, an enhanced expression compared to levels seen in unpolluted/poly(I:C)-treated cells. Interestingly, both GaHV-2 and poly(I:C) are known to significantly up-regulate TLR3 mRNA in primary CEF after 8 h (Haunshi and Cheng 2014;Hu et al 2016). However, additional signals provided by GaHV-2, like the production of DAMPs, might (in contrast to in poly(I:C)-treated cells) be a reason for the significant expression of TLR3-induced defense mechanisms like the activation of NF-jB signaling.…”

“…CEFs have been shown to be competent in inducing various genes that encode for proteins involved in inflammation, as well as miRNA, upon GaHV-2 infection (Burnside et al 2006;Burnside and Morgan 2007). Therefore, CEFs are widely used as suitable models for GaHV-2 infections (Haunshi and Cheng 2014;Hu et al 2016). By analyzing the expression profile of NF-jB1, tumor necrosis factor (TNF)-a, IL-8, and IL-4 (mRNA), and mir-155 in response to GaHV-2 or to the synthetic viral double-stranded (ds) RNA analog polyinosinic-polycytidylic acid (poly I:C), the present study sought to investigate natural defense mechanisms by the cells as well as differences between a RNA virus analog and an actual dsDNA virus infection.…”

Selective breeding on natural antibodies in chickens

“…Only two of these are directly related to health and disease susceptibility: The same region was found for natural autoantibodies IgM levels (Bao, submitted), and for susceptibility to Marek's disease virus (Heifetz et al, 2007). Though this association with Marek's susceptibility was stronger around TLR3 (also located on chromosome 4, around 62 Mbp), which is involved in the recognition of viruses, including Marek's disease virus infections (Hu et al, 2016a). Other characteristics associated to these region were for example age at first egg (Podisi et al, 2011), eggshell breaking strength (Sasaki et al, 2004), eggshell color (Goto et al, 2011;Wolc et al, 2014), egg weight (Tuiskula-Haavisto et al, 2002;Sasaki et al, 2004;Schreiweis et al, 2006), feed intake (Tuiskula-Haavisto et al, 2002), growth/body weight at several ages (Carlborg et al, 2004;Zhou et al, 2006a;Nadaf et al, 2009;Ankra-Badu et al, 2010;Podisi et al, 2011;Goraga et al, 2012;Podisi et al, 2013;Nassar et al, 2015), liver weight (Navarro et al, 2005), and spleen weight (Zhou et al, 2006b).…”

In vitro estimation of metal-induced disturbance in chicken gut-oviduct chemokine circuit

“…Moreover, induced pluripotency in chicken eF can generate germ cells and facilitate their optimal survival and migration to embryonic gonads via the chemokine receptor-linked pathway 19,20 . in addition to impacts on egg development, eF can play key roles in the innate immunological recognition and tissue repair following infection and inflammatory insults to the reproductive organs [21][22][23] . in the present study, eFs were used to compare the relative toxicities of inorganic heavy metals, which are known to contaminate mammalian and avian diets as well as drinking water.…”