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Hepatitis C Virus Driven AXL Expression Suppresses the Hepatic Type I Interferon Response.

Read SA, Tay ES, Shahidi M, O'Connor KS, Booth DR, George J, Douglas MW - PLoS ONE (2015)

Bottom Line: AXL inhibited type IFNα mediated ISG expression resulting in a decrease in its antiviral efficacy against HCV in vitro.Furthermore, patients possessing the favourable IFNL3 rs12979860 genotype associated with treatment response, showed lower AXL expression in the liver and a stronger induction of AXL in the blood, following their first dose of IFN.Together, these data suggest that elevated AXL expression in the liver may mediate an IFN-refractory phenotype characteristic of patients possessing the unfavourable rs12979860 genotype, which is associated with lower rates of viral clearance.

View Article: PubMed Central - PubMed

Affiliation: Storr Liver Centre, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia.

ABSTRACT
Treatment of chronic hepatitis C virus (HCV) infection is evolving rapidly with the development of novel direct acting antivirals (DAAs), however viral clearance remains intimately linked to the hepatic innate immune system. Patients demonstrating a high baseline activation of interferon stimulated genes (ISGs), termed interferon refractoriness, are less likely to mount a strong antiviral response and achieve viral clearance when placed on treatment. As a result, suppressor of cytokine signalling (SOCS) 3 and other regulators of the IFN response have been identified as key candidates for the IFN refractory phenotype due to their regulatory role on the IFN response. AXL is a receptor tyrosine kinase that has been identified as a key regulator of interferon (IFN) signalling in myeloid cells of the immune system, but has not been examined in the context of chronic HCV infection. Here, we show that AXL is up-regulated following HCV infection, both in vitro and in vivo and is likely induced by type I/III IFNs and inflammatory signalling pathways. AXL inhibited type IFNα mediated ISG expression resulting in a decrease in its antiviral efficacy against HCV in vitro. Furthermore, patients possessing the favourable IFNL3 rs12979860 genotype associated with treatment response, showed lower AXL expression in the liver and a stronger induction of AXL in the blood, following their first dose of IFN. Together, these data suggest that elevated AXL expression in the liver may mediate an IFN-refractory phenotype characteristic of patients possessing the unfavourable rs12979860 genotype, which is associated with lower rates of viral clearance.

No MeSH data available.


Related in: MedlinePlus

HCV infection mediates AXL expression in vitro and in vivo.AXL and SOCS3 expression are significantly increased in JFH1 infected Huh-7 cells, but decreased in cells containing a genotype 2a HCV subgenomic replicon (SGR), which lacks structural proteins. This was demonstrated at the mRNA level by qPCR (A), and confirmed at the protein level by western blot (B). Genotype dependent (GT1>3) induction of AXL and SOCS3 was observed in HepG2 cells transfected with baculovirus expressing HCV core protein (C), as well as in Huh-7 cells infected with core chimeric HCV viruses (D) (* p<0.05, ** p<0.01). Data represents the mean and standard error of three biological replicates, each with duplicate samples.
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pone.0136227.g001: HCV infection mediates AXL expression in vitro and in vivo.AXL and SOCS3 expression are significantly increased in JFH1 infected Huh-7 cells, but decreased in cells containing a genotype 2a HCV subgenomic replicon (SGR), which lacks structural proteins. This was demonstrated at the mRNA level by qPCR (A), and confirmed at the protein level by western blot (B). Genotype dependent (GT1>3) induction of AXL and SOCS3 was observed in HepG2 cells transfected with baculovirus expressing HCV core protein (C), as well as in Huh-7 cells infected with core chimeric HCV viruses (D) (* p<0.05, ** p<0.01). Data represents the mean and standard error of three biological replicates, each with duplicate samples.

Mentions: We previously demonstrated that infection of Huh-7 cells with HCV (JFH1 strain) induces the expression of AXL as well as its downstream target SOCS3 [13]. To further confirm the mechanism by which AXL and SOCS3 are induced during HCV infection, we examined their expression in Huh-7 cells containing a HCV subgenomic replicon (SGR), which expresses only non-structural viral proteins, and in cells containing fully replicating JFH1 virus. Both AXL and SOCS3 were up-regulated approximately 2 fold in JFH1 infected cells (minimum 2 passages, 1 week post infection, 90% infectivity), but were surprisingly down-regulated in a stable cell line of Huh-7s harbouring a genotype 2a SGR [19] (Fig 1A). SOCS1 demonstrated an opposite expression pattern, being up-regulated 2 fold in cells harbouring the SGR (p<0.05). To determine whether the AXL protein is activated and thus able to induce SOCS3 in JFH1 infected Huh-7 cells, we examined AXL phosphorylation at tyrosine 779 by western blot. Interestingly, both total AXL and phosphorylated AXL were up-regulated in JFH1 infected cells (Fig 1B). Furthermore, both glycosylation states of AXL, represented by bands at approximately 110 and 140 kDa, were increased in JFH1 infected cells. These data suggest that AXL may drive SOCS3 expression in these cells, as has been shown in other models [12,20].


Hepatitis C Virus Driven AXL Expression Suppresses the Hepatic Type I Interferon Response.

Read SA, Tay ES, Shahidi M, O'Connor KS, Booth DR, George J, Douglas MW - PLoS ONE (2015)

HCV infection mediates AXL expression in vitro and in vivo.AXL and SOCS3 expression are significantly increased in JFH1 infected Huh-7 cells, but decreased in cells containing a genotype 2a HCV subgenomic replicon (SGR), which lacks structural proteins. This was demonstrated at the mRNA level by qPCR (A), and confirmed at the protein level by western blot (B). Genotype dependent (GT1>3) induction of AXL and SOCS3 was observed in HepG2 cells transfected with baculovirus expressing HCV core protein (C), as well as in Huh-7 cells infected with core chimeric HCV viruses (D) (* p<0.05, ** p<0.01). Data represents the mean and standard error of three biological replicates, each with duplicate samples.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4551482&req=5

pone.0136227.g001: HCV infection mediates AXL expression in vitro and in vivo.AXL and SOCS3 expression are significantly increased in JFH1 infected Huh-7 cells, but decreased in cells containing a genotype 2a HCV subgenomic replicon (SGR), which lacks structural proteins. This was demonstrated at the mRNA level by qPCR (A), and confirmed at the protein level by western blot (B). Genotype dependent (GT1>3) induction of AXL and SOCS3 was observed in HepG2 cells transfected with baculovirus expressing HCV core protein (C), as well as in Huh-7 cells infected with core chimeric HCV viruses (D) (* p<0.05, ** p<0.01). Data represents the mean and standard error of three biological replicates, each with duplicate samples.
Mentions: We previously demonstrated that infection of Huh-7 cells with HCV (JFH1 strain) induces the expression of AXL as well as its downstream target SOCS3 [13]. To further confirm the mechanism by which AXL and SOCS3 are induced during HCV infection, we examined their expression in Huh-7 cells containing a HCV subgenomic replicon (SGR), which expresses only non-structural viral proteins, and in cells containing fully replicating JFH1 virus. Both AXL and SOCS3 were up-regulated approximately 2 fold in JFH1 infected cells (minimum 2 passages, 1 week post infection, 90% infectivity), but were surprisingly down-regulated in a stable cell line of Huh-7s harbouring a genotype 2a SGR [19] (Fig 1A). SOCS1 demonstrated an opposite expression pattern, being up-regulated 2 fold in cells harbouring the SGR (p<0.05). To determine whether the AXL protein is activated and thus able to induce SOCS3 in JFH1 infected Huh-7 cells, we examined AXL phosphorylation at tyrosine 779 by western blot. Interestingly, both total AXL and phosphorylated AXL were up-regulated in JFH1 infected cells (Fig 1B). Furthermore, both glycosylation states of AXL, represented by bands at approximately 110 and 140 kDa, were increased in JFH1 infected cells. These data suggest that AXL may drive SOCS3 expression in these cells, as has been shown in other models [12,20].

Bottom Line: AXL inhibited type IFNα mediated ISG expression resulting in a decrease in its antiviral efficacy against HCV in vitro.Furthermore, patients possessing the favourable IFNL3 rs12979860 genotype associated with treatment response, showed lower AXL expression in the liver and a stronger induction of AXL in the blood, following their first dose of IFN.Together, these data suggest that elevated AXL expression in the liver may mediate an IFN-refractory phenotype characteristic of patients possessing the unfavourable rs12979860 genotype, which is associated with lower rates of viral clearance.

View Article: PubMed Central - PubMed

Affiliation: Storr Liver Centre, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia.

ABSTRACT
Treatment of chronic hepatitis C virus (HCV) infection is evolving rapidly with the development of novel direct acting antivirals (DAAs), however viral clearance remains intimately linked to the hepatic innate immune system. Patients demonstrating a high baseline activation of interferon stimulated genes (ISGs), termed interferon refractoriness, are less likely to mount a strong antiviral response and achieve viral clearance when placed on treatment. As a result, suppressor of cytokine signalling (SOCS) 3 and other regulators of the IFN response have been identified as key candidates for the IFN refractory phenotype due to their regulatory role on the IFN response. AXL is a receptor tyrosine kinase that has been identified as a key regulator of interferon (IFN) signalling in myeloid cells of the immune system, but has not been examined in the context of chronic HCV infection. Here, we show that AXL is up-regulated following HCV infection, both in vitro and in vivo and is likely induced by type I/III IFNs and inflammatory signalling pathways. AXL inhibited type IFNα mediated ISG expression resulting in a decrease in its antiviral efficacy against HCV in vitro. Furthermore, patients possessing the favourable IFNL3 rs12979860 genotype associated with treatment response, showed lower AXL expression in the liver and a stronger induction of AXL in the blood, following their first dose of IFN. Together, these data suggest that elevated AXL expression in the liver may mediate an IFN-refractory phenotype characteristic of patients possessing the unfavourable rs12979860 genotype, which is associated with lower rates of viral clearance.

No MeSH data available.


Related in: MedlinePlus