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Tim-3 negatively regulates IL-12 expression by monocytes in HCV infection.

Zhang Y, Ma CJ, Wang JM, Ji XJ, Wu XY, Jia ZS, Moorman JP, Yao ZQ - PLoS ONE (2011)

Bottom Line: Tim-3 expression is significantly reduced and IL-12 expression increased upon stimulation with Toll-like receptor 4 (TLR4) ligand--lipopolysaccharide (LPS) and TLR7/8 ligand--R848.Notably, Tim-3 is over-expressed on un-stimulated as well as TLR-stimulated M/M(Ø), which is inversely associated with the diminished IL-12 expression in chronically HCV-infected individuals when compared to healthy subjects.Tim-3 blockade reduces HCV core-mediated expression of the negative immunoregulators PD-1 and SOCS-1 and increases STAT-1 phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Department of Internal Medicine, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, United States of America.

ABSTRACT
T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) is a newly identified negative immunomodulator that is up-regulated on dysfunctional T cells during viral infections. The expression and function of Tim-3 on human innate immune responses during HCV infection, however, remains poorly characterized. In this study, we report that Tim-3 is constitutively expressed on human resting CD14(+) monocyte/macrophages (M/M(Ø)) and functions as a cap to block IL-12, a key pro-inflammatory cytokine linking innate and adaptive immune responses. Tim-3 expression is significantly reduced and IL-12 expression increased upon stimulation with Toll-like receptor 4 (TLR4) ligand--lipopolysaccharide (LPS) and TLR7/8 ligand--R848. Notably, Tim-3 is over-expressed on un-stimulated as well as TLR-stimulated M/M(Ø), which is inversely associated with the diminished IL-12 expression in chronically HCV-infected individuals when compared to healthy subjects. Up-regulation of Tim-3 and inhibition of IL-12 are also observed in M/M(Ø) incubated with HCV-expressing hepatocytes, as well as in primary M/M(Ø) or monocytic THP-1 cells incubated with HCV core protein, an effect that mimics the function of complement C1q and is reversible by blocking the HCV core/gC1qR interaction. Importantly, blockade of Tim-3 signaling significantly rescues HCV-mediated inhibition of IL-12, which is primarily expressed by Tim-3 negative M/M(Ø). Tim-3 blockade reduces HCV core-mediated expression of the negative immunoregulators PD-1 and SOCS-1 and increases STAT-1 phosphorylation. Conversely, blocking PD-1 or silencing SOCS-1 gene expression also decreases Tim-3 expression and enhances IL-12 secretion and STAT-1 phosphorylation. These findings suggest that Tim-3 plays a crucial role in negative regulation of innate immune responses, through crosstalk with PD-1 and SOCS-1 and limiting STAT-1 phosphorylation, and may be a novel target for immunotherapy to HCV infection.

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A Model for the HCV core/gC1qR-induced negative signaling (Tim-3/PD-1/SOCS-1) molecules in regulation of IL-12 and Th1/Tc1 responses during HCV infection.We have previously shown that HCV core/gC1qR interaction up-regulates PD-1 and SOCS-1 negative signaling molecules, leading to suppression of TLR-mediated IL-12 production. In this study, we further demonstrated that the Tim-3 inhibitory pathway is involved in the HCV core/gC1qR-induced inhibition of IL-12 expression by M/MФ during HCV infection. Specifically, we found that Tim-3 can be up-regulated by HCV core/gC1qR interaction, which in turn, inhibits TLR-mediated IL-12 production. We also found that Tim-3 can crosstalk with other inhibitory molecules such as PD-1 and SOCS-1 to coordinately inhibit TLR-mediated IL-12 signaling pathways during HCV infection. We conclude that HCV-mediated innate immune dysregulation (impaired M/MФ IL-12 production) may ultimately lead to adaptive Th1/Tc1 dysfunction, and thus, HCV persistence.
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pone-0019664-g009: A Model for the HCV core/gC1qR-induced negative signaling (Tim-3/PD-1/SOCS-1) molecules in regulation of IL-12 and Th1/Tc1 responses during HCV infection.We have previously shown that HCV core/gC1qR interaction up-regulates PD-1 and SOCS-1 negative signaling molecules, leading to suppression of TLR-mediated IL-12 production. In this study, we further demonstrated that the Tim-3 inhibitory pathway is involved in the HCV core/gC1qR-induced inhibition of IL-12 expression by M/MФ during HCV infection. Specifically, we found that Tim-3 can be up-regulated by HCV core/gC1qR interaction, which in turn, inhibits TLR-mediated IL-12 production. We also found that Tim-3 can crosstalk with other inhibitory molecules such as PD-1 and SOCS-1 to coordinately inhibit TLR-mediated IL-12 signaling pathways during HCV infection. We conclude that HCV-mediated innate immune dysregulation (impaired M/MФ IL-12 production) may ultimately lead to adaptive Th1/Tc1 dysfunction, and thus, HCV persistence.

Mentions: Studies on the pathogenesis of HCV have been significantly advanced since the establishment of an in vitro cell culture model using Huh-7 hepatocytes-transfected with HCV-JFH-1 strain [19]–[20]. With the aid of Drs T. Wakita and T.J. Liang [19]–[20], we have successfully established an HCV-transfected Huh-7 model co-cultured with purified M/MØ, a model which provides us with a unique cell culture system to study host cell interactions that can more closely mimic the in vivo setting. By employing this novel system in our present study, we have demonstrated that Tim-3 is up-regulated by HCV to inhibit IL-12 expression. Based on this and our previous studies, we propose a pathogenesis model (Fig. 9) in that HCV core protein secreted from HCV-infected hepatocytes binds to gC1qR displayed on macrophages, up-regulating Tim-3, PD-1, and SOCS-1 negative immunomodulators that can crosstalk each other and coordinately inhibit cell signaling transduction, resulting in an impaired innate immune response with a cytokine environment (deficient IL-12/TNFα/IFN-γ) that is permissive for suppression of adaptive immune responses in the liver so as to facilitate the establishment of persistent infection. Whether other structural or non-structural proteins in additional to HCV core protein contribute to Tim-3/IL-12 dysregulation is under investigation in our laboratory using this model system.


Tim-3 negatively regulates IL-12 expression by monocytes in HCV infection.

Zhang Y, Ma CJ, Wang JM, Ji XJ, Wu XY, Jia ZS, Moorman JP, Yao ZQ - PLoS ONE (2011)

A Model for the HCV core/gC1qR-induced negative signaling (Tim-3/PD-1/SOCS-1) molecules in regulation of IL-12 and Th1/Tc1 responses during HCV infection.We have previously shown that HCV core/gC1qR interaction up-regulates PD-1 and SOCS-1 negative signaling molecules, leading to suppression of TLR-mediated IL-12 production. In this study, we further demonstrated that the Tim-3 inhibitory pathway is involved in the HCV core/gC1qR-induced inhibition of IL-12 expression by M/MФ during HCV infection. Specifically, we found that Tim-3 can be up-regulated by HCV core/gC1qR interaction, which in turn, inhibits TLR-mediated IL-12 production. We also found that Tim-3 can crosstalk with other inhibitory molecules such as PD-1 and SOCS-1 to coordinately inhibit TLR-mediated IL-12 signaling pathways during HCV infection. We conclude that HCV-mediated innate immune dysregulation (impaired M/MФ IL-12 production) may ultimately lead to adaptive Th1/Tc1 dysfunction, and thus, HCV persistence.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3102652&req=5

pone-0019664-g009: A Model for the HCV core/gC1qR-induced negative signaling (Tim-3/PD-1/SOCS-1) molecules in regulation of IL-12 and Th1/Tc1 responses during HCV infection.We have previously shown that HCV core/gC1qR interaction up-regulates PD-1 and SOCS-1 negative signaling molecules, leading to suppression of TLR-mediated IL-12 production. In this study, we further demonstrated that the Tim-3 inhibitory pathway is involved in the HCV core/gC1qR-induced inhibition of IL-12 expression by M/MФ during HCV infection. Specifically, we found that Tim-3 can be up-regulated by HCV core/gC1qR interaction, which in turn, inhibits TLR-mediated IL-12 production. We also found that Tim-3 can crosstalk with other inhibitory molecules such as PD-1 and SOCS-1 to coordinately inhibit TLR-mediated IL-12 signaling pathways during HCV infection. We conclude that HCV-mediated innate immune dysregulation (impaired M/MФ IL-12 production) may ultimately lead to adaptive Th1/Tc1 dysfunction, and thus, HCV persistence.
Mentions: Studies on the pathogenesis of HCV have been significantly advanced since the establishment of an in vitro cell culture model using Huh-7 hepatocytes-transfected with HCV-JFH-1 strain [19]–[20]. With the aid of Drs T. Wakita and T.J. Liang [19]–[20], we have successfully established an HCV-transfected Huh-7 model co-cultured with purified M/MØ, a model which provides us with a unique cell culture system to study host cell interactions that can more closely mimic the in vivo setting. By employing this novel system in our present study, we have demonstrated that Tim-3 is up-regulated by HCV to inhibit IL-12 expression. Based on this and our previous studies, we propose a pathogenesis model (Fig. 9) in that HCV core protein secreted from HCV-infected hepatocytes binds to gC1qR displayed on macrophages, up-regulating Tim-3, PD-1, and SOCS-1 negative immunomodulators that can crosstalk each other and coordinately inhibit cell signaling transduction, resulting in an impaired innate immune response with a cytokine environment (deficient IL-12/TNFα/IFN-γ) that is permissive for suppression of adaptive immune responses in the liver so as to facilitate the establishment of persistent infection. Whether other structural or non-structural proteins in additional to HCV core protein contribute to Tim-3/IL-12 dysregulation is under investigation in our laboratory using this model system.

Bottom Line: Tim-3 expression is significantly reduced and IL-12 expression increased upon stimulation with Toll-like receptor 4 (TLR4) ligand--lipopolysaccharide (LPS) and TLR7/8 ligand--R848.Notably, Tim-3 is over-expressed on un-stimulated as well as TLR-stimulated M/M(Ø), which is inversely associated with the diminished IL-12 expression in chronically HCV-infected individuals when compared to healthy subjects.Tim-3 blockade reduces HCV core-mediated expression of the negative immunoregulators PD-1 and SOCS-1 and increases STAT-1 phosphorylation.

View Article: PubMed Central - PubMed

Affiliation: Division of Infectious Diseases, Department of Internal Medicine, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, United States of America.

ABSTRACT
T cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) is a newly identified negative immunomodulator that is up-regulated on dysfunctional T cells during viral infections. The expression and function of Tim-3 on human innate immune responses during HCV infection, however, remains poorly characterized. In this study, we report that Tim-3 is constitutively expressed on human resting CD14(+) monocyte/macrophages (M/M(Ø)) and functions as a cap to block IL-12, a key pro-inflammatory cytokine linking innate and adaptive immune responses. Tim-3 expression is significantly reduced and IL-12 expression increased upon stimulation with Toll-like receptor 4 (TLR4) ligand--lipopolysaccharide (LPS) and TLR7/8 ligand--R848. Notably, Tim-3 is over-expressed on un-stimulated as well as TLR-stimulated M/M(Ø), which is inversely associated with the diminished IL-12 expression in chronically HCV-infected individuals when compared to healthy subjects. Up-regulation of Tim-3 and inhibition of IL-12 are also observed in M/M(Ø) incubated with HCV-expressing hepatocytes, as well as in primary M/M(Ø) or monocytic THP-1 cells incubated with HCV core protein, an effect that mimics the function of complement C1q and is reversible by blocking the HCV core/gC1qR interaction. Importantly, blockade of Tim-3 signaling significantly rescues HCV-mediated inhibition of IL-12, which is primarily expressed by Tim-3 negative M/M(Ø). Tim-3 blockade reduces HCV core-mediated expression of the negative immunoregulators PD-1 and SOCS-1 and increases STAT-1 phosphorylation. Conversely, blocking PD-1 or silencing SOCS-1 gene expression also decreases Tim-3 expression and enhances IL-12 secretion and STAT-1 phosphorylation. These findings suggest that Tim-3 plays a crucial role in negative regulation of innate immune responses, through crosstalk with PD-1 and SOCS-1 and limiting STAT-1 phosphorylation, and may be a novel target for immunotherapy to HCV infection.

Show MeSH
Related in: MedlinePlus