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Blockage of indoleamine 2,3-dioxygenase regulates Japanese encephalitis via enhancement of type I/II IFN innate and adaptive T-cell responses.

Kim SB, Choi JY, Uyangaa E, Patil AM, Hossain FM, Hur J, Park SY, Lee JH, Kim K, Eo SK - J Neuroinflammation (2016)

Bottom Line: Indoleamine 2,3-dioxygenase (IDO) has been identified as an enzyme associated with immunoregulatory function.Furthermore, inhibition of IDO activity enhanced resistance to JE, reduced the viral burden in lymphoid and CNS tissues, and resulted in early and increased CNS infiltration by Ly-6C(hi) monocytes, NK, CD4(+), and CD8(+) T-cells.Therefore, our data provide valuable insight into the use of IDO inhibition by specific inhibitors as a promising tool for therapeutic and prophylactic strategies against viral encephalitis caused by neurotropic viruses.

View Article: PubMed Central - PubMed

Affiliation: College of Veterinary Medicine and Bio-Safety Research Institute, Chonbuk National University, Iksan, 54596, Republic of Korea.

ABSTRACT

Background: Japanese encephalitis (JE), a leading cause of viral encephalitis, is characterized by extensive neuroinflammation following infection with neurotropic JE virus (JEV). Indoleamine 2,3-dioxygenase (IDO) has been identified as an enzyme associated with immunoregulatory function. Although the regulatory role of IDO in viral replication has been postulated, the in vivo role of IDO activity has not been fully addressed in neurotropic virus-caused encephalitis.

Methods: Mice in which IDO activity was inhibited by genetic ablation or using a specific inhibitor were examined for mortality and clinical signs after infection. Neuroinflammation was evaluated by central nervous system (CNS) infiltration of leukocytes and cytokine expression. IDO expression, viral burden, JEV-specific T-cell, and type I/II interferon (IFN-I/II) innate responses were also analyzed.

Results: Elevated expression of IDO activity in myeloid and neuron cells of the lymphoid and CNS tissues was closely associated with clinical signs of JE. Furthermore, inhibition of IDO activity enhanced resistance to JE, reduced the viral burden in lymphoid and CNS tissues, and resulted in early and increased CNS infiltration by Ly-6C(hi) monocytes, NK, CD4(+), and CD8(+) T-cells. JE amelioration in IDO-ablated mice was also associated with enhanced NK and JEV-specific T-cell responses. More interestingly, IDO ablation induced rapid enhancement of type I IFN (IFN-I) innate responses in CD11c(+) dendritic cells (DCs), including conventional and plasmacytoid DCs, following JEV infection. This enhanced IFN-I innate response in IDO-ablated CD11c(+) DCs was coupled with strong induction of PRRs (RIG-I, MDA5), transcription factors (IRF7, STAT1), and antiviral ISG genes (Mx1, Mx2, ISG49, ISG54, ISG56). IDO ablation also enhanced the IFN-I innate response in neuron cells, which may delay the spread of virus in the CNS. Finally, we identified that IDO ablation in myeloid cells derived from hematopoietic stem cells (HSCs) dominantly contributed to JE amelioration and that HSC-derived leukocytes played a key role in the enhanced IFN-I innate responses in the IDO-ablated environment.

Conclusions: Inhibition of IDO activity ameliorated JE via enhancement of antiviral IFN-I/II innate and adaptive T-cell responses and increased CNS infiltration of peripheral leukocytes. Therefore, our data provide valuable insight into the use of IDO inhibition by specific inhibitors as a promising tool for therapeutic and prophylactic strategies against viral encephalitis caused by neurotropic viruses.

No MeSH data available.


Related in: MedlinePlus

IDO ablation enhances CD4+ and CD8+ T-cell responses specific for JEV antigen. a JEV E-specific IgM and IgG response. Sera were collected from surviving mice 7 dpi and used in ELISA to detect IgM and IgG levels specific for the JEV E protein. The data show the average ± SD of the JEV E-specific IgM and IgG levels derived from surviving mice (n = 6–8). b, c CD4+ T-cell response specific for JEV antigen. The splenocytes prepared from surviving mice (n = 4–5) were stimulated with the JEV epitope peptides of CD4+ T-cells (NS1132–145 and NS3563–574) for 12 h. The frequency (b) and absolute number (c) of CD4+ T-cells specific for the JEV epitope peptides were determined by intracellular CD154, IFN-γ, or TNF-α staining, combined with surface CD4 staining. d, e CD8+ T-cell response specific for JEV antigen. The frequency (d) and absolute number (e) of CD8+ T-cells specific for the JEV epitope peptide (NS4B215–223) were determined by intracellular IFN-γ or TNF-α staining after an 8-h stimulation with peptide. Values in the representative dot plots denote the average percentage of the indicated cell population, and the bar charts show the average ± SD of the values derived from at least four mice per group. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups
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Fig5: IDO ablation enhances CD4+ and CD8+ T-cell responses specific for JEV antigen. a JEV E-specific IgM and IgG response. Sera were collected from surviving mice 7 dpi and used in ELISA to detect IgM and IgG levels specific for the JEV E protein. The data show the average ± SD of the JEV E-specific IgM and IgG levels derived from surviving mice (n = 6–8). b, c CD4+ T-cell response specific for JEV antigen. The splenocytes prepared from surviving mice (n = 4–5) were stimulated with the JEV epitope peptides of CD4+ T-cells (NS1132–145 and NS3563–574) for 12 h. The frequency (b) and absolute number (c) of CD4+ T-cells specific for the JEV epitope peptides were determined by intracellular CD154, IFN-γ, or TNF-α staining, combined with surface CD4 staining. d, e CD8+ T-cell response specific for JEV antigen. The frequency (d) and absolute number (e) of CD8+ T-cells specific for the JEV epitope peptide (NS4B215–223) were determined by intracellular IFN-γ or TNF-α staining after an 8-h stimulation with peptide. Values in the representative dot plots denote the average percentage of the indicated cell population, and the bar charts show the average ± SD of the values derived from at least four mice per group. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups

Mentions: In addition to NK cells, adaptive immune responses specific for JEV antigen are required for the regulation of JE progression through peripheral control of JEV replication [38–41]. Furthermore, IDO may in some cases affect antigen-specific antibody responses [42, 43], which contribute to the control of JEV dissemination and replication in the brain. Our data revealed that IDO ablation induced no significant changes in serum IgM and IgG specific for JEV antigen (Fig. 5a). Because IDO is known to suppress T-cell-mediated adaptive immune responses in a range of clinically relevant syndromes, including autoimmune, allergic, and infectious diseases [9, 10], we also evaluated CD4+ and CD8+ T-cell responses specific for JEV antigen in surviving BL/6 and IDO-ablated mice 7 dpi. IDO ablation resulted in moderately increased JEV-specific CD4+ T-cell responses when CD4+ T-cell responses were evaluated by intracellular CD154, IFN-γ, and TNF-α staining in response to stimulation with two epitope-peptides (NS1132–145 and NS3563–574) derived from JEV (Fig. 5b). Consistent with this finding, the total number of CD4+ T-cells producing IFN-γ or TNF-α in response to JEV epitope stimulation was higher in IDO-ablated mice (Fig. 5c). Furthermore, somewhat interestingly, IDO-ablated mice displayed markedly increased CD8+ T-cell responses with three- to fivefold higher levels, compared to BL/6 mice (Fig. 5d), and consistently contained a higher total number of JEV-specific CD8+ T-cells producing IFN-γ or TNF-α in response to a JEV CD8+ T-cell epitope (NS4B215–223) (Fig. 5e). These results indicate that the increased CD4+ and CD8+ T-cell responses generated in IDO-ablated mice could contribute to the control of JE progression during the late stage of infection.Fig. 5


Blockage of indoleamine 2,3-dioxygenase regulates Japanese encephalitis via enhancement of type I/II IFN innate and adaptive T-cell responses.

Kim SB, Choi JY, Uyangaa E, Patil AM, Hossain FM, Hur J, Park SY, Lee JH, Kim K, Eo SK - J Neuroinflammation (2016)

IDO ablation enhances CD4+ and CD8+ T-cell responses specific for JEV antigen. a JEV E-specific IgM and IgG response. Sera were collected from surviving mice 7 dpi and used in ELISA to detect IgM and IgG levels specific for the JEV E protein. The data show the average ± SD of the JEV E-specific IgM and IgG levels derived from surviving mice (n = 6–8). b, c CD4+ T-cell response specific for JEV antigen. The splenocytes prepared from surviving mice (n = 4–5) were stimulated with the JEV epitope peptides of CD4+ T-cells (NS1132–145 and NS3563–574) for 12 h. The frequency (b) and absolute number (c) of CD4+ T-cells specific for the JEV epitope peptides were determined by intracellular CD154, IFN-γ, or TNF-α staining, combined with surface CD4 staining. d, e CD8+ T-cell response specific for JEV antigen. The frequency (d) and absolute number (e) of CD8+ T-cells specific for the JEV epitope peptide (NS4B215–223) were determined by intracellular IFN-γ or TNF-α staining after an 8-h stimulation with peptide. Values in the representative dot plots denote the average percentage of the indicated cell population, and the bar charts show the average ± SD of the values derived from at least four mice per group. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4835894&req=5

Fig5: IDO ablation enhances CD4+ and CD8+ T-cell responses specific for JEV antigen. a JEV E-specific IgM and IgG response. Sera were collected from surviving mice 7 dpi and used in ELISA to detect IgM and IgG levels specific for the JEV E protein. The data show the average ± SD of the JEV E-specific IgM and IgG levels derived from surviving mice (n = 6–8). b, c CD4+ T-cell response specific for JEV antigen. The splenocytes prepared from surviving mice (n = 4–5) were stimulated with the JEV epitope peptides of CD4+ T-cells (NS1132–145 and NS3563–574) for 12 h. The frequency (b) and absolute number (c) of CD4+ T-cells specific for the JEV epitope peptides were determined by intracellular CD154, IFN-γ, or TNF-α staining, combined with surface CD4 staining. d, e CD8+ T-cell response specific for JEV antigen. The frequency (d) and absolute number (e) of CD8+ T-cells specific for the JEV epitope peptide (NS4B215–223) were determined by intracellular IFN-γ or TNF-α staining after an 8-h stimulation with peptide. Values in the representative dot plots denote the average percentage of the indicated cell population, and the bar charts show the average ± SD of the values derived from at least four mice per group. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups
Mentions: In addition to NK cells, adaptive immune responses specific for JEV antigen are required for the regulation of JE progression through peripheral control of JEV replication [38–41]. Furthermore, IDO may in some cases affect antigen-specific antibody responses [42, 43], which contribute to the control of JEV dissemination and replication in the brain. Our data revealed that IDO ablation induced no significant changes in serum IgM and IgG specific for JEV antigen (Fig. 5a). Because IDO is known to suppress T-cell-mediated adaptive immune responses in a range of clinically relevant syndromes, including autoimmune, allergic, and infectious diseases [9, 10], we also evaluated CD4+ and CD8+ T-cell responses specific for JEV antigen in surviving BL/6 and IDO-ablated mice 7 dpi. IDO ablation resulted in moderately increased JEV-specific CD4+ T-cell responses when CD4+ T-cell responses were evaluated by intracellular CD154, IFN-γ, and TNF-α staining in response to stimulation with two epitope-peptides (NS1132–145 and NS3563–574) derived from JEV (Fig. 5b). Consistent with this finding, the total number of CD4+ T-cells producing IFN-γ or TNF-α in response to JEV epitope stimulation was higher in IDO-ablated mice (Fig. 5c). Furthermore, somewhat interestingly, IDO-ablated mice displayed markedly increased CD8+ T-cell responses with three- to fivefold higher levels, compared to BL/6 mice (Fig. 5d), and consistently contained a higher total number of JEV-specific CD8+ T-cells producing IFN-γ or TNF-α in response to a JEV CD8+ T-cell epitope (NS4B215–223) (Fig. 5e). These results indicate that the increased CD4+ and CD8+ T-cell responses generated in IDO-ablated mice could contribute to the control of JE progression during the late stage of infection.Fig. 5

Bottom Line: Indoleamine 2,3-dioxygenase (IDO) has been identified as an enzyme associated with immunoregulatory function.Furthermore, inhibition of IDO activity enhanced resistance to JE, reduced the viral burden in lymphoid and CNS tissues, and resulted in early and increased CNS infiltration by Ly-6C(hi) monocytes, NK, CD4(+), and CD8(+) T-cells.Therefore, our data provide valuable insight into the use of IDO inhibition by specific inhibitors as a promising tool for therapeutic and prophylactic strategies against viral encephalitis caused by neurotropic viruses.

View Article: PubMed Central - PubMed

Affiliation: College of Veterinary Medicine and Bio-Safety Research Institute, Chonbuk National University, Iksan, 54596, Republic of Korea.

ABSTRACT

Background: Japanese encephalitis (JE), a leading cause of viral encephalitis, is characterized by extensive neuroinflammation following infection with neurotropic JE virus (JEV). Indoleamine 2,3-dioxygenase (IDO) has been identified as an enzyme associated with immunoregulatory function. Although the regulatory role of IDO in viral replication has been postulated, the in vivo role of IDO activity has not been fully addressed in neurotropic virus-caused encephalitis.

Methods: Mice in which IDO activity was inhibited by genetic ablation or using a specific inhibitor were examined for mortality and clinical signs after infection. Neuroinflammation was evaluated by central nervous system (CNS) infiltration of leukocytes and cytokine expression. IDO expression, viral burden, JEV-specific T-cell, and type I/II interferon (IFN-I/II) innate responses were also analyzed.

Results: Elevated expression of IDO activity in myeloid and neuron cells of the lymphoid and CNS tissues was closely associated with clinical signs of JE. Furthermore, inhibition of IDO activity enhanced resistance to JE, reduced the viral burden in lymphoid and CNS tissues, and resulted in early and increased CNS infiltration by Ly-6C(hi) monocytes, NK, CD4(+), and CD8(+) T-cells. JE amelioration in IDO-ablated mice was also associated with enhanced NK and JEV-specific T-cell responses. More interestingly, IDO ablation induced rapid enhancement of type I IFN (IFN-I) innate responses in CD11c(+) dendritic cells (DCs), including conventional and plasmacytoid DCs, following JEV infection. This enhanced IFN-I innate response in IDO-ablated CD11c(+) DCs was coupled with strong induction of PRRs (RIG-I, MDA5), transcription factors (IRF7, STAT1), and antiviral ISG genes (Mx1, Mx2, ISG49, ISG54, ISG56). IDO ablation also enhanced the IFN-I innate response in neuron cells, which may delay the spread of virus in the CNS. Finally, we identified that IDO ablation in myeloid cells derived from hematopoietic stem cells (HSCs) dominantly contributed to JE amelioration and that HSC-derived leukocytes played a key role in the enhanced IFN-I innate responses in the IDO-ablated environment.

Conclusions: Inhibition of IDO activity ameliorated JE via enhancement of antiviral IFN-I/II innate and adaptive T-cell responses and increased CNS infiltration of peripheral leukocytes. Therefore, our data provide valuable insight into the use of IDO inhibition by specific inhibitors as a promising tool for therapeutic and prophylactic strategies against viral encephalitis caused by neurotropic viruses.

No MeSH data available.


Related in: MedlinePlus