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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

IFN-I innate immune responses of IDO-ablated myeloid-derived cells after JEV infection. Primary bone marrow-derived conventional DCs (BMDCs), plasmacytoid DCs (pDCs), and macrophages (BMDMs) recovered from BL/6 and IDO KO mice were infected with JEV at MOIs of 0.1, 1.0, and 10 for viral replication and 10 for cytokine expression. JEV replication and the expression of cytokines and IFN-α/β were evaluated by real-time qRT-PCR using extracted total RNA. a–c JEV replication in BMDCs, BMDMs, and pDCs. d, e IFN-α/β, IL-6, and TNF-α expression in BMDCs, pDCs, and BMDMs. The bar charts show the average ± SD of the values derived from BMDCs, BMDMs, and pDCs assayed in quadruplicates. *p < 0.05; **p < 0.01; p < 0.001 compared with levels in the indicated groups
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Fig7: IFN-I innate immune responses of IDO-ablated myeloid-derived cells after JEV infection. Primary bone marrow-derived conventional DCs (BMDCs), plasmacytoid DCs (pDCs), and macrophages (BMDMs) recovered from BL/6 and IDO KO mice were infected with JEV at MOIs of 0.1, 1.0, and 10 for viral replication and 10 for cytokine expression. JEV replication and the expression of cytokines and IFN-α/β were evaluated by real-time qRT-PCR using extracted total RNA. a–c JEV replication in BMDCs, BMDMs, and pDCs. d, e IFN-α/β, IL-6, and TNF-α expression in BMDCs, pDCs, and BMDMs. The bar charts show the average ± SD of the values derived from BMDCs, BMDMs, and pDCs assayed in quadruplicates. *p < 0.05; **p < 0.01; p < 0.001 compared with levels in the indicated groups

Mentions: Myeloid cells, including DCs and macrophages, are the primary target cells of JEV infection in the peripheral tissues and function to regulate the spread of virus to distant tissues such as the CNS [23]. Furthermore, myeloid cells can produce IFN-I via PRR recognition upon JEV infection, which plays a crucial role in controlling viral replication [51, 52]. Additionally, IDO ablation appears to regulate viral replication via IFN-I production [21]. Because viral loads at the periphery in IDO-ablated mice were lower than in wild-type BL/6 mice, we evaluated the contribution of DC subsets (conventional and plasmacytoid) and macrophages to the IFN-I innate immune responses caused by JEV infection in the IDO-ablated environment. In order to assess the role of IDO in inducing the IFN-I innate response of JEV-infected DC subsets and macrophages, BMDCs, pDCs, and macrophages (BMDMs) prepared from IDO-ablated mice were infected with JEV and used to evaluate viral replication and the induction of IFN-I and pro-inflammatory cytokines. Interestingly, IDO-ablated BMDCs and pDCs, but not BMDMs, showed significantly lower JEV replication (Fig. 7a–c). Notably, BMDCs derived from IDO-ablated mice exhibited impaired JEV replication throughout the examination period compared to replication in cells from wild-type BL/6 mice. Furthermore, the inhibition of JEV replication in BMDCs and pDCs derived from IDO-ablated mice was closely associated with enhanced expression of IFN-I (IFN-α/β) following JEV infection (Fig. 7d). IDO-ablated BMDCs and pDCs, but not BMDMs, showed rapid induction of IFN-α/β in response to JEV infection compared to levels measured in cells from wild-type BL/6 mice. However, it was curious that pDCs showed less apparent regulation of viral replication than BMDCs, despite pDCs inducing stronger IFN-I innate responses. Presumably, this discrepancy is related to cell-intrinsic properties or other mechanisms involved in regulating viral replication. In addition, rapid and increased induction of IL-6 and TNF-α mRNAs was observed upon JEV infection in IDO-ablated BMDCs (Fig. 7e). Collectively, these results imply that rapid and increased IFN-I innate responses in CD11c+ DC subsets (conventional DCs and pDCs) may contribute to the early control of viral replication in the absence of IDO. To further characterize IFN-I innate responses in JEV-infected DC subsets derived from IDO-ablated mice, we also measured the induction levels of ISG genes. We specifically focused on pattern recognition receptors ( PRRs; RIG-I [DDX1], MDA5 [IFITH1], PKR), transcription factors (STAT1, IRF3, IRF7), IFN-induced antivirus-related genes (Oas1, Oasl-1, Mx1, Mx2), and several ISG genes (ISG49 [IFIT3], ISG54 [IFIT2], ISG56 [IFIT1]). Our results revealed that BMDCs and pDCs derived from IDO-ablated mice showed rapid and enhanced expression of the STAT1, Oas1, Mx1, Mx2, and ISG genes with slightly different patterns at 24 h pi, whereas BMDMs derived from IDO-ablated mice showed either no alteration or a slight decrease in the expression of PRRs, IFR3 and IRF7, and ISG genes (Fig. 8). Also, it was interesting that BMDCs and pDCs derived from IDO-ablated mice displayed early enhanced induction of PRRs (RIG-I and MDA5) and their transcription factor (IRF7) at 24 h pi. This indicates that rapid and increased expression of ISG genes in JEV-infected BMDCs and pDCs follows the inhibition of JEV replication via enhanced expression of IFN-α/β. Collectively, IDO ablation appears to provide rapid and increased responses of IFN-I innate immunity in myeloid-derived DCs and pDCs upon JEV infection, thereby contributing to the amelioration of JE through early control of viral replication.Fig. 7


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)

IFN-I innate immune responses of IDO-ablated myeloid-derived cells after JEV infection. Primary bone marrow-derived conventional DCs (BMDCs), plasmacytoid DCs (pDCs), and macrophages (BMDMs) recovered from BL/6 and IDO KO mice were infected with JEV at MOIs of 0.1, 1.0, and 10 for viral replication and 10 for cytokine expression. JEV replication and the expression of cytokines and IFN-α/β were evaluated by real-time qRT-PCR using extracted total RNA. a–c JEV replication in BMDCs, BMDMs, and pDCs. d, e IFN-α/β, IL-6, and TNF-α expression in BMDCs, pDCs, and BMDMs. The bar charts show the average ± SD of the values derived from BMDCs, BMDMs, and pDCs assayed in quadruplicates. *p < 0.05; **p < 0.01; p < 0.001 compared with levels in the indicated groups
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Fig7: IFN-I innate immune responses of IDO-ablated myeloid-derived cells after JEV infection. Primary bone marrow-derived conventional DCs (BMDCs), plasmacytoid DCs (pDCs), and macrophages (BMDMs) recovered from BL/6 and IDO KO mice were infected with JEV at MOIs of 0.1, 1.0, and 10 for viral replication and 10 for cytokine expression. JEV replication and the expression of cytokines and IFN-α/β were evaluated by real-time qRT-PCR using extracted total RNA. a–c JEV replication in BMDCs, BMDMs, and pDCs. d, e IFN-α/β, IL-6, and TNF-α expression in BMDCs, pDCs, and BMDMs. The bar charts show the average ± SD of the values derived from BMDCs, BMDMs, and pDCs assayed in quadruplicates. *p < 0.05; **p < 0.01; p < 0.001 compared with levels in the indicated groups
Mentions: Myeloid cells, including DCs and macrophages, are the primary target cells of JEV infection in the peripheral tissues and function to regulate the spread of virus to distant tissues such as the CNS [23]. Furthermore, myeloid cells can produce IFN-I via PRR recognition upon JEV infection, which plays a crucial role in controlling viral replication [51, 52]. Additionally, IDO ablation appears to regulate viral replication via IFN-I production [21]. Because viral loads at the periphery in IDO-ablated mice were lower than in wild-type BL/6 mice, we evaluated the contribution of DC subsets (conventional and plasmacytoid) and macrophages to the IFN-I innate immune responses caused by JEV infection in the IDO-ablated environment. In order to assess the role of IDO in inducing the IFN-I innate response of JEV-infected DC subsets and macrophages, BMDCs, pDCs, and macrophages (BMDMs) prepared from IDO-ablated mice were infected with JEV and used to evaluate viral replication and the induction of IFN-I and pro-inflammatory cytokines. Interestingly, IDO-ablated BMDCs and pDCs, but not BMDMs, showed significantly lower JEV replication (Fig. 7a–c). Notably, BMDCs derived from IDO-ablated mice exhibited impaired JEV replication throughout the examination period compared to replication in cells from wild-type BL/6 mice. Furthermore, the inhibition of JEV replication in BMDCs and pDCs derived from IDO-ablated mice was closely associated with enhanced expression of IFN-I (IFN-α/β) following JEV infection (Fig. 7d). IDO-ablated BMDCs and pDCs, but not BMDMs, showed rapid induction of IFN-α/β in response to JEV infection compared to levels measured in cells from wild-type BL/6 mice. However, it was curious that pDCs showed less apparent regulation of viral replication than BMDCs, despite pDCs inducing stronger IFN-I innate responses. Presumably, this discrepancy is related to cell-intrinsic properties or other mechanisms involved in regulating viral replication. In addition, rapid and increased induction of IL-6 and TNF-α mRNAs was observed upon JEV infection in IDO-ablated BMDCs (Fig. 7e). Collectively, these results imply that rapid and increased IFN-I innate responses in CD11c+ DC subsets (conventional DCs and pDCs) may contribute to the early control of viral replication in the absence of IDO. To further characterize IFN-I innate responses in JEV-infected DC subsets derived from IDO-ablated mice, we also measured the induction levels of ISG genes. We specifically focused on pattern recognition receptors ( PRRs; RIG-I [DDX1], MDA5 [IFITH1], PKR), transcription factors (STAT1, IRF3, IRF7), IFN-induced antivirus-related genes (Oas1, Oasl-1, Mx1, Mx2), and several ISG genes (ISG49 [IFIT3], ISG54 [IFIT2], ISG56 [IFIT1]). Our results revealed that BMDCs and pDCs derived from IDO-ablated mice showed rapid and enhanced expression of the STAT1, Oas1, Mx1, Mx2, and ISG genes with slightly different patterns at 24 h pi, whereas BMDMs derived from IDO-ablated mice showed either no alteration or a slight decrease in the expression of PRRs, IFR3 and IRF7, and ISG genes (Fig. 8). Also, it was interesting that BMDCs and pDCs derived from IDO-ablated mice displayed early enhanced induction of PRRs (RIG-I and MDA5) and their transcription factor (IRF7) at 24 h pi. This indicates that rapid and increased expression of ISG genes in JEV-infected BMDCs and pDCs follows the inhibition of JEV replication via enhanced expression of IFN-α/β. Collectively, IDO ablation appears to provide rapid and increased responses of IFN-I innate immunity in myeloid-derived DCs and pDCs upon JEV infection, thereby contributing to the amelioration of JE through early control of viral replication.Fig. 7

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