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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

Induction of IFN-I and ISGs in primary cortical neurons derived from IDO KO mice after JEV infection. Primary cortical neurons generated from BL/6 and IDO KO mice were infected at MOIs of 0.001 and 0.01, and viral replication and IFN-I responses 24, 48, and 72 h pi were analyzed by real-time qRT-PCR. a JEV replication. b IFN-I (IFN-α/β) expression. c–e Induction of ISGs, RLRs, and IRFs in infected primary cortical neuron. The expression of IFN-I (b), ISGs (c), RLRs (d), and IRFs (e) was determined using primary cortical neuron infected with JEV (0.1 MOI) 24 h pi. The bar charts show the average ± SD of values derived from primary cortical neurons in quadruplicate. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups
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Fig10: Induction of IFN-I and ISGs in primary cortical neurons derived from IDO KO mice after JEV infection. Primary cortical neurons generated from BL/6 and IDO KO mice were infected at MOIs of 0.001 and 0.01, and viral replication and IFN-I responses 24, 48, and 72 h pi were analyzed by real-time qRT-PCR. a JEV replication. b IFN-I (IFN-α/β) expression. c–e Induction of ISGs, RLRs, and IRFs in infected primary cortical neuron. The expression of IFN-I (b), ISGs (c), RLRs (d), and IRFs (e) was determined using primary cortical neuron infected with JEV (0.1 MOI) 24 h pi. The bar charts show the average ± SD of values derived from primary cortical neurons in quadruplicate. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups

Mentions: Neurons are the main target cell of JEV replication within the CNS, and their death is a key factor in the pathogenesis and neurological sequelae of JEV [23]. Furthermore, neuron cells have also been shown to produce antiviral IFN-I in response to viral infection and are consequently involved in controlling viral replication in the CNS [54, 55]. Therefore, we examined viral replication and IFN-I innate immune responses in primary cortical neuron cells generated from wild-type BL/6 and IDO-ablated mice after JEV infection. Consistent with the results obtained from BMDCs and pDCs, primary cortical neurons derived from IDO-ablated mice showed transiently reduced JEV replication (Fig. 10a). This transient reduction of JEV replication in IDO-ablated neurons was associated with significantly increased induction of IFN-I (IFN-α/β), relative to the levels measured in cells from wild-type BL/6 mice (Fig. 10b). Also, it seemed that the expression of antiviral ISG genes (ISG49, ISG54, ISG59) in IDO-ablated neurons followed IFN-I innate responses and the transient reduction in viral replication (Fig. 10c), whereas the expression levels of transcription factors (IRF3, IRF7), but not PRRs (RIG-I, MDA5), were decreased by JEV infection (Fig. 10d, e). Therefore, these results suggest that the ablation of IDO could provide enhanced IFN-I innate immune responses in neuron cells to regulate the spread of JEV in the CNS.Fig. 10


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)

Induction of IFN-I and ISGs in primary cortical neurons derived from IDO KO mice after JEV infection. Primary cortical neurons generated from BL/6 and IDO KO mice were infected at MOIs of 0.001 and 0.01, and viral replication and IFN-I responses 24, 48, and 72 h pi were analyzed by real-time qRT-PCR. a JEV replication. b IFN-I (IFN-α/β) expression. c–e Induction of ISGs, RLRs, and IRFs in infected primary cortical neuron. The expression of IFN-I (b), ISGs (c), RLRs (d), and IRFs (e) was determined using primary cortical neuron infected with JEV (0.1 MOI) 24 h pi. The bar charts show the average ± SD of values derived from primary cortical neurons in quadruplicate. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig10: Induction of IFN-I and ISGs in primary cortical neurons derived from IDO KO mice after JEV infection. Primary cortical neurons generated from BL/6 and IDO KO mice were infected at MOIs of 0.001 and 0.01, and viral replication and IFN-I responses 24, 48, and 72 h pi were analyzed by real-time qRT-PCR. a JEV replication. b IFN-I (IFN-α/β) expression. c–e Induction of ISGs, RLRs, and IRFs in infected primary cortical neuron. The expression of IFN-I (b), ISGs (c), RLRs (d), and IRFs (e) was determined using primary cortical neuron infected with JEV (0.1 MOI) 24 h pi. The bar charts show the average ± SD of values derived from primary cortical neurons in quadruplicate. *p < 0.05; **p < 0.01; ***p < 0.001 compared with levels in the indicated groups
Mentions: Neurons are the main target cell of JEV replication within the CNS, and their death is a key factor in the pathogenesis and neurological sequelae of JEV [23]. Furthermore, neuron cells have also been shown to produce antiviral IFN-I in response to viral infection and are consequently involved in controlling viral replication in the CNS [54, 55]. Therefore, we examined viral replication and IFN-I innate immune responses in primary cortical neuron cells generated from wild-type BL/6 and IDO-ablated mice after JEV infection. Consistent with the results obtained from BMDCs and pDCs, primary cortical neurons derived from IDO-ablated mice showed transiently reduced JEV replication (Fig. 10a). This transient reduction of JEV replication in IDO-ablated neurons was associated with significantly increased induction of IFN-I (IFN-α/β), relative to the levels measured in cells from wild-type BL/6 mice (Fig. 10b). Also, it seemed that the expression of antiviral ISG genes (ISG49, ISG54, ISG59) in IDO-ablated neurons followed IFN-I innate responses and the transient reduction in viral replication (Fig. 10c), whereas the expression levels of transcription factors (IRF3, IRF7), but not PRRs (RIG-I, MDA5), were decreased by JEV infection (Fig. 10d, e). Therefore, these results suggest that the ablation of IDO could provide enhanced IFN-I innate immune responses in neuron cells to regulate the spread of JEV in the CNS.Fig. 10

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