AA IDO1 Variant Genotype (G2431A,rs3739319) Is Associated with Severe Dengue Risk Development in a DEN-3 Brazilian Cohort

Abstract

Dengue is considered one of the most challenging public health threats in the world. Infection may be clinically asymptomatic but can result in severe forms. The indoleamine 2,3 dioxygenase (IDO) gene encodes one of first enzymes (IDO) of the kynurenine pathway. This study aimed to verify the association between G2431A IDO1 gene single nucleotide polymorphism (SNP) (rs3739319) and dengue fever development. We included 299 dengue-infected individuals in the study and 96 dengue-free controls. We collected clinical and diagnostic test data and divided the patients with dengue infection into three groups, based on World Health Organization (WHO) criteria: 131 Dengue without warning signs (DWOS), 143 Dengue with warning signs (DWS), and 25 severe dengue (SD). We genotyped 193 of the dengue cases using quantitative polymerase chain reaction to the SNP rs3739319. The other 106 dengue cases and 96 dengue-free controls had previously been genotyped using the Illumina Genotyping Kit. Genotyping of the infected patients revealed frequencies of 106 GG (35.4%), 126 GA (42.1%), and 67 AA (22.4%), whereas the nondengue exposed control group showed similar frequencies, 29 GG (30.2%), 52 GA (54.2%), and 15 AA (15.6%). Under risk analysis we found that AA genotype patients had a higher risk of developing SD in a codominant model (AA × GG; odds ratio [OR] = 11.5-fold in comparison to non-SD group -DWOS and -DWS patients; confidence interval [CI] = 0.02–0.32; Yates correction = 1.9e-05) and in a recessive model (AA × AG+GG; OR = 9.41; CI = 3.62–26.7; Yates correction = 4.8e-08). An allelic model reinforced the association between A allele and SD phenotype development that was found in the SD versus DWOS+DWS analysis (OR = 3.59; CI = 1.50–9.56; Yates correction = 0.0033). Our data show an association between the IDO G2431A variant and the risk for SD. This SNP may be relevant for further investigation into disease mechanisms and host factors in future genetic and pathophysiological studies.

Introduction

Dengue virus (DENV) is one of the biggest public health challenges in the world (5). Estimates point to 50–100 million cases annually worldwide, encompassing tropical and subtropical regions of the globe, and infection may cause a spectrum of disease: from asymptomatic to severe dengue (SD) forms (5,24). The DENV is enveloped, having an icosahedral capsid whose genetic material is an 11 Kb RNA single strand (12,21). It belongs to the Flavivirus genus, Flaviviridae family, and is transmitted by hematophagous arthropod vectors, usually from Aedes genus (especially Aedes aegypti and Aedes Albopictus) (20).

Dengue clinical pathogenesis is controversial (21). The World Health Organization (WHO) classification system, developed in 2009, groups cases on the basis of clinical features. Dengue without warning signs (DWOS) cases are characterized by headache, myalgia, arthralgia, nausea, vomiting, rash, and other common symptoms to other arboviruses. Dengue with warning signs (DWS) encompasses disease where patients develop mucosal bleeding, ascites, abdominal pain, and persistent vomiting in the defervescence phase of the disease. In SD patients presents bleeding, shock, and severe organ involvement (26,45).

Several important factors have been associated with disease progression, including environment, immune status, virus strain, and host genetic background (40). For the latter, it is relevant to mention the influence of single nucleotide polymorphisms (SNPs) on disease progression, beyond complex multiple signatures between SNPs (6,13,46). Some SNPs have been discovered as potential influencers of severe disease development, such as rs1799964 (TNFα), rs1143627 (IL1β), and rs1800871 (IL10), which are cytokine genes related to induction of fever during disease and increase of vascular permeability (6,37,38). Other SNPs from genes, such as rs222270 (VDR), rs4804803 (CD209), exon 1 and promoter SNPs (MBL2), rs3753394, and rs800292, belonging to the complement factor H gene (CFH), have also been described to contribute to the development of severe disease (1,7,15,31,43,44).

The gene indoleamine 2,3 dioxygenase (IDO1) is 14,9 Kb and encodes the IDO protein, an important regulator of the immune response (22). IDO is one of first enzymes of the kynurenine pathway that converts tryptophan to N-formylkynurenine by means of oxidation of its pyrrole ring (17). N-formylkynurenine is metabolized to kynurenine, which can be released or catabolized to generate new products, among them nicotinamide adenine dinucleotide (NAD⁺), the end product of the whole reaction.

In dengue, infected febrile individuals may have high IDO transcripts in blood cells, suggesting that this enzyme may be involved in the disease pathophysiology (9). Taking into account the connection between some innate immune genes (SNPs) and dengue development, and high IDO levels in dengue in acute dengue patients, this study aimed to verify the relationship between the SNP rs3739319 (IDO1 gene) and SD development. There are very few studies characterizing the relevance of the IDO SNP in dengue patients. We describe an association between the presence of the IDO1 G2431A variant and an increased risk for SD, highlighting the importance of host genetics to DENV pathophysiology. This SNP may be a useful target for further investigation in future genetic and pathophysiological studies.

Material and Methods

Patients and clinical definition

Patients with dengue-related symptoms ≥5 years of age, without any other disease that might interfere with diagnostic test results–such as Zika virus, another flavivirus—were screened from three hospitals in Recife, Brazil: Oswaldo Cruz Hospital, Santa Joana Hospital, Esperança Hospital and Instituto Materno Infantil de Pernambuco (IMIP). All enrolled patients gave their informed consent and the project was approved by the Ethics Committee of FIOCRUZ-PE (CEP/CPQAM no.11/11, C.A.A.E. 0009.0.095.000-11, IORG0001419). Clinical details of the patients obtained included age, sex, and serum anti-DENV IgG levels (Table 1).

Table 1.

Clinical Details of the Control Subgroup and Brazilian Dengue 3 Patients

Characteristics	Clinical aspects
Characteristics	Control (n = 96)	DWOS (n = 131)	DWS (n = 143)	SD (n = 25)
Age	20 ± 27	21 ± 16	28 ± 23	39 ± 36
Sex (% female)	49	53	48	76
Dengue IgG-positive (%)	—^a	60	59	52

All control patients are IgG negative.

DWOS, Dengue without warning signs; DWS, Dengue with warning signs; SD, Severe dengue.

Patients were examined from the first to the fourth day of the disease, with additional evaluations every 24–48 h. Each volunteer donated ∼20 mL of blood over the course of the first 30 days after symptom onset. DENV (serotype 3) was detected by reverse transcriptase–polymerase chain reaction (RT-PCR) according to Lanciotti et al. (27) and the virus isolation in C6/36 cell line was identified by immunofluorescence testing (19) with serotype-specific and anti-dengue monoclonal antibodies (Bio-Manguinhos, Fundação Oswaldo Cruz, Brazil).

Dengue cases were classified in accordance with the WHO guidelines, as described (45). After clinical and laboratorial evaluation, a subset of 299 well-characterized dengue cases was selected for genotyping of the SNP rs3739319 in IDO1 gene: 131 DWOS, 143 DWS, and 25 SD. The control group was formed of 96 healthy volunteers that were negative for dengue tests described above.

DNA extraction and patient genotyping

The IDO1 gene G2431A region of 96 healthy Brazilian blood donors and 299 dengue-positive selected was genotyped to identify the allele and genotype frequencies as described below. Genomic DNA was extracted from PBMCs of the patients by using the Qiagen Genomic Prep Mini Spin Kit following the manufacturer's protocol.

For 193 of the 299 dengue-infected cases, we used a TaqMan Applied Genotyping quantitative PCR (qPCR) Assay (C_9036149_10) to genotype the rs3739319 locus following the recommended protocol: 6.25 μL Master Mix (TaqMan Genotyping Master Mix; Applied Biosystems/Thermo Fisher), 0.625 μL probe, 3.125 μL sterile H₂O, and 3 μL DNA to 13 μL of final volume. The amplification reaction was performed in Applied Biosystems 7500 machine, using the following cycling profile: 95°C/10 min, 40 cycles of: 92°C/15 sec and annealing/extension 60°C/1 min, besides the post-PCR at 60°C/30 sec.

We used the Illumina GoldenGate Genotyping Kit (Cat no. GT-901-1001) to genotype the other 106 dengue-infected cases and 96 controls included in the study. The Illumina system uses chips, with specific primers for regions to be studied, and genotypes for a locus of interest through a multiplex system associated with a scanning system. The BeadChip is read by a BeadArray Reader through two channels of high resolution lasers. This reading generates one file per channel that is interpreted by the iScan software to determine intensity values for each bead. Finally, Genome Studio analyzes the data in conjunction with bead pool map (* .bpm) or manifest file (* .bgx).

Statistical analysis

The risk analysis and plotting were carried out using the open source R statistical package version i386 3.5.0. To study the association between genotype groups and clinical dengue categories, Fisher's exact test was performed, using the R function fisher test, which was also used to find the associated odds ratio (OR), using a conditional maximum-likelihood method. Codominant model (GG vs. AA), dominant model (GG vs. GA+AA), recessive model (GG+GA vs. AA), overdominant model (GA vs. GG+AA), and allelic model (G vs. A) were used to investigate risk factors for SD with a hemorrhagic phenotype development. The Hardy–Weinberg equilibrium was evaluated using chi-square test and values were considered significant when p < 0.05. Yates correction test was applied to verify the possibility of risk maintenance in the population.

Results

Two hundred ninety-nine DNA samples from well-characterized dengue patients (DENV-3 genotype III, Srilankan–India strain) were genotyped for locus G2431A (rs3739319) in IDO1 gene. Dengue patients revealed genome frequencies of 106 GG (35.4%), 126 GA (42.1%), and 67 AA (22.4%), whereas the control group had frequencies of 29 GG (30.2%), 52 GA (54.2%), and 15 AA (15.6%) (Table 2).

Table 2.

IDO G2431A (rs3739319) Genotype/Allele Frequencies in Control Group and Brazilian Dengue 3 Patients

	G2431A (rs3739319)
SNP Groups	G/G	G/A	A/A	G	A
Control	29 (30.2)	52 (54.2)	15 (15.6)	81 (54.7)	67 (45.3)
DEN	106 (35.4)	126 (42.1)	67 (22.4)	232 (54.6)	193 (45.4)
DWOS	48 (36.6)	55 (42.0)	28 (21.4)	103 (55.4)	83 (44.6)
DWS	55 (38.5)	66 (46.2)	22 (15.4)	121 (57.9)	88 (42.1)
SD	3 (12.0)	5 (20.0)	17 (68.0)	8 (26.7)	22 (73.3)

DEN, Dengue group; SNP, single nucleotide polymorphism.

An interesting fact, depicted in Table 2, is the high frequency of the AA genotype in SD patients (68%) compared with DWOS and DWS patients, with AA frequencies of 21.4% and 15.4%, respectively. This tendency was either observed for allele frequencies (Table 2), where A allele shows a frequency of 73%, much higher than dengue group (45%).

To determine if there was any association between severity of dengue disease and the 2431A locus (rs3739319 SNP), the five models cited in the methodology were used. We describe our results fully in Table 3. In the codominant model, AA genotype patients showed a risk of 11.5-fold to develop SD in comparison with DWOS/DWS group (OR = 11.5; confidence interval [CI] = 0.02–0.32; Yates correction = 1.9e-05). Corroborating with this result, the dominant model revealed that a GG genotype provides protection against disease progression to SD (OR = 0.22; CI = 0.04–0.78, Yates correction = 0.0194). In the same way, when recessive analyses were considered, the AA genotype exhibited an increased risk for SD (SD vs. control, SD vs. DWOS+DWS). One expressive result was seen when SD was compared with DWOS+DWS (OR = 9.41; CI = 3.62–26.7; Yates correction = 4.8e-08).

Table 3.

IDO G2431A (rs3739319) Allele/Genotype Risk Analysis (rs3739319) Between Control Group and Brazilian Dengue 3 Patients

SNP model	DEN vs. control		DWOS vs. control		DWS vs. control		SD vs. control		Yates test	SD vs. DWOS		Yates test	SD vs. DWOS+DWS		Yates test	SD+DWS vs. DWOS
SNP model	OR (95% CI)	p	OR (95% CI)	p	OR (95% CI)	p	OR (95% CI)	p	p	OR (95% CI)	p	p	OR (95% CI)	p	p	OR (95% CI)	p
IDO1 (G2431A)
Codominant	1.22 (0.58–2.64)	NS	1.13 (0.48–2.67)	NS	0.78 (0.32–1.87)	NS	10.52 (2.49–64.95)	3.1e-04	4.6e-04	9.49 (2.44–54.91)	1.3e-04	3.3e-04	11.5 (0.02–0.32)	9.3e-06	1.9e-05	1.15 (0.59–2.24)	NS
Dominant	1.27 (0.75–2.17)	NS	1.33 (0.74–2.45)	NS	1.44 (0.80–2.61)	NS	0.32 (0.06–1.18)	NS	NS	0.23 (0.04–0.85)	0.019	0.030	0.22 (0.04–0.78)	0.009	0.019	0.91 (0.55–1.51)	NS
Recessive	1.56 (0.82–3.10)	NS	1.46 (0.70–3.16)	NS	0.98 (0.46–2.16)	NS	11.15 (3.78–35.88)	8.2e-07	4.8e-07	7.68 (2.80–22.9)	9.7e-06	7.6e-06	9.41 (3.62–26.7)	3.8e-07	4.8e-08	1.11 (0.62–2.01)	NS
Overdominant	0.62 (0.38–1.00)	0.045	0.61 (0.35–1.08)	NS	0.74 (0.42–1.28)	NS	0.21 (0.05–0.65)	0.003	0.005	0.34 (0.10–1.03)	0.044	NS	0.31 (0.09–0.9)	0.020	0.033	1.01 (0.62–1.65)	NS
Allele	1.00 (0.68–1.49)	NS	0.97 (0.62–1.54)	NS	0.88 (0.56–1.38)	NS	3.30 (1.31–9.16)	0.008	0.009	3.39 (1.37–9.29)	0.005	0.006	3.59 (1.50–9.56)	0.002	0.003	0.96 (0.64–1.45)	NS

The analyses were performed using the Fisher exact test. The results that presented statistical significance (P ≤ 0.05) are highlighted in bold, and these are also specified by the Yates correction.

NS, no significance; CI, confidence interval; OR, odds ratio.

The overdominant model showed that an AG genotype protects against SD (OR = 0.31; CI = 0.09–0.9; Yates correction = 0.033). This can be explained by the fact that only one copy of the G allele is sufficient to confer protection against SD, since this allele is dominant when compared with the A allele.

Finally, the risk analysis was done based on the allelic model. This reinforced the connection of the A allele with the development of SD, since there was a risk relation in the three analyzes performed (SD vs. control; SD vs. DWOS; SD vs. DWOS+DWS). The higher risk of A allele was found when SD versus DWOS+DWS analysis was performed (OR = 3.59; CI = 1.50–9.56; Yates correction = 0.0033).

Discussion

In this work we performed a study to understand the relationship between 2431A polymorphism (rs3739319) and severity of dengue disease. To do this, 299 dengue patients and 96 healthy controls were genotyped. It was found that patients with an AA genotype have a higher risk of developing SD, while the presence of a G allele is protective against this severe disease phenotype.

The IDO1 gene is located on chromosome 8 and encodes the enzyme indoleamine 2,3 dioxygenase (IDO), a very important immunoregulatory protein for the catabolism of the amino acid tryptophan (Trp). It is usually expressed by antigen-presenting cells under the stimulus of proinflammatory factors, such as tumor necrosis factor (TNF-α) and interferons (IFN) (8,10,23). In addition, its activity is associated with the functioning of various metabolic pathways and the maintenance of immune homeostasis (35,36).

The SNP G2431A is located in an intronic region between exons 9 and 10, near enhancer gene regulatory regions and promoter flanks. Its role in immunopathology of viral and nonviral diseases is still poorly understood, a coincident fact shared by other IDO1. Functional associations have been found between the SNP rs7820268 and a series of diseases, including systemic sclerosis, accompanied by a decrease in CD8⁺ Treg activity (42); aspirin-induced asthma (39) in a Japanese population; and, singly, with type 1 diabetes mellitus (DM1), with an OR of 1.69 (p = 0.014), whereas in the haplotype model (H1/H1 haplotype) the OR was 1.9 (p = 0.042) for disease development (30).

For viral disease, results from chronic hepatitis C patients indicated that the rs9657182 was related with moderate or severe clinical depressive behavior during treatment with IFN-α, affecting its efficacy (41). Moreover, this SNP and G2431A (rs3739319) were analyzed in patients vaccinated or infected by hepatitis B virus (HBV) to assess HBV anti-HBs antibody responses. Both SNPs were not associated with antibody response activity. However, the TT genotype of rs9657182 was related to increase in mortality in HBV-infected patients (18).

It is observed that IDO1 is overexpressed in viral diseases due to the presence of ISREs (IFN-stimulated response elements) in the promoter region in addition to other sites that are activated by IFN-γ (34). Under gene ablation or inhibition of the enzyme by a drug during a given infection, the organism can become reactive by developing a memory T cell response, as well as having high expression of IFN-γ by CD4⁺ and CD8⁺ T cells, as occurs during influenza virus infection (35). In HIV-positive patients, plasma levels of IDO have already been used as a biomarker for tuberculosis (3).

It has also been reported in viral diseases that IDO is involved in growth inhibition of the herpes virus, cytomegalovirus and parainfluenza virus type 3 (HPIV3) (2,11,32), whereas respiratory syncytial virus induces the expression and activity of IDO, which is possibly related to the development of allergic disease (4,33). In Puumala hantavirus infection, IDO activity is associated with a severe course of Nephropathia epidemica (form of hemorrhagic fever with renal syndrome) due to the suppressive capability of Treg cells (26). Another study has shown that IDO inhibition generates a more robust T cell response to influenza virus and the authors suggest this as a potential approach to increase the cell-mediated immune response to vaccination (16).

Some studies have evaluated the activity of the IDO enzyme in viral infections caused by flaviviruses and have shown its importance in the immunological response. In Japanese Encephalitis (JE), it has been observed that decreased IDO1 expression is associated with suppressed viral replication, which causes an increase in resistance to the development of the disease (25,47). In West Nile virus fever, the decrease in L-Trp caused by increased IDO1 expression attenuated viral replication (29). Moreover, overexpression of hepatic IDO before hepatitis C virus (HCV) infection markedly impaired HCV replication in hepatocytes, suggesting that IDO limits the spread of HCV within the liver beyond IFN to be stimulated. Furthermore, it also regulates host immune responses through an inhibitory effect on CD4⁺ T cell proliferation (28).

Regarding dengue, one study observed a synergistic effect between DENV and IFN-γ on induction of the IDO1 gene and a partial dependence of the activity of this enzyme on the antiviral response to DENV caused by IFN-γ. In this study, an increase in the IDO1 gene expression in response to infection by DENV in human umbilical vein endothelial cells (HUVECs) was found in vitro. In the serum of dengue-infected subjects, a decrease in tryptophan levels and an increase in kynurenine levels was observed, indicating an increase in tryptophan catabolism by IDO activity (14). Another study carried out with DENV-4-infected individuals showed an increase in IDO in blood monocytes from dengue patients, especially in nonclassical monocytes with high CD14⁺ and CD16⁺ expression. A correlation of IDO with IL-10, an anti-inflammatory cytokine, was also found. Based on these findings, it has been proposed that this enzyme may be exerting both antiviral effects and modulating the exacerbated immune response during dengue (14). However, no difference was found between the levels of IDO in pairs with classical dengue and SD (43).

While our results deliver novel understanding, we recognize that sample size is a limitation of our study. There is now a need to perform larger studies and to study other SNPs that might influence this pathway, such as SNPs in cytokine genes, or molecules that are associated with this response, such as IFN-γ.

We are presenting the first significant evidence of an association between the IDO1 G2431A variant and the risk for SD. We believe that this SNP can be a potential target to other genetic and pathophysiological studies that examine the role of host genetic factors in human dengue disease.

Footnotes

Acknowledgments

The authors are grateful to Dr. Suzannah Lant for all the support for this work.

Author Disclosure Statement

No competing financial interests exist.

References

Acioli-Santos

, Segat

, Dhalia

, et al. MBL2 gene polymorphisms protect against development of thrombocytopenia associated with severe dengue phenotype. Hum Immunol, 2008; 69:122–128.

Adams

, Besken

, Oberdorfer

, et al. Role of indoleamine 2,3-dioxygenase in alpha/beta and gamma interferon-mediated antiviral effects against herpes simplex virus infections, J Virol, 2004; 78:2632–2636.

Adu-Gyamfi

, Snyman

, Hoffman

, et al. Plasma indoleamine 2, 3-dioxygenase, a biomarker for tuberculosis in human immunodeficiency virus-infected patients. Clin Infect Dis, 2018; 65:1356–1358.

Ajamian

, Wu

, Ebeling

, et al. Respiratory syncytial virus induces indoleamine 2,3-dioxygenase activity: a potential novel role in the development of allergic disease. Clin Exp Allergy, 2015; 45:644–659.

Alagarasu

, Bachal

, Damle

, et al. Association of FCGR2A p.R131H and CCL2 c.-2518 A>G gene variants with thrombocytopenia in patients with dengue virus infection. Hum Immunol, 2015; 76:819–822.

Alagarasu

, Bachal

, Tillu

, et al. Association of combinations of interleukin-10 and pro-inflammatory cytokine gene polymorphisms with dengue hemorrhagic fever. Cytokine, 2015; 74:130–136.

Alagarasu

, Honap

, Mulay

, et al. Association of vitamin D receptor gene polymorphisms with clinical outcomes of dengue virus infection. Hum Immunol, 2012; 73:1194–1199.

Baumgartner

, Forteza

, Ketelhuth

DFJ

. The interplay between cytokines and the Kynurenine pathway in inflammation and atherosclerosis. Cytokine, 2017; S1043-4666:1–9.

Becerra

, Warke

, Martin

, et al. Gene expression profiling of dengue infected human primary cells identifies secreted mediators in vivo . J Med Virol, 2009; 81:1403–1411.

10.

Belladonna

, Volpi

, Bianchi

, et al. Cutting edge: autocrine TGF-beta sustains default tolerogenesis by IDO competent dendritic cells. J Immunol, 2008; 181:5194–5198.

11.

Bodaghi

, Goureau

, Zipeto

, et al. Role of IFN-c-induced indoleamine 2,3 dioxygenase and inducible nitric oxide synthase in the replication of human cytomegalovirus in retinal pigment epithelial cells. J Immunol, 1999; 162:957–964.

12.

Chao

, Jang

, Johnson

, et al. How small-molecule inhibitors of dengue-virus infection interfere with viral membrane fusion. eLife, 2018; 7:1–11.

13.

Davi

CCM

, Pastor

, Oliveira

, et al. Severe dengue prognosis using human genome data and machine learning. IEEE Trans Biomed Eng, 2019; DOI: 10.1109/TBME.2019.2897285.

14.

Fialho

, Torrentes-Carvalho

, Cunha

, et al. Induced nitric oxide synthase (iNOS) and indoleamine 2,3-dioxygenase (IDO) detection in circulating monocyte subsets from Brazilian patients with dengue-4. Virol Rep, 2017; 7:9–19.

15.

Figueiredo

, Cezar

, Freire

, et al. Mannose-binding lectin gene (MBL2) polymorphisms related to the mannose-binding lectin low levels are associated to dengue disease severity. Hum Immunol, 2016; 77:571–575.

16.

Fox

, Sage

, Huang

, et al. Inhibition of indoleamine 2,3-dioxygenase enhances the T-cell response to influenza virus infection. J Gen Virol, 2013; 94:1451–1461.

17.

Freewan

, Rees

, Plaza

, et al. Human Indoleamine 2,3-dioxygenase is a catalyst of physiological heme peroxidase reactions:implications for the inhibition of dioxygenase activity by hydrogen peroxide. J Biol Chem, 2013; 288:1548–1567.

18.

Grzegorzewska

, Winnicka

, Warchol

, et al. Correlations of indoleamine 2,3-dioxygenase, interferon-λ3, and anti-HBs antibodies in hemodialysis patients. Vaccine, 2018; 36:4454–4461.

19.

Gubler

, Kuno

, Sather

, et al. Use of mosquito cell cultures and specific monoclonal antibodies in surveillance for dengue virus. Am J Trop Med Hyg, 1984; 33:158–165.

20.

Guzman

, Halstead

, Artsob

, et al. Dengue: a continuing global threat. Nat Rev Micro, 2010; 8:S7–S16.

21.

Halstead

. Controversies in dengue pathogenesis. Paediatr Int Child Health, 2012; 32:5–9.

22.

Jones

, Guillemin

, Brew

. The kynurenine pathway in stem cell biology. Int J Tryptophan Res, 2013; 6:57–66.

23.

Jurgens

, Hainz

, Fuchs

, et al. Interferon-gammatriggered indoleamine 2,3-dioxygenase competence in human monocyte-derived dendritic cells induces regulatory activity in allogeneic T cells. Blood, 2009; 114:3235–3243.

24.

Kalayanarooj

. Clinical manifestations and Management of Dengue/DHF/DSS. Trop Med Health, 2011; 39:83–87.

25.

Kim

, Choi

, Uyangaa

, et al. Blockage of indoleamine 2,3-dioxygenase regulates Japanese encephalitis via enhancement of type I/II IFN innate and adaptive T-cell responses. J Neuroinflamm, 2016; 13:1–23.

26.

Koivula

, Tuulasvaara

, Hetemaki

, et al. Indoleamine 2,3-dioxygenase activity is associated with regulatory T cell response in acute Puumala hantavirus infection. Pathog Dis, 2017; 75:1–4.

27.

Lanciotti

, Calisher

, Gubler

, et al. Rapid detection and typing of dengue viruses from clinical samples by using reverse transcriptase-polymerase chain reaction. J Clin Microbiol, 1992; 30:545–551.

28.

Lepiller

, Soulier

, Li

, et al. Antiviral and immunoregulatory effects of indoleamine-2,3 dioxygenase in hepatitis C virus infection. J Innate Immun, 2015; 7:530–544.

29.

Munoz-Erazo

, Natoli

, Provis

, et al. Microarray analysis of gene expression in West Nile virus-infected human retinal pigment epithelium. Mol Vis, 2012; 18:730–743.

30.

Orabona

, Mondanelli

, Pallotta

, et al. Deficiency of immunoregulatory indoleamine 2,3-dioxygenase 1 in juvenile diabetes. JCI insight, 2018; 3:1–18.

31.

Pastor

, Rodrigues Moura

, Neto

, et al. Complement factor H gene (CFH) polymorphisms C-257T, G257A and haplotypes are associated with protection against severe dengue phenotype, possible related with high CFH expression. Hum Immunol, 2013; 74:1225–1230.

32.

Rabbani

, Ribaudo

, Guo

, et al. Identification of Interferon-Stimulated Gene Proteins That Inhibit Human Parainfluenza Virus Type 3. J Virol, 2016; 90:11145–11156.

33.

Rajan

, Chinnadurai

, O'Keefe

, et al. Protective role of indoleamine 2,3 dioxygenase in respiratory syncytial virus associated immune response in airway epithelial cells. Virology, 2017; 512:144–150.

34.

Robinson

, Shirey

, Carlin

. Synergistic transcriptional activation of indoleamine dioxygenase by IFN-gamma and tumor necrosis factor-alpha. J Interferon Cytokine Res, 2003; 23:413–421.

35.

Sage

, Fox

, Mellor

et al. Indoleamine 2,3-dioxygenase (IDO) activity during the primary immune response to influenza infection modifies the memory T cell response to influenza challenge. Viral Immunol, 2014; 27:112–123.

36.

Sainio

, Pulkki

, Young

. L-Tryptophan: biochemical, nutritional and pharmacological aspects. Amino Acids, 1996; 10:21–47.

37.

Sa-Ngasang

, Ohashi

, Naka

, et al. Association of IL1B–31C/T and IL1RA variable number of an 86-bp tandem repeat with dengue shock syndrome in Thailand. J Infect Dis, 2014; 210:138–145.

38.

Santos

ACM

, de Moura

, Ferreira

, et al. Association of TNFA (−308G/A), IFNG (+874 A/T) and IL-10 (−819 C/T) polymorphisms with protection and susceptibility to dengue in Brazilian population. Asian Pac J Trop Med, 2017; 10:1065–1071.

39.

Sekigawa

, Tajima

, Hasegawa

, et al. Gene-expression profiles in human nasal polyp tissues and identification of genetic susceptibility in aspirin-intolerant asthma. Clin Exp Allergy, 2009; 39:1–9.

40.

Sierra

, Triska

, Soares

, et al. OSBPL10, RXRA and lipid metabolism confer African-ancestry protection against dengue haemorrhagic fever in admixed Cubans. PLoS Pathog, 2017; 13:1–21.

41.

Smith

, Simon

, Gustafson

, et al. Association of a polymorphism in the indoleamine- 2,3-dioxygenase gene and interferon-α-induced depression in patients with chronic hepatitis C. Mol Psychiatry, 2012; 17:781–789.

42.

Tardito

, Negrini

, Conteduca

, et al. Indoleamine 2,3 dioxygenase gene polymorphisms correlate with CD8+ Treg impairment in systemic sclerosis. Hum Immunol, 2013; 74:166–169.

43.

Villar

, Gélvez

, Rodríguez

, et al. Biomarkers for the prognosis of severe dengue. Biomédica, 2013; 33:108–116.

44.

Wang

, Chen

, Liu

, et al. DC-SIGN (CD209) promoter 2336 A/G polymorphism is associated with dengue hemorrhagic fever and correlated to DC-SIGN expression and immune augmentation. Plos Negl Trop Dis, 2011; 5:1–10.

45.

WHO. Dengue Guidelines for Diagnosis, Treatment, Prevention and Control. 3nd ed. Geneva: World Health Organization, 2009.

46.

Xavier-Carvalho

, Cezar

RDDS

, Freire NM et al. Association of rs1285933 single nucleotide polymorphism in CLEC5A gene with dengue severity and its functional effects. Hum Immunol, 2017; 78:649–656.

47.

Yeung

, Wu

, Freewan

, et al. Flavivirus infection induces indoleamine 2,3-dioxygenase in humann monocyte-derived macrophages via tumor necrosis factor and NF-κB. J Leukoc Biol, 2012; 91:657–666.