Antiviral and Immunoregulatory Effects of Indoleamine-2,3-Dioxygenase in Hepatitis C Virus Infection

Recombinant Human Bone Morphogenetic Protein-2 Priming of Mesenchymal Stem Cells Ameliorate Acute Lung Injury by Inducing Regulatory T Cells

Mesenchymal stromal/stem cells (MSCs) possess immunoregulatory properties and their regulatory functions represent a potential therapy for acute lung injury (ALI). However, uncertainties remain with respect to defining MSCs-derived immunomodulatory pathways. Therefore, this study aimed to investigate the mechanism underlying the enhanced effect of human recombinant bone morphogenic protein-2 (rhBMP-2) primed ES-MSCs (MSCBMP2) in promoting Tregs in ALI mice. MSC were preconditioned with 100 ng/ml rhBMP-2 for 24 h, and then administrated to mice by intravenous injection after intratracheal injection of 1 mg/kg LPS. Treating MSCs with rhBMP-2 significantly increased cellular proliferation and migration, and cytokines array reveled that cytokines release by MSCBMP2 were associated with migration and growth. MSCBMP2 ameliorated LPS induced lung injury and reduced myeloperoxidase activity and permeability in mice exposed to LPS. Levels of inducible nitric oxide synthase were decreased while levels of total glutathione and superoxide dismutase activity were further increased via inhibition of phosphorylated STAT1 in ALI mice treated with MSCBMP2. MSCBMP2 treatment increased the protein level of IDO1, indicating an increase in Treg cells, and Foxp3+CD25+ Treg of CD4+ cells were further increased in ALI mice treated with MSCBMP2. In co-culture assays with MSCs and RAW264.7 cells, the protein level of IDO1 was further induced in MSCBMP2. Additionally, cytokine release of IL-10 was enhanced while both IL-6 and TNF-α were further inhibited. In conclusion, these findings suggest that MSCBMP2 has therapeutic potential to reduce massive inflammation of respiratory diseases by promoting Treg cells.

Modeling the Immune Response for Pathogenic and Nonpathogenic Orthohantavirus Infections in Human Lung Microvasculature Endothelial Cells

Hantaviruses, genus Orthohantavirus, family Hantaviridae, order Bunyavirales, are negative-sense, single-stranded, tri-segmented RNA viruses that persistently infect rodents, shrews, and moles. Of these, only certain virus species harbored by rodents are pathogenic to humans. Infection begins with inhalation of virus particles into the lung and trafficking to the lung microvascular endothelial cells (LMVEC). The reason why certain rodent-borne hantavirus species are pathogenic has long been hypothesized to be related to their ability to downregulate and dysregulate the immune response as well as increase vascular permeability of infected endothelial cells. We set out to study the temporal dynamics of host immune response modulation in primary human LMVECs following infection by Prospect Hill (nonpathogenic), Andes (pathogenic), and Hantaan (pathogenic) viruses. We measured the level of RNA transcripts for genes representing antiviral, proinflammatory, anti-inflammatory, and metabolic pathways from 12 to 72 h with time points every 12 h. Gene expression analysis in conjunction with mathematical modeling revealed a similar profile for all three viruses in terms of upregulated genes that partake in interferon signaling (TLR3, IRF7, IFNB1), host immune cell recruitment (CXCL10, CXCL11, and CCL5), and host immune response modulation (IDO1). We examined secreted protein levels of IFN-β, CXCL10, CXCL11, CCL5, and IDO in two male and two female primary HLMVEC donors at 48 and 60 h post infection. All three viruses induced similar levels of CCL5, CXCL10, and CXCL11 within a particular donor, and the levels were similar in three of the four donors. All three viruses induced different protein secretion levels for both IFN-β and IDO and secretion levels differed between donors. In conclusion, we show that there was no difference in the transcriptional profiles of key genes in primary HLMVECs following infection by pathogenic and nonpathogenic hantaviruses, with protein secretion levels being more donor-specific than virus-specific.

Evaluation of the effect of direct-acting antiviral agents on melatonin level and lipid peroxidation in chronic hepatitis C patients

Background: Oxidative stress and its end products, such as malondialdehyde (MDA) play a leading role in the pathogenesis of hepatitis C. Melatonin is a hormone that helps regulate circadian rhythms, which likely play a role in infectious diseases in terms of susceptibility, clinical expression, and outcome. Objective: The present study was conducted to assess serum malondialdehyde and melatonin levels in patients with chronic hepatitis C infection before and after the intake of direct-acting antivirals. Method: Forty hepatitis C patients were the subjects of this study. While ten healthy volunteers who matched in age and socioeconomic status served as the control subjects. Malondialdehyde and melatonin were assayed in the serum of the three groups, and the results were statistically analyzed. Results: Hepatitis C patients had significantly higher malondialdehyde (p < 0.001) but significantly lower melatonin (p < 0.001) as compared to the healthy controls. After 12 weeks of treatment with direct-acting antivirals, the malondialdehyde level decreased significantly (p < 0.001) and the melatonin level increased significantly (p < 0.001). A significant negative correlation between malondialdehyde and melatonin was observed. Conclusion: The present findings suggest that treatment of hepatitis C patients with Direct-acting antivirals improves liver function parameters and antioxidant profiles.

Indoleamine 2,3-Dioxygenase (IDO) Activity: A Perspective Biomarker for Laboratory Determination in Tumor Immunotherapy

Indoleamine 2,3-dioxygenase 1 (IDO1) is a heme enzyme involved in catalyzing the conversion of tryptophan (Trp) into kynurenine (Kyn) at the first rate-limiting step in the kynurenine pathway of L-tryptophan metabolism. It has been found to be involved in several biological functions such as aging, immune microorganism, neurodegenerative and infectious diseases, and cancer. IDO1 plays an important role in immune tolerance by depleting tryptophan in the tumor microenvironment and inhibiting the proliferation of effector T cells, which makes it an important emerging biomarker for cancer immunotherapy. Therefore, the research and development of IDO1 inhibitors are of great importance for tumor therapy. Of interest, IDO activity assays are of great value in the screening and evaluation of inhibitors. Herein, we mainly review the biological functions of IDO1, immune regulation, key signaling molecules in the response pathway, and the development of IDO1 inhibitors in clinical trials. Furthermore, this review provides a comprehensive overview and, in particular, a discussion of currently available IDO activity assays for use in the evaluation of IDO inhibitors in human blood. We believe that the IDO activity is a promising biomarker for the immune escape and laboratory evaluation of tumor immunotherapy.

Synthesis and Crystal Structure of Adamantylated 4,5,6,7-Tetrahalogeno-1H-benzimidazoles Novel Multi-Target Ligands (Potential CK2, M2 and SARS-CoV-2 Inhibitors); X-ray/DFT/QTAIM/Hirshfeld Surfaces/Molecular Docking Study

A series of new congeners, 1-[2-(1-adamantyl)ethyl]-1H-benzimidazole (AB) and 1-[2-(1-adamantyl)ethyl]-4,5,6,7-tetrahalogeno-1H-benzimidazole (Hal=Cl, Br, I; tClAB, tBrAB, tIAB), have been synthesized and studied. These novel multi-target ligands combine a benzimidazole ring known to show antitumor activity and an adamantyl moiety showing anti-influenza activity. Their crystal structures were determined by X-ray, while intermolecular interactions were studied using topological Bader's Quantum Theory of Atoms in Molecules, Hirshfeld Surfaces, CLP and PIXEL approaches. The newly synthesized compounds crystallize within two different space groups, P-1 (AB and tIAB) and P2₁/c (tClAB and tBrAB). A number of intramolecular hydrogen bonds, C-H⋯Hal (Hal=Cl, Br, I), were found in all halogen-containing congeners studied, but the intermolecular C-H⋯N hydrogen bond was detected only in AB and tIAB, while C-Hal⋯π only in tClAB and tBrAB. The interplay between C-H⋯N and C-H⋯Hal hydrogen bonds and a shift from the strong (C-H⋯Cl) to the very weak (C-H⋯I) attractive interactions upon Hal exchange, supplemented with Hal⋯Hal overlapping, determines the differences in the symmetry of crystalline packing and is crucial from the biological point of view. The hypothesis about the potential dual inhibitor role of the newly synthesized congeners was verified using molecular docking and the congeners were found to be pharmaceutically attractive as Human Casein Kinase 2, CK2, inhibitors, Membrane Matrix 2 Protein, M2, blockers and Severe Acute Respiratory Syndrome Coronavirus 2, SARS-CoV-2, inhibitors. The addition of adamantyl moiety seems to broaden and modify the therapeutic indices of the 4,5,6,7-tetrahalogeno-1H-benzimidazoles.

Herpes Simplex Virus-1 Induced Serotonin-Associated Metabolic Pathways Correlate With Severity of Virus- and Inflammation-Associated Ocular Disease

Herpes simplex virus-associated diseases are a complex interaction between cytolytic viral replication and inflammation. Within the normally avascular and immunoprivileged cornea, HSV ocular infection can result in vision-threatening immune-mediated herpetic keratitis, the leading infectious cause of corneal blindness in the industrialized world. Viral replicative processes are entirely dependent upon numerous cellular biosynthetic and metabolic pathways. Consistent with this premise, HSV infection was shown to profoundly alter gene expression associated with cellular amino acid biosynthetic pathways, including key tryptophan metabolism genes. The essential amino acid tryptophan is crucial for pathogen replication, the generation of host immune responses, and the synthesis of neurotransmitters, such as serotonin. Intriguingly, Tryptophan hydroxylase 2 (TPH2), the neuronal specific rate-limiting enzyme for serotonin synthesis, was the most significantly upregulated gene by HSV in an amino acid metabolism PCR array. Despite the well-defined effects of serotonin in the nervous system, the association of peripheral serotonin in disease-promoting inflammation has only recently begun to be elucidated. Likewise, the impact of serotonin on viral replication and ocular disease is also largely unknown. We therefore examined the effect of HSV-induced serotonin-associated synthesis and transport pathways on HSV-1 replication, as well as the correlation between HSV-induced ocular serotonin levels and disease severity. HSV infection induced expression of the critical serotonin synthesis enzymes TPH-1, TPH-2, and DOPA decarboxylase (DDC), as well as the serotonin transporter, SERT. Concordantly, HSV-infected cells upregulated serotonin synthesis and its intracellular uptake. Increased serotonin synthesis and uptake was shown to influence HSV replication. Exogenous addition of serotonin increased HSV-1 yield, while both TPH-1/2 and SERT pharmacological inhibition reduced viral yield. Congruent with these in vitro findings, rabbits intraocularly infected with HSV-1 exhibited significantly higher aqueous humor serotonin concentrations that positively and strongly correlated with viral load and ocular disease severity. Collectively, our findings indicate that HSV-1 promotes serotonin synthesis and cellular uptake to facilitate viral replication and consequently, serotonin's proinflammatory effects may enhance the development of ocular disease.

Characterization of SARS-CoV-2 ORF6 deletion variants detected in a nosocomial cluster during routine genomic surveillance, Lyon, France

During routine molecular surveillance of SARS-CoV-2 performed at the National Reference Center of Respiratory Viruses (Lyon, France) (n = 229 sequences collected February-April 2020), two frameshifting deletions were detected in the open reading frame 6, at the same position (27267). While a 26-nucleotide deletion variant (D26) was only found in one nasopharyngeal sample in March 2020, the 34-nucleotide deletion (D34) was found within a single geriatric hospital unit in 5/9 patients and one health care worker in April 2020. Phylogeny analysis strongly suggested a nosocomial transmission of D34, with potential fecal transmission, as also identified in a stool sample. No difference in disease severity was observed between patients hospitalized in the geriatric unit infected with WT or D34. In vitro D26 and D34 characterization revealed comparable replication kinetics with the wild-type (WT), but differential host immune responses. While interferon-stimulated genes were similarly upregulated after infection with WT and ORF6 variants, the latter specifically induced overexpression of 9 genes coding for inflammatory cytokines in the NF-kB pathway, including CCL2/MCP1, PTX3, and TNFα, for which high plasma levels have been associated with severe COVID-19. Our findings emphasize the need to monitor the occurrence of ORF6 deletions and assess their impact on the host immune response.

Short- and Long-Term Immunological Responses in Chronic HCV/HIV Co-Infected Compared to HCV Mono-Infected Patients after DAA Therapy

Background: Direct-acting antivirals (DAAs) treatment, although highly efficacious for the treatment of hepatitis C virus (HCV) infection, may not completely reconstitute the HCV-mediated dysregulated immune system, especially in patients co-infected with human immunodeficiency virus (HIV) and HCV. Objectives: We aimed to evaluate the impact of HCV eradication following DAA therapy on the immune system and liver disease improvement through comparative monitoring of 10 HCV mono-infected and 10 HCV/HIV co-infected patients under combined antiretroviral therapy (cART). Early and late longitudinal phenotypic changes in peripheral blood mononuclear cell (PBMC) subsets, T-cell activation, differentiation and exhaustion, as well as inflammatory biomarkers, indoleamine 2-3 dioxygenase (IDO) activity, and liver stiffness, APRI and FIB-4 scores were assessed. Materials and Methods: Samples were obtained at baseline (T0), week 1 (T1), week 2 (T2), week 12 (T3, end of treatment, EOT), and month 9 (T4, end of follow-up, 36 weeks post EOT). Results: All patients achieved a sustained virological response (SVR 12) after DAA treatment. Overall, changes of the T-cell immune phenotypes were greater in HCV/HIV co-infected than in HCV mono-infected, due to an increase in CD4+ and CD8+ T-cell percentages and of CD8+ T-cell activation and memory markers, in particular at the end of follow-up. On the other end, HCV mono-infected showed changes in the activation profile and in the memory CD4+ T-cell compartment. In HCV/HIV co-infected, a decrease in the IDO activity by DAA treatment was observed; conversely, in HCV mono-infected, it resulted unmodified. Regarding inflammatory mediators, viral suppression was associated with a reduction in IP-10 levels, while interferon regulatory factor (IRF)-7, interferon (IFN)-β, and interferon (IFN)-γ levels were downregulated during therapy and increased post therapy. A decrease in liver stiffness, APRI, and FIB-4 scores was also observed. Conclusions: Our study suggests that, although patients achieved HCV eradication, the immune activation state in both HCV mono-infected and HCV/HIV co-infected patients remains elevated for a long time after the end of DAA therapy, despite an improvement of liver-specific outcomes, meanwhile highlighting the distinct immunophenotypic and inflammatory biomarker profile between the groups of patients.

Metabolomics: Impact of Comorbidities and Inflammation on Sickness Behaviors for Individuals with Chronic Wounds

Significance: Approximately 6.5 million people in the United States suffer from chronic wounds. The chronic wound population is typically older and is characterized by a number of comorbidities associated with inflammation. In addition to experiencing wound-related pain, individuals with chronic wounds commonly experience multiple concurrent psychoneurological symptoms such as fatigue and depression, which delay wound healing. However, these distressing symptoms have been relatively overlooked in this population, although their adverse effects on morbidity are well established in other chronic disease populations. Recent Advances: Inflammation is involved in multiple pathways, which activate brain endothelial and innate immune cells that release proinflammatory cytokines, which produce multiple symptoms known as sickness behaviors. Inflammation-based activation of the kynurenine (KYN) pathway and its metabolites is a mechanism associated with chronic illnesses. Critical Issues: Although putative humoral and neuronal routes have been identified, the specific metabolic variations involved in sickness behaviors in chronic wound patients remain unclear. To improve health outcomes in the chronic wound population, clinicians need to have better understanding of the mechanisms underlying sickness behaviors to provide appropriate treatments. Future Directions: This article presents a synthesis of studies investigating associations between inflammation, metabolic pathways, and sickness behaviors in multiple chronic diseases. The presentation of a theoretical framework proposes a mechanism underlying sickness behaviors in the chronic wound population. By mediating the immune system response, dysregulated metabolites in the KYN pathway may play an important role in sickness behaviors in chronic inflammatory conditions. This framework may guide researchers in developing new treatments to reduce the disease burden in the chronic wound population.

Soluble CD83 inhibits acute rejection by up regulating TGF-β and IDO secretion in rat liver transplantation

BACKGROUND

Allogeneic transplantation immune tolerance is currently a hot research issue and soluble CD83(sCD83) is a novel immunomodulator with great potential in inducing transplantation tolerance.

OBJECTIVE

To investigate the mechanism of the immune tolerance effect of sCD83 on rat liver transplantation.

METHOD

A rat liver transplantation model was established to study the effects of sCD83 on the expression levels of IL-2, IL-10, and TGF-β in peripheral blood and the mRNA expressions of foxp3, TGF-β, and Indoleamine 2,3-dioxygenase (IDO) in liver. The expression changes of costimulatory molecules CD80, CD86, and MHC-II on the surface of DC cells and the expressions of IDO + DC cell, TGF-β + CD4 + T cell, and CD4 + CD25 + Foxp3 + T cell were analyzed and compared.

RESULTS

sCD83 alleviated the rejection activity index (RAI) of rat liver transplantation in the early stage, increased the expressions of TGF-β, IL-10 in peripheral blood and the mRNAs of IDO, TGF-β and foxp3 in the transplanted liver, and down-regulated the expressions of MHC-II, CD86, and CD80 in DC cells, resulting in significant increased numbers of tolerogenic TGF-β + CD4 + T cells, Treg cells, and IDO + DC cells with low expression.

CONCLUSION

sCD83 inhibited acute rejection after liver transplantation in an allogeneic rat, and the mechanism was associated with the effect that sCD83 increased the expression of TGF-β, activated IDO immunosuppressive pathway, and increased tolerogenic DC cells and Treg cells.

The aging transcriptome and cellular landscape of the human lung in relation to SARS-CoV-2

Age is a major risk factor for severe coronavirus disease-2019 (COVID-19). Here, we interrogate the transcriptional features and cellular landscape of the aging human lung. By intersecting these age-associated changes with experimental data on SARS-CoV-2, we identify several factors that may contribute to the heightened severity of COVID-19 in older populations. The aging lung is transcriptionally characterized by increased cell adhesion and stress responses, with reduced mitochondria and cellular replication. Deconvolution analysis reveals that the proportions of alveolar type 2 cells, proliferating basal cells, goblet cells, and proliferating natural killer/T cells decrease with age, whereas alveolar fibroblasts, pericytes, airway smooth muscle cells, endothelial cells and IGSF21+ dendritic cells increase with age. Several age-associated genes directly interact with the SARS-CoV-2 proteome. Age-associated genes are also dysregulated by SARS-CoV-2 infection in vitro and in patients with severe COVID-19. These analyses illuminate avenues for further studies on the relationship between age and COVID-19.

A narrative review of the roles of indoleamine 2,3-dioxygenase and tryptophan-2,3-dioxygenase in liver diseases

Indoleamine 2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO) are induced by several immune factors, such as interferon-γ, and act as intracellular enzymes that catabolize essential amino acid tryptophan into kynurenine and other downstream metabolites, including kynurenic acid (KYNA), xanthurenic acid (XA) and so on. IDO and TDO work as a double-edge sword. On one hand, they exert the immunomodulatory effects, especially immunosuppressive effects on the microenvironment including infections, pregnancy, tumor cells escape and transplantation. TDO plays the major role under basal conditions, while IDO comes into play under different circumstances of immune activation, thus IDO has a wider spectrum of immune regulation. On the other hand, these enzymes also inhibit pathogens such as Chlamydia pneumoniae, Staphylococcus aureus, Toxoplasma gondii and so on. Moreover, IDO regulates metabolic health through shaping intestinal microbiota. Recently, these enzymes have attracted more and more attention in liver diseases. Several studies have indicated that IDO and TDO can modulate viral hepatitis, autoimmune liver diseases, non-alcoholic fatty liver disease (NAFLD), liver cirrhosis, liver cancer even liver transplantation. Targeting them or their antagonists may provide novel therapeutic treatments for liver diseases. In this review, we will discuss the exact roles that IDO and TDO play in diverse hepatic diseases.

Diverse chemical space of indoleamine-2,3-dioxygenase 1 (Ido1) inhibitors

Indoleamine-2,3-dioxygenase 1 (IDO1) catalyses the first and rate limiting step of kynurenine pathway accounting for the major contributor of L-Tryptophan degradation. The Kynurenine metabolites are identified as essential cofactors, antagonists, neurotoxins, immunomodulators, antioxidants as well as carcinogens. The catalytic active site of IDO1 enzyme consists of hydrophobic Pocket-A positioned in the distal heme site and remains connected to a second hydrophobic Pocket-B towards the entrance of the active site. IDO1 enzyme also relates directly to the modulation of the innate and adaptive immune system. Various studies proved that the over expression of IDO1 enzyme play a predominant role in the escape of immunity during cancer progression. Recently, there has been considerable interest in evaluating the potential of IDO1 inhibitors to mobilize the body's immune system against solid tumours. In the last two decades, enormous attempts to advance new IDO1 inhibitors are on-going both in pharmaceutical industries and in academia which resulted in the discovery of a diverse range of selective and potent IDO1 inhibitors. The IDO1 inhibitors have therapeutic utility in various diseases and in the near future, it may have utility in the treatment of COVID-19. Despite various reviews on IDO1 inhibitors in last five years, none of the reviews provide a complete overview of diverse chemical space including naturally occurring and synthetic IDO1 inhibitors with detailed structure activity relationship studies. The present work provides a complete overview on the IDO1 inhibitors known in the literature so far along with the Structure-Activity Relationship (SAR) in each class of compounds.

Indoleamine 2,3-Dioxygenase Is Involved in Interferon Gamma's Anti-BKPyV Activity in Renal Cells

Reactivation of BK polyomavirus (BKPyV) infection is frequently increasing in transplant recipients treated with potent immunosuppressants and highlights the importance of immune system components in controlling viral reactivation. However, the immune response to BKPyV in general and the role of antiviral cytokines in infection control in particular are poorly understood. Here, we investigated the efficacy of interferons (IFN) alpha, lambda and gamma with regard to the BKPyV multiplication in Vero cells. Treatment with IFN-gamma inhibited the expression of the viral protein VP1 in a dose-dependent manner and decreased the expression of early and late viral transcripts. Viral inhibition by IFN-gamma was confirmed in human cells (Caki-1 cells and renal proximal tubular epithelial cells). One of the IFN-stimulated genes most strongly induced by IFN-gamma was the coding for the enzyme indoleamine 2,3 dioxygenase (IDO), which is known to limit viral replication and regulates the host immune system. The antiviral activity induced by IFN-gamma could be reversed by the addition of an IDO inhibitor, indicating that IDO has a specific role in anti-BKPyV activity. A better understanding of the action mechanism of these IFN-gamma-induced antiviral proteins might facilitate the development of novel therapeutic strategies.

High Kynurenine:Tryptophan Ratio Is Associated With Liver Fibrosis in HIV-Monoinfected and HIV/Hepatitis C Virus-Coinfected Women

Background

Tryptophan catabolism, measured by the kynurenine:tryptophan (kyn/trp) ratio, is associated with gut microbiota alterations in people with HIV (PWH). We examined the association of the kyn/trp ratio with liver fibrosis in women with/without HIV infection.

Methods

The plasma kyn/trp ratio was measured in 137 HIV-monoinfected, HIV/hepatitis C virus (HCV)–coinfected, and uninfected women in the Women’s Interagency HIV Study. Fibrosis was estimated using FIB-4 in all participants and vibration-controlled transient elastography liver stiffness measurement (LSM) in a subset (n = 83). We used multivariable linear regression to evaluate the associations of infection status and kyn/trp ratio with relative differences in fibrosis estimates.

Results

The median kyn/trp ratio (interquartile range) was 0.056 (0.045–0.066) in HIV/HCV-coinfected, 0.038 (0.032–0.046) in HIV-monoinfected, and 0.031 (0.025–0.034) in uninfected women (P < .001). After adjustment for sociodemographic, lifestyle, and metabolic factors, HIV monoinfection and HIV/HCV coinfection were associated with 37% (95% confidence interval [CI], 9% to 73%) and 164% (95% CI, 100% to 250%) greater FIB-4, respectively. When kyn/trp ratio was included, higher kyn/trp ratio was associated with greater FIB-4 (27% per kyn/trp doubling; 95% CI, 5% to 53%), and the associations of HIV monoinfection (29% per kyn/trp doubling; 95% CI, 2% to 63%) and HIV/HCV coinfection (123% per kyn/trp doubling; 95% CI, 63% to 203%) with greater FIB-4 were attenuated. Among those with LSM, higher kyn/trp ratio was associated with greater LSM (43% per kyn/trp doubling; 95% CI, 15% to 79%) in multivariable analysis.

Conclusions

The kyn/trp ratio is elevated in PWH and is associated with greater liver fibrosis. Tryptophan catabolism may modify the relationships between HIV, HCV, and fibrosis.

Measurement of melatonin, indole-dioxygenase, IL-6, IL-18, ferritin, CRP, and total homocysteine levels during herpes zoster

The risk of herpes zoster (HZ) increases with age and declining immune function. Increased oxidative stress and inflammatory conditions may cause a negative impact on the immune responses. The present study aimed to assess the levels of oxidative/inflammatory stress biomarkers in HZ patients compared with the controls. This case-control study included 43 HZ patients and 47 age-matched controls. Melatonin (MLT), Indole-dioxygenase (IDO), Interleukin-18 (IL-18), Interleukin-6 (IL-6), ferritin, C-reactive protein (hsCRP), and total homocysteine (tHcy) levels were measured and compared in both groups. The significant high levels of IDO, IL-18, IL-6, ferritin, hsCRP, and tHcy, as well as low levels of MLT were found in HZ patients compared with the controls (P < 0.001); these significant differences were also associated with rash and pain severity (P < 0.001). The final logistic regression model with the area under the curve (0.99; 95% confidence interval [CI], 0.98-1.00) showed the association of HZ with decreased level of MLT (odds ratio [OR], 0.95; 95% CI, 0.92-0.98; P = 0.007) and increased levels of tHcy (OR, 1.53; 95% CI, 1.06-2.19; P = 0.02). The findings showed increased inflammation-associated oxidative stress in HZ patients. Elevated tHcy levels and reduced MLT levels may be associated with the manifestation of HZ. More investigations are required to confirm the results.

The role of IDO, IL-10, and TGF-β in the HCV-associated chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma

Indoleamine-2,3-dioxygenase (IDO) is an enzyme that catalyzes tryptophan to kynurenine and studies have revealed that IDO play a vital role in regulation of liver immunity and inflammation activities. This study investigated the association between plasma IDO and disease severity and the possible marker role of IDO in the inflammatory process of hepatitis C. In this study, 80 individuals with HCV infection were retrospectively selected. Plasma levels of IDO, IL-10, and TGF-β were assayed by ELISA. Clinical characteristics of patients, including the levels of ALT, AST, and total bilirubin (TBil) were collected from clinical databases. HCV-related liver cirrhosis (HC-Cirr) and HCV-related Hepatocellular carcinoma (HCV-HCC) had significantly high plasma levels of IDO compared to other patient groups and healthy controls. Plasma IL-10 level were significantly greater in all chronic liver disease groups and with respect to TGF-β, the level was high in all the selected patients with HCV infection compare with controls. Moreover, HCV-HCC patients showed highest values for both IL-10 and TGF-β, with significant difference compared with other groups. In addition, plasma IDO was positively correlated with TGF-β among all patients with HCV infection (r = 0.4509, P < 0.0001), with IL-10 in CHC patients (r = 0.4787, P = 0.0047), with TBil in HCV-Cirr patients (r = 0.4671; P = 0.0093). High level of IDO and TGF-β is associated with hepatocyte necrosis and intrahepatic inflammation, and may be used as an index of disease progression for patients with chronic HCV infection.

Genome-wide DNA methylation and transcriptome analyses reveal genes involved in immune responses of pig peripheral blood mononuclear cells to poly I:C

DNA methylation changes play essential roles in regulating the activities of genes involved in immune responses. Understanding of variable DNA methylation linked to immune responses may contribute to identifying biologically promising epigenetic markers for pathogenesis of diseases. Here, we generated genome-wide DNA methylation and transcriptomic profiles of six pairs of polyinosinic-polycytidylic acid-treated pig peripheral blood mononuclear cell (PBMC) samples and corresponding controls using methylated DNA immunoprecipitation sequencing and RNA sequencing. Comparative methylome analyses identified 5,827 differentially methylated regions and 615 genes showing differential expression between the two groups. Integrative analyses revealed inverse associations between DNA methylation around transcriptional start site and gene expression levels. Furthermore, 70 differentially methylated and expressed genes were identified such as TNFRSF9, IDO1 and EBI3. Functional annotation revealed the enriched categories including positive regulation of immune system process and regulation of leukocyte activation. These findings demonstrated DNA methylation changes occurring in immune responses of PBMCs to poly I:C stimulation and a subset of genes potentially regulated by DNA methylation in the immune responses. The PBMC DNA methylome provides an epigenetic overview of this physiological system in response to viral infection, and we expect it to constitute a valuable resource for future epigenetic epidemiology studies in pigs.

IFN-α-based treatment of patients with chronic HCV show increased levels of cells with myeloid-derived suppressor cell phenotype and of IDO and NOS

INTRODUCTION

Hepatitis C virus (HCV) infection causes chronic hepatitis, which is often associated with suppressed anti-HCV immune responses. We have recently reported accumulation of myeloid-derived suppressor cells (MDSCs) and suppressed immunity in cancer patients.

AIM

The main aim of this study was to determine whether chronic HCV patients harbor high of MDSCs in general and in nonresponders to IFN-based therapy in particular as well as to analyze the immune suppressive molecules.

METHODS

Peripheral blood samples withdrawn from 154 patients with chronic HCV infection and were categorized into responders and nonresponders based on viral titer upon IFN-α treatment.

RESULTS

The relative and absolute numbers of MDSCs defined as Lin^-/HLA-DR^-/CD33⁺/CD11b⁺ increased in all HCV patients, where they were higher in nonresponders than in responders. Additionally, the levels of MDSCs after 4-6 months of treatment in responders were lower than during the course of treatment. The responders also showed higher levels of IL-2 coincided with increased numbers of dendritic cells (DCs), CD4⁺ and CD8⁺ T cells. The levels of total NOS and IDO were also higher in nonresponders as compared to responders and healthy controls, while the expression levels of CD3ζ was lower in responders as compared to nonresponders and healthy volunteers.

CONCLUSION

Chronic HCV patients harbor high numbers of MDSCs, which are higher in nonresponders than in responders. The higher numbers of MDSCs associated with increases in the suppressing factors.

Indoleamine 2,3-dioxygenase 1 deficiency attenuates CCl4-induced fibrosis through Th17 cells down-regulation and tryptophan 2,3-dioxygenase compensation

Indoleamine 2,3-dioxygenase 1 (IDO1) is an intracellular rate-limiting enzyme in the metabolism of tryptophan along the kynurenine pathway, subsequently mediating the immune response; however, the role of IDO1 in liver fibrosis and cirrhosis is still unclear. In this study, we investigated the role of IDO1 in the development of hepatic fibrosis and cirrhosis. Patients with hepatitis B virus-induced cirrhosis and healthy volunteers were enrolled. For animals, carbon tetrachloride (CCl4) was used to establish liver fibrosis in wild-type and IDO1 knockout mice. Additionally, an IDO1 inhibitor (1-methyl-D-tryptophan) was administered to WT fibrosis mice. Liver lesions were positively correlated with serum IDO1 levels in both the clinical subjects and hepatic fibrosis mice. A positive correlation between serum IDO1 levels and liver stiffness values was found in the cirrhosis patients. Notably, IDO1 knockout mice were protected from CCl4-induced liver fibrosis, as reflected by unchanged serum alanine transaminase and aspartate transaminase levels and lower collagen deposition, α-smooth muscle actin expression and apoptotic cell death rates. On the other hand, tryptophan 2,3-dioxygenase (TDO), another systemic tryptophan metabolism enzyme, exhibited a compensatory increase as a result of IDO1 deficiency. Moreover, hepatic interleukin-17a, a characteristic cytokine of T helper 17 (Th17) cells, and downstream cytokines' mRNA levels showed lower expression in the IDO1-/- model mice. IDO1 appears to be a potential hallmark of liver lesions, and its deficiency protects mice from CCl4-induced fibrosis mediated by Th17 cells down-regulation and TDO compensation.

Indoleamine 2,3-dioxygenase: As a potential prognostic marker and immunotherapeutic target for hepatocellular carcinoma

Tumor cells induce an immunosuppressive microenvironment which leads towards tumor immune escape. Understanding the intricacy of immunomodulation by tumor cells is essential for immunotherapy. Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme which mediates tumor immune escape in various cancers including hepatocellular carcinoma (HCC). IDO up-regulation in HCC may lead to recruitment of regulatory T-cells into tumor microenvironment and therefore inhibit local immune responses and promote metastasis. HCC associated fibroblasts stimulate natural killer cells dysfunction through prostaglandin E2 and subsequently IDO promotes favorable condition for tumor metastasis. IDO up-regulation induces immunosuppression and may enhance the risk of hepatitis C virus and hepatitis B virus induced HCC. Therefore, IDO inhibitors as adjuvant therapeutic agents may have clinical implications in HCC. This review proposes future prospects of IDO not only as a therapeutic target but also as a prognostic marker for HCC.

Indoleamine 2,3-dioxygenase activity is associated with regulatory T cell response in acute Puumala hantavirus infection

High indoleamine 2,3-dioxygenase (IDO) activity is associated with clinically severe acute infection caused by Puumala hantavirus. The immunoregulatory effects of IDO can be mediated either through metabolic control of effector T cells, caused by depletion of the essential amino acid tryptophan, or intercellular signaling and activation of regulatory T cell responses. Here, we have studied 24 patients with acute Puumala hantavirus infection to distinguish between these possibilities. Maximum IDO activity showed a significant positive correlation with FOXP3 expression levels in regulatory T cells, a quantitative surrogate marker for suppressive capability. In contrast, IDO activity did not correlate with the frequency of CD8⁺ effector cells in cell cycle. The data suggest that in Puumala infection, the mechanism responsible for the suppressive effect of IDO is not metabolic control of effector cells but rather the signaling mediated by tryptophan breakdown products, such as kynurenine.

Mood, food, and cognition: role of tryptophan and serotonin

PURPOSE OF REVIEW

Food is not only necessary as a metabolic fuel for the body, it becomes more and more evident that there exists an association between food and brain functions like mood and cognition. Tryptophan represents a key element for brain functioning, because of its role as a precursor for production of neurotransmitter serotonin (5-hydroxytryptamine). In clinical conditions, which involve chronic immune system activation or under cytokine therapy, lower tryptophan levels because of high catabolism of tryptophan as indicated by the kynurenine to tryptophan ratio are common and often associate with depressive mood.

RECENT FINDINGS

Studies in the in vitro model of mitogen-stimulated peripheral blood mononuclear cells revealed that several phytocompounds, mainly antioxidants like polyphenols and vitamins, can interfere with inflammatory signaling cascades including tryptophan breakdown. If extrapolated to the in vivo situation, such compounds could increase blood and brain tryptophan availability for serotonin production. Although there is some in vivo evidence for the effect of such compounds, outcomes are hardly predictable and most likely depend on the individual's immunological state.

SUMMARY

Not only a diet rich in tryptophan but also a diet rich in antioxidants can have a positive impact on mood and cognition. This could be of special relevance for individuals who present with low grade inflammation conditions.

Indoleamine-2,3-dioxygenase as an effector and an indicator of protective immune responses in patients with acute hepatitis B

Indoleamine-2, 3-dioxygenase (IDO), an interferon-γ-inducible enzyme catalyzing tryptophan into kynurenine, exerts dual functions in infectious diseases, acting as a suppressor of intracellular pathogens and as an immune regulator. We explored the roles of IDO in hepatitis B virus (HBV) clearance from infected patients. We examined IDO activity, serum chemokines, and cytokines in 53 HBV-positive patients (25 acute hepatitis, 14 chronic hepatitis, and 14 hepatic flare) and 14 healthy volunteers. In order to clarify the mechanisms of IDO induction and its impact on HBV replication, we used a culture model consisting of human natural killer cells, plasmacytoid dendritic cells, and HBV-transfected Huh7 cells in which IDO expression is controlled. A robust activation of IDO with an inverse correlation of alanine aminotransferase at the peak was observed in patients with acute hepatitis B but not in patients with hepatic flare. In acute hepatitis patients who eventually cleared HBV, IDO activity, chemokine (C-X-C motif) ligand 9 (CXCL9), CXCL10, and CXCL11 increased at the peak of alanine aminotransferase. In contrast, in patients with hepatic flare, IDO activity remained at lower levels during the observation period, regardless of the surge of CXCL9, CXCL10, and CXCL11 at the alanine aminotransferase peak. Natural killer cells and plasmacytoid dendritic cells synergistically produced interferon-γ and interferon-α, thereby enhancing IDO activity and HBV suppression in Huh7 cells. Such suppressor capacity of IDO on HBV was abrogated in IDO-knockout cells and recovered by the reinduction of IDO in the cells.

CONCLUSION

IDO is an anti-HBV effector and an indicator of subsequent immune responses operative during the early phase of infection; its activity is boosted by coexisting natural killer cells and plasmacytoid dendritic cells.

Tryptophan Catabolism in Chronic Viral Infections: Handling Uninvited Guests

l-Tryptophan (l-Trp) is an essential amino acid that possesses diverse metabolic, neurological, and immunological roles spanning from the synthesis of proteins, neurotransmitter serotonin, and neurohormone melatonin, to its degradation into immunosuppressive catabolites by indoleamine-2, 3-dioxygenase (IDO) in the kynurenine pathway (KP). Trp catabolites, by activating aryl hydrocarbon receptor (AhR), play an important role in antimicrobial defense and immune regulation. IDO/AhR acts as a double-edged sword by both depleting l-Trp to starve the invaders and by contributing to the state of immunosuppression with microorganisms that were not cleared during acute infection. Pathogens experiencing Trp deprivation by IDO-mediated degradation include certain bacteria, parasites, and less likely viruses. However, chronic viral infections highjack the host immune response to create a state of disease tolerance via kynurenine catabolites. This review covers the latest data involving chronic viral infections such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), herpes, and cytomegalovirus (CMV) and their cellular interplay with Trp catabolites. Strategies developed by viruses to escape immune control also represent new avenues for therapeutic interventions based on Trp metabolism.