Low adiposity during early infancy is associated with a low risk for developing dengue hemorrhagic fever: a preliminary model.

Dengue virus (DENV) infections range from asymptomatic or mild illness to a severe and potentially life threatening disease, dengue hemorrhagic fever (DHF). DHF occurs in primary DENV infections during early infancy. A prospective clinical study of DENV infections during infancy was conducted in San Pablo, Philippines. We found that infants who developed DHF with a primary DENV infection had higher WHO weight-for-age z scores before and at the time of infection compared to infants with primary DENV infections who did not develop DHF. In addition, TLR 7/8-stimulated tumor necrosis factor-α (TNF-α) production from myeloid-derived cells was higher among well-nourished infants. Leptin augmented TLR 7/8-mediated TNF-α production in monocytes and decreased intracellular cAMP levels. Circulating leptin levels were elevated during early infancy and correlated with WHO weight-for-age z scores. Our data support a plausible hypothesis as to why well-nourished infants are at risk for developing DHF with their first DENV infection.

Dengue virus type 2 modulates endothelial barrier function through CD73.

Dengue hemorrhagic fever is characterized by a unique vascular leakage syndrome. The mechanisms of endothelial barrier dysfunction in dengue hemorrhagic fever are not well understood. We examined the modulation of endothelial barrier function in dengue virus type 2 (DENV2) infections using primary human umbilical vein endothelial cells. We demonstrated that the increase in endothelial barrier function within 72 hours after DENV2 infection is mediated by type I interferon-dependent CD73 up-regulation. After 72 hours, DENV2 slowed the recovery of endothelial barrier function in response to tumor necrosis factor-α or vascular endothelial growth factor. This phenomenon was likely caused by type I interferon receptor signaling inhibition and lower CD73 levels in DENV2-infected endothelial cells. Our findings suggest that during DENV2 infection, endothelial barrier homeostasis is maintained by a balance between pro-inflammatory and pro-angiogenic cytokines, and type I interferon-dependent CD73 expression and activity.

Comparación de los perfiles de transcripción de pacientes con fiebre de dengue y fiebre hemorrágica por dengue que muestra diferencias en la respuesta inmunitaria y claves en la inmunopatogénesis / Comparison of the transcriptional profiles of patients with dengue fever and dengue hemorrhagic fever reveals differences in the immune response and clues in immunopathogenesis

Introducción. El dengue puede manifestarse como una enfermedad leve o evolucionar hasta una enfermedad grave, llamada fiebre hemorrágica por dengue, cuyos mecanismos de inmunopatogénesis no son claros. Objetivo. Utilizar un análisis de microarreglos para identificar los genes de la respuesta inmunitaria diferencialmente expresados en niños colombianos con dengue leve y grave. Materiales y métodos. Se evaluaron los cambios de la expresión génica de células mononucleares de sangre periférica de niños con fiebre de dengue y fiebre hemorrágica por dengue en fase aguda, mediante el microarreglo de Affymetrix HG-U133_Plus_2. Resultados. Los pacientes con fiebre hemorrágica por dengue expresaron transcritos para interleucina 6, quimiocinas, complemento y pentraxina 3, al igual que inhibidores de la actividad de linfocitos (gen 3 de activación de linfocitos y catepsina L1). Un modelo de interacción desarrollado para estos genes mostró al factor tisular como central en la red generada. Por el contrario, los pacientes con fiebre de dengue expresaron inhibidores de la actividad de citocinas, complemento y leucotrienos lactotransferrina, inhibidor peptidasa serpina del complemento C1, leucotrieno B (4-omega hidroxilasa 2). Conclusiones. Los resultados podrían indicar que durante la fiebre de dengue, los inhibidores de citocinas y del complemento logran controlar el daño al endotelio y el aumento de la permeabilidad vascular, mientras que, en los pacientes con fiebre hemorrágica por dengue, la disfunción de las células inmunitarias y la acción no regulada del complemento y de las citocinas, conducen a un estado de “hipercoagulacion” y daño endotelial. La identificación del papel patógeno de las moléculas encontradas podría contribuir a la interpretación de la patogenia y al desarrollo de fármacos terapéuticos. Palabras clave: dengue, transcripción genética, análisis de micromatrices, fiebre hemorrágica del dengue, proteínas del sistema del complemento, citocinas.

[Comparison of the transcriptional profiles of patients with dengue fever and dengue hemorrhagic fever reveals differences in the immune response and clues in immunopathogenesis]. / Comparación de los perfiles de transcripción de pacientes con fiebre de dengue y fiebre hemorrágica por dengue que muestra diferencias en la respuesta inmunitaria y claves en la inmunopatogénesis.

INTRODUCTION: Dengue infection demonstrates a wide spectrum of clinical manifestations from mild disease (dengue fever) to severe dengue hemorrhagic fever, but the immunopathogenic mechanisms involved in disease severity are not clear. OBJECTIVE: Differentially expressed genes associated to immune response were identified from peripheral blood mononuclear cells of Colombian children with dengue fever and dengue hemorrhagic fever. MATERIALS AND METHODS: Microarray analysis was used as a tool to establish and compare transcriptional profiles of peripheral blood mononuclear cells of six children in acute phase of dengue fever and dengue hemorrhagic fever. The commercial gene chip used was Affymnetrix GeneChip HG_U133_Plus_2. RESULTS: Dengue hemorrhagic fever patients expressed interleukin 6, chemokines, complement proteins and pentraxin 3, along with the lymphocyte inhibitors lymphocyte-activation gene 3 and cathepsin L1. An interaction model for these genes showed tissue factor playing a central role in the network generated. In contrast, dengue fever patients expressed cytokines, complement and the leukotrienes inhibitors lactotransferrin, C1 inhibitor, and leukotriene-B (4-omega-hydroxylase 2). CONCLUSIONS: These results indicate that in dengue fever, cytokine and complement inhibitors are able to limit endothelial damage and prevent increases in vascular permeability, whereas dengue- hemorrhagic fever patients have immune cell dysfunction and unregulated complement and cytokine action. This leads to "hypercoagulation" and endothelial damage, thereby increasing disease severity. Verification of the pathogenic role of the identified molecules will contribute to understanding of dengue pathogenesis and lead to rational development of therapeutic drugs.

Efficient dengue virus (DENV) infection of human muscle satellite cells upregulates type I interferon response genes and differentially modulates MHC I expression on bystander and DENV-infected cells.

Dengue virus (DENV) is a mosquito-borne flavivirus that causes an acute febrile disease in humans, characterized by musculoskeletal pain, headache, rash and leukopenia. The cause of myalgia during DENV infection is still unknown. To determine whether DENV can infect primary muscle cells, human muscle satellite cells were exposed to DENV in vitro. The results demonstrated for the first time high-efficiency infection and replication of DENV in human primary muscle satellite cells. Changes in global gene expression were also examined in these cells following DENV infection using Affymetrix GeneChip analysis. The differentially regulated genes belonged to two main functional categories: cell growth and development, and antiviral type I interferon (IFN) response genes. Increased expression of the type I IFN response genes for tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), melanoma-derived antigen 5 (MDA-5), IFN-gamma-inducible protein 10 (IP-10), galectin 3 soluble binding protein (LGals3BP) and IFN response factor 7 (IRF7) was confirmed by quantitative RT-PCR. Furthermore, higher levels of cell-surface-bound intracellular adhesion molecule-1 (ICAM-1) and soluble ICAM-1 in the cell-culture medium were detected following DENV infection. However, DENV infection impaired the ability of the infected cells in the culture medium to upregulate cell-surface expression of MHC I molecules, suggesting a possible mechanism of immune evasion by DENV. The findings of this study warrant further clinical research to identify whether muscle cells are targets for DENV infection during the acute stage of the disease in vivo.

TRAIL is a novel antiviral protein against dengue virus.

Dengue fever is an important tropical illness for which there is currently no virus-specific treatment. To shed light on mechanisms involved in the cellular response to dengue virus (DV), we assessed gene expression changes, using Affymetrix GeneChips (HG-U133A), of infected primary human cells and identified changes common to all cells. The common response genes included a set of 23 genes significantly induced upon DV infection of human umbilical vein endothelial cells (HUVECs), dendritic cells (DCs), monocytes, and B cells (analysis of variance, P < 0.05). Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), one of the common response genes, was identified as a key link between type I and type II interferon response genes. We found that DV induces TRAIL expression in immune cells and HUVECs at the mRNA and protein levels. The induction of TRAIL expression by DV was found to be dependent on an intact type I interferon signaling pathway. A significant increase in DV RNA accumulation was observed in anti-TRAIL antibody-treated monocytes, B cells, and HUVECs, and, conversely, a decrease in DV RNA was seen in recombinant TRAIL-treated monocytes. Furthermore, recombinant TRAIL inhibited DV titers in DV-infected DCs by an apoptosis-independent mechanism. These data suggest that TRAIL plays an important role in the antiviral response to DV infection and is a candidate for antiviral interventions against DV.