Inhibition of the Type I Interferon Response in Human Dendritic Cells by Dengue Virus Infection Requires a Catalytically Active NS2B3 Complex

Abstract

Dengue virus (DENV) is the most prevalent arthropod-borne human virus, able to infect and replicate in human dendritic cells (DCs), inducing their activation and the production of proinflammatory cytokines. However, DENV can successfully evade the immune response in order to produce disease in humans. Several mechanisms of immune evasion have been suggested for DENV, most of them involving interference with type I interferon (IFN) signaling. We recently reported that DENV infection of human DCs does not induce type I IFN production by those infected DCs, impairing their ability to prime naive T cells toward Th1 immunity. In this article, we report that DENV also reduces the ability of DCs to produce type I IFN in response to several inducers, such as infection with other viruses or exposure to Toll-like receptor (TLR) ligands, indicating that DENV antagonizes the type I IFN production pathway in human DCs. DENV-infected human DCs showed a reduced type I IFN response to Newcastle disease virus (NDV), Sendai virus (SeV), and Semliki Forest virus (SFV) infection and to the TLR3 agonist poly(I:C). This inhibitory effect is DENV dose dependent, requires DENV replication, and takes place in DENV-infected DCs as early as 2 h after infection. Expressing individual proteins of DENV in the presence of an IFN-␣/␤ production inducer reveals that a catalytically active viral protease complex is required to reduce type I IFN production significantly. These results provide a new mechanism by which DENV evades the immune system in humans.Dengue virus (DENV), a member of the Flaviviridae family and grouped within the Flavivirus genus (27), is the most prevalent arthropod-borne human virus with significant medical and biodefense importance (8,27). DENV is transmitted by mosquitoes, usually Aedes aegypti, with an estimated 100 million cases per year and 2.5 billion people at risk (53). Clinical manifestations include dengue fever, a febrile illness with rash, and dengue hemorrhagic fever, a severe and often lethal illness (53). There are four DENV serotypes (DENV1 to -4), and infection with one serotype confers life-long protection against that serotype at least by the induction of neutralizing antibodies (17). Currently there is no vaccine or effective antiviral treatment against this virus, and the most effective protective measures involve mosquito control.The DENV genome is a positive-strand RNA molecule of about 11 kb in length, with one single open reading frame (ORF) flanked by 5Ј and 3Ј nontranslated regions (27). After viral infection and the release of the viral nucleocapsid into the cytosol, a 3,391-amino-acid (aa)-long polyprotein is translated from the viral RNA at the surface of the endoplasmic reticulum (ER) (27). This polyprotein is cleaved into three structural (C, prM, and E) and seven nonstructural (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) proteins due to the combined and coordinated activities of host cell proteases in the ER and the viral protease complex (NS2B3) in the cytoplasm (27). The viral protease cle...

Delayed Cytosolic Exposure of Japanese Encephalitis Virus Double-Stranded RNA Impedes Interferon Activation and Enhances Viral Dissemination in Porcine Cells

“…This further implies that JEV-encoded proteins are not the major components that inhibit IFN induction, contrary to what has been reported for other flaviviral proteins (24,27,36,48). In similar experiments, DENV was able to inhibit IFN activation using various inducers (36), but WNV and TBEV failed to inhibit IFN activation by poly(I ⅐ C) (6,30), suggesting that not all flaviviruses possess an active mechanism to antagonize the host IFN pathway. The intact and functional IFN system of PS cells during JEV infection reinforces the idea that the virus (i.e., dsRNA) is simply not detected at early stages of infection.…”

Dengue Virus Subverts Host Innate Immunity by Targeting Adaptor Protein MAVS

“…DENV is known to be a weak inducer of type I IFN, and DENVinfected human dendritic cells exhibit an impaired type I IFN response to infection with several viruses and to stimulation with poly(I·C) (14,44,45). Thus far, the functional significance of NS4A in viral replication remains poorly characterized.…”

“…Previous studies have shown that DENV infection usually leads to low levels of IFN-␣ and -␤, thus suggesting that DENV may inhibit IFN production after DENV infection (12)(13)(14)(15)(16). Several research groups have reported that prevention of STAT1 phosphorylation or induction of STAT2 degradation is a mechanism possibly underlying the antagonistic effects of DENV on IFN signaling (17)(18)(19)(20)(21)(22).…”

Dengue Virus Type 3 Isolated from a Fatal Case with Visceral Complications Induces Enhanced Proinflammatory Responses and Apoptosis of Human Dendritic Cells

“…These mutations contribute to a lower ability of the American genotype strains to replicate in human monocyte-derived macrophages and dendritic cells (7,38). Conversely, the five mutations we report in nonstructural proteins may interfere with viral replication (10) and inhibit type I interferon (IFN) signaling (1,31,41).…”