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Dengue virus (DV) infection is one of the most common mosquito-borne viral diseases in the world. The innate immune system is important for the early detection of virus and for mounting a cascade of defense measures which include the production of type 1 interferon (IFN). Hence, a thorough understanding of the innate immune response during DV infection would be essential for our understanding of the DV pathogenesis. A recent application of the microarray to dengue virus type 1 (DV1) infected lung carcinoma cells revealed the increased expression of both extracellular and cytoplasmic pattern recognition receptors; retinoic acid inducible gene-I (RIG-I), melanoma differentiation associated gene-5 (MDA-5) and Toll-like receptor-3 (TLR3). These intracellular RNA sensors were previously reported to sense DV infection in different cells. In this study, we show that they are collectively involved in initiating an effective IFN production against DV. Cells silenced for these genes were highly susceptible to DV infection. RIG-I and MDA5 knockdown HUH-7 cells and TLR3 knockout macrophages were highly susceptible to DV infection. When cells were silenced for only RIG-I and MDA5 (but not TLR3), substantial production of IFN-β was observed upon virus infection and vice versa. High susceptibility to virus infection led to ER-stress induced apoptosis in HUH-7 cells. Collectively, our studies demonstrate that the intracellular RNA virus sensors (RIG-I, MDA5 and TLR3) are activated upon DV infection and are essential for host defense against the virus. Author Summary: Dengue fever, dengue haemmorhagic fever and dengue shock syndrome, which are caused by dengue virus infection, are a major public health problem in many parts of the world, especially South East Asia. The investigation of host cell transcriptional changes in response to virus infection using DNA microarray technology has been an area of great interest. In our previous study, we used microarray technology to study expression of individual human genes in relation to dengue virus infection. Most of the genes that were upregulated were type 1 interferon related genes. To gain a better understanding of the innate immune response to dengue virus, we knocked down RIG-I, MDA5 and TLR3 genes in HUH-7 cells. Silencing these genes using siRNA technology resulted in significant increase in viral replication. This increase in viral load induced ER stress leading to apoptosis. This study demonstrates a synergistic role for RIG-I, MDA5 and TLR3 in restricting dengue virus infection. [ABSTRACT FROM AUTHOR]