NF-kB is an essential molecule in the TLR signaling pathway for inducing type I IFN-b and cytokines [16, 28, 29] . In our infection system, two strains of DENV-2, PL046 and NGC, triggered low degree of NFkB p65 nuclear translocation. Nuclear staining of p65 was noted in 7% and 13% of PL046-and NGCinfected cells, respectively ( Figure S2A panels b and c) ; in contrast, about 80% of the control virus infected cells showed nuclear staining of NF-kB p65 ( Figure S2A, panel d) . Thus, we checked whether DENV-2 could suppress NF-kB activation triggered by TLRs engagement. With use of a NF-kB-dependent luciferase reporter, NF-kB activation stimulated by the TLR ligands LPS and polyI:C was readily blocked in DENV-2-infected cells at 12 and 24 h post stimulation ( Figure 3A ). Immunoblotting result of DENV-2 NS3 indicated that the virus was replicating in A549 cells and was not affected by LPS and polyI:C posttreatment ( Figure 3B ). As well, DENV-2 infection blocked LPS-triggered NF-kB activation in Vero cells as measured by nuclear translocation of NF-kB p65 ( Figure 4A) ; similar results were also observed in J774A.1 macrophages ( Figure S2B ). Nuclear translocation of NF-kB p65 was slightly increased in A549 cells up to 60 h post DENV-2 infection, but the polyI:C-triggered p65 nuclear translocation was greatly blocked in DENV-2 infected cells ( Figure  S2C ). We also tested the influence of TLR singling in DENV-2 replication, polyI:C pretreatment blocked DENV-2 replication; whereas, the antiviral effect of polyI:C was not seen in cells with established DENV-2 infection ( Figure 4B ). This data is consistent with previous report [30] and suggest that DENV-2 inhibits TLR signaling to benefit its replication. DENV-2 replication in these two cell lines, A549 and Vero, was confirmed by qPCR with viral 59 UTR primers and plaque assay for virion production ( Figure  S3 ). Thus, DENV-2 downregulates TLR-activated NF-kB, which leads to reduced cytokine expression.