Dengue Virus (DV) Replication in Monocyte-Derived Macrophages Is Not Affected by Tumor Necrosis Factor Alpha (TNF-α), and DV Infection Induces Altered Responsiveness to TNF-α Stimulation

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Abstract
Tumor necrosis factor alpha (TNF-α) is believed to play a significant role in the pathogenesis of dengue virus (DV) infection, with elevated levels of TNF-α in the sera of DV-infected patients paralleling the severity of disease and TNF-α release being coincident with the peak of DV production from infected monocyte-derived macrophages (MDM) in vitro. Since macrophages are a primary cell target in vivo for DV infection, we investigated the potential antiviral role of TNF-α in regulating DV replication in MDM. While pretreatment of MDM with TNF-α had a minor inhibitory effect, addition of TNF-α to MDM with established DV infection had no effect on DV replication as measured by DV RNA levels or progeny virus production. Blocking endogenous TNF-α using short interfering RNA or inhibitory TNF-α antibodies also had no effect on infectious DV production or viral RNA synthesis. Together, these results demonstrate that DV replication in MDM is not affected by TNF-α. Additionally, normal cellular TNF-α signaling, measured by quantitation of TNF-α-induced stimulation of transcription from an NF-κB-responsive reporter plasmid or NF-κB protein nuclear translocation, was blocked in DV-infected MDM and Huh7 cells. Thus, DV replication in MDM is not affected by TNF-α, and infected cells do not respond normally to TNF-α stimulation. It is therefore unlikely that the increased production of TNF-α seen in DV infection directly effects DV clearance by reducing DV replication, and the ability of DV to alter TNF-α responsiveness highlights another example of viral subversion of cellular functions.

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