Dengue virus NS1 protein conveys pro‐inflammatory signals by docking onto high‐density lipoproteins

Abstract

The dengue virus nonstructural protein 1 (NS1) is a secreted virulence factor that modulates complement, activates immune cells and alters endothelial barriers. The molecular basis of these events remains incompletely understood. Here we describe a functional high affinity complex formed between NS1 and human high‐density lipoproteins (HDL). Collapse of the soluble NS1 hexamer upon binding to the lipoprotein particle leads to the anchoring of amphipathic NS1 dimeric subunits into the HDL outer layer. The stable complex can be visualized by electron microscopy as a spherical HDL with rod‐shaped NS1 dimers protruding from the surface. We further show that the assembly of NS1‐HDL complexes triggers the production of pro‐inflammatory cytokines in human primary macrophages while NS1 or HDL alone do not. Finally, we detect NS1 in complex with HDL and low‐density lipoprotein (LDL) particles in the plasma of hospitalized dengue patients and observe NS1‐apolipoprotein E‐positive complexes accumulating overtime. The functional reprogramming of endogenous lipoprotein particles by NS1 as a means to exacerbate systemic inflammation during viral infection provides a new paradigm in dengue pathogenesis.

CryoEM structures of the multimeric secreted NS1, a major factor for dengue hemorrhagic fever

“…This is similar to our structure of 5E3 complexed with NS1 dimeric obtained after Fab 5E3 has dismantled the loose tetramer and hexameric sNS1 structures. Both Benfrid et al 23 and Chew et al 27 did not show any high-resolution structures of sNS1 complexed with HDL, likely because their samples might be very heterogeneous and/or flexible, thus complicating cryoEM structural determination. Thus our cryoEM study shows the sNS1 structures before it is complexed with any host proteins.…”

“…Benfrid et al 23 also showed that sNS1 it binds to low-density lipoproteins, albeit with lower affinity. Benfrid et al 23 reported negative-stain EM 2D class averages of the purified sNS1:HDL complex containing heterogeneous particles with either two, three, and four NS1 dimers on the HDL surface. They suggested how a hexameric sNS1 could rearrange into three dimers on the HDL surface.…”

“…sNS1 has been previously thought to be homogeneously hexameric in structure 14,15,22 . These studies were done by using DENV1 FGA/ 89 strain 15 and DENV2 sNS1 16681 strain 23 and they might have different oligomerization distributions compared to our sNS1 from DENV2 PVP94/07 clinical isolate. Nonetheless, we compared our cryoEM 2D class averages of the picked particles to that in their samples (Supplementary Fig.…”

“…This might increase the number of structural classes making cryoEM structural determination much more difficult and complicated. There are examples where sNS1 bind to host proteins: Benfrid et al 23 and Chew et al 27 showed that sNS1 binds to human/bovine highdensity lipoproteins (HDL). Benfrid et al 23 also showed that sNS1 it binds to low-density lipoproteins, albeit with lower affinity.…”

“…There are examples where sNS1 bind to host proteins: Benfrid et al 23 and Chew et al 27 showed that sNS1 binds to human/bovine highdensity lipoproteins (HDL). Benfrid et al 23 also showed that sNS1 it binds to low-density lipoproteins, albeit with lower affinity. Benfrid et al 23 reported negative-stain EM 2D class averages of the purified sNS1:HDL complex containing heterogeneous particles with either two, three, and four NS1 dimers on the HDL surface.…”