Receptor-activated human α2-macroglobulin interacts with the envelope protein of dengue virus and protects virions from temperature-induced inactivation through multivalent binding

Abstract

Based on the hypothesis that interactions between virions and serum components may influence the outcome of dengue virus (DENV) infections, we decided to use affinity chromatography with domain III from the envelope (E) protein of DENV2 (DIIIE2) as a ligand to isolate virus-binding proteins from human plasma. This approach yielded serum amyloid P (SAP) and a 2 -macroglobulin (a 2 M) as novel viral interactors. After confirming the specific binding of both SAP and a 2 M to DIIIE2 by ELISA, the latter interaction was examined in greater detail. We obtain evidence suggesting that the binding species was actually the receptor-activated form of a 2 M (a 2 M*), that a 2 M* could bind monovalently to recombinant domain III from all four DENV serotypes with affinities in the micromolar range ranking as DENV4.DENV1~DENV2.DENV3 and that this interaction exhibited a strong avidity effect when multivalent binding was favoured (K D 8¾10"8 M for DIIIE2). We also showed that a 2 M* bound to DENV virions of the four serotypes, protecting the virus from temperature-induced inactivation in the absence of serum and enhancing infectivity. The latter effect exhibited an ED 50 of 2.9¾10 "8 M, also suggesting an avidity effect due to multivalent binding. These results will further contribute to the characterization of the virus-host factor interaction network during human DENV infection.

The low-density lipoprotein receptor-related protein-1 is essential for Dengue virus infection

“…Our results show that LRP1 binds DENV virions (Fig 3C) and that this interaction competes, with potency at the nanomolar range, with DENV virion interactions involving other cell surface molecules (Fig 2E). Previous research has already shown that DENV virions can also bind LRP1 ligands [36,65,66], and in the case of α2M, it has been proven that this interaction augments infection [65]. Whether DENV infection may proceed through the formation of a ternary DENV:α2M:LRP1 complex is the subject of ongoing research, but we would like to point out that the pathogenicity of WNV, a flavivirus closely related to DENV, is severely reduced in knockout mice defective for the expression of α2M homologs [67].…”

“…The procedures for the expression, purification and general characterization of the proteins corresponding to the domain III of the E protein of the four DENV serotypes namely DIIIE1-4, were conducted as previously described. [37]. Receptor-activated α2M was purified from human plasma also following the procedure described elsewhere [37].…”

“…[37]. Receptor-activated α2M was purified from human plasma also following the procedure described elsewhere [37].…”

“…SPR analyses were performed on a Biacore X unit (General Electric, USA). Proteins were covalently immobilized on CM5 chips using amine coupling chemistry as previously described [37]. DIIIE1 (30 μg/ml) and RAP (20 μg/ml) proteins were dissolved in 10 mM sodium acetate buffer pH 5 and loaded into the system.…”

“…We have found that proteins participating in these processes are significantly enriched within the plasma DENV interactome [35,36]. Also we have shown that α2M*, a ligand of LRP1, directly binds DENV virions and favors DENV infection [37].…”