Role of DC-SIGN in Lassa Virus Entry into Human Dendritic Cells

Abstract

The arenavirus Lassa virus (LASV) causes a severe hemorrhagic fever with high mortality in humans. Antigen-presenting cells, in particular dendritic cells (DCs), are early and preferred targets of LASV, and their productive infection contributes to the virusinduced immunosuppression observed in fatal disease. Here, we characterized the role of the C-type lectin DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN) in LASV entry into primary human DCs using a chimera of the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) expressing the LASV glycoprotein (rLCMV-LASVGP). We found that differentiation of human primary monocytes into DCs enhanced virus attachment and entry, concomitant with the upregulation of DC-SIGN. LASV and rLCMV-LASVGP bound to DC-SIGN via mannose sugars located on the N-terminal GP1 subunit of LASVGP. We provide evidence that DC-SIGN serves as an attachment factor for rLCMV-LASVGP in monocyte-derived immature dendritic cells (MDDC) and can accelerate the capture of free virus. However, in contrast to the phlebovirus Uukuniemi virus (UUKV), which uses DC-SIGN as an authentic entry receptor, productive infection with rLCMV-LASVGP was less dependent on DC-SIGN. In contrast to the DC-SIGN-mediated cell entry of UUKV, entry of rLCMV-LASVGP in MDDC was remarkably slow and depended on actin, indicating the use of different endocytotic pathways. In sum, our data reveal that DC-SIGN can facilitate cell entry of LASV in human MDDC but that its role seems distinct from the function as an authentic entry receptor reported for phleboviruses.

Lassa Virus Cell Entry via Dystroglycan Involves an Unusual Pathway of Macropinocytosis

“…Over the past few years, several novel candidate LASV receptors have been identified, suggesting complex receptor use (24,25,57). Recent work provided further insights into the endosomal transport of the virus (31) and uncovered a receptor switch at the level of the late endosome (35) that shows interesting parallels to that in filoviruses (36).…”

“…Since initial studies on LASV entry claimed the involvement of CME (29), we applied two well-established clathrin inhibitors, pitstop-2 (63) and chlorpromazine, which perturb the assembly of clathrincoated pits at the plasma membrane. Neither of them affected ϩ) for Tyro3 and DC-SIGN, respectively, as described previously (25). Primary antibodies were detected with HRP-conjugated secondary antibodies using enhanced chemiluminescence (ECL) for development.…”

“…Recent expression cloning identified the TAM receptors Axl and Tyro3, as well as the C-type lectins DC-SIGN and LSECtin, to be candidate LASV receptors (24). On the basis of their known expression patterns, DC-SIGN and LSECtins may contribute to LASV entry into some cell types (77), but their exact role is currently unclear (25). The TAM kinases Tyro3 and Axl are broadly expressed and highly conserved receptors for the phosphatidylserine (PS)-binding serum proteins Gas6 and protein S, which are involved in removal of apoptotic cells (26,52).…”

“…A recent genome-wide haploid screen revealed that the molecular mechanisms of receptor recognition of LASV strikingly mimic those of receptor recognition of host-derived ECM proteins (23). More recently, the Tyro3/Axl/Mer (TAM) receptor tyrosine kinases (RTKs) Axl and Tyro3/Dtk, as well as the C-type lectins DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN) and LSECtin, have been identified to be candidate LASV receptors (24,25). The coexpression of DG with TAM receptors on many human cell types implicated in LASV infection (26) suggests complex receptor use.…”

Lassa Virus Cell Entry Reveals New Aspects of Virus-Host Cell Interaction

“…In vitro studies on monocytederived human DC revealed that high-mannose N-glycans displayed on LASV GP1 may engage DC-SIGN during attachment (46). However, DC-SIGN seemed dispensable for subsequent viral entry.…”