Dendritic Cell-specific Intercellular Adhesion Molecule 3-grabbing Non-integrin (DC-SIGN)-mediated Enhancement of Dengue Virus Infection Is Independent of DC-SIGN Internalization Signals

Dengue virus (DV) is a mosquito-borne flavivirus that causes hemorrhagic fever in humans. In the natural infection, DV is introduced into human skin by an infected mosquito vector where it is believed to target immature dendritic cells (DCs) and Langerhans cells (LCs). We found that DV productively infects DCs but not LCs. We show here that the interactions between DV E protein, the sole mannosylated glycoprotein present on DV particles, and the C-type lectin dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) are essential for DV infection of DCs. Binding of mannosylated N-glycans on DV E protein to DC-SIGN triggers a rapid and efficient internalization of the viral glycoprotein. However, we observed that endocytosis-defective DC-SIGN molecules allow efficient DV replication, indicating that DC-SIGN endocytosis is dispensable for the internalization step in DV entry. Together, these results argue in favor of a mechanism by which DC-SIGN enhances DV entry and infection in cis. We propose that DC-SIGN concentrates mosquito-derived DV particles at the cell surface to allow efficient interaction with an as yet unidentified entry factor that is ultimately responsible for DV internalization and pH-dependent fusion into DCs. Dengue virus (DV) is a mosquito-borne flavivirus that causes hemorrhagic fever in humans. In the natural infection, DV is introduced into human skin by an infected mosquito vector where it is believed to target immature dendritic cells (DCs) and Langerhans cells (LCs). We found that DV productively infects DCs but not LCs. We show here that the interactions between DV E protein, the sole mannosylated glycoprotein present on DV particles, and the C-type lectin dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) are essential for DV infection of DCs. Binding of mannosylated N-glycans on DV E protein to DC-SIGN triggers a rapid and efficient internalization of the viral glycoprotein. However, we observed that endocytosis-defective DC-SIGN molecules allow efficient DV replication, indicating that DC-SIGN endocytosis is dispensable for the internalization step in DV entry. Together, these results argue in favor of a mechanism by which DC-SIGN enhances DV entry and infection in cis. We propose that DC-SIGN concentrates mosquito-derived DV particles at the cell surface to allow efficient interaction with an as yet unidentified entry factor that is ultimately responsible for DV internalization and pH-dependent fusion into DCs. IntroductionDengue virus (DV) 1The abbreviations used are: DV, dengue virus; Ab, antibody; BHK, baby hamster kidney; BSA, bovine serum albumin; DC, dendritic cell; DC-SIGN, dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin; DMJ, 1-deoxymannojirimycin hydrochloride; EndoH, endoglycosidase H; FACS, fluorescence-activated cell sorting; FITC, fluorescein isothiocyanate; FCS, fetal calf serum; GM-CSF, granulocyte macrophage colony-stimulating factor; HCV, hepatitis C virus; HIV, human immunodeficiency virus; HMAF, hyperimmune mouse ascites fluids; L-SIGN, liver cell-specific intercellular adhesion molecule 3-grabbing non-integrin; LC, Langerhans cell; mAb, monoclonal antibody; m.o.i., multiplicity of infection; PBS, phosphate-buffered saline; PE, phycoerythrin; PNGase F, peptide:N-glycosydase F; sE, DV-soluble E protein; SFV, Semliki forest virus; WT, wild type. is an arthropod-borne flavivirus that belongs to the Flaviviridae family (1Chambers T.J. Monath T.P. The Flavivirus: Pathogenesis and Immunity. Elsevier Science Publishing Co., New York2003Google Scholar). The four serotypes of DV (DV-1 to DV-4) are transmitted to humans by the mosquito vector Aedes aegypti (1Chambers T.J. Monath T.P. The Flavivirus: Pathogenesis and Immunity. Elsevier Science Publishing Co., New York2003Google Scholar, 2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar). DV infection results in a spectrum of illnesses, ranging from a flu-like disease (dengue fever) to dengue hemorrhagic fever that can progress to dengue shock syndrome and death (1Chambers T.J. Monath T.P. The Flavivirus: Pathogenesis and Immunity. Elsevier Science Publishing Co., New York2003Google Scholar).DV is a lipid-enveloped virus with a single-stranded, positive sense RNA genome, which replicates in the cytoplasm of infected cells (2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar, 3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar). The 11-kb viral RNA encodes for a large polyprotein precursor, which is processed by both host and viral proteases to yield the non-structural proteins NS1 to NS5 and three structural proteins: C (core), prM (the intracellular precursor of the M protein), and E (envelope) glycoprotein (2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar, 3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar). The E protein is assumed to bind cellular receptors that direct DV particles to the endocytic pathway. The acidic environment in the endosome is believed to trigger major conformational changes in the E protein, which induce fusion of the viral and host cell membranes, resulting in entry of the virion into the cytoplasm (3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar).In the natural infection, DV is introduced into human skin by an infected mosquito during a blood meal (2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar). Immature dendritic cells (DCs) and Langerhans cells (LCs), which are normally resident in the skin, have been to infected by DV and are believed to the cells by the virus Nat. PubMed Scopus Google Scholar). We have the interactions between DV and human DCs to cellular for virus entry. We and S. S. PubMed Scopus Google Scholar, PubMed Scopus Google have DC-SIGN as an essential molecule for DV infection of immature DC-SIGN molecules DV is a C-type lectin that present on the surface of viral as human immunodeficiency virus and hepatitis C virus S. PubMed Scopus Google Scholar, S. PubMed Scopus Google Scholar, Nat. Rev. 3: PubMed Scopus Google Scholar). The DV E protein, which is the glycoprotein on the surface of DV is responsible for to the host cell surface and an in viral entry (3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar, R.J. Rossmann M.G. S. PubMed Scopus Google Scholar). present on the E glycoprotein have been to for virus to host cells PubMed Scopus Google Scholar). In to viral that bind DC-SIGN and are DV E protein at and which are used by the four DV serotypes PubMed Scopus Google Scholar). The interactions of E protein with DC-SIGN, believed to a for DV entry into are to DC-SIGN, DV is believed to and to an acidic where fusion (3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar). of cells with which the DV infection PubMed Scopus Google Scholar). DC-SIGN is an endocytic that been to Nat. Rev. 3: PubMed Scopus Google Scholar, R.J. S. 2004; PubMed Scopus Google Scholar, Immunity. PubMed Scopus Google Scholar, PubMed Scopus Google it is DC-SIGN is responsible for DV to it the of in the of a entry we have the of DC-SIGN in the of DV entry into DCs. results the E protein as the DV responsible for to DC-SIGN and a for N-glycans in interactions between DV E protein and We that DV endocytosis is dispensable for DV infection of target cells and propose that DC-SIGN as a DV factor that interaction of viral particles with an as yet unidentified cellular which to DV of and DC-SIGN for the of prM and E proteins PubMed Scopus Google Scholar). used as a to Semliki forest virus for the DV prM and of E protein The for prM protein and the of E protein in the DV by the sense and the The encodes for the The for E with and and introduced into of the vector PubMed Scopus Google DC-SIGN wild vector Immunity. PubMed Scopus Google Scholar). DC-SIGN DC-SIGN and DC-SIGN by and into 2004; PubMed Scopus Google DC-SIGN by the protein with a DC-SIGN WT, DC-SIGN DC-SIGN DC-SIGN DC-SIGN the of the of the DC-SIGN mouse monoclonal from and from and from The and have been in and Immunity. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar, 2004; PubMed Scopus Google Scholar). DV with hyperimmune mouse ascites to a from and PubMed Scopus Google Scholar). The used a is the and PubMed Scopus Google Scholar). mouse and and in with fetal calf serum and cells in with and DC-SIGN by with the vector DC-SIGN as 2004; PubMed Scopus Google Scholar). cells with of DC-SIGN by of cells by DC-SIGN vector at of infection as PubMed Scopus Google Scholar). cells by cell and Langerhans as 2004; PubMed Scopus Google Scholar). human blood cells from by with with a of and at in with FCS, human and human granulocyte macrophage colony-stimulating factor for from human blood as PubMed Scopus Google Scholar). cells in with FCS, cell factor and cells and for in with FCS, GM-CSF, and and DV and in mosquito cell in on and virus on cells by as PubMed Scopus Google infection, cells to DV for at at in with BSA, with to virus and at The cells cells with for at of DV and with the as PubMed Scopus Google viral with to cells and by and to cells in for at by with in with the for at with the to by mAb, and with in and in bovine serum from by with at a a for at and with to and with and of proteins S. PubMed Scopus Google Scholar). DV in baby hamster cells in the of and S. PubMed Scopus Google Scholar). by with endoglycosidase F; New S. PubMed Scopus Google Scholar). by at a S. PubMed Scopus Google Binding and cells in of and for at to endocytosis glycoprotein by with cells with in for at of protein used at internalization cells proteins for the at at to the cells at both and with at for to cell surface of The of the cells with at for to the glycoprotein. cells in to in to of and in a cells DC-SIGN on The cells with the in for at three with to and to for to allow DC-SIGN with for in PBS, and with for with of and for cells with and in on with the and a but by the of DV to immature DCs and we DCs as as from blood and and to DV cell the of DCs and cells for of DC-SIGN, and a C-type lectin by and in the of a the Nat. Rev. 2: PubMed Scopus Google Scholar, S. S. Immunity. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). DCs as of DC-SIGN and In not the C-type lectin which is present on of the LCs. for PubMed Scopus Google we found that in not DC-SIGN Immature DCs and infected with the in Aedes at by for NS1 protein, a non-structural protein during DV in of DCs productively infected by In of to the DV in infection of of results with DV serotypes not that DV productively infects immature DCs and not of DCs by the DV the interaction of DV with DCs in we immature DCs with mosquito-derived DV from the four serotypes at that to productively human immature DCs. that infection of DCs by is by DC-SIGN and by results with DV serotypes and not of from DCs with the four DV serotypes that infected DCs of viral of DCs with to infection virus of immature DCs to DV particles been to induce S. T.P. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). viral infection, we immature DCs with at an of in the of cell surface of and by with of immature DCs with DV in a of and cell surface a of in cells infected with We found that surface of in DC-SIGN not with Ab, of cells with as by the of and in infected cells results with the DV serotypes not In of immature DCs with DV not induce that is on viral of DV particles by DCs not these that DC-SIGN is a factor for infection of DCs by DV serotypes and for is for infection of DCs by the four DV serotypes and for DCs infected with mosquito-derived DV at of and cells and with to infection by as infection in DCs. DCs infected with at a of in the of the a cells for the NS1 and viral infection by as of in DCs. infected with to at a of for in the of and at for in as in infection of DCs in a DC-SIGN DCs infected with of in the of The of and by The are of three by the of DC-SIGN to DV entry and in human cell and which DC-SIGN with virus vector particles, human with and for a of DC-SIGN We found that and cells are to DV In DC-SIGN in these cell efficient viral of and and of positive for NS1 results human and cell DC-SIGN, as not and which of DC-SIGN cell found to to that DV infection is DC-SIGN cell surface with we cells DC-SIGN at and that DV infection is in with DC-SIGN We observed that DC-SIGN are for viral entry and infection these results that of DC-SIGN cell by DV, the of DC-SIGN in DV entry into immature of DC-SIGN enhances DV and cells with vector DC-SIGN by and and cells infected with at a of for the NS1 non-structural and viral infection by cells of DC-SIGN by and for DC-SIGN with a and by The are in and and infected by of and for the NS1 non-structural DV infection with DC-SIGN are as the of on the The are of three DV E with E protein at and that are believed to DV to DC-SIGN S. S. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). the interaction of E protein with DC-SIGN, the for and the of E to of polyprotein of to bovine at the C into a protein, cells infected with the precursor protein and with that protein is the major protein by as by with the natural vector of DV is the Aedes aegypti the E protein at the surface of transmitted to humans (2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar, PubMed Scopus Google Scholar). we cells with and The resulting protein, N-glycans as by to In in cells and However, both and to PNGase which both and N-glycans at the resulting in a E We found that proteins bind to cells DC-SIGN but not to cells In to we observed that sE, which to bind to indicating that N-glycans on the DV E protein are for interactions with DC-SIGN of proteins to cells is by and the we found that immature which DC-SIGN, interaction is by and by Together, these results DV E as a protein and a for N-glycans in DV E glycoprotein to glycoprotein to DC-SIGN mannosylated cells infected with for prM and and with proteins with an an an and by in cells in the of and sE, E proteins to with PNGase and by but not sE, to and for at with and three for at with and three of of to cells with in the of DC-SIGN as and an as F, DC-SIGN to dendritic with DCs in the of and and The are of three are as the of into E protein is by DC-SIGN, we cells on with to cells on to for with for to E protein from E protein to DC-SIGN at the cell We found that of the E protein to DC-SIGN by cells at In for at we observed that a large of protein to indicating that DC-SIGN internalization of DV E protein at of E protein endocytosis that DV E protein endocytosis is as of E protein is at internalization of to cells for at to and for at with to from cell surface E glycoprotein. internalization of in The are of are as the of of DC-SIGN in DV and three in that are believed to in internalization endocytic Nat. Rev. 3: PubMed Scopus Google Scholar, Nat. Rev. 2: PubMed Scopus Google Scholar). a a which are both internalization and a Nat. Rev. 3: PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). the of these three in DC-SIGN and DV we DC-SIGN at the into the cells with virus vector particles, DC-SIGN with that DC-SIGN WT, and proteins at at the cell surface used to DC-SIGN endocytosis in cells with the for at and to to DC-SIGN DC-SIGN and receptors at the cell at we observed a of in DC-SIGN WT, and with an intracellular of that WT, and DC-SIGN receptors are in cells In we found that the of receptors at the surface of cells that the is for efficient DC-SIGN endocytosis and intracellular of and DC-SIGN cells with a vector for of DC-SIGN and for DC-SIGN are in of and DC-SIGN in with cells DC-SIGN WT, and proteins for at to and for at with a surface and intracellular of DC-SIGN by The are of three and proteins bind DV with DC-SIGN with efficient internalization and infection of DV, we DV entry in cells a endocytic pathway. cells and DC-SIGN molecules infected with the virus at that molecules DV infection as as DC-SIGN WT, and results in cell DC-SIGN C and a of in DV infection, we cells a DC-SIGN surface of DC-SIGN found to DC-SIGN infection show that DC-SIGN is to DV entry of cells DC-SIGN molecules with the a of Together, these that of DV entry is a pH-dependent which internalization of the However, results show that DC-SIGN endocytosis is dispensable for DV to DV entry into cells can from and internalization infection not DC-SIGN for at with and three cells infected with at for the NS1 and by infection as the of cells with a vector for WT, DC-SIGN molecules and for DC-SIGN cells WT, DC-SIGN infected with at of infection by and as the of are as the of The are of three entry by DC-SIGN cells DC-SIGN DC-SIGN infected with at a of in the of the at cells for the NS1 and viral infection by The are of and S. S. PubMed Scopus Google Scholar, PubMed Scopus Google have that the C-type lectin DC-SIGN is an essential cellular factor for DV infection of immature DCs. The of DC-SIGN on skin DCs with the of lectin to DV infection that DC-SIGN a factor the of DV In we into the by which DC-SIGN DV particles and viral of DCs in human skin, the of DV Nat. Rev. 2: PubMed Scopus Google Scholar). skin immature a found in the are believed to productively infected by DV and to the cells by the virus Nat. PubMed Scopus Google Scholar). in the skin of a human a DV have been to for DV E protein Nat. PubMed Scopus Google Scholar). cells from human skin with DV particles found to DV Nat. PubMed Scopus Google Scholar). However, these not that immature DV, the cells are a of both and DCs. progress in and DCs in as as the of and cell and DC-SIGN, of DV target cells in human DC-SIGN and are C-type that and have both been to with Nat. Rev. 2: PubMed Scopus Google Scholar, S. Nat. 3: PubMed Scopus Google Scholar). and DV particles in cells are in DV transmitted by infected DC-SIGN to target However, results show in to DCs in are by these results not the that with DV, argue a of as of DV infection and results that during DV from mosquito to that are infected by the of as HIV, and S. PubMed Scopus Google Scholar, Immunity. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). In we that DV E protein, the sole glycoprotein at the surface of DV particles, to results that the of E protein is for DV to We observed that mannosylated E and not protein with is to with In with we have that of DV particles with to immature DCs PubMed Scopus Google Scholar). Together, these results that the present at the surface of mosquito-derived are essential for DV interaction with DC-SIGN and viral entry into DCs. are found in the DV E protein PubMed Scopus Google Scholar). The is to DV, is to and E proteins are at the and E proteins are at both and PubMed Scopus Google Scholar). results show four DV serotypes DC-SIGN to productively immature in with S. S. PubMed Scopus Google Scholar). that is to DV interaction with DC-SIGN and infection of DCs. However, we the that to the interaction between DC-SIGN and to the of these in DV is at the cell surface 2004; PubMed Scopus Google and DC-SIGN molecules bind mannosylated N-glycans with S. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). that between DC-SIGN and N-glycans on viral and that the of an interaction is a of the S. PubMed Scopus Google Scholar, S. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar, R.J. PubMed Scopus Google Scholar, 2005; PubMed Scopus Google Scholar). In of we found that the of DC-SIGN for DV E protein, which to that observed for the and proteins and S. PubMed Scopus Google Scholar, S. S. PubMed Scopus Google Scholar). of on cells not observed with of not are in with the of a in that a interaction between E protein and DC-SIGN 2005; PubMed Scopus Google but with the of DC-SIGN to DV of DV particles a of E protein on the virion surface R.J. Rossmann M.G. S. PubMed Scopus Google Scholar, Kuhn R.J. Rossmann M.G. PubMed Scopus Google Scholar, S. S.C. S. PubMed Scopus Google Scholar). we that a interaction between DC-SIGN and the E glycoprotein is to efficient DV we propose that the structural of N-glycans on the surface of viral particles favor the of E proteins by allow a interaction between DC-SIGN and DV particles, resulting in efficient viral and to DV is assumed to entry into target cells by to viral fusion in (3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar). In with show that DV entry into cells is that of DV E protein to DC-SIGN triggers a rapid and efficient internalization of the viral the of the endocytic in DV However, these not to DC-SIGN as cell surface factor as an entry that virus The DC-SIGN internalization and a and a that is believed to in intracellular Nat. Rev. 3: PubMed Scopus Google Scholar, PubMed Scopus Google Scholar, Immunity. PubMed Scopus Google Scholar). of the by DC-SIGN endocytosis by In we found that both the and the are not in DC-SIGN is to that acidic in receptors are in the of to the major S. PubMed Scopus Google Scholar). to the in DC-SIGN a and is in of We observed that the endocytosis-defective DC-SIGN molecules and DV entry with to results that DV entry into cells from DC-SIGN that DC-SIGN a not as a DV cell surface factor and argue in favor of a mechanism by which DC-SIGN enhances DV entry in cis. results not the that in immature DV particles to DC-SIGN by as as for entry of PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). we the in to the major a of DV immature DCs DC-SIGN and to the of entry the of a for DV internalization into DCs. We that a molecule is present at on DCs and DV entry with in the of molecules as and proteins have been to in DV entry into target cells but as cellular receptors for DV R.J. Nat. 3: PubMed Scopus Google Scholar, PubMed Google Scholar, S. 2004; PubMed Scopus Google Scholar, S. 2005; PubMed Scopus Google Scholar). In we propose that DC-SIGN with an unidentified cellular entry to infection of skin DCs during the blood DV of the to the host and the infection to these are with by DV infection The of an to the by DC-SIGN in DV in to these and to DV IntroductionDengue virus (DV) 1The abbreviations used are: DV, dengue virus; Ab, antibody; BHK, baby hamster kidney; BSA, bovine serum albumin; DC, dendritic cell; DC-SIGN, dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin; DMJ, 1-deoxymannojirimycin hydrochloride; EndoH, endoglycosidase H; FACS, fluorescence-activated cell sorting; FITC, fluorescein isothiocyanate; FCS, fetal calf serum; GM-CSF, granulocyte macrophage colony-stimulating factor; HCV, hepatitis C virus; HIV, human immunodeficiency virus; HMAF, hyperimmune mouse ascites fluids; L-SIGN, liver cell-specific intercellular adhesion molecule 3-grabbing non-integrin; LC, Langerhans cell; mAb, monoclonal antibody; m.o.i., multiplicity of infection; PBS, phosphate-buffered saline; PE, phycoerythrin; PNGase F, peptide:N-glycosydase F; sE, DV-soluble E protein; SFV, Semliki forest virus; WT, wild type. is an arthropod-borne flavivirus that belongs to the Flaviviridae family (1Chambers T.J. Monath T.P. The Flavivirus: Pathogenesis and Immunity. Elsevier Science Publishing Co., New York2003Google Scholar). The four serotypes of DV (DV-1 to DV-4) are transmitted to humans by the mosquito vector Aedes aegypti (1Chambers T.J. Monath T.P. The Flavivirus: Pathogenesis and Immunity. Elsevier Science Publishing Co., New York2003Google Scholar, 2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar). DV infection results in a spectrum of illnesses, ranging from a flu-like disease (dengue fever) to dengue hemorrhagic fever that can progress to dengue shock syndrome and death (1Chambers T.J. Monath T.P. The Flavivirus: Pathogenesis and Immunity. Elsevier Science Publishing Co., New York2003Google Scholar).DV is a lipid-enveloped virus with a single-stranded, positive sense RNA genome, which replicates in the cytoplasm of infected cells (2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar, 3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar). The 11-kb viral RNA encodes for a large polyprotein precursor, which is processed by both host and viral proteases to yield the non-structural proteins NS1 to NS5 and three structural proteins: C (core), prM (the intracellular precursor of the M protein), and E (envelope) glycoprotein (2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar, 3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar). The E protein is assumed to bind cellular receptors that direct DV particles to the endocytic pathway. The acidic environment in the endosome is believed to trigger major conformational changes in the E protein, which induce fusion of the viral and host cell membranes, resulting in entry of the virion into the cytoplasm (3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar).In the natural infection, DV is introduced into human skin by an infected mosquito during a blood meal (2Weaver S.C. Barrett A.D. Nat. Rev. Microbiol. 2004; 2: 789-801Crossref PubMed Scopus (447) Google Scholar). Immature dendritic cells (DCs) and Langerhans cells (LCs), which are normally resident in the skin, have been to infected by DV and are believed to the cells by the virus Nat. PubMed Scopus Google Scholar). We have the interactions between DV and human DCs to cellular for virus entry. We and S. S. PubMed Scopus Google Scholar, PubMed Scopus Google have DC-SIGN as an essential molecule for DV infection of immature DC-SIGN molecules DV is a C-type lectin that present on the surface of viral as human immunodeficiency virus and hepatitis C virus S. PubMed Scopus Google Scholar, S. PubMed Scopus Google Scholar, Nat. Rev. 3: PubMed Scopus Google Scholar). The DV E protein, which is the glycoprotein on the surface of DV is responsible for to the host cell surface and an in viral entry (3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar, R.J. Rossmann M.G. S. PubMed Scopus Google Scholar). present on the E glycoprotein have been to for virus to host cells PubMed Scopus Google Scholar). In to viral that bind DC-SIGN and are DV E protein at and which are used by the four DV serotypes PubMed Scopus Google Scholar). The interactions of E protein with DC-SIGN, believed to a for DV entry into are to DC-SIGN, DV is believed to and to an acidic where fusion (3Mukhopadhyay S. Kuhn R.J. Rossmann M.G. Nat. Rev. Microbiol. 2005; 3: 13-22Crossref PubMed Scopus (869) Google Scholar). of cells with which the DV infection PubMed Scopus Google Scholar). DC-SIGN is an endocytic that been to Nat. Rev. 3: PubMed Scopus Google Scholar, R.J. S. 2004; PubMed Scopus Google Scholar, Immunity. PubMed Scopus Google Scholar, PubMed Scopus Google it is DC-SIGN is responsible for DV to it the of in the of a entry we have the of DC-SIGN in the of DV entry into DCs. results the E protein as the DV responsible for to DC-SIGN and a for N-glycans in interactions between DV E protein and We that DV endocytosis is dispensable for DV infection of target cells and propose that DC-SIGN as a DV factor that interaction of viral particles with an as yet unidentified cellular which to DV entry.