DC-SIGN Increases the Affinity of HIV-1 Envelope Glycoprotein Interaction with CD4

Karolin Hijazi,Beth Haggarty,Jan Balzarini,Colin Longstaff,Robin Shattock,Dominique Schols,Daniel Stieh,Carlo Scala,Ian M Jones,Charles G Kelly,Guido Vanham,Yufei Wang,James Hoxie,Simon Jeffs

doi:10.1371/journal.pone.0028307

Abstract

Mannose-binding C-type lectin receptors, expressed on Langerhans cells and subepithelial dendritic cells (DCs) of cervico-vaginal tissues, play an important role in HIV-1 capture and subsequent dissemination to lymph nodes. DC-SIGN has been implicated in both productive infection of DCs and the DC-mediated trans infection of CD4+ T cells that occurs in the absence of replication. However, the molecular events that underlie this efficient transmission have not been fully defined. In this study, we have examined the effect of the extracellular domains of DC-SIGN and Langerin on the stability of the interaction of the HIV-1 envelope glycoprotein with CD4 and also on replication in permissive cells. Surface plasmon resonance analysis showed that DC-SIGN increases the binding affinity of trimeric gp140 envelope glycoproteins to CD4. In contrast, Langerin had no effect on the stability of the gp140:CD4 complex. In vitro infection experiments to compare DC-SIGN enhancement of CD4-dependent and CD4-independent strains demonstrated significantly lower enhancement of the CD4-independent strain. In addition DC-SIGN increased the relative rate of infection of the CD4-dependent strain but had no effect on the CD4-independent strain. DC-SIGN binding to the HIV envelope protein effectively increases exposure of the CD4 binding site, which in turn contributes to enhancement of infection.

Highlights

Dendritic cell (DC) subsets [1,2,3] as well as Langerhans cells (LCs) [4,5,6] in genital mucosal tissue may play a key role in transmission of human immunodeficiency virus type 1 (HIV-1) to CD4+ T cells
Recombinant polypeptides comprising the extracellular domains of DC-SIGN and Langerin, respectively, were expressed in E. coli, refolded and purified by affinity chromatography on Ni2+ and mannose resins sequentially
We have demonstrated that DC-SIGN-mediated enhancement of infection with HIV-1 is the result of increasing the concentration of virus at the cell surface as suggested previously [24] and of the increased affinity of the DC-SIGN:gp120 complex for CD4

Summary

Introduction

Dendritic cell (DC) subsets [1,2,3] as well as Langerhans cells (LCs) [4,5,6] in genital mucosal tissue may play a key role in transmission of human immunodeficiency virus type 1 (HIV-1) to CD4+ T cells. DCs and LCs bind HIV and transfer virus to permissive CD4+ T cells in a process termed trans infection that does not require HIV replication in DCs or LCs [4,9]. Within 24 hours of exposure to HIV, DCs transmit either surface bound virus or internalised virus in trans (in the absence of productive replication) [18]. Beyond this time-point, immature DCs that have been infected transmit progeny rather than input virus to permissive target cells that express CD4 and chemokine receptors [16,17]

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Results

Conclusion