| Dendritic cells promote human immunodeficiency virus type 1 (HIV-1) pathogenesis through trans infection, whereby HIV-1 particles are captured and transferred to CD4+ T cells without a productive dendritic cell (DC) infection. Though much of the research studying HIV-1/DC interactions has concentrated on HIV-1 envelope glycoprotein (gp120)-dependent attachment factors, specifically DC-specific intercellular adhesion molecule-3 (ICAM-3) grabbing non-integrin (DC-SIGN), there are multiple examples of HIV-1/DC attachment and transmission to T cells independent of DC-SIGN and other known attachment factors. Hence, our studies explored the relative contribution of gp120-dependent and -independent mechanisms of virus capture and trans infection by DCs. Initially, our studies focused on determining the mechanism of DC-SIGN-mediated HIV-1 internalization that might allow for virus to escape from degradative pathways in DCs. Specifically, we investigated the role of the transmembrane domain (TMD) of DC-SIGN in mediating lipid raft localization of DC-SIGN and endocytosis of HIV-1 particles. Despite introduction of mutations within putative lipid raft localization motifs or replacement of the DC-SIGN TMD with the TMD of a non-raft protein, transferrin receptor, we were unsuccessful in targeting DC-SIGN away from lipid rafts or inhibiting DC-SIGN-mediated HIV-1 endocytosis.;Interestingly, DCs can also capture HIV-1 particles derived from varied cellular sources, including primary CD4+ T cells and macrophages, independently of the glycoprotein, gp120. Besides gp120, HIV-1 particles also incorporate host cell-derived proteins and glycosphingolipids in their particle membrane. While protease treatment of virus particles did not affect virus capture by DCs, reduction in the glycosphingolipid (GSL) content of HIV-1 particles produced from cells treated with the GSL synthesis inhibitors, Fumonisin B1 (FB1) and 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), resulted in significant attenuation in virus capture by DCs, and inhibition of DC-mediated HIV-1 trans infection. Additionally, altering the location of HIV-1 assembly away from the plasma membrane to intracellular membranes via selective mutations in the viral matrix protein reduced the GSL content of virus-like particles and thereby inhibited DC-mediated capture of these particles. Together, these studies provide initial evidence for the role of HIV-1 particle membrane-associated GSLs in HIV-1 capture by DCs and as an important host-encoded determinant necessary for HIV-1 access to DC-mediated HIV-1 trans infection pathway. |
