Sialoadhesin expressed on IFN-induced monocytes binds HIV-1 and enhances infectivity

PLoS One. 2008 Apr 16;3(4):e1967. doi: 10.1371/journal.pone.0001967.


Background: HIV-1 infection dysregulates the immune system and alters gene expression in circulating monocytes. Differential gene expression analysis of CD14(+) monocytes from subjects infected with HIV-1 revealed increased expression of sialoadhesin (Sn, CD169, Siglec 1), a cell adhesion molecule first described in a subset of macrophages activated in chronic inflammatory diseases.

Methodology/principal findings: We analyzed sialoadhesin expression on CD14(+) monocytes by flow cytometry and found significantly higher expression in subjects with elevated viral loads compared to subjects with undetectable viral loads. In cultured CD14(+) monocytes isolated from healthy individuals, sialoadhesin expression was induced by interferon-alpha and interferon-gamma but not tumor necrosis factor-alpha. Using a stringent binding assay, sialoadhesin-expressing monocytes adsorbed HIV-1 through interaction with the sialic acid residues on the viral envelope glycoprotein gp120. Furthermore, monocytes expressing sialoadhesin facilitated HIV-1 trans infection of permissive cells, which occurred in the absence of monocyte self-infection.

Conclusions/significance: Increased sialoadhesin expression on CD14(+) monocytes occurred in response to HIV-1 infection with maximum expression associated with high viral load. We show that interferons induce sialoadhesin in primary CD14(+) monocytes, which is consistent with an antiviral response during viremia. Our findings suggest that circulating sialoadhesin-expressing monocytes are capable of binding HIV-1 and effectively delivering virus to target cells thereby enhancing the distribution of HIV-1. Sialoadhesin could disseminate HIV-1 to viral reservoirs during monocyte immunosurveillance or migration to sites of inflammation and then facilitate HIV-1 infection of permissive cells.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Adhesion
  • Cell Line
  • Cloning, Molecular
  • Flow Cytometry
  • Gene Expression Profiling
  • Gene Expression Regulation*
  • HIV Infections / metabolism*
  • HIV-1 / metabolism*
  • Humans
  • Interferons / metabolism*
  • Lipopolysaccharide Receptors / biosynthesis
  • Membrane Glycoproteins / biosynthesis*
  • Models, Biological
  • Monocytes / metabolism*
  • Receptors, Immunologic / biosynthesis*
  • Sialic Acid Binding Ig-like Lectin 1
  • Viral Load


  • Lipopolysaccharide Receptors
  • Membrane Glycoproteins
  • Receptors, Immunologic
  • SIGLEC1 protein, human
  • Sialic Acid Binding Ig-like Lectin 1
  • Interferons