CD163, a marker of perivascular macrophages, is up-regulated by microglia in simian immunodeficiency virus encephalitis after haptoglobin-hemoglobin complex stimulation and is suggestive of breakdown of the blood-brain barrier

Am J Pathol. 2008 Mar;172(3):725-37. doi: 10.2353/ajpath.2008.070848. Epub 2008 Feb 14.


Macrophages and microglia are the major cell types infected by human immunodeficiency virus and simian immunodeficiency virus (SIV) in the central nervous system. Microglia are likely infected in vivo, but evidence of widespread productive infection (ie, presence of viral RNA and protein) is lacking. This conclusion is controversial because, unlike lymphocytes, macrophages and microglia cannot be discreetly immunophenotyped. Of particular interest in the search for additional monocyte/macrophage-lineage cell markers is CD163; this receptor for haptoglobin-hemoglobin (Hp-Hb) complex, which forms in plasma following erythrolysis, is expressed exclusively on cells of monocyte/macrophage lineage. We examined CD163 expression in vitro and in vivo by multiple techniques and at varying times after SIV infection in macaques with or without encephalitis. In normal and acutely SIV-infected animals, and in SIV-infected animals without encephalitis, CD163 expression was detected in cells of monocyte/macrophage lineage, including perivascular macrophages, but not in parenchymal microglia. However, in chronically infected animals with encephalitis, CD163 expression was detected in activated microglia surrounding SIV encephalitis lesions in the presence of Hp-Hb complex, suggesting leakage of the blood-brain barrier. CD163 expression was also induced on microglia in vitro after stimulation with Hp-Hb complex. We conclude that CD163 is a selective marker of perivascular macrophages in normal macaques and during the early phases of SIV infection; however, later in infection in animals with encephalitis, CD163 is also expressed by microglia, which are probably activated as a result of vascular compromise.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Antigens, CD / genetics*
  • Antigens, CD / metabolism
  • Antigens, Differentiation, Myelomonocytic / genetics*
  • Antigens, Differentiation, Myelomonocytic / metabolism
  • Biomarkers / metabolism
  • Blood Vessels / drug effects
  • Blood Vessels / metabolism
  • Blood-Brain Barrier / drug effects
  • Blood-Brain Barrier / metabolism
  • Blood-Brain Barrier / virology
  • Cell Membrane Permeability / genetics
  • Cells, Cultured
  • Encephalitis, Viral / etiology
  • Encephalitis, Viral / genetics*
  • Haptoglobins / pharmacology*
  • Hemoglobins / pharmacology*
  • Macaca mulatta
  • Macrophages / metabolism
  • Microglia / drug effects
  • Microglia / metabolism*
  • Receptors, Cell Surface / genetics*
  • Receptors, Cell Surface / metabolism
  • Simian Acquired Immunodeficiency Syndrome / complications
  • Simian Acquired Immunodeficiency Syndrome / genetics*
  • Simian Immunodeficiency Virus* / physiology
  • Time Factors
  • Up-Regulation / drug effects


  • Antigens, CD
  • Antigens, Differentiation, Myelomonocytic
  • Biomarkers
  • CD163 antigen
  • Haptoglobins
  • Hemoglobins
  • Receptors, Cell Surface
  • haptoglobin-hemoglobin complex