Platelet activation and platelet-monocyte aggregate formation contribute to decreased platelet count during acute simian immunodeficiency virus infection in pig-tailed macaques

J Infect Dis. 2013 Sep;208(6):874-83. doi: 10.1093/infdis/jit278. Epub 2013 Jul 11.


Platelets are key participants in innate immune responses to pathogens. As a decrease in circulating platelet count is one of the initial hematologic indicators of human immunodeficiency virus (HIV) infection, we sought to determine whether decline in platelet number during acute infection results from decreased production, increased antibody-mediated destruction, or increased platelet activation in a simian immunodeficiency virus (SIV)/macaque model. During acute SIV infection, circulating platelets were activated with increased surface expression of P-selection, CD40L and major histocompatibility complex class I. Platelet production was maintained and platelet autoantibodies were not detected during acute infection. Concurrent with a decrease in platelet numbers and an increase in circulating monocytes, platelets were found sequestered in platelet-monocyte aggregates, thereby contributing to the decline in platelet counts. Because the majority of circulating CD16(+) monocytes formed complexes with platelets during acute SIV infection, a decreased platelet count may represent platelet participation in the innate immune response to HIV.

Keywords: CD16+ monocyte; HIV; SIV; macaque; platelet activation; platelet-monocyte aggregate; thrombocytopenia.

Publication types

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

MeSH terms

  • Animals
  • Autoantibodies / immunology
  • Blood Platelets / immunology*
  • Blood Platelets / virology
  • CD40 Ligand / metabolism
  • Cell Aggregation
  • Disease Models, Animal
  • Genes, MHC Class I
  • Immunity, Innate*
  • Macaca
  • Male
  • Monocytes / immunology*
  • Monocytes / virology
  • P-Selectin / metabolism
  • Platelet Activation*
  • Platelet Count
  • Simian Acquired Immunodeficiency Syndrome / pathology*
  • Simian Immunodeficiency Virus
  • Swine


  • Autoantibodies
  • P-Selectin
  • CD40 Ligand