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Platelet Factor 4 Inhibits and Enhances HIV-1 Infection in a Concentration-Dependent Manner by Modulating Viral

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Platelet factor 4 (PF4) shows biphasic effects on human immunodeficiency virus type 1 (HIV-1) infection. At low concentrations, monomeric PF4 inhibits HIV-1, but higher concentrations of oligomeric PF4 enhance viral infection.

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Area of Science:

  • Virology
  • Immunology
  • Hematology

Background:

  • Platelet factor 4 (PF4) is known to inhibit human immunodeficiency virus type 1 (HIV-1) in vitro.
  • The precise mechanism and concentration-dependent effects of PF4 on HIV-1 infection require further elucidation.

Purpose of the Study:

  • To investigate the concentration-dependent effects of Platelet factor 4 (PF4) on human immunodeficiency virus type 1 (HIV-1) infection in vitro.
  • To determine the role of PF4 oligomeric state in modulating HIV-1 infectivity.

Main Methods:

  • In vitro infection assays using various concentrations of PF4.
  • Analysis of PF4 oligomeric states (monomeric vs. tetrameric/higher-order).
  • Assessment of PF4 binding to HIV-1 envelope protein and cell surface glycosaminoglycans (GAGs).

Main Results:

  • Monomeric PF4 inhibited HIV-1 attachment by binding to the viral envelope protein.
  • Oligomeric PF4 enhanced HIV-1 infection by interacting with viral envelope protein and cell surface GAGs.
  • This enhancement effect was observed with some, but not all, other viruses tested.

Conclusions:

  • PF4 exhibits biphasic effects on HIV-1 infection, with inhibition at low (monomeric) and enhancement at high (oligomeric) concentrations.
  • Physiologically relevant concentrations of oligomeric PF4 may enhance HIV-1 infection, suggesting PF4 is not a viable antiviral agent.
  • PF4's role in enhancing viral infection could contribute to hematologic abnormalities in HIV-infected individuals, particularly in the bone marrow.