A Bioassay for HIV-1 Based on Env-CD4 Interaction

AIDS Res Hum Retroviruses. 1990 Nov;6(11):1281-7. doi: 10.1089/aid.1990.6.1281.


The binding of human immunodeficiency virus type 1 (HIV-1) gp120env to CD4 is the first event leading to infection and represents an important target for possible therapeutic intervention. To provide a tool for screening and quantitation of the effects of drugs inhibiting the Env-CD4 interaction, we developed a simple, fast and quantitative bioassay measuring the fusion between two cell lines generated by stable transfection: one expressing high levels of HIV-1 proteins but no infectious virus (HL2/3), and the other expressing the CD4 receptor and containing an inducible chloramphenicol acetyltransferase (CAT) gene linked to the HIV-1 long terminal repeat (HLCD4-CAT). Upon cocultivation of HL2/3 and HLCD4-CAT cells, efficient cell fusion is observed within 8 h. The efficiency of fusion can be evaluated visually and quantitated by measuring CAT enzyme. This novel bioassay allows testing for drugs capable of interfering with the CD4-Env interaction. HL2/3 cell line secretes gp120env in the medium and can be used for the production of Env protein.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biological Assay
  • CD4 Antigens / metabolism*
  • CD4 Antigens / pharmacology
  • Cell Fusion / drug effects
  • Cell Line
  • Dextran Sulfate / pharmacology
  • Giant Cells / cytology
  • Giant Cells / drug effects
  • HIV Envelope Protein gp120 / metabolism*
  • HIV Long Terminal Repeat
  • HIV-1 / physiology*
  • HeLa Cells
  • Humans
  • Microscopy, Electron
  • Transfection


  • CD4 Antigens
  • HIV Envelope Protein gp120
  • Dextran Sulfate