Biological correlates of HIV-1 heterosexual transmission

AIDS. 1997 Jul 15;11(9):1089-94. doi: 10.1097/00002030-199709000-00002.


Objectives: To study the role of HIV-1 biological phenotype, viral load and neutralizing antibodies in male-to-female heterosexual transmission of HIV-1.

Methods: Seven transmitting and seven non-transmitting HIV-1-seropositive heterosexual male index cases were included in the present study. All couples had engaged in unprotected sex for a period of over 1 year. Transmission was defined by the seroconversion of the female sexual partner. Virus isolates were tested in MT-2 cells for replication and syncytia induction. HIV-1 RNA plasma load was measured by the branched DNA technique. Serum neutralizing activity to primary HIV-1 isolates was tested by using peripheral blood mononuclear cells (PBMC) as target cells.

Results: Non-transmitting index cases had a lower HIV-1 RNA concentration in plasma than transmitting index cases. Non-transmitting index cases also tended to have serum neutralizing activity with broad specificity and to have viruses with low replicative capacity, as characterized by 50% infectious dose titres in PBMC and by the lack of MT-2 tropism.

Conclusions: The results indicate that plasma viral-RNA load is a marker for transmission. Moreover, an interplay between the host immune response and viral replication may modulate the level of viral load and thereby influence HIV-1 transmission.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cytopathogenic Effect, Viral
  • Female
  • HIV Antibodies / blood
  • HIV Infections / immunology
  • HIV Infections / transmission*
  • HIV Infections / virology
  • HIV Seropositivity / immunology
  • HIV Seropositivity / virology
  • HIV-1* / isolation & purification
  • HIV-1* / pathogenicity
  • HIV-1* / physiology
  • Humans
  • Male
  • Neutralization Tests
  • Phenotype
  • RNA, Viral / blood
  • Sexuality
  • Virus Replication


  • HIV Antibodies
  • RNA, Viral