title: Biological correlates of HIV-1 heterosexual transmission.
abstract: OBJECTIVE
  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.
authors.affiliation: Microbiology and Tumorbiology Centre, Karolinska Institute, Stockholm, Sweden.
authors.forename: J R
authors.initials: JR
authors.lastname: Fiore
authors.forename: Y J
authors.initials: YJ
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Björndal
authors.forename: M
authors.initials: M
authors.lastname: Di Stefano
authors.forename: G
authors.initials: G
authors.lastname: Angarano
authors.forename: G
authors.initials: G
authors.lastname: Pastore
authors.forename: E M
authors.initials: EM
authors.lastname: Fenyö
mesh_terms: D002460:Cell Line; D003588:Cytopathogenic Effect, Viral; D005260:Female; D015483:HIV Antibodies / Q000097:blood; D015658:HIV Infections / Q000276:immunology / Q000635:transmission* / Q000821:virology; D006679:HIV Seropositivity / Q000276:immunology / Q000821:virology; D015497:HIV-1 / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology; D006801:Humans; D008297:Male; D009500:Neutralization Tests; D010641:Phenotype; D012367:RNA, Viral / Q000097:blood; D019529:Sexuality; D014779:Virus Replication
chemical_list: D015483:HIV Antibodies; D012367:RNA, Viral