title: Cervicovaginal fluid and semen block the microbicidal activity of hydrogen peroxide produced by vaginal lactobacilli.
abstract: BACKGROUND
  H2O2 produced by vaginal lactobacilli is believed to protect against infection, and H2O2-producing lactobacilli inactivate pathogens in vitro in protein-free salt solution. However, cervicovaginal fluid (CVF) and semen have significant H2O2-blocking activity.
  
  
  METHODS
  We measured the H2O2 concentration of CVF and the H2O2-blocking activity of CVF and semen using fluorescence and in vitro bacterial-exposure experiments.
  
  
  RESULTS
  The mean H2O2 measured in fully aerobic CVF was 23 +/- 5 microM; however, 50 microM H2O2 in salt solution showed no in vitro inactivation of HSV-2, Neisseria gonorrhoeae, Hemophilus ducreyii, or any of six BV-associated bacteria. CVF reduced 1 mM added H2O2 to an undetectable level, while semen reduced 10 mM added H2O2 to undetectable. Moreover, the addition of just 1% CVF supernatant abolished in vitro pathogen-inactivation by H2O2-producing lactobacilli.
  
  
  CONCLUSIONS
  Given the H2O2-blocking activity of CVF and semen, it is implausible that H2O2-production by vaginal lactobacilli is a significant mechanism of protection in vivo.
authors.affiliation: Mucosal Protection Laboratory, Thomas C, Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA. eohanlon@jhu.edu
authors.forename: Deirdre E
authors.initials: DE
authors.lastname: O'Hanlon
authors.forename: Blair R
authors.initials: BR
authors.lastname: Lanier
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Moench
authors.forename: Richard A
authors.initials: RA
authors.lastname: Cone
mesh_terms: D000293:Adolescent; D000328:Adult; D000890:Anti-Infective Agents / Q000037:antagonists & inhibitors*; D001826:Body Fluids / Q000737:chemistry*; D005260:Female; D006191:Haemophilus ducreyi / Q000187:drug effects; D018258:Herpesvirus 2, Human / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors*; D007778:Lactobacillus / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009344:Neisseria gonorrhoeae / Q000187:drug effects; D016877:Oxidants / Q000037:antagonists & inhibitors*; D012661:Semen / Q000737:chemistry*; D055815:Young Adult
chemical_list: D000890:Anti-Infective Agents; D016877:Oxidants; D006861:Hydrogen Peroxide