title: Decreased cervical epithelial sensitivity to nonoxynol-9 (N-9) after four daily applications in a murine model of topical vaginal microbicide safety.
abstract: BACKGROUND
  The disappointing clinical failures of five topical vaginal microbicides have provided new insights into factors that impact microbicide safety and efficacy. Specifically, the greater risk for human immunodeficiency virus type 1 (HIV-1) acquisition associated with multiple uses of a nonoxynol-9 (N-9)-containing product has highlighted the importance of application frequency as a variable during pre-clinical microbicide development, particularly in animal model studies.
  
  
  METHODS
  To evaluate an association between application frequency and N-9 toxicity, experiments were performed using a mouse model of cervicovaginal microbicide safety. In this model system, changes in cervical and vaginal epithelial integrity, cytokine release, and immune cell infiltration were assessed after single and multiple exposures to N-9.
  
  
  RESULTS
  After the initial application of N-9 (aqueous, 1%), considerable damage to the cervical epithelium (but not the vaginal epithelium) was observed as early as 10 min post-exposure and up to 8 h post-exposure. Subsequent daily exposures (up to 4 days) were characterized by diminished cervical toxicity relative to single exposures of like duration. Levels of pro-inflammatory cytokines released into the cervicovaginal lumen and the degree of CD14-positive immune cell infiltration proximal to the cervical epithelium were also dependent on the number of N-9 exposures.
  
  
  CONCLUSIONS
  Rather than causing cumulative cervical epithelial damage, repeated applications of N-9 were characterized by decreased sensitivity to N-9-associated toxicity and lower levels of immune cell recruitment. These results provide new insights into the failure of N-9-based microbicides and illustrate the importance of considering multiple exposure protocols in pre-clinical microbicide development strategies.
authors.affiliation: Department of Microbiology and Immunology, and Center for Molecular Therapeutics and Resistance, Center for Sexually Transmitted Disease, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA 19102, USA.
authors.forename: Karissa
authors.initials: K
authors.lastname: Lozenski
authors.forename: Robert
authors.initials: R
authors.lastname: Ownbey
authors.forename: Brian
authors.initials: B
authors.lastname: Wigdahl
authors.forename: Tina
authors.initials: T
authors.lastname: Kish-Catalone
authors.forename: Fred C
authors.initials: FC
authors.lastname: Krebs
mesh_terms: D000818:Animals; D000891:Anti-Infective Agents, Local / Q000008:administration & dosage / Q000633:toxicity*; D002584:Cervix Uteri / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D016207:Cytokines / Q000276:immunology; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D004848:Epithelium / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D005260:Female; D051379:Mice; D017137:Nonoxynol / Q000008:administration & dosage / Q000633:toxicity*; D013089:Spermatocidal Agents / Q000008:administration & dosage / Q000633:toxicity*; D014621:Vagina / Q000187:drug effects* / Q000276:immunology / Q000473:pathology
chemical_list: D000891:Anti-Infective Agents, Local; D016207:Cytokines; D013089:Spermatocidal Agents; D017137:Nonoxynol