Objective: The purpose of this study was to investigate the possible antichlamydial activity of vaginal secretion and to partially characterize the inhibitory principle.
Study design: Vaginal secretions obtained from 156 women attending a family planning or gynecologic outpatient clinic for contraceptive advice were studied for the influence on the inclusion formation of Chlamydia trachomatis in cycloheximide-treated McCoy cell cultures.
Results: Vaginal secretions from 156 women inhibited the inclusion formation of Chlamydia trachomatis. The inhibition was concentration dependent and the inhibitory principle had a molecular weight of < 10,000 d. It was heat labile. It was not related to antichlamydial antibodies in vaginal secretions. Only three (2%) of the women had a positive culture for Chlamydia trachomatis. Three had immunoglobulin A and three had immunoglobulin G antichlamydial antibodies in vaginal secretions. Secretions of those with a vaginal pH of 3.5 to 4.5 decreased the chlamydial inclusion count by 75% compared with controls. The corresponding percentage for those with a pH of 5.0 to 6.0 was 48% and for those with pH > 6 was 33%. Vaginal secretions of oral contraceptive users and nonusers did not differ in the capacity to decrease the chlamydial inclusion count, p > 0.01.
Conclusions: When vaginal secretions were added to McCoy cell cultures infected by Chlamydia trachomatis, the chlamydia inclusion number decreased. There was a correlation between pH of the vaginal secretion and the inhibitory principle. Oral contraceptive use had no influence on the inhibition.