Vaginal myeloperoxidase and flora in the pig-tailed macaque

Myeloperoxidase (MPO) is an enzyme in neutrophils and monocytes which react s with H2O2 and chloride to kill microbes after phagocytosis. Instillation of MPO into the vagina may augment vaginal defenses against sexually transm itted diseases, since the normal vaginal flora is characterized by the pres ence of H2O2-producing lactobacilli. We assessed the menstrual cycle stage, vaginal flora, pH, macroscopic appearance, and endogenous MPO in the adult female pig-tailed macaque (Macaca nemestrina) at baseline (n = 26; 60 obse rvations) and at 0, 4. and 24 hours in untreated animals (n = 6) or in anim als treated with intravaginal MPO gel at time 0 (n = 5). Baseline MPO level s were highly variable, and there was no detectable effect of cycle stage. In untreated animals, there was no significant effect of vaginal swab colle ction on vaginal flora or MPO levels. MPO treatment did not reduce vaginal H2O2-producing organisms, and vaginal MPO levels tended to increase at 4 ho urs in treated animals. Vaginal/cervical colposcopic changes were not detec ted in either group.