Synergistic therapeutic effects of endolysin BNT331 and a Lactobacillus crispatus consortium in a human vagina chip model of bacterial vaginosis

Abstract

Bacterial vaginosis (BV) is a vaginal infection caused by an imbalance in the vaginal microbiome characterized by a decrease in healthy bacteria dominated by Lactobacillus crispatus along with a concomitant increase in dysbiotic bacteria, such as Gardnerella. Current treatments commonly fail to fully eradicate BV, and the lack of more effective therapies is due in part to the absence of relevant human models. Here, we used a human vagina-on-a-chip (Vagina Chip) microfluidic culture device that has been previously shown to faithfully recapitulate the human vaginal microenvironment as well as the inflammatory and injurious effects of G. vaginalis to test the therapeutic efficacy of a consortium of L. crispatus alone or in combination with endolysin BNT331, which specifically targets and lyses Gardnerella. These studies revealed that when L. crispatus was added alone, it suppressed inflammation even though it failed to engraft or displace the G. vaginalis bacteria. In contrast, BNT331 effectively killed Gardnerella in dysbiotic Vagina Chip. Importantly, the combined administration of both treatments resulted in restoration of a healthier vaginal microenvironment, as indicated by higher engraftment of L. crispatus on-chip, inhibition of G. vaginalis, and a reduction in inflammation. Similar effects of this combined treatment were observed when administered to Vagina Chips infected with vaginal swab samples from BV patients. These data suggest that combination of a live biotherapeutic product composed of a L. crispatus consortium with a potent antimicrobial agent that targets G. vaginalis, such as BNT331, may offer an effective therapeutic strategy for patients with BV. One Sentence SummaryEndolysin BNT331 combined with Lactobacillus crispatus reduces bacterial load and suppresses inflammation in a human vagina chip model of bacterial vaginosis.