The vaginal microbiota shape local and systemic inflammation during Chlamydia trachomatis infection in non-human primate.

Abstract

Chlamydiosis, a sexually transmitted infection induced by Chlamydia trachomatis (CT), increases local inflammation (cytokine production, recruitment of neutrophils). Vaginal microbiota (VM) is involved in the regulation of local immune responses and STI acquisition where Lactobacillus spp are associated with protection. In this study, the VM of cynomolgus macaques was enriched with Lactobacillus crispatus after local metronidazole treatment followed by repeated intravaginal inoculations of CT. Metronidazole treatment induced drastic VM modifications (decrease abundance of several anaerobes and increase of natural Lactobacillus spp ). After CT exposure, a non-persisting CT infection and no association between Lactobacillus crispatus enrichment and a lower CT susceptibility were detected. However, serum specific anti-CT IgG production was higher in treated animals. High concentration of blood cytokines after CT infection was observed in untreated animals, whereas treated animals exhibited an increased production of cervicovaginal cytokines. Blood neutrophils were more mature and activated after CT infection in both groups. These results suggest an efficient local immune response associated with a controlled systemic inflammation (low cytokine production and higher anti-CT IgG titer) upon CT infection in Lactobacillus crispatus treated animals. This study confirmed that VM composition can be a powerful tool to modulate local immune responses to STIs.