Directed shift of vaginal microbiota induced by vaginal application of sucrose gel in rhesus macaques

Abstract

Sucrose gel was used to treat bacterial vaginosis in a phase III clinical trial. However, the changes of vaginal flora after treatment were only examined by Nugent score in that clinical trial, While the vaginal microbiota of rhesus macaques is characterized by anaerobic, Gram-negative bacteria, few lactobacilli, and pH levels above 4.6, similar to the microbiota of patients with bacterial vaginosis. This study is aimed to investigate the change of the vaginal microbiota of rehsus macaques after topical use of sucrose gel to reveal more precisely the bacterial population shift after the topical application of sucrose gel. Sixteen rhesus macaques were treated with 0.5 g sucrose gel vaginally and three with 0.5 g of placebo gel. Vaginal swabs were collected daily following treatment. Vaginal pH levels and Nugent scores were recorded. The composition of the vaginal micotbiota was tested by V3∼V4 16S rDNA metagenomic sequencing. Dynamic changes in the Lactobacillus genus were analyzed by qPCR. The vaginal microbiota of rhesus macaques are dominated by anaerobic Gram-negative bacteria, with few lactobacilli and high pH levels above 4.6. After five days' treatment with topical sucrose gel, the component percentage of Lactobacillus in vaginal microbiota increased from 1.31% to 81.59%, while the component percentage of Porphyromonas decreased from 18.60% to 0.43%, Sneathia decreased from 15.09% to 0.89%, Mobiluncus decreased from 8.23% to 0.12%, etc.. The average vaginal pH values of 16 rhesus macaques of the sucrose gel group decreased from 5.4 to 3.89. There were no significant changes in microbiota and vaginal pH observed in the placebo group. Rhesus macaques can be used as animal models of bacterial vaginosis to develop drugs and test treatment efficacy. Furthermore, the topical application of sucrose gel induced the shifting of vaginal flora of rhesus macaques from a BV kind of flora to a lactobacilli-dominating flora.