The cervicovaginal microbiome associates with spatially restricted host transcriptional signatures throughout the human ectocervical epithelium and submucosa

The cervicovaginal microbiome is a key biological determinant of human immunodeficiency virus (HIV) susceptibility, but its underlying impact on the ectocervical transcriptional landscape is unclear. Ectocervical tissue samples from Kenyan female sex workers were categorized into pre-defined cervicovaginal microbiome groups based on dominant compositions: Lactobacillus crispatus/acidophilus, Lactobacillus iners, Gardnerella, and 'highly diverse'. The tissue samples (n = 21) were assessed using spatial transcriptomics, revealing three epithelial, one mixed border, and nine submucosal gene clusters. Differential gene expression analysis across the microbiome groups and gene clusters identified 3,771 unique genes. The highly diverse microbiome group associated with the largest differences, mostly located near the epithelial basal membrane, encompassing genes involved in epithelial maintenance, submucosal extracellular matrix structures, and immune function. The L. crispatus/acidophilus-dominated group was identified by genes involved in active immune engagement, supporting mucosal barrier integrity. Weighted gene co-expression analysis confirmed tissue-wide altered gene expression associated with all microbiome groups and with individual bacterial taxa. Despite the assumption that microbiome colonization is restricted to the luminal surface, the transcriptional landscape was affected throughout the mucosa, with the most pronounced effect near both sides of the basal membrane. This broad association with the mucosal barrier integrity could affect susceptibility to HIV acquisition.