Integrated analysis of rectal mucosal microbiome and transcriptome reveals a distinct microenvironment among young MSM.

Cross-talk between the microbiome and gut mucosa-resident immune cells plays a pivotal role in modulating immune responses to pathogens, including responses to HIV infection. However, how these interactions may differ between young MSM (YMSM) disproportionately impacted by HIV, as compared to older adult MSM (AMSM), is not well understood. A broad analysis of associations between the microbiome and rectal transcriptome revealed 10 microbial families/genera correlated with immunologic gene pathways. Specifically, the rectal transcriptome of YMSM is characterized by upregulation of T cell activation/differentiation pathways and signaling from multiple cytokine families, compared to AMSM. The microbiome of YMSM is enriched with pathogenic genera including Peptostreptococcus, shown to be positively correlated with type I interferon pathways important for antiviral immunity. These findings demonstrate that YMSM have a unique immune phenotype and rectal microenvironment and support further evaluation of biological factors that influence rectal HIV transmission.