Integrated Host Genetics and Skin Microbiome Profiling Suggest an HLA-C-Peptostreptococcus Axis in Psoriasis

Psoriasis is a chronic immune-mediated disease driven by genetic susceptibility and environmental factors, including microbial exposure. While HLA-C-linked variants represent the strongest genetic risk factors, their relationship with the cutaneous microbiome remains incompletely understood. This study aimed to investigate host-microbiome interactions in psoriasis through integrative multi-omics analysis. Skin microbiome profiling using 16S rRNA sequencing and targeted genotyping of psoriasis-associated single-nucleotide polymorphisms (SNPs) was performed in lesional and non-lesional skin from patients with plaque psoriasis and in healthy controls. Integrated analysis was conducted using supervised multivariate modeling (DIABLO) to identify coordinated genetic and microbial features associated with disease status. Combined genetic and microbial signatures differentiated lesional, non-lesional, and healthy skin. Variants within the HLA-C susceptibility region, including rs12191877, rs10484554, and rs4406273, showed contributions to group separation and demonstrated positive associations with Peptostreptococcus anaerobius. Associations involving ERAP1 variants linked antigen-processing pathways with inflammation-associated microbial taxa in lesional skin. Importantly, genotype-microbiome correlations were also detected in clinically non-lesional skin, where an increased psoriasis risk allele dosage co-varied with a higher relative abundance of P. anaerobius and Aerococcus urinae. In contrast, commensal-associated taxa were enriched in healthy controls and formed genotype-linked clusters only in non-lesional skin. These findings suggest that psoriasis is characterized by coordinated host genetic and microbial interaction patterns centered on antigen presentation pathways. The presence of a genotype-microbiome coupling in non-lesional skin may indicate that genetically determined immune configurations could shape microbial community structure prior to visible lesion development. Rather than reflecting uniform dysbiosis, psoriasis may represent a dynamic host-microbe ecosystem in which genetic susceptibility influences microbial persistence and inflammatory readiness.