Among YMSM without STI, 23 genes were significantly (padj<0.1) differentially expressed between YMSM with and without HIV (Fig 4A), five of which (HSPB7, B3GNT3, AHNAK2, TMEM47, and COL28A1) were also among the 47 significant interaction genes identified. This evidence concerns the gene COL28A1 and sexually transmitted disease.