The five key prognostic genes associated with HP infection in STAD comprised 1 “protective” gene (CTLA4) and 4 “risk” genes (CPVL, EMB, FAM241A, and CXCR4), and the riskscore exhibited a negative correlation with the infiltration levels of most immune cells and positive correlation with several immune checkpoint genes. This evidence concerns the gene CTLA4 and gastric adenocarcinoma.