Chronic HIV infection changes CD4+CD25+ Treg tissue distribution [128] with an increase of these cells in peripheral lymph nodes and mucosal lymphoid tissues where most HIV replication occurs: when frequencies of Tregs are compared in peripheral blood and in duodenal mucosa, the frequency and the absolute count of mucosal Tregs are highly increased in untreated HIV patients [129–131]. This evidence concerns the gene CD4 and HIV infectious disease.