CD4 and HIV-1 infection: Intestinal mucosa is a preferential site of HIV-1 replication, associated with a severe CD4+ LPLs depletion and a loss of mucosal integrity; the disruption of intestinal architecture and homeostasis that rapidly occurs after HIV-1 infection is thus considered a hallmark of HIV immunopathogenesis, characterized by epithelial cell apoptosis and lymphocytes depletion, hence the mucosal barrier impaired functionality.