Pioneering studies documented that HIV-1 infection is associated with changes in the expression of the gut-homing molecule integrin (Itg)α4β7 on the peripheral CD4+ T-cells [35,36,37] and that the expression of the Itgα4β7 on blood CD4+ T-cells mirrors events taking place in the gut and predicts the risk of HIV acquisition/disease progression [38]. Here, CD4 is linked to HIV-1 infection.