It has been suggested that the restriction of HIV infection in trophoblast cells is due to the lack of the appropriate receptors on the cell surface; indeed the levels of CD4 and the two co-receptors vary during pregnancy and several reports have confirmed the variable expression of CD4, CCR5, CXCR4 and other chemokine receptors [25,26]. Here, CXCR4 is linked to HIV infectious disease.