However, whereas higher expression levels of DC-SIGN enhanced binding of IIIB and IIIBx to the same extent, the actual infection of the CD4 dependent IIIB is more enhanced (p = 0.001) than that of the CD4 independent IIIBx (34-fold increase for IIIB, 8-fold increase for IIIBx). This evidence concerns the gene CD4 and infection.