CD4 and HIV infectious disease: We used TZM-bl cells that are HeLa cellsstably expressing large amounts of CD4, CXCR4, and CCR5, thus beinghighly susceptible to HIV-infection, with integrated luciferase andbeta-galactosidase genes under the control of the HIV-1 promoter.We first tested NDI–tetraazacycloalkane conjugates’cytotoxicity on TZM-bl cells by treating them with increasing amountsof compounds (0.097–25 μM) for 24 and 48 h.