CD4 and infection: To further characterize at which step of infection CE inhibited HIV-1, multi-dosing time assay experiments were performed with U373-CD4-CXCR4/CCR5 cells against infection of pseudotyped virus pNL4.3ΔEnvLuc-HXB2 and pNL4.3ΔEnvLuc-BAL.Pseudotyped viruses pNL4.3ΔEnvLuc-HXB2/BAL are only able for one cycle of viral infection and allow us to assess the infection level by measuring the luciferase value in the cell supernatant.