CD4 and HIV infectious disease: On this note, analysis of Jurkat T cell lines expressing varying levels of CD4 and/or BST2 clearly revealed the relative contributions of CD4 and BST2 expression to the increase in Env staining by A32 and 2G12 in the context of WT and ∆Nef and/or ∆Vpu HIV infections (Additional file 2: Figure S2).