ERVW-1 and infection: Env pseudoviruses were generated by cotransfection with the pNL43-ΔEnv-vpr+-luc+ clone that expresses luciferase upon infection and were used to infect a panel of NP-2 cell lines that express CD4 and one of two major coreceptors (CCR5 or CXCR4) or other commonly used coreceptors (FPRL1, APJ, CCR3 or GPR15)19, 20, 21, 22.