Generation of SIVmac251-derived vectors.

The genome of an infectious molecular clone of SIVmac (SIVmac251) (A) was used to derive constructs encoding the packaging functions and constructs carrying the transfer vector (B). Expression constructs expressing various viral GPs were also designed. The filled boxes represent the viral genes. The open boxes show thecis-acting sequences. LTR indicates long terminal repeat; CMV, human cytomegalovirus immediate-early promoter; PBS, primer binding site; MSD, major splice donor site; Ψ, packaging sequence; RRE, Rev-responsive element; P_HMG, HMG promoter; polyA, polyadenylation site; SD, splice donor site; SA, splice acceptor site; SV40, simian virus 40 early promoter. Vector particles were produced by cotransfection of plasmids harboring the packaging functions, the viral GPs, and the transfer vector into 293T cells. The supernatants of transfected cells were collected during transient expression, concentrated by ultracentrifugation, and used for target cell transduction.