(A) Schematic of an LR recombination reaction and the resulting vector. Site-specific recombination events (red lines) between attR and attL sites from a 5’, middle, and 3’ entry vector with a destination vector replaces the ccdB/Cm^R selection cassette of the destination vector with the mobile DNA elements from the entry vectors, leaving destination vector-specific 5’ and 3’ sequences intact. (B) Schematic of lentiviral destination vectors pEpic and pEpic_Lite. attR3 and 4 sites flanking the ccdB/Cm^R selection cassette are positioned in an anti-sense orientation to viral RNA expression driven by a Rous sarcoma virus (RSV) promoter. pEpic_Lite lacks puromycin resistance (Puro^R). LTR = long terminal repeat; RRE = Rev response element; cPPT = central polypurine tract; ccdB = E. coli ccdB toxin; Cm^R = chloramphenicol resistance; mPGK = mouse phosphoglycerate kinase promoter; WPRE = woodchuck hepatitis virus posttranslational regulatory element.