A noninfectious provirus transgene was engineered from an infectious clone of an integrated HIV virus (pNL4-3) by deleting 3.1 kb of sequence between the Sphl site at base position 1443 and the Ball site at position 4551 (Fig. 1A). The in-frame deletion of gag and pol sequences encompasses the coding sequences for p24, p15, protease, reverse transcriptase, and the amino-terminus of p34 endonuclease. This construct, designated pEVdl443, expressed HIV-1 envelope glycoproteins and Tat protein and encodes the regulatory gene products Nef and Rev, as well as Vpu, Vpr, Vif, and a pl7/p34 fusion gene product. In addition to transgenic line 26, lines 22c and 25 were also established.