Constitutive expression of HIV-1 tat protein in human Jurkat T cells using a BK virus vector. The production and characterization of Jurkat cell lines that constitutively express functional human immune deficiency virus type 1 (HIV-1) tat protein, using a BK virus plasmid expression vector and HIV-1 tat cDNA, is described. An increased growth rate of these Jurkat-tat cell lines as compared with control cell lines was observed.