HBZ and p19 Gag protein expression in stably transfected cell lines. (A) HBZ protein was detected in stable provirus expressing cell lines by Western blot using a rabbit polyclonal antibody against HBZ. HBZ was not detected in 729 control and 729.HTLV-1ΔHBZ as expected. HBZ polypeptide of the expected molecular weight was detected in SLB-1, 729.HTLV-1, and 729.HTLV-1HBZΔLZ. (B) HTLV-1 p19 Gag was quantified by ELISA from 3 independently isolated stable 729 transfectants expressing wild-type HTLV-1, HTLV-1ΔHBZ, or HTLV-1HBZΔLZ. HBZ mutant virus producers expressed statistically greater amounts of p19 Gag than wild-type virus producers, which was consistent with a repressive role of HBZ on viral transcription. p19 Gag production of the 2 mutant virus producers (HTLV-1ΔHBZ and HTLV-1HBZΔLZ) were not statistically significant. Statistical significance was determined by ANOVA followed by Tukey test. The histogram presents the average values from 3 independent experiments; error bars denote SDs.