TAT-MEDIATED DELIVERY OF HETEROLOGOUS PROTEINS INTO CELLS

The Tat protein of human inmunodeficiency virus 1 (HIV-1) can enter ce lls efficiently when added exogenously in tissue culture. To assess if Tat can carry other molecules into cells, we chemically cross-linked Tat peptides (residues 1-72 or 37-72) to beta-galactosidase, horseradi sh peroxidase, RNase A, and domain III of Pseudomonas exotoxin A (PE) and monitored uptake colorimetrically or by cytotoxicity. The Tat chim eras were effective on all cell types tested, with staining showing up take into all tells in each experiment. In mice, treatment with Tat-be ta-galactosidase chimeras resulted in delivery to several tissues, wit h high levels in heart, liver, and spleen, low to-moderate levels in l ung and skeletal muscle, and little or no activity in kidney and brain . The primary target within these tissues was the cells surrounding th e blood vessels, suggesting endothelial cells, Kupffer cells, and/or s plenic macrophages. Tat mediated uptake may allow the therapeutic deli very of macromolecules previously thought to be impermeable to living cells.