Patent ID: 7261887

Claim:
A biological carrier for delivering proteins or peptides to a mammalian cell selected from the group consisting of macrophages and dendritic cells, the carrier comprising: a Leishmania capable of infecting the mammalian cell and having been transgenically modified to include one or more genes expressing the proteins or peptides in the carrier and being further modified to have δ-aminolevulinate dehydratase (ALAD) activity and porphobilinogen deaminase (PBGD) activity; the Leishmania lacks δ-aminolevulinate synthetase (ALAS) activity and lacks at least one enzyme of the heme biosynthetic pathway downstream of PBGD; and wherein the Leishmania is responsive to exposure to δ-aminolevulinate (ALA) to develop porphyria and lyse the carrier to release the proteins or peptides into the mammalian cell.