Targeting of specific neuronal types in the non-human primate brain by using a murine CD25-specific recombinant immunotoxin.

Immunotoxin (ITX)-mediated cell targeting enables selective elimination of neuronal types of interest from a complex neural network. In this technology, human interleukin-2 receptor α-subunit or CD25 (hCD25) is expressed in specific cell types in transgenic rodents, and then the animals are treated with a recombinant ITX composed of monoclonal antibody variable regions for hCD25 fused to a Pseudomonas exotoxin fragment (PE38), resulting in the ablation of hCD25-expressing cells. However, there is a critical issue on the cross-reactivity of the recombinant ITX for endogenous CD25 in non-human primates (NHPs), leading to off-target effects. Here we generated a mouse CD25 (mCD25)-specific recombinant ITX, termed anti-mCD25-PE38, based on variable regions of a rabbit monoclonal antibody that specifically reacts to mCD25, but not to hCD25. Anti-mCD25-PE38 showed high-affinity binding to mCD25 and cytotoxic activity toward mCD25-expressing cells. Injection of anti-mCD25-PE38 into the ventral midbrain of common marmosets, in which the mCD25 transgene was expressed in dopamine neurons by a lentiviral vector for retrograde gene transfer, induced a significant loss of midbrain dopamine neurons. Therefore, anti-mCD25-PE38 provides a useful strategy for selective targeting of neuronal types to study the behavioral and neurological functions of these neurons in the NHP brain.