Stable expression of biologically active recombinant bovine interleukin-4 in Trypanosoma brucei.

We have explored the potential of Trypanosoma brucei as a eukaryotic expression system. Procyclic forms, which correspond to an insect-adapted stage, can easily be cultured in vitro. The cells grow to densities approximately 10-fold greater than higher eukaryotic cells and are not infectious for mammals. An expression vector which can stably integrate into the genome was used to express high levels of recombinant bovine interleukin-4 (IL-4). Trypanosome-derived IL-4 is released into the medium and is biologically active. The recombinant protein down-regulates CD14 expression in human macrophages and inhibits NO production by stimulated bovine macrophages.