Mik-beta 1(Fv)-PE40, a recombinant immunotoxin cytotoxic toward cells bearing the beta-chain of the IL-2 receptor

J Immunol. 1992 Oct 15;149(8):2810-5.

Abstract

Mik-beta 1 is a mAb that binds to the beta subunit of the IL-2R. We have constructed a recombinant single chain immunotoxin Mik-beta 1(Fv)-PE40 by genetically fusing the H and L V domains of Mik-beta 1 to each other via a peptide linker, and then to PE40, a derivative of Pseudomonas exotoxin. Mik-beta 1(Fv)-PE40 was selectively cytotoxic for cells expressing high levels of IL-2R beta (p75) subunit. Mik-beta 1(Fv)-PE40 was cytotoxic to the NK cell line YT-S, which expresses p75 but not p55 subunits, with an IC50 of 6 ng/ml. The ATL line HUT-102 was less sensitive, with an IC50 of 200 ng/ml. However, the IC50 could be lowered to 11 ng/ml when Mik-beta 1(Fv)-PE40 was allowed to bind to HUT-102 cells at 4 degrees C for 4 h before overnight incubation at 37 degrees C. An excess of Mik-beta 1 but not of anti-Tac, the anti-p55 mAb, prevented the cytotoxicity of Mik-beta 1(Fv)-PE40. We constructed a more active version of Mik-beta 1(Fv)-PE40, designated Mik-beta 1(Fv)-PE40KDEL, by converting the carboxyl-terminus of the toxin from -REDLK to -KDEL. Mik-beta 1(Fv)-PE40KDEL showed an IC50 of 2 ng/ml toward YT-S cells and 35 ng/ml toward HUT-102 cells. Binding studies using radioiodinated Mik-beta 1 showed that Mik-beta 1(Fv)-PE40 bound to the p75 receptor subunit with 11% of the affinity of the native Mik-beta 1 antibody. Mik-beta 1(Fv)-PE40 may be a useful reagent to study cells that express IL-2R, and it deserves further study as a possible treatment for cancers in which the malignant cells express high numbers of p75 subunit.

MeSH terms

  • ADP Ribose Transferases*
  • Amino Acid Sequence
  • Bacterial Toxins*
  • Base Sequence
  • Cell Line
  • Exotoxins / pharmacology*
  • Humans
  • Immunotoxins / chemistry
  • Immunotoxins / genetics
  • Immunotoxins / pharmacology*
  • Molecular Sequence Data
  • Protein Biosynthesis
  • Pseudomonas aeruginosa Exotoxin A
  • Receptors, Interleukin-2 / immunology*
  • Recombinant Proteins / pharmacology
  • Temperature
  • Virulence Factors*

Substances

  • Bacterial Toxins
  • Exotoxins
  • Immunotoxins
  • Receptors, Interleukin-2
  • Recombinant Proteins
  • Virulence Factors
  • ADP Ribose Transferases