title: An immunotoxin with greatly reduced immunogenicity by identification and removal of B cell epitopes.
abstract: Recombinant immunotoxins are hybrid proteins composed of an Fv that binds to a tumor antigen fused to a bacterial or plant toxin. Immunotoxin BL22 targets CD22 positive malignancies and is composed of an anti-CD22 Fv fused to a 38-kDa fragment of Pseudomonas exotoxin A (PE38). BL22 has produced many complete remissions in drug-resistant Hairy cell leukemia, where many treatment cycles can be given, because neutralizing antibodies do not form. In marked contrast, only minor responses have been observed in trials with immunotoxins targeting solid tumors, because only a single treatment cycle can be given before antibodies develop. To allow more treatment cycles and increase efficacy, we have produced a less immunogenic immunotoxin by identifying and eliminating most of the B cell epitopes on PE38. This was accomplished by mutation of specific large hydrophilic amino acids (Arg, Gln, Glu, Lys) to Ala, Ser, or Gly. The new immunotoxin (HA22-8X) is significantly less immunogenic in three strains of mice, yet retains full cytotoxic and anti-tumor activities. Elimination of B-cell epitopes is a promising approach to the production of less immunogenic proteins for therapeutic purposes.
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4264, USA.
authors.forename: Masanori
authors.initials: M
authors.lastname: Onda
authors.forename: Richard
authors.initials: R
authors.lastname: Beers
authors.forename: Laiman
authors.initials: L
authors.lastname: Xiang
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nagata
authors.forename: Qing-Cheng
authors.initials: QC
authors.lastname: Wang
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D019943:Amino Acid Substitution / Q000276:immunology; D000818:Animals; D000906:Antibodies / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D001427:Bacterial Toxins / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000276:immunology; D004768:Enterotoxins / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D018985:Epitopes, B-Lymphocyte / Q000235:genetics* / Q000276:immunology*; D005098:Exotoxins / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D006801:Humans; D007943:Leukemia, Hairy Cell / Q000188:drug therapy / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D020125:Mutation, Missense / Q000276:immunology; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D037521:Virulence Factors / Q000235:genetics* / Q000276:immunology* / Q000627:therapeutic use; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000906:Antibodies; D001427:Bacterial Toxins; D004768:Enterotoxins; D018985:Epitopes, B-Lymphocyte; D005098:Exotoxins; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C431326:RFB4(dsFv)-PE38 recombinant immunotoxin