title: Elimination of murine and human T-cell epitopes in recombinant immunotoxin eliminates neutralizing and anti-drug antibodies in vivo.
abstract: Antibodies against the toxin portion of recombinant immunotoxins (RIT) reduce their efficacy and pose a potential safety risk. To overcome this problem we mutated the very immunogenic immunotoxin SS1P to produce LMB-T20, a de-immunized RIT that has the eight human T-cell epitopes in SS1P modified or removed. To determine the effect of T-cell epitope removal in vivo we mapped the T-cell epitopes in immune-competent BALB/c mice and found that these mice recognize two epitopes. One corresponds to the human immunodominant T-cell epitope and the other to a human subdominant epitope; both were eliminated in LMB-T20. We found that mice immunized with LMB-T20 did not have T-cell activation and did not develop anti-drug antibodies (ADA), whereas mice immunized with SS1P, showed T-cell activation, and developed ADA detected by both ELISA and drug neutralizing assays. The ability of the mice treated with LMB-T20 to respond to other antigens was not compromised. We conclude that elimination of T-cell epitopes is sufficient to prevent formation of antibodies to an immunogenic foreign protein.
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Ronit
authors.initials: R
authors.lastname: Mazor
authors.affiliation: Leidos Biomedical Research, Inc., National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Devorah
authors.initials: D
authors.lastname: Crown
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Selamawit
authors.initials: S
authors.lastname: Addissie
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Youjin
authors.initials: Y
authors.lastname: Jang
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Gilad
authors.initials: G
authors.lastname: Kaplan
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000276:immunology*; D057134:Antibodies, Neutralizing / Q000276:immunology*; D000917:Antibody Formation / Q000276:immunology*; D018984:Epitopes, T-Lymphocyte / Q000276:immunology*; D005260:Female; D006801:Humans; D007114:Immunization; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000906:Antibodies; D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D018984:Epitopes, T-Lymphocyte; C474515:SS1(dsFv)PE38