title: Removal of B-cell epitopes for decreasing immunogenicity in recombinant immunotoxin against B-cell malignancies.
abstract: Recombinant immunotoxin HA22, composed of an anti- CD22 Fv fragment fused to PE38, a truncated portion of Pseudomonas Exotoxin A (PE), has been developed for targeted treatment of various B-cell malignancies. As a foreign, internalized macromolecule, PE38 often induces lysosomal degradation and neutralizing antibodies to limit the efficacy of treating B-cell malignancies. The region of PE38 containing lysosomal protease cleavage sites deleted, leaving only furin processing site. The resulting immunotoxin HA22-LR (lysosome resistant) retains excellent biologic activity and removes immunogenic epitopes as an additional benefit. Another approach for avoiding immunogenicity is to identify B-cell epitopes and remove them by mutagenesis. Previously, to determine B-cell epitopes on PE38, murine Ab as a model, 7 major mouse-specific B-cell epitope groups with 13 subgroups were identified and located through a series of point mutations. Two new mutants, HA22-8X and HA22-LR-8X, were prepared, containing 8 epitope-silencing mutations which greatly reduced immunogenicity in mice. Later, by phage-display assay, human Fvs against PE toxin were isolated and human-specific B-cell epitopes were located by alanine scanning mutagenesis. HA22-LR as a scaffold, HA22-LR-LO10 with 7 point mutations was constructed, has low reactivity with human antisera, yet has high cytotoxic and antitumor activity. In this review, theoretical aspects and experimental evidence for the removal of B-cell epitope is discussed.
authors.affiliation: Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study, University of South China, Hengyang, China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Hu
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Caiping
authors.initials: C
authors.lastname: Zhang
authors.forename: Shiyin
authors.initials: S
authors.lastname: Long
authors.forename: Wuzhou
authors.initials: W
authors.lastname: Wang
authors.forename: Weidong
authors.initials: W
authors.lastname: Yin
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Cao
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D018604:Epitope Mapping; D018985:Epitopes, B-Lymphocyte / Q000235:genetics / Q000276:immunology*; D019337:Hematologic Neoplasms / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D006801:Humans; D007167:Immunotherapy / Q000009:adverse effects / Q000379:methods*; D000922:Immunotoxins / Q000009:adverse effects / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use*; D016246:Lymphocytes, Tumor-Infiltrating / Q000187:drug effects* / Q000276:immunology; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011994:Recombinant Proteins / Q000009:adverse effects / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D018985:Epitopes, B-Lymphocyte; D000922:Immunotoxins; D011994:Recombinant Proteins