title: Streptavidin-biotin immunotoxins: a new approach to purging bone marrow.
abstract: Immunotoxins have been used both experimentally and clinically to purge bone marrow of tumor cells or T cells before transplantation. We describe the synthesis of a streptavidin-biotin-toxin conjugate using whole ricin. Streptavidin-biotin-ricin (SA-BR) conjugates were synthesized by biotinylation of whole ricin, which was then complexed with streptavidin. Hybrid molecules consisting of a single biotinylated ricin moiety linked to a streptavidin molecule were separated by gel filtration. This SA-BR conjugate was used in an indirect cytotoxicity assay. The assay involved sensitizing of target cells with biotinylated monoclonal antibody (B-MCAB) followed by treatment with dilutions of SA-BR conjugate. The assay demonstrated a specific antibody-directed cytotoxicity. The strength of this SA-BR system is that a single conjugate was able to be used in conjunction with a library of B-MCABs to selectively target phenotypically different cell types. The application of the SA-BR conjugate is thus only restricted by the availability of B-MCABs specific for the desired target cells. The high affinity of avidin for biotin (Kd approximately 10(-15)) and the ability of a single conjugate to target phenotypically different cells through utilization of a library of B-MCABs gives SA-BR conjugates great potential in the selective targeting of individual cell types.
authors.affiliation: Department of Haematology, Royal Perth Hospital, Western Australia.
authors.forename: B F
authors.initials: BF
authors.lastname: Meyer
authors.forename: M L
authors.initials: ML
authors.lastname: Stoner
authors.forename: C L
authors.initials: CL
authors.lastname: Raphael
authors.forename: R E
authors.initials: RE
authors.lastname: Davis
authors.forename: R P
authors.initials: RP
authors.lastname: Herrmann
mesh_terms: D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D001710:Biotin; D001853:Bone Marrow / Q000473:pathology*; D002469:Cell Separation / Q000379:methods*; D000922:Immunotoxins; D007938:Leukemia / Q000473:pathology*; D012276:Ricin; D019809:Streptavidin; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D000922:Immunotoxins; D001710:Biotin; D012276:Ricin; D019809:Streptavidin