Identification of immunoreactive monoclonal antibody fragments for improved immunoscintigraphy.
Results obtained in animal models suggest that antibody fragments may have advantages over whole immunoglobulin for in vivo localisation studies. Proteolytic digestion of monoclonal antibodies may however yield a mixture of products unsuitable for in vivo use. This report describes a method whereby the immunoreactive products of antibody digestion can be identified by probing nitrocellulose blots of the gel-separated digest with the specific antigen. Optimum conditions for the production of the reactive fragments can then be determined and once identified they can be purified to homogeneity. Using this method conditions have been defined for the production of F(ab)2 and Fab fragments from a papain digest of an antibody to placental alkaline phosphatase (H17E2). In this case the antigen has enzyme activity which can be used to detect binding to the immunoreactive bands on the Western blots. In vivo experiments in nude mice carrying xenografts of a tumour expressing the H17E2 reactive antigen were performed to determine the efficacy of localisation of the purified fragments as compared to the whole antibody. As expected the absolute levels of radioactivity localised in the tumour was highest using whole antibody, whereas the F(ab)2 fragments produced the highest tumour:blood ratios.
D000469:Alkaline Phosphatase; D000818:Animals; D000911:Antibodies, Monoclonal; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D058851:GPI-Linked Proteins; D007140:Immunoglobulin Fab Fragments / Q000302:isolation & purification*; D007074:Immunoglobulin G; D007527:Isoenzymes / Q000276:immunology; D051379:Mice; D008819:Mice, Nude; D009363:Neoplasm Proteins / Q000276:immunology; D009374:Neoplasms, Experimental / Q000000981:diagnostic imaging* / Q000276:immunology; D010447:Peptide Hydrolases; D011877:Radionuclide Imaging
D000911:Antibodies, Monoclonal; D058851:GPI-Linked Proteins; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D007527:Isoenzymes; D009363:Neoplasm Proteins; D000469:Alkaline Phosphatase; C019839:alkaline phosphatase, placental; D010447:Peptide Hydrolases