RECOMBINANT ANTI-HUMAN MELANOMA ANTIBODIES ARE VERSATILE MOLECULES

The low cost, high versatility, and reliable production of bacterially produced recombinant antibody fragments speeds up the development of tumor-targeting agents. High-quality recombinant antimelanoma antibodi es are much sought after in the scientific community. We cloned the mu rine antibody 225.28S, currently used in radioimmunoimaging of human m elanoma lesions, in single-chain Fv configuration (scFv) or soluble ex pression in bacteria. The recombinant antibody fragment conserved the binding specificity of the parental antibody. In order to arm the scFv (225,28S) with biologically useful effector functions, we developed ve ctors for soluble expression of scFv(225.28S) in bacteria that allow b oth covalent and noncovalent chemical antibody modification at positio ns that do not interfere with antigen binding. An expression vector wa s developed that appends a cysteine residue at the C-terminal extremit y of the recombinant antibody, thus allowing reaction with thiol-speci fic reagents, including Tc-99m labeling, at a position that does not i nterfere with antigen binding. The scFv(225,28S) was also successfully expressed with a casein kinase II substrate tag that enables efficien t and stable P-32 labeling. For noncovalent antibody modification, we developed an expression vector that appends the human calmodulin gene at the C-terminal extremity of scFv(225.28S). The calmodulin domain is poorly immunogenic and can be targeted with chemically modified high- affinity calmodulin. ligands. The recombinant anti-human melanoma anti bodies described in this article should prove useful ''building blocks '' for the development of anti-melanoma diagnostic and therapeutic str ategies.