Chimeric human antibody expression vectors are constructed by inserting the
heavy chain variable region-encoding cDNA and antibody light chain
variable region-encoding cDNA isolated from hybridomas producing a mouse
or rat monoclonal antibody reacting with the ganglioside GM.sub.2
respectively into an expression vector which contains the human antibody
heavy chain constant region- or human antibody light chain constant
region-encoding cDNA. The expression vectors are introduced into animal
cells and the transformant thus obtained is cultured to produce a chimeric
human antibody reacting with the ganglioside GM.sub.2. In contrast to
mouse monoclonal antibodies, the chimeric human antibodies of the
invention will not cause anti-mouse immunoglobulin antibody production in
the patient's body but show a prolonged blood half-life, with a reduced
frequency of adverse effects, so that it can be expected to be superior to
mouse monoclonal antibodies in the efficacy in the treatment of human
cancer, for instance.
