Characterization of a mouse monoclonal IgG3 antibody to the tumor-associated globo H structure produced by immunization with a synthetic glycoconjugate

Globo H (Fuc alpha 1-->2Gal beta 1-->3GalNAc beta 1-->3Gal alpha 1-->4Gal beta 1-->4Glc) is a carbohydrate structure that shows enhanced expression in many human carcinomas. From mice immunized with a globo H-KLH (keyhole limpet hemocyanin) synthetic conjugate an IgG3 monoclonal antibody (mAb VK-9) was derived that recognizes the globo H structure. Serological analysis showed that the minimal structure recognized by this mAb was the tetrasaccharide sequence Fuc alpha 1-->2Gal beta 1-->3Gal-NAc beta 1-->3Gal. An isomeric structure with an internal alpha GalNAc linkage was also recognized but less efficiently. mAb VK-9 did not react with many related structures, such as galactosylgloboside, globoside, H type 1, H type 2 blood group structures or fucosyl-gangliotetraosyl ceramide, but did react weakly with globo A ceramide. Not only did mAb VK-9 react with carbohydrate-protein conjugates but it could also recognize globo H-ceramide and human tumor cells expressing globo H. These results suggest that globo H-KLH could be explored as a vaccine in the treatment of carcinoma patients.