During the process of vectorization of anti-CTLA4 monoclonal antibodies (MAbs) into an oncolytic vaccinia virus, for the purpose of local delivery into the tumor of this efficient but rather toxic molecule, two enzyme-linked immunosorbent assays (ELISAs) were set up to monitor quantitatively the human CTLA4 (hCTLA4)-hCD80/hCD86 blocking activities of the vectorized MAbs. This evidence concerns the gene CTLA4 and neoplasm.