1. A nucleic acid encoding a bispecific antibody construct comprising a first binding domain which binds to human epidermal growth factor receptor VIII (EGFRVIII) on the surface of a target cell and a second binding domain which binds to human CD3 on the surface of a T cell, wherein the first binding domain comprises a polypeptide comprising the amino acid sequence of SEQ ID NO: 157 and a polypeptide comprising the amino acid sequence of SEQ ID NO: 158.