sing the amino acid sequence of residues n-456 of SEQ ID NO:8, where n is an integer in the range of ???16 to 26; (t) a nucleotide sequence encoding a polypeptide comprising the amino acid sequence of residues ???16 to m of SEQ ID NO:8, where m is an integer in the range of 446 to 456; (u) a nucleotide sequence encoding a polypeptide having the amino acid sequence consisting of residues n-m of SEQ