Glyco-replica Peptides which Mimic Glycosphingolipids
	In 1990, Scott and Smith reported the construction of a phage-displayed peptide library in which a randomly arranged hexamer peptide is expressed on a surface protein (pIII) of the phage (1). This library was first developed for the selection of peptides which are recognized by a monoclonal antibody or a receptor. We applied the phage peptide library technique to the preparation of peptides which mimic non-peptide molecules such as glycosphingolipids (2,3). This work is based on the molecular mimicry hypothesis that peptides recognized by an antibody against glycosphingolipid can mimic the structure of the antigen. We named these oligosaccharide-mimicking peptides "glyco-replica peptides" (2). Westerink et al. (4) selected a tripeptide, YRY (Tyr-Arg-Tyr), by the phage peptide library and a monoclonal antibody against alpha2-9 sialic acid linkage of meningococcal group C capsular polysaccharide. The peptide was found to mimic not only the alpha2-9 sialic acid linkage but also Fuc alpha1-3GlcNAc of LeY. The anti-YRY antiserum obtained by immunization with the peptide cross-reacted with both LeY and envelope glycoprotein (gp120) of HIV. Furthermore, they found that HIV infection was suppressed by the anti-YRY antiserum, indicating that glyco-replica peptides are useful tools for adjuvant therapy against infectious diseases and cancer. Recently, we found that a disialoganglioside GD1a expressed on cell surface of murine lymphosarcoma cell line, RAW117-H10, which has a high metastatic tendency for the liver, is involved in the adhesion between RAW117-H10 and hepatic sinusoidal endothelial (HSE) cells. GD1a-replica peptides obtained from a phage peptide library inhibited both the adhesion of RAW117-H10 cells to HSE cells in vitro and metastasis of the tumor cells to the liver, spleen, and lung in vivo (3). In other cases, we found that paragloboside (nLc4Cer)-replica peptides have a binding property to Ricinus communis lectin and regulate beta-galactosidase activity when paragloboside is used as the substrate. Since the glyco-replica peptides prepared by the present method are shown to mimic the functional roles of the oligosaccharides, the phage displayed peptide library will be used more widely in the research field of glycoconjugates.
Monoclonal antibody is immobilized on a plastic plate. Phage peptide library (108 library size) is incubated with the antibody. Bound phage to the antibody is eluted with acid solution and amplified. The amino acid sequence expressed on the selected phage is determined from DNA sequence analysis.
	Dai Ishikawa and Takao Taki (Cellular Technology Institute. Otsuka Pharmaceutical Co., Ltd.)
	References (1) Scott, JK, Smith, GP, Science, 249, 386-390, 1990 (2) Taki, T, Ishikawa, D, Haamasaki, H, Handa, S, FEBS Lett. 418, 219-223, 1997 (3) Ishikawa, D, Kikkawa, H, Ogino, K, Hirabayashi, Y, Oku, N, Taki, T, FEBS Lett. 441, 20-24, 1998 (4) Agadjanyan, M, Luo, P, Westerink, MA et al. Nature Biotech. 15, 547-551, 1997
Mar.15, 1999