Peptide Mimotopes of Neisseria meningitidis Group B Capsular Polysaccharide

The antigenic similarity between Neisseria meningitidis group B (NMGB) capsular polysaccharide (PS) and human polysialic acid (PSA) has hampered the development of a NMGB PS-based vaccine. But the possibility of a safe vaccine based on NMGB PS has been demonstrated by the existence of the NMGB PS-associated nonautoreactive epitope, which is distinct from those present on human PSA. To obtain peptide mimotopes of NMGB PS, we used HmenB3, a protective and nonautoreactive monoclonal antibody, to screen a phage library with 12 amino acids. We obtained 23 phage clones that bound to HmenB3 but not in the presence of E. coli K1 PS [which is alpha (2-8) -linked PSA like NMGB PS]. The clones contained 3 mimotopes and differed from previously described NMGB PS mimotopes. Immunization with a synthetic peptide of one mimotope elicited anti-NMGB antibodies in BALB/c mice. These mimotopes may be useful in the development of group B meningococcal vaccines.

Definition of the peptide mimotope of cellular receptor for hepatitis C virus E2 protein using random peptide library

BACKGROUND: Hepatitis C virus(HCV), a family of Flaviviridae, has a host cell-derived envelope containing a positive-stranded RNA genome, and has been known as the maj or etiological agent for chronic hepatitis, hepatic cirrhosis, and hepatocellular carcinoma. There remains a need to dissect a molecular mechanism of pathogenesis for the development of therapeutic and effective preventive measure for HCV. Identification of cellular receptor is of central importance not only to understand the viral pathogenesis, but also to exploit strategies for prevention of HCV. This study was aimed at identifying peptide mimotopes inhibiting the binding of E2 protein of HCV to MOLT-4 cell . METHODS: In this study, phage peptide library displaying a random peptides consisting of 7 or 12 random peptides was employed in order to pan against E2 protein. Free HCV particles were separated from the immune complex forms by immunoprecipitation using anti-human IgG antibody, and used for HCV-capture ELISA. To identify the peptides inhibiting E2-binding to MOLT-4 cells, E2 protein was subj ect to bind to MOLT-4 cells under the competition with phage peptides. RESULTS: Several phage peptides were selected for their specific binding to E2 protein, which showed the conserved sequence of SHFWRAP from 3 different peptide sequences. They were also able to recognize the HCV particles in the sera of HCV patient s captured by monoclonal antibody against E2 protein. Two of them, showing peptide sequence of HLGPWMSHWFQR and WAPPLERSSLFY respectively, were revealed to inhibit the binding of E2 protein to MOLT-4 cell efficiently in dose dependent mode. However, few membrane-associated receptor candidates were seen using Fasta3 programe for homology search with these peptides. CONCLUSION: Phage peptides containing HLGPWMSHWFQR and WAPPLERSSLFY respectively, showed the inhibition of E2-binding to MOLT-4 cells. However, they did not reveal any homologues to cellular receptors from GenBank database. In further study, cellular receptor could be identified through the screening of cDNA library from MOLT-4 or hepatocytes using antibodies against these peptide mimotopes.