[Study on mimotopes of E.coli lipopolysaccharide 2630].

AIM: To screen mimotopes of E.coli lipopolysaccharide(LPS) 2630 from c7c phage display peptide library. METHODS: The LPS mimotopes were screened from c7c phage display peptide library by using affinity chromatograph-purified polyclonal antibody against E.coli LPS 2630(L2630), and the antigenicity of selected clones was identified by ELISA. RESULTS: After 3 rounds of biopanning, 12 out of 20 phage clones were identified as positive clones which could bind to polyclonal anti-L2630 antibody, and 5 of these 12 clones could bind to polyclonal anti-S.typhi LPS 7261(L7261) antibody. The deduced amino acid sequence analysis showed that 8 of 12 clones had the conservative sequence: X-DGLL-XX or X-EDGLL-X. CONCLUSION: The peptides displayed on these phage clones can mimic the epitopes of L2630, and 5 of these phage clones mimic the common epitopes of L2630 and L7261.

[Screening and identification of human telomerase reverse transcriptase epitopes from random phage display peptide library].

OBJECTIVE: To identify and characterize the epitopes of human telomerase reverse transcriptase (hTERT). METHODS: A random phage displayed dodecapeptide library was screened with anti-hTERT antibody. The selected phage clones were identified by sandwich enzyme-linked immunosorbent assay, anti-hTERT antibody blocking assay and competitive inhibition assay. RESULTS: After 3 rounds of screening, 13 of 24 randomly selected phage clones were identified as positive clones that could specifically bind to anti-hTERT antibody but not to normal mouse IgG. Amino acid sequences deduced from DNA sequences showed 11 different sequences with high percentage of histone and hydrophilic amino acids. CONCLUSION: Eleven epitopes have been obtained that can effectively mimic hTERT, which will be useful for the research of small-molecule inhibitor targeting at hTERT.

[Screening of mimotope of Salmonella typhimurium lipopolysaccharide from phage-displayed peptide].

OBJECTIVE: To identify and characterize the mimotope of lipopolysaccharide (LPS) from cyclic 7-mer phage peptide library. METHODS: Cyclic 7-mer phage-displayed peptide library was screened using monoclonal antibody 2F4 (mAb 2F4) against Salmonella typhimurium LPS as the target, and the selected clones were tested by sandwich enzyme-linked immunosorbent assay (ELISA) and specific antigen inhibition ELISA. RESULTS: After 3 round of screening, 34 of the 38 selected clones were identified as positive for binding to mAb 2F4. Salmonella typhimurium LPS was capable of inhibiting the binding between the cones and mAb 2F4, with the 50% inhibitory concentration of all the positive clones within the range of 0.125-0.250 microg/ml. Sequence analysis was performed for 10 of the positive clones, whose amino acid sequences were subsequently deduced, and 7 of them had conservative amino acid of P-X-WAS-X-W with the mean hydrophobic amino acid content of 71.4% in all the sequences. CONCLUSION: The phage-displayed peptide is capable of simulating the epitope of Salmonella typhimurium LPS.

[Screening of short peptides that bind specifically to osteosarcoma cells by phage-displayed peptide library].

OBJECTIVE: To obtain short peptides which bind specifically to osteosarcoma cells os-732 by means of screening from 12 peptide libraries. METHODS: Osteosarcoma cells os-732 were used as the target cells and osteoblasts as the absorber cells for subtraction biopanning from a 12-mer peptide phage-display library. After 3 rounds of screening, the positive phage clones were identified by cell enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, and the amino acid sequences were deduced by DNA sequencing. RESULTS: Nine positive phage clones screened out of 20 clones showed specific binding with osteosarcoma os-732, but no conserved motif was found in these peptides. CONCLUSION: The specific peptides screened from the phage library may be used as potential candidates as ligands for tumor-targeting therapy. The results also suggested that there are different epitopes on the surface of tumor cells.