Phage displaying peptides mimic schistosoma antigenic epitopes selected by rat natural antibodies and protective immunity induced by their immunization in mice

AIM: To obtain the short peptides mimic antigenic epitopes selected by rat natural antibodies to schistosomes, and to explore their immunoprotection against schistosomiasis in mice.METHODS: Adults worm antigens (AWA) were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked transferred immunoblotting methods with normal SD rat sera (NRS). The killing effects on schistosomula with fresh and heat-inactivated sera from SD rats were observed. Then the purified IgG from sera of SD rats was used to biopan a phage random peptide library and 20 randomly selected positive clones were detected by ELISA and 2 of them were sequenced.Sixty female mice were immunized thrice with positive phage clones (0, 2nd, 4th wk). Each mouse was challenged with 40 cercariae, and all mice were killed 42 d after challenge. The worms and the liver eggs were counted. RESULTS: NRS could specifically react to the molecules of 75 000, 47 000, 34 500 and 23 000 of AWA. Sera from SD rats showed that the mortality rate of schistosomula was 76.2%, and when the sera were heat-inactivated in vitro, the mortality rate was decreased to 41.0% after being cultured for 48 h. The specific phages bound to IgG were enriched about 300-folds after three rounds of biopanning. Twenty clones were detected by ELISA, 19 of them bound to the specific IgG of rat sera. Immunization with these epitopes was carried out in mice. Compared with the control groups, the mixture of two mimic peptides could induce 34.9% (P = 0.000) worm reduction and 67.6% (P = 0.000) total liver egg reduction in mice. Two different mimic peptides could respectively induce 31.0% (P = 0.001), 14.5% (P = 0.074) worm reduction and 61.2% (P = 0.000), 35.7% (P = 0.000) total liver egg reduction. The specific antibody could be induced by immunization of the mimic peptides, and the antibody titer in immunized mice reached more than 1:6 400 as detected by ELISA.CONCLUSION: Specific peptides mimic antigenic molecules can be obtained by biopanning the phage random peptide library and a partially protective immunity against schistosome infection can be stimulated by these phage epitopes in mice.

Effective Penetration of Cell-permeable Peptide Mimic of Tyrosine Residue 654 Domain of β-catenin into Human Renal Tubular Epithelial Cells

Phosphorylation of β-catenin tyrosine residue 654 plays an important role in the epithelial to myofibroblast transition （EMT）. Introducing mimic peptide of tyrosine residue 654 domain of β-catenin into cells may influence phosphorylation of β-catenin tyrosine residue 654. To deliver this mimic peptide into renal epithelial cells, we used penetratin as a vector, which is a novel cell permeable peptide, to deliver hydrophilic molecules into cells. A tyrosine 654 residue domain mimic peptide of β-catenin （PM） with fused penetratin was constructed, purified and then detected for the penetration of the mimic peptide into human renal tubular epithelial cells （HK-2）. The results showed that purified fusion mimic peptide could efficiently and rapidly translocate into human renal tubular epithelial cells. It is concluded that a cell-permeable peptides mimic of tyrosine residue 654 domain of β-catenin was successfully obtained, which may provide a useful reagent for interfering the human renal tubular epithelial-mesenchymal transition.

Seven amino acid peptide mimic from HVR1 of HCV influences cytokine profile of immune cells

Objective:To investigate the actions of cytokine profile in the immune cells by a seven amino acid peptide mimic from HVR1 of HCV (GQTYTSG,named 7P).Methods:The peripheral blood mononuclear cells (PBMCs) from 17 healthy blood donors were stimulated with 7P,and the cytokine levels in CD4+CD8-,CD4-CD8+ T cells,NK,NKT cells were analyzed by the intracellular cytokine staining.Results:The frequency of cells which secreted interferon-γ (IFN-γ) was found to be significantly increased in all cells,interleukin-10(IL-10) was significantly increased in CD4+CD8-,CD4-CD8+ T cells but decreased in NK,NKT cells,and tumor necrosis factor-α (TNF-α) was decreased in CD4+CD8-,CD4-CD8+ but increased in NK cells.Conclusion:7P could induce a cytokine profile in different immune cells in vitro and there was some difference between the CD4+CD8-,CD4-CD8+ T cells which represented the adaptive immunity cells and NK,NKT cells which represented the innate immunity cells.This kind of variation of cytokine profile might contribute to anti-virus and anti-inflammatory immune reaction.

Selection of Immunogenic Peptide Mimics of Male Worm Origin of Schistosoma Japonicum using Phage Display Peptide Library

To select the immunogenic short peptide mimics of male worm origin of Schistosoma japonicum (Sj) and to explore their protection effect against schistosomiasis in mice, the random phage display peptide library of 12-mer was screened with IgG to soluble male worm antigen of Sj, and the specific positive clones selected through three rounds of screenings were detected by Dot-ELISA, and then injected subcutaneously into mice for vaccination and protection assessment against Sj. It was found that 18 randomly picked phage displayed clones all showed definite antigenicity with various intensities. The pooled phages displayed clones could induce production of specific antibodies and cause 31.72% of worm reduction rate and 51.54% of egg reduction rate in mice, revealing a significant difference (P<0.001) in comparison with those of the controls. It concludes that the short peptide mimics of male worm origin of Sj obtained by affinity screening phage display peptide library can elicit partial protection against this pathogen.

Nitric oxide-generating compound and bio-clickable peptide mimic for synergistically tailoring surface anti-thrombogenic and anti-microbial dual-functions

Application of extracorporeal circuits and indwelling medical devices has saved many lives.However,it is accompanied with two major complications:thrombosis and infection.To address this issue,we apply therapeutic nitric oxide gas(NO)and antibacterial peptide for synergistically tailoring such devices for surface anti-thrombogenic and antifouling dual functions.Such functional surface is realized by stepwise conjugation of NO-generating compound of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid(DOTA)chelated copper ions(Cu-DOTA)and dibenzylcyclooctyne-(DBCO-)modified antimicrobial peptide based on carbodiimide and click chemistry respectively.The integration of peptide and Cu-DOTA grants the modified surface the ability to not only efficiently inhibit bacterial growth,but also catalytically generate NO from endogenous s-nitrosothiols(RSNO)to reduce adhesion and activation of platelets,preventing the formation of thrombus.We envision that the stepwise synergistic modification strategy by using anticoagulant NO and antibacterial peptide would facilitate the surface multifunctional engineering of extracorporeal circuits and indwelling medical devices,with reduced clinical complications associated with thrombosis and infection.

Alkali-metal hexamethyldisilazide initiated polymerization on alpha-amino acid N-substituted N-carboxyanhydrides for facile polypeptoid synthesis

Polypeptoids have been explored as mimics of polypeptides,owing to polypeptoids'superior stability upon proteolysis.Polypeptoids can be synthesized from one-pot ring-opening polymerization of amino acid N-substituted N-carboxyanhydrides(NNCAs).However,the speed of polymerization of NNCAs can be very slow,especially for NNCAs bearing a bulky N-substitution group.This hindered the exploration on polypeptoids with more diverse structures and functions.Therefore,it is in great need to develop advanced strategies that can accelerate the polymerization on inactive NNCAs.Hereby,we report that lithium/sodium/potassium hexamethyldisilazide(Li/Na/KHMDS)initiates a substantially faster polymerization on NNCAs than do commonly used amine initiators,especially for NNCAs with bulky N-substitution group.This fast NNCA polymerization will increase the structure diversity and application of polypeptoids as synthetic mimics of polypeptides.