Immunostimulatory Peptides Research Articles

Immunostimulatory and immunomodulatory peptides derived from the α1 domain of HLA-B27 in experimental autoimmune diseases in Lewis rats

Peptides derived from amino acid sequence 60–80 of HLA-B27 (B27PA, aa 60–72 and B2702PA, aa 60–80) mimic cytokeratin and are able to induce in vitro proliferation of human peripheral blood lymphocytes as well as arthritis in Lewis rats. Here we show that the pathogenic epitope recognized by autoaggressive rat T cells is located at the N-terminus of the sequence, between aa 60 and 72. A C-terminally elongated 25mer peptide (B2702.60–84) showed increased pathogenicity, indicating either a second arthritogenic epitope or an immunomodulatory region within this peptide. B2702.60–84 has been described to inhibit murine and human CD8 + cytotoxic T cells (CTL) and was even successfully used for the treatment of allograft rejection. In addition to pathogenicity we have investigated the immunomodulatory effect of peptide B2702.60–84 in our rat model of experimental autoimmune uveitis (EAU), induced with retinal S-Antigen peptide PDSAg. We found that disease exacerbated following coimmunization of PDSAg with B2702.60–84. In vitro, the B27-peptide enhanced the proliferation of CD4 + T cell lines specific for retinal autoantigen peptides during coincubation of B2702.60–84 with the respective antigen. Oral tolerance induction, an effective mechanism to prevent uveitis in Lewis rats, is abrogated by cofeeding peptide B2702.60–84 with the tolerogen PDSAg. In rat EAU, naturally occurring regulatory T cells and orally induced γδTCR + suppressor cells are CD8 +, which might be impeded by peptide B2702.60–84. As a consequence of their abrogated suppressive capacity disease was exacerbated. We propose a similar role of HLA-B27 in man: disturbing the mechanisms down-regulating self-responses might lead to autoimmune diseases. This could explain the high association of HLA-B27 with a variety of autoimmune diseases targeting different organs or tissues.

Prolyl Endopeptidase-Mediated Destruction of T Cell Epitopes in Whole Gluten: Chemical and Immunological Characterization

Celiac Sprue is a widely prevalent immune disease of the small intestine induced by dietary gluten intake in genetically susceptible individuals. It has been suggested that prolyl endopeptidases (PEPs) may be useful catalysts for gluten detoxification. We have investigated this hypothesis using food-grade gluten as the target antigen, and a combination of mass spectrometry and patient-derived T cells as quantitative assay systems. Spectrometric characterization of physiologically proteolyzed gluten revealed a number of 10 to 50 residue peptides containing known T cell epitopes involved in Celiac Sprue pathogenesis. Several of these peptides were multivalent, suggesting they may be potent triggers of the inflammatory response to gluten in celiac patients. Treatment of proteolyzed gluten with recombinant bacterial PEP decreased the number of potentially immunostimulatory peptides. Substantially reduced immunogenicity was also quantified in 12 of 14 intestinal polyclonal T cell lines from celiac patients. Kinetic investigations using eight T cell clones showed rapid destruction of alpha-gliadin epitopes, but less complete processing of gamma-gliadin epitopes. Given the difficulty associated with a strict lifelong gluten-exclusion diet, the ability of a single enzyme to greatly reduce the antigenic burden of grocery store gluten reinforces the case for developing oral peptidase therapy against Celiac Sprue.

Immunostimulatory Role of Tryptic Digest of Abrus Agglutinin

Many bioactive peptides are in therapeutic use as immunomodulators at present. The origin of these bioactive peptides is diverse. Such bioactive peptides are reported to be present in enzymatic digest of food and milk proteins. In our previous work we have reported that Abrus agglutinin retains its bioactivity even after heat denaturation but loses its haemagglutination properties. This leads to the supposition that immunostimulatory regions in the protein might be responsible for its in vivo and in vitro stimulatory properties. Thus the bioactivity of tryptic digest of Abrus agglutinin (TDA) was checked in vitro to ascertain the presence of some bioactive region in the protein, which will lead to the discovery of certain immunostimulatory peptides which might be of use in nonspecific immunotherapy. In this study it is observed that TDA stimulates macrophage increasing the phagocytic and bactericidal activity as well as hydrogen peroxide production. TDA also proliferates splenocytes leading to Th1 response and NK cell activation.

Genetically engineered dendritic cell-based cancer vaccines (Review)

Dendritic cells (DCs) are the most potent professional antigen-presenting cells with exquisite capacity to interact with T cells and initiate their responses; the antigen-presenting capabilities of DCs make them attractive vehicles for the delivery of therapeutic cancer vaccines. The working hypothesis for utilization of DC-based cancer vaccines is that lack of efficient tumour antigen presentation on mature DCs, which is frequently observed in tumour-bearing individuals, can be bypassed by direct loading of DCs with oncoproteins in vitro, thus ensuring the transfer of immunostimulatory peptides on the respective antigen-presenting molecules. To enhance loading of DCs with oncoproteins in vitro and to increase the efficacy of the vaccines, a variety of genetic manipulations have been proposed and shown to be efficient in experimental tumour models. DCs were transfected either with polynucleotides, DNA or RNA, coding for tumour-associated antigens (TAAs), or with DNA encoding immunostimulatory cytokines and co-stimulatory molecules. The delivery of genes coding for antigenic epitopes or other molecules with a recombinant retrovirus, adenovirus, or poxvirus into dendritic cells has also been used for transduction and therapy. As an alternative method for TAA delivery into DCs, fusion of DCs with tumour cells has been utilized and the hybrid cell-based vaccines have been found to be highly therapeutically active, even in cancer patients. The purpose of this review is to summarize the approaches used for making and utilization of the genetically engineered DC-based cancer vaccines, to evaluate the therapeutic results obtained with the vaccines, and to discuss prospects and limitations of the vaccination.

Dendritic cell-based vaccines for therapy of HPV16-induced tumours.

Dendritic cells (DCs) are the most potent professional antigen-presenting cells with exquisite capacity to interact with T cells and initiate their responses; the antigen-presenting capabilities of DCs make them attractive vehicles for the delivery of therapeutic cancer vaccines. The working hypothesis for utilization of DC-based cancer vaccines is that lack of efficient tumour antigen presentation on mature DCs, which is frequently observed in tumour-bearing individuals, can be bypassed by direct loading of DCs with oncoproteinsin vitrothus ensuring the transfer of immunostimulatory peptides on the respective antigen-presenting molecules.KeywordsDetail MaterialTherapeutic Cancer VaccineAttractive VehicleSyngeneic Spleen CellLocal PretreatmentThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Immunostimulatory peptides from fish waste hydrolysates

Immunostimulatory peptides from fish waste hydrolysates

Immunomodulatory Effect of Bovine Lactoferrin Pepsin Hydrolysate on Murine Splenocytes and Peyer's Patch Cells

The effects were examined of a pepsin hydrolysate of bovine lactoferrin on the proliferation of murine splenocytes. The hydrolysate enhanced [3H]thymidine uptake by splenocytes, but undigested bovine lactoferrin exerted an inhibitory effect. The hydrolysate had the ability to inhibit the blastogenesis that was induced by mitogens such as concanavalin A, phyto-hemagglutinin, and lipopolysaccharide; inhibition was similar to that with undigested lactoferrin. These results suggested that the hydrolysate contained both immunostimulatory and immunoinhibitory peptides. The stimulatory effect of the hydrolysate in the absence of mitogens was then explored in more detail using nonadherent splenocytes. The proliferative response of splenocytes to the hydrolysate was much greater in the fraction that was enriched with B cells than in the fraction that was enriched with T cells. The hydrolysate did not affect thymocyte proliferation. These data indicated that the adherent cells resembling macrophages and found among the splenocytes were not the target cells of the hydrolysate. The stimulatory effect of the hydrolysate was due to the activation of B cells by the hydrolysate and enhanced immunoglobulin production by splenocytes. Because the hydrolysate also enhanced the proliferation and immunoglobulin A production of Peyer's Patch cells, the immunostimulatory effect of the hydrolysate in vivo was examined using mice that had been orally immunized with cholera toxin. The concentrations of immunoglobulin A conjugated against cholera toxin in bile and in the intestinal contents of mice fed liquid diets containing 1% (wt/vol) lactoferrin hydrolysate were greater than those of mice fed control diets. This result suggested that the use of the lactoferrin hydrolysate is beneficial to enhance mucosal immunity.

Characterization of the antigenic structure of human type II collagen.

A series of 101 peptides each 20 amino acids in length (10-residue overlap) spanning the helical portion of the mature alpha-chain of human type II collagen (CII) was synthesized. DBA/1 (H-2q) mice were immunized with individual peptides, and draining lymph node cells were challenged in vitro. Strong responses were measured to three peptides: peptide I (residues 74-93), peptide 14 (residues 254-273), and peptide 81 (residues 924-943). B10.Q (H-2q) mice were responsive to peptides I and 81 but not to peptide 14. B10.RIII (H-2r) mice, which are resistant to arthritis induction following immunization with human CII, were unresponsive to peptides I, 14, and 81. Using single amino acid truncated peptides, we determined minimal immunostimulatory lengths for peptides I and 81. Residues critical to antigenicity were identified by introducing alanine and glycine substitutions into minimal length immunostimulatory peptides. The determinants within peptides I and 81 are 100% homologous to mouse CII and are autoantigens. Peptide 81 has homology to viral proteins. Peptide 14 is 90% homologous to mouse CII and has homology to heat shock proteins.

Characterization and kinetics of gastric emptying of peptides derived from milk proteins in the preruminant calf.

The gastric emptying kinetics of peptides derived from milk protein were studied in vivo in preruminant calves by collecting and characterizing the whole effluent leaving the stomach for 12 h after ingestion of crude skim milk. Peptides were isolated by reversed-phase HPLC and identified. Particular attention was paid to biologically active peptides and to peptides that could be precursors of biologically active sequences. A gastrin inhibitor, the caseinomacropeptide, was emptied from the stomach only during the first 0.5 h of digestion and rapidly hydrolysed. Precursors of immunostimulatory peptides from alpha s1- and beta-caseins were emptied throughout digestion in the gastric effluent. A precursor of beta-casomorphins (peptide 58-93 of beta-casein) was emptied from the stomach 3.5 h after the meal when it was taken on an empty stomach. From this precursor, peptides that may be resistant to hydrolysis by intestinal peptidase were obtained after in vitro hydrolysis by pancreatic enzymes. A phosphopeptide (fragment 110-142 of alpha s1-casein) was also found in digesta after a few hours of digestion. When the meal was not taken on an empty stomach, these peptides were emptied in the first digesta at a low concentration. The potential activity of these peptides is discussed. The results support the hypothesis that active sequences could still be present in the gut after the action of pancreatic enzymes.