Fluorescence labeling of anchor-modified Mart-1 peptide for increasing its affinity for HLA-A*0201: Hit two targets with one arrow

One of the most successful strategies in designing peptide-based cancer vaccines is modifying natural epitope peptides to increase their binding strength to human leukocyte antigens (HLAs). Anchor-modified Mart-1 peptide (ELAGIGILTV) is among the artificial epitope peptides with the highest binding affinity for HLA-A*0201. In this study, by fluorescence labeling of its either C- or N-terminus with Nε -(5-carboxyfluorescein)-l-lysine, we not only made it traceable but also drastically increased its binding strength to HLA-A*0201. HLA streptamer, for the first time, is introduced for measuring the binding constants (Ka ) of the labeled peptides. The affinity of the labeled peptides for the HLA-A*201 of the MCF-7 cells was extraordinarily high and co-incubating them with the highest possible amount of the unlabeled peptide, as a competitor, did not significantly prohibit them from binding to the HLA. The reproducibility of the obtained results was confirmed by using the T2 cell line. The HLA-deficient K562 cell line was used as the negative control. With in silico simulations, we found two hydrophobic pockets on both sides of HLA-A*0201 for anchoring the C- or N-terminal 5-carboxyfluorescein probe, which can explain the extraordinary affinity of the labeled peptides for the HLA-A*0201.

Development of antigen-prediction algorithm for personalized neoantigen vaccine using human leukocyte antigen transgenic mouse

Immunotherapy is currently recognized as the fourth modality in cancer therapy. CTLs can detect cancer cells via complexes involving human leukocyte antigen (HLA) class I molecules and peptides derived from tumor antigens, resulting in antigen-specific cancer rejection. The peptides may be predicted in silico using machine learning-based algorithms. Neopeptides, derived from neoantigens encoded by somatic mutations in cancer cells, are putative immunotherapy targets, as they have high tumor specificity and immunogenicity. Here, we used our pipeline to select 278 neoepitopes with high predictive "SCORE" from the tumor tissues of 46 patients with hepatocellular carcinoma or metastasis of colorectal carcinoma. We validated peptide immunogenicity and specificity by in vivo vaccination with HLA-A2, A24, B35, and B07 transgenic mice using ELISpot assay, in vitro and in vivo killing assays. We statistically evaluated the power of our prediction algorithm and demonstrated the capacity of our pipeline to predict neopeptides (area under the curve = 0.687, p < 0.0001). We also analyzed the potential of long peptides containing the predicted neoepitopes to induce CTLs. Our study indicated that the short peptides predicted using our algorithm may be intrinsically present in tumor cells as cleavage products of long peptides. Thus, we empirically demonstrated that the accuracy and specificity of our prediction tools may be potentially improved in vivo using the HLA transgenic mouse model. Our data will help to feedback algorithms to improve in silico prediction, potentially allowing researchers to predict peptides for personalized immunotherapy.

Neutralizing antibody PR8-23 targets the footprint of the sialoglycan receptor binding site of H1N1 hemagglutinin

Influenza virus cause seasonal influenza epidemic and seriously sporadic influenza pandemic outbreaks. Hemagglutinin (HA) is an important target in the therapeutic treatment and diagnostic detection of the influenza virus. Variation in the sialic acid receptor binding site leads to strain-specific binding and results in different binding modes to the host receptors. Here, we evaluated the neutralizing activity and hemagglutination inhibition activity of a prepared murine anti-H1N1 monoclonal antibody PR8-23. Then we identified the epitope peptide of antibody PR8-23 by phage display technique from phage display peptide libraries. The identified epitope, 63-IAPLQLGKCNIA-74, containing two α-helix and two β-fold located at the footprint of the sialoglycan receptor on the RBS in the globular head domain of HA. It broads the growing arsenal of motifs for the amino acids on the globular head domain of HA in sialic acid receptor binding site and neutralizing antibody production.

Peptides-Based Vaccine MP3RT Induced Protective Immunity Against Mycobacterium Tuberculosis Infection in a Humanized Mouse Model

Background

Tuberculosis (TB) is still a global infectious disease that seriously threatens human beings. The only licensed TB vaccine Bacille Calmette-Guérin (BCG)’s protective efficacy varies significantly among populations and regions. It is very urgent to develop more effective vaccines.

Methods

In this study, eleven candidate proteins of Mycobacterium tuberculosis were selected to predict peptides with high-affinity binding capacity for the HLA-DRB1*01:01 molecule. The immunodominant peptides were identified with the enzyme-linked immunospot assay (ELISPOT) and linked in silico to result in a novel polypeptide vaccine in Escherichia coli cells. The vaccine’s protective efficacy was evaluated in humanized and wild-type C57BL/6 mice. The potential immune protective mechanisms were explored with Enzyme-linked Immunosorbent Assay (ELISA), flow cytometry, and ELISPOT.

Results

Six immunodominant peptides screened from 50 predicted peptides were used to construct a new polypeptide vaccine named MP3RT. After challenge with M. tuberculosis, the colony-forming units (CFUs), lung lesion area, and the number of inflammatory cells in humanized mice rather than wild-type mice vaccinated with MP3RT were significantly lower than these in mice immunized with PBS. The humanized mice vaccinated with MP3RT revealed significant increases in IFN-γ cytokine production, IFN-γ⁺ T lymphocytes, CD3⁺IFN-γ⁺ T lymphocytes, and the MP3RT-specific IgG antibody.

Conclusions

Taken together, MP3RT is a promising peptides-based TB vaccine characterized by inducing high levels of IFN-γ and CD3⁺IFN-γ⁺ T lymphocytes in humanized mice. These new findings will lay a foundation for the development of peptides-based vaccines against TB.

Point mutation screening of tumor neoantigens and peptide-induced specific cytotoxic T lymphocytes using The Cancer Genome Atlas database

The aim of the present study was to use The Cancer Genome Atlas (TCGA) database to identify tumor neoantigens, combined with a bioinformatics analysis to design and analyze antigen epitope peptides. Epitopes were screened using immunogenicity tests to identify the ideal epitope peptides to target tumor neoantigens, which can specifically activate the immune response of T cells. The high-frequency mutation loci (top 10) of colorectal, lung and liver cancer genes were screened using TCGA database. The antigenic epitope peptides with high affinity for major histocompatibility complex molecules were selected and synthesized using computer prediction algorithms, and were subsequently detected using flow cytometry. The cytotoxicity of specific cytotoxic T lymphocytes (CTLs) on peptide-loaded T2 cells was initially verified using interferon IFN-γ detection and a calcein-acetoxymethyl (Cal-AM) release assay. Tumor cell lines expressing point mutations in KRAS, TP53 and CTNNB1 genes were constructed respectively, and the cytotoxicity of peptide-induced specific CTLs on wild-type and mutant tumor cells was verified using a Cal-AM release assay and carboxyfluorescein succinimidyl ester-propidium iodide staining. The high-frequency gene mutation loci of KRAS proto-oncogene (KRAS) G12V, tumor protein p53 (TP53) R158L and catenin β1 (CTNNB1) K335I were identified in TCGA database. A total of 3 groups of wild-type and mutant peptides were screened using a peptide prediction algorithm. The CTNNB1 group had a strong affinity for the human leukocyte antigen-A2 molecule, as determined using flow cytometry. The IFN-γ secretion of specific CTLs in the CTNNB1 group was the highest, followed by the TP53 and the KRAS groups. The killing rate of mutant peptide-induced specific CTLs on peptide-loaded T2 cells in the CTNNB1 group was higher compared with that observed in the other groups. The killing rate of specific CTLs induced by mutant peptides present on tumor cells was higher compared with that induced by wild-type peptides. However, when compared with the TP53 and KRAS groups, specific CTLs induced by mutant peptides in the CTNNB1 group had more potent cytotoxicity towards mutant and wild-type tumor cells. In conclusion, point mutant tumor neoantigens screened in the three groups improved the cytotoxicity of specific T cells, and the mutant peptides in the CTNNB1 group were more prominent, indicating that they may activate the cellular immune response more readily.

Identification of a novel HLA-A24-restricted cytotoxic T lymphocyte epitope peptide derived from mesothelin in pancreatic cancer

Pancreatic cancer involves highly malignant tumors, and the development of new therapeutic strategies is critical. Mesothelin is overexpressed in infiltrating pancreatic cancer cells and plays an important role in the invasion and migration processes. In this study, we focused on mesothelin as a tumor-specific antigen target for a pancreatic cancer vaccine. We first investigated the mesothelin-derived epitope peptide restricted to HLA-A^*2402. A total of 19 candidate peptides were synthesized, and we then determined their potential to induce peptide-specific cytotoxic T lymphocytes (CTLs). Peptide-specific CTLs were induced by five peptides derived from mesothelin, and these CTLs successfully exhibited peptide-specific IFN-γ production. After the expansion of each CTL, two CTL lines were established, which were induced by mesothelin-10-5 peptide (AFYPGYLCSL). These CTL lines exhibited peptide-specific cytotoxicity and IFN-γ production. Moreover, we were able to generate mesothelin-10-5 peptide-specific CTL clones. These CTL clones also had specific cytotoxic activity against HLA-A^*2402-positive pancreatic cancer cells that endogenously expressed mesothelin. These results indicate that the mesothelin-10-5 peptide is a novel HLA-A^*2402 restricted CTL epitope and that it is a promising candidate target for antigen-specific immunotherapy against pancreatic cancers.

Transcutaneous Peptide Immunotherapy of Japanese Cedar Pollinosis Using Solid-in-Oil Nanodispersion Technology

Peptide immunotherapy is an attractive approach to relieve allergic symptoms such as rhinitis and asthma. Treatment of Japanese cedar pollinosis (Cryptomeria japonica; Cj), from which over one quarter of Japanese population suffer, is becoming a great concern. Recently, oral feeding of a peptide (7crp) consisting of seven immunodominant human T cell epitopes derived from two enzymes present in Cj pollen was demonstrated to have a benefit in treating Cj pollinosis. In this work, we aimed to apply a novel transcutaneous administration system as a simple and easy peptide delivery for an immunotherapy using a T cell epitope peptide. A modified 7crp peptide (7crpR) which contained triarginine linkers between each epitopes was designed to increase water solubility and was encapsulated in a unique solid-in-oil (S/O) nanodispersion. The S/O nanodispersion consists of a nano-sized peptide-surfactant complex dispersed in an oil vehicle. The S/O nanopartilces having an average diameter of 230 nm facilitated the permeation of the peptide 7crpR into the skin and suppressed serum total IgE and antigen-specific IgE levels in a Cj pollinosis mouse model. Transcutaneous administration of the T cell epitope peptide using the S/O nanodispersion system has potential for future simple and easy immunotherapy of Cj pollinosis.

In vitro induction of HLA-A2402-restricted and carcinoembryonic-antigen-specific cytotoxic T lymphocytes on fixed autologous peripheral blood cells

HLA-A2402-restricted and carcinoembryonic-antigen(CEA)-specific cytotoxic T lymphocytes (CTL) were induced by culturing human peripheral blood mononuclear cells (PBMC) on formalin-fixed autologous adhesive PBMC that had been loaded with CEA-bound latex beads. The CTL killed the CEA-producing HLA-type matched cancer cells, but not the non-producers of CEA, at an effector/target ratio of 10 within 24 h. On the basis of available HLA-A24-binding peptides, we have also attempted to identify the epitope peptide recognized by the CTL. The peptide CEA652(9), TYACFVSNL, stimulated the CTL most strongly when pulsed on HLA-A2402-expressing target cells. The other nine peptides so far tested were also active, but less efficient in their effect on CTL. The CTL failed to kill target cells pulsed with the HLA-A2-binding CEA peptide, CAP-1. The CTL were also generated on the fixed adherent cells previously pulsed with the peptide CEA652(9). Cytotoxic activity of the CTL was inhibited by monoclonal antibodies against CD3, CD8, and MHC class I molecules. These results suggest that human autologous CTL will be inducible on the autologous fixed PBMC without use of the cultured target cancer cells if tumor antigenic protein is available.