Dendritic cell vaccination induces cross-reactive cytotoxic T lymphocytes specific for wild-type and natural variant human immunodeficiency virus type 1 epitopes in HLA-A*0201/Kb transgenic mice

Pan-Specific Prediction of Peptide-MHC Class I Complex Stability, a Correlate of T Cell Immunogenicity

Binding of peptides to MHC class I (MHC-I) molecules is the most selective event in the processing and presentation of Ags to CTL, and insights into the mechanisms that govern peptide-MHC-I binding should facilitate our understanding of CTL biology. Peptide-MHC-I interactions have traditionally been quantified by the strength of the interaction, that is, the binding affinity, yet it has been shown that the stability of the peptide-MHC-I complex is a better correlate of immunogenicity compared with binding affinity. In this study, we have experimentally analyzed peptide-MHC-I complex stability of a large panel of human MHC-I allotypes and generated a body of data sufficient to develop a neural network-based pan-specific predictor of peptide-MHC-I complex stability. Integrating the neural network predictors of peptide-MHC-I complex stability with state-of-the-art predictors of peptide-MHC-I binding is shown to significantly improve the prediction of CTL epitopes. The method is publicly available at http://www.cbs.dtu.dk/services/NetMHCstabpan.

Acceleration of bone-defect repair by using A-W MGC loaded with BMP2 and triple point-mutant HIF1α-expressing BMSCs

Background

The goal of this study is to explore the effects of A-W MGC (apatite-wollastonite magnetic bioactive glass-ceramic) loaded with BMP2 (bone morphogenetic protein 2)- and HIF1α^mu (hypoxia-inducible factor 1 mutation)-expressing BMSCs (bone marrow mesenchymal stem cells) on the bone defect repair.

Methods

(1) BMSCs were infected with viral solution containing BMP2 and HIF1α^mu with the best MOI (multiplicity of infection). The efficiency was observed via hrGFP (human renilla reniformis green fluorescent protein). (2) The cells were divided into five groups (A–E), and ALP (alkaline phosphatase) activity was measured. (3) BMP2 and HIF1α (hypoxia-inducible factor 1α) protein were measured. (4) A-W MGC was loaded with BMSCs that contain the genes and implanted into the bone defect model. The animals were sacrificed 8 and 12 weeks later. (5) The healing was measured with X-ray, histology, and biomechanics.

Results

(1) BMSCs in A–D showed high transfection efficiency. (2) ALP in A and B was higher than the others (p = 0.041 or 0.038); A was higher than B (p = 0.038); (3) BMP2 in A and B was higher than the others (p = 0.014). HIF1α in A and C was higher than the others (p = 0.020). (4) 8 and 12 weeks after, an X-ray indicated that bone defect was nearly fully repaired in A and C. (5) 12 weeks after, the bone remodeling was complete in A and C. (6) The flexural strength in A and C was stronger than the others (p = 0.043).

Conclusion

Engineered A-W MGC with BMP2 and HIF1α^mu-expressing BMSCs exhibits comparable therapeutic effects of bone-defect repair as an autologous bone graft.

Immunoproteomics: current technology and applications

The varied landscape of the adaptive immune response is determined by the peptides presented by immune cells, derived from viral or microbial pathogens or cancerous cells. The study of immune biomarkers or antigens is not new and classical methods such as agglutination, enzyme-linked immunosorbent assay, or Western blotting have been used for many years to study the immune response to vaccination or disease. However, in many of these traditional techniques, protein or peptide identification has often been the bottleneck. Recent advances in genomics and proteomics, has led to many of the rapid advances in proteomics approaches. Immunoproteomics describes a rapidly growing collection of approaches that have the common goal of identifying and measuring antigenic peptides or proteins. This includes gel based, array based, mass spectrometry, DNA based, or in silico approaches. Immunoproteomics is yielding an understanding of disease and disease progression, vaccine candidates, and biomarkers. This review gives an overview of immunoproteomics and closely related technologies that are used to define the full set of antigens targeted by the immune system during disease.

A broadly applicable approach to T cell epitope identification: application to improving tumor associated epitopes and identifying epitopes in complex pathogens

Epitopes are a hallmark of the antigen specific immune response. The identification and characterization of epitopes is essential for modern immunologic studies, from investigating cellular responses against tumors to understanding host/pathogen interactions especially in the case of bacteria with intracellular residence. Here, we have utilized a novel approach to identify T cell epitopes exploiting the exquisite ability of particulate antigens, in the form of beads, to deliver exogenous antigen to both MHC class I and class II pathways for presentation to T cell hybridomas. In the current study, we coupled this functional assay with two distinct protein expression libraries to develop a methodology for the characterization of T cell epitopes. One set of expression libraries containing single amino acid substitutions in a defined epitope sequence was interrogated to identify epitopes with enhanced T cell stimulation for a MHC class I epitope. The second expression library is comprised of the majority of open reading frames from the intracellular pathogen and potential biowarfare agent, Francisella tularensis. By automating aspects of this technology, we have been able to functionally screen and identify novel T cell epitopes within F. tularensis. We have also expanded upon these studies to generate a novel expression vector that enables immunization of recombinant protein into mice, which has been utilized to facilitate T cell epitope discovery for proteins that are critically linked to Francisella pathogenicity. This methodology should be applicable to a variety of systems and other pathogens.

HLA class I transgenic mice: development, utilisation and improvement

Classical major histocompatibility complex (MHC) class I antigens are trimeric molecules found on the surface of nucleated cells in all jawed vertebrates. MHC I are recognised by two families of receptors: clonotypic T cell receptors expressed on the surface of CD8+ cytotoxic T lymphocytes (CTLs), and monomorphic receptors expressed by both natural killer cells and CTLs. The production of MHC I molecules within the cells is a sequential process performed with the help of interacting proteins: proteases, chaperones, transporters and so on. Although largely homologous in their structure, organisation and function, the human and mouse MHC I antigen processing and presentation machineries show fine differences. Transgenesis and 'knockout' or 'knock-in' technologies permit the addition of relevant human genes or the replacement of mouse genes by their human orthologues in order to produce immunologically humanised mice. Such experimental animals are especially relevant for the comparative evaluation of immunotherapies and for the characterisation of MHC I peptide epitopes. This review presents the similarities and differences between mouse and human MHC I antigen processing machinery, and describes the development and utilisation of improving mouse models of human cytotoxic T cell immunity.

Increased immunogenicity of human immunodeficiency virus gp120 engineered to express Galalpha1-3Galbeta1-4GlcNAc-R epitopes

The glycan shield comprised of multiple carbohydrate chains on the human immunodeficiency virus (HIV) envelope glycoprotein gp120 helps the virus to evade neutralizing antibodies. The present study describes a novel method for increasing immunogenicity of gp120 vaccine by enzymatic replacement of sialic acid on these carbohydrate chains with Galalpha1-3Galbeta1-4GlcNAc-R (alpha-gal) epitopes. These epitopes are ligands for the natural anti-Gal antibody constituting approximately 1% of immunoglobulin G in humans. We hypothesize that vaccination with gp120 expressing alpha-gal epitopes (gp120(alphagal)) results in in vivo formation of immune complexes with anti-Gal, which targets vaccines for effective uptake by antigen-presenting cells (APC), due to interaction between the Fc portion of the antibody and Fcgamma receptors on APC. This in turn results in effective transport of the vaccine to lymph nodes and effective processing and presentation of gp120 immunogenic peptides by APC for eliciting a strong anti-gp120 immune response. This hypothesis was tested in alpha-1,3-galactosyltransferase knockout mice, which produce anti-Gal. Mice immunized with gp120(alphagal) produced anti-gp120 antibodies in titers that were >100-fold higher than those measured in mice immunized with comparable amounts of gp120 and effectively neutralized HIV. T-cell response, measured by ELISPOT, was much higher in mice immunized with gp120(alphagal) than in mice immunized with gp120. It is suggested that gp120(alphagal) can serve as a platform for anti-Gal-mediated targeting of additional vaccinating HIV proteins fused to gp120(alphagal), thereby creating effective prophylactic vaccines.