Detection of Antigen-Specific T Cells Using In Situ MHC Tetramer Staining

The screening, identification, design and clinical application of tumor-specific neoantigens for TCR-T cells

Recent advances in neoantigen research have accelerated the development of tumor immunotherapies, including adoptive cell therapies (ACTs), cancer vaccines and antibody-based therapies, particularly for solid tumors. With the development of next-generation sequencing and bioinformatics technology, the rapid identification and prediction of tumor-specific antigens (TSAs) has become possible. Compared with tumor-associated antigens (TAAs), highly immunogenic TSAs provide new targets for personalized tumor immunotherapy and can be used as prospective indicators for predicting tumor patient survival, prognosis, and immune checkpoint blockade response. Here, the identification and characterization of neoantigens and the clinical application of neoantigen-based TCR-T immunotherapy strategies are summarized, and the current status, inherent challenges, and clinical translational potential of these strategies are discussed.

Advances of mRNA vaccine in tumor: a maze of opportunities and challenges

High-frequency mutations in tumor genomes could be exploited as an asset for developing tumor vaccines. In recent years, with the tremendous breakthrough in genomics, intelligence algorithm, and in-depth insight of tumor immunology, it has become possible to rapidly target genomic alterations in tumor cell and rationally select vaccine targets. Among a variety of candidate vaccine platforms, the early application of mRNA was limited by instability low efficiency and excessive immunogenicity until the successful development of mRNA vaccines against SARS-COV-2 broken of technical bottleneck in vaccine preparation, allowing tumor mRNA vaccines to be prepared rapidly in an economical way with good performance of stability and efficiency. In this review, we systematically summarized the classification and characteristics of tumor antigens, the general process and methods for screening neoantigens, the strategies of vaccine preparations and advances in clinical trials, as well as presented the main challenges in the current mRNA tumor vaccine development.

Vaccination against Atherosclerosis: Is It Real?

Atherosclerosis has been known in medicine for several centuries. As early as 1755, the Swedish anatomist Albrecht von Haller used the term "atheroma" to describe vascular lesions. Atherosclerosis may originate from an unbalanced diet or bad habits, and is mainly found in developed countries. Clinical trials have been conducted to establish the causes of atherosclerosis, and also to develop treatments for this disease. However, prevention of the disease has always been better than treatment, so vaccination may be the key to saving thousands of lives. The creation of a vaccine may be directly related to the study of autoimmune processes occurring in the body, immunity. This review considers the issues related to the involvement of the immune response in the development of atherosclerotic lesions. Modern concepts of atherogenesis, immune inflammation in atherosclerosis, and potential vaccine targets are also discussed. There is a particular focus on experimental and clinical data supporting the development of immune therapies to reduce cardiovascular risk.

CAR/CXCR5-T cell immunotherapy is safe and potentially efficacious in promoting sustained remission of SIV infection

During chronic human immunodeficiency virus (HIV) or simian immunodeficiency virus (SIV) infection prior to AIDS progression, the vast majority of viral replication is concentrated within B cell follicles of secondary lymphoid tissues. We investigated whether infusion of T cells expressing an SIV-specific chimeric antigen receptor (CAR) and the follicular homing receptor, CXCR5, could successfully kill viral-RNA+ cells in targeted lymphoid follicles in SIV-infected rhesus macaques. In this study, CD4 and CD8 T cells from rhesus macaques were genetically modified to express antiviral CAR and CXCR5 moieties (generating CAR/CXCR5-T cells) and autologously infused into a chronically infected animal. At 2 days post-treatment, the CAR/CXCR5-T cells were located primarily in spleen and lymph nodes both inside and outside of lymphoid follicles. Few CAR/CXCR5-T cells were detected in the ileum, rectum, and lung, and no cells were detected in the bone marrow, liver, or brain. Within follicles, CAR/CXCR5-T cells were found in direct contact with SIV-viral RNA+ cells. We next infused CAR/CXCR5-T cells into ART-suppressed SIV-infected rhesus macaques, in which the animals were released from ART at the time of infusion. These CAR/CXCR5-T cells replicated in vivo within both the extrafollicular and follicular regions of lymph nodes and accumulated within lymphoid follicles. CAR/CXR5-T cell concentrations in follicles peaked during the first week post-infusion but declined to undetectable levels after 2 to 4 weeks. Overall, CAR/CXCR5-T cell-treated animals maintained lower viral loads and follicular viral RNA levels than untreated control animals, and no outstanding adverse reactions were noted. These findings indicate that CAR/CXCR5-T cell treatment is safe and holds promise as a future treatment for the durable remission of HIV.

Evaluation of a fit-for-purpose assay to monitor antigen-specific functional CD4+ T-cell subpopulations in rheumatoid arthritis using flow cytometry-based peptide-MHC class-II tetramer staining

Antigen-specific T cells can serve as a response biomarker in non-clinical or clinical immunotherapy studies in autoimmune disease. There are protocols with optimized multimer staining methods to detect peptide (p)MHCII+ CD4+ T cells, and some qualified and validated protocols for pMHCI+ CD8+ T cells. However, no protocol is fully or partially qualified to enumerate and characterize antigen-specific pMHCII+ CD4+ T cells from patient samples. Implementing such an assay requires a desired level of specificity and precision, in terms of assay repeatability and reproducibility. In transgenic type II collagen (CII)-immunized HLA-DR1/DR4 humanized mouse models of collagen-induced arthritis (CIA), CII_259-273-specific T cells dominantly expand. Therefore antigen-specific T cells recognizing this epitope presented by rheumatoid arthritis (RA)-associated risk HLA-DR allomorphs are of interest to understand disease progression and responses to immunotherapy in RA patients. Using HLA-DRB1∗04:01 or ∗01:01-collagen type II (CII)_259–273 tetramers, we evaluated parameters influencing precision and reproducibility of an optimized flow cytometry–based method for antigen-specific CD4+ T cells and eight specific subpopulations with and without tetramer positivity. We evaluated specificity, precision, and reproducibility for research environments and non-regulated laboratories. The assay has excellent overall precision with %CV<25% for intra-assay repeatability, inter-analyst precision, and inter-assay reproducibility. The precision of the assay correlated negatively with the cell viability after thawing, indicating that post-thaw viability is a critical parameter for reproducibility. This assay is suitable for longitudinal analysis of treatment response and disease activity outcome in RA patients, and adaptable for translational or immunotherapy clinical trial settings.

Establishment and Clinical Application of a Method for Detecting T Lymphocyte Subsets by Cellular Immunochip Technology

Objective

To establish and verify the method for detecting the immune phenotype of peripheral blood T lymphocytes by cellular immune chip technology, analyze the immune status, and discuss its clinical diagnostic value of different populations in the Qingyuan area.

Methods

First, a cellular immune chip was used to detect the number of T lymphocyte subsets CD3+, CD4+, CD8+, and CD4/CD8, followed by evaluating the accuracy and precision through a comparison with flow cytometry. After passing the performance verification, a large-scale detection was performed by a cellular immune chip in 8389 cases. Immunochip technology detects the expression of T lymphocyte subsets and analyzes the differences in cellular immune function among people with physical examination, inflammation, and cancer, as well as different cancer types and in genders.

Results

The cell immunochip method and flow cytometry method have the same accuracy and precision in detecting specimens, and the former is fast and simple, and is suitable for clinical use; big data analysis is expected to establish a reference range for CD3+, CD4+, and CD8+ T cell counts in Qingyuan. There are statistical differences in CD3+, CD4+, CD8+ T cell counts in physical examination, inflammation and cancer populations; there are also certain differences in CD3+, CD4+, CD8+ T cell counts and CD4/CD8 ratios between different cancer types and different diseases.

Conclusion

The method of cell immunochip technology to detect T lymphocyte subsets is simple and practical, with accurate results and rapid detection. It can be used for immune function monitoring and treatment prognosis evaluation of people with different diseases, and it is worthy of popularization and application in clinical practice.

Identification of novel HLA-restricted preferentially expressed antigen in melanoma peptides to facilitate off-the-shelf tumor-associated antigen-specific T-cell therapies

BACKGROUND AIMS

Preferentially expressed antigen in melanoma (PRAME) is a cancer/testis antigen that is overexpressed in many human malignancies and poorly expressed or absent in healthy tissues, making it a good target for anti-cancer immunotherapy. Development of an effective off-the-shelf adoptive T-cell therapy for patients with relapsed or refractory solid tumors and hematological malignancies expressing PRAME antigen requires the identification of major histocompatibility complex (MHC) class I and II PRAME antigens recognized by the tumor-associated antigen (TAA) T-cell product. The authors therefore set out to extend the repertoire of HLA-restricted PRAME peptide epitopes beyond the few already characterized.

METHODS

Peptide libraries of 125 overlapping 15-mer peptides spanning the entire PRAME protein sequence were used to identify HLA class I- and II-restricted epitopes. The authors also determined the HLA restriction of the identified epitopes.

RESULTS

PRAME-specific T-cell products were successfully generated from peripheral blood mononuclear cells of 12 healthy donors. Ex vivo-expanded T cells were polyclonal, consisting of both CD4+ and CD8+ T cells, which elicited anti-tumor activity in vitro. Nine MHC class I-restricted PRAME epitopes were identified (seven novel and two previously described). The authors also characterized 16 individual 15-mer peptide sequences confirmed as CD4-restricted epitopes.

CONCLUSIONS

TAA T cells derived from healthy donors recognize a broad range of CD4+ and CD8+ HLA-restricted PRAME epitopes, which could be used to select suitable donors for generating off-the-shelf TAA-specific T cells.

Monitoring T Cells Responses Mounted by Therapeutic Cancer Vaccines

With the regulatory approval of Provenge and Talimogene laherparepvec (T-VEC) for the treatment of metastatic prostate cancer and advanced melanoma respectively, and other promising clinical trials outcomes, cancer vaccine is gaining prominence as a cancer therapeutic agent. Cancer vaccine works to induce T cell priming, expansion, and infiltration resulting in antigen-specific cytotoxicity. Such an approach that can drive cytotoxicity within the tumor could complement the success of checkpoint inhibitors as tumors shown to have high immune cell infiltration are those that would respond well to these antibodies. With the advancements in cancer vaccine, methods to monitor and understand how cancer vaccines modify the immune milieu is under rapid development. This includes using ELISpot and intracellular staining to detect cytokine secretion by activated T cells; tetramer and CyTOF to quantitate the level of antigen specific T cells; proliferation and cell killing assay to detect the expansion of T cell and specific killing activity. More recently, T cell profiling has provided unprecedented detail on immune cell subsets and providing clues to the mechanism involved in immune activation. Here, we reviewed cancer vaccines currently in clinical trials and highlight available techniques in monitoring the clinical response in patients.

ApoB-Specific CD4+ T Cells in Mouse and Human Atherosclerosis

Atherosclerosis is a chronic inflammatory condition of the arterial wall that leads to the formation of vessel-occluding plaques within the subintimal space of middle-sized and larger arteries. While traditionally understood as a myeloid-driven lipid-storage disease, growing evidence suggests that the accumulation of low-density lipoprotein cholesterol (LDL-C) ignites an autoimmune response with CD4⁺ T-helper (T_H) cells that recognize self-peptides from Apolipoprotein B (ApoB), the core protein of LDL-C. These autoreactive CD4⁺ T cells home to the atherosclerotic plaque, clonally expand, instruct other cells in the plaque, and induce clinical plaque instability. Recent developments in detecting antigen-specific cells at the single cell level have demonstrated that ApoB-reactive CD4⁺ T cells exist in humans and mice. Their phenotypes and functions deviate from classical immunological concepts of distinct and terminally differentiated T_H immunity. Instead, ApoB-specific CD4⁺ T cells have a highly plastic phenotype, can acquire several, partially opposing and mixed transcriptional programs simultaneously, and transit from one T_H subset into another over time. In this review, we highlight adaptive immune mechanisms in atherosclerosis with a focus on CD4⁺ T cells, introduce novel technologies to detect ApoB-specific CD4⁺ T cells at the single cell level, and discuss the potential impact of ApoB-driven autoimmunity in atherosclerosis.

Immunophenotyping of Rhesus CMV-Specific CD8 T-Cell Populations

A vaccine to ameliorate cytomegalovirus (CMV)-related pathogenicity in transplantation patients is considered a top priority. A therapeutic vaccine must include components that elicit both neutralizing antibodies, and highly effective CD8 T-cell responses. The most important translational model of vaccine development is the captive-bred rhesus macaque (Macaca mulatta) of Indian origin. There is a dearth of information on rhesus cytomegalovirus (rhCMV)-specific CD8 T cells due to the absence of well-defined CD8 T-cell epitopes presented by classical MHC-I molecules. In the current study, we defined two CD8 T-cell epitopes restricted by high-frequency Mamu alleles: the Mamu-A1*002:01 restricted VY9 (VTTLGMALY aa291-299) epitope of protein IE-1, and the Mamu-A1*008:01 restricted NP8 (NPTDRPIP aa96-103) epitope of protein phosphoprotein 65-2. We developed tetramers and determined the level, phenotype, and functional capability of the two epitope-specific T-cell populations in circulation and various tissues. We demonstrated the value of these tetramers for in situ tetramer staining. Here, we first provided critical reagents and established a flow cytometric staining strategy to study rhCMV-specific T-cell responses in up to 40% of captive-bred rhesus macaques. © 2020 The Authors. Cytometry Part A published by Wiley Periodicals LLC on behalf of International Society for Advancement of Cytometry.

Peptides for Health Benefits 2019

In recent years, peptides have received increased interest in pharmaceutical, food, cosmetics and various other fields [...].