Antigen-specific and cross-reactive T cells in protection and disease

General and individualized changes in T cell immunity during aging

Functional alterations with age are observed in all human systems, but the aging of the adaptive immune system displays both general changes affecting all individuals, and idiosyncratic changes that are unique to individuals. In the T cell compartment, general aging manifests in three ways: (1) the reduction of naïve T cells, (2) the accumulation of differentiated memory T cells, and (3) a reduced overall T cell receptor (TCR) repertoire. Idiosyncratic impacts of aging, such as changes in the TCR repertoires of altered memory and naïve T cells are shaped by each person's life exposures. Recent advancements in single-cell sequencing provide new information including the identification of new subpopulations of T cells, characteristics of transcriptome changes in T cells and their TCR clonotype with age, and measurement of individual cell age. Here, we focus on the changes in T cell subpopulations, transcriptomes and TCR repertoires in overall and antigen-specific T cell population with aging.

Mutation of lysine-specific demethylase 5 is associated with enhanced tumor immunity and favorable outcomes in pan-cancer immune checkpoint blockade

The lysine-specific demethylase 5 (KDM5) family, a key post-translational modification of chromatin, can shape tumor immune microenvironment. Here, we performed an extensive clinical and bioinformatic analysis to explore the association between KDM5 mutation and tumor immunity and its impact on the outcomes in pan-cancer immunotherapy. In 2943 patients across 12 tumor types treated with immune checkpoint inhibitors, KDM5-mutant tumors were associated with favorable overall survival (hazard ratio, 0.72; 95% confidence interval, 0.59-0.87; P = 0.004) and objective response rate (41.7% vs. 26.8%; P = 0.001). Further multi-omics analysis revealed KDM5 mutation was related to boosted tumor immunogenicity, enriched infiltration of immune cells, and improved immune responses. In summary, KDM5 mutation indicates enhanced tumor immunity and favorable outcomes in pan-cancer immune checkpoint blockade. These results have implication for treatment decision-making and developing immunotherapy for personalized care.

DNA barcoded peptide-MHC multimers to measure and monitor minor histocompatibility antigen-specific T cells after allogeneic stem cell transplantation

Allogeneic stem cell transplantation (alloSCT) provides a curative treatment option for hematological malignancies. After HLA-matched alloSCT, donor-derived T cells recognize minor histocompatibility antigens (MiHAs), which are polymorphic peptides presented by HLA on patient cells. MiHAs are absent on donor cells due to genetic differences between patient and donor. T cells targeting broadly expressed MiHAs induce graft-versus-leukemia (GvL) reactivity as well as graft-versus-host disease (GvHD), while T cells for MiHAs with restricted or preferential expression on hematopoietic or non-hematopoietic cells may skew responses toward GvL or GvHD, respectively. Besides tissue expression, overall strength of GvL and GvHD is also determined by T-cell frequencies against MiHAs.Here, we explored the use of DNA barcode-labeled peptide-MHC multimers to detect and monitor antigen-specific T cells for the recently expanded repertoire of HLA-I-restricted MiHAs. In 16 patients who experienced an immune response after donor lymphocyte infusion, variable T-cell frequencies up to 30.5% of CD8+ T cells were measured for 49 MiHAs. High T-cell frequencies above 1% were measured in 12 patients for 19 MiHAs, with the majority directed against mismatched MiHAs, typically 6-8 weeks after donor lymphocyte infusion and at the onset of GvHD. The 12 patients included 9 of 10 patients with severe GvHD, 2 of 3 patients with limited GvHD and 1 of 3 patients without GvHD.In conclusion, we demonstrated that barcoded peptide-MHC multimers reliably detect and allow monitoring for MiHA-specific T cells during treatment to investigate the kinetics of immune responses and their impact on development of GvL and GvHD after HLA-matched alloSCT.

Distinct adaptive immune receptor feature of adipose-derived mesenchymal stem cells (AD-MSCs) treatment of psoriasis

Psoriasis (Ps) is one of the most common chronic inflammatory skin disorders with its pathogenesis correlated with dysregulated innate and adaptive system. Even though biological agents have advanced the treatment of psoriasis, however, there are huge limitations, like high adverse reactions and relapse rate. Therefore, it is of great interest in searching clinical resolutions with better safety and efficacy. In the current study, we utilized the adipose-derived mesenchymal stem cell (AD-MSCs) to treat moderate/severe cases of psoriasis in a single-arm clinical study. This AD-MSC treatment has proven to be clinically safe and effective. Interestingly, a trend of adaptome improvement, including increased diversity, elevated uCDR3s and decreased large clone after AD-MSC treatment in a short (2 weeks) and long (12 weeks) terms. In conclusion, allogenic AD-MSC treatment has shown a good safety and efficacy in treating Ps and can effectively improve the compromised adaptive immune system of Ps patients.

Similar usage of T-cell receptor β-chain between tumor and adjacent normal tissue in hepatocellular carcinoma

BACKGROUND

In this study, we comprehensively profiled the T-cell receptor (TCR) repertoire of the tumor and adjacent normal tissue in patients with HBV-associated hepatocellular carcinoma (HCC) and determined the baseline characteristics and clinical significance of TCR.

METHODS

High-throughput sequencing was used to determine the profile of complementarity-determining region 3 (CDR3) of the TCR-β chain variable (TRBV) in the tumor and normal tissue samples of 14 HCC patients. At the same time, TRBV diversity and differences in expression between tumor and normal tissues were investigated. The cumulative frequency of top 100 CDR3 (CF100), clonality, and Shannon entropy as indices to evaluate diversity, RESULTS: The diversity of TRBV CDR3 showed no significant difference between tumor and normal tissues. Of the 58 V gene segments in TRBV, TRBV16 and TRBV7-6 had a significantly higher frequency in the tumor group than in the normal group (p < 0.05). The frequency of 14 J gene segments showed no significant difference between tumor and normal tissues. In contrast, the frequency of 22 TRBVx/BJx combinations was significantly higher in the tumor than in the normal tissue. In addition, the length and type of TRBV CDR3 were similar in tumor and normal tissues, and a Gaussian distribution was observed in both groups.

CONCLUSION

This study provided a large amount of information about the TCR lineage in HBV-associated HCC, laying the foundation for further research. In addition, the fact that the immune repertoire (TRBV CDR3) hardly differs between tumor and adjacent normal tissue provides a new clue for exploring the mechanism of the liver as an organ with immune privileges.

Exercise-Mediated Protection against Air Pollution-Induced Immune Damage: Mechanisms, Challenges, and Future Directions

Air pollution, a serious risk factor for human health, can lead to immune damage and various diseases. Long-term exposure to air pollutants can trigger oxidative stress and inflammatory responses (the main sources of immune impairment) in the body. Exercise has been shown to modulate anti-inflammatory and antioxidant statuses, enhance immune cell activity, as well as protect against immune damage caused by air pollution. However, the underlying mechanisms involved in the protective effects of exercise on pollutant-induced damage and the safe threshold for exercise in polluted environments remain elusive. In contrast to the extensive research on the pathogenesis of air pollution and the preventive role of exercise in enhancing fitness, investigations into exercise resistance to injury caused by air pollution are still in their infancy. In this review, we analyze evidence from humans, animals, and cell experiments on the combined effects of exercise and air pollution on immune health outcomes, with an emphasis on oxidative stress, inflammatory responses, and immune cells. We also propose possible mechanisms and directions for future research on exercise resistance to pollutant-induced damage in the body. Furthermore, we suggest strengthening epidemiological studies at different population levels and investigations on immune cells to guide how to determine the safety thresholds for exercise in polluted environments.

Pandemic H1N1 influenza virus triggers a strong T helper cell response in human nasopharynx-associated lymphoid tissues

The pH1N1 belongs to influenza A family that is sometimes transmitted to humans via contact with pigs. Human tonsillar immune cells are widely used as in vitro models to study responses to influenza viruses. In the current study, human memory (M) and naïve (N) T cells responses in mononuclear cells of tonsil (TMCs) and peripheral blood (PBMCs) were stimulated by pH1N1/sH1N1, and then stained for estimation of T cells proliferation index. Individuals with an anti-pH1N1 hemagglutination (HA) inhibition (HAI) titer of forty or greater exhibited stronger HA-specific M-CD4+ T cells responses to pH1N1 in TMCs/PBMCs than those with an HAI titer of less than forty (P < 0.01). In addition, a positive correlation was observed between proliferation indices of M-CD4+ T cells induced by exposure to sH1N1/pH1N1 (p < 0.01). Moreover, a strong correlation (p < 0.001) was detected between subjects' age and their HA-specific M-CD4+ T cells induced by pH1N1 exposure, indicating that this response was age-dependent. Finally, stimulation of TMCs with pH1N1-HA resulted in a significant M-CD8+ T cells response (p < 0.05). In conclusion, pH1N1 HA elicits a strong M-CD4+ T cells response in TMCs. Additionally, this response correlates with the response to sH1N1 suggesting cross-reactivity in T cells epitopes directed against HAs of both viral strains.

Landscape of T cell epitopes displays hot mutations of SARS-CoV-2 variant spikes evading cellular immunity

The continuous evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been accompanied by the emergence of viral mutations that pose a great challenge to existing vaccine strategies. It is not fully understood with regard to the role of mutations on the SARS-CoV-2 spike protein from emerging viral variants in T cell immunity. In the current study, recombinant eukaryotic plasmids were constructed as DNA vaccines to express the spike protein from multiple SARS-CoV-2 strains. These DNA vaccines were used to immunize BALB/c mice, and cross-T cell responses to the spike protein from these viral strains were quantitated using interferon-γ (IFN-γ) Elispot. Peptides covering the full-length spike protein from different viral strains were used to detect epitope-specific IFN-γ+ CD4+ and CD8+ T cell responses by fluorescence-activated cell sorting. SARS-CoV-2 Delta and Omicron BA.1 strains were found to have broad T cell cross-reactivity, followed by the Beta strain. The landscapes of T cell epitopes on the spike protein demonstrated that at least 30 mutations emerging from Alpha to Omicron BA.5 can mediate the escape of T cell immunity. Omicron and its sublineages have 19 out of these 30 mutations, most of which are new, and a few are inherited from ancient circulating variants of concerns. The cross-T cell immunity between SARS-CoV-2 prototype strain and Omicron strains can be attributed to the T cell epitopes located in the N-terminal domain (181-246 aa [amino acids], 271-318 aa) and C-terminal domain (1171-1273 aa) of the spike protein. These findings provide in vivo evidence for optimizing vaccine manufacturing and immunization strategies for current or future viral variants.

Potential clinical implications of molecular mimicry-induced autoimmunity

BACKGROUND

Molecular mimicry is hypothesized to be a mechanism by which autoimmune diseases are triggered. It refers to sequence or structural homology between foreign antigens and self-antigens, which can activate cross-reactive lymphocytes that attack host tissues. Elucidating the role of molecular mimicry in human autoimmunity could have important clinical implications.

OBJECTIVE

To review evidence for the role of molecular mimicry in major autoimmune diseases and discuss potential clinical implications.

METHODS

Comprehensive literature review of clinical trials, observational studies, animal models, and immunology studies on molecular mimicry in multiple sclerosis, type 1 diabetes, rheumatoid arthritis, lupus, Guillain-Barre syndrome, autoimmune myocarditis, and primary biliary cirrhosis published from 2000-2023.

RESULTS

Substantial indirect evidence supports molecular mimicry as a contributor to loss of self-tolerance in several autoimmune conditions. Proposed microbial triggers include Epstein-Barr virus, coxsackievirus, Campylobacter jejuni, and bacterial commensals. Key mechanisms involve cross-reactive T cells and autoantibodies induced by epitope homology between microbial and self-antigens. Perpetuation of autoimmunity involves epitope spreading, inflammatory mediators, and genetic factors.

CONCLUSIONS

Molecular mimicry plausibly explains initial stages of autoimmune pathogenesis induced by infection or microbiota disturbances. Understanding mimicry antigens and pathways could enable improved prediction, monitoring, and antigen-specific immunotherapy for autoimmune disorders. However, definitive proof of causation in humans remains limited. Further research should focus on establishing clinical evidence and utility.

Antibody Cross-Reactivity in Auto-Immune Diseases

Autoimmunity is defined by the presence of antibodies and/or T cells directed against self-components. Although of unknown etiology, autoimmunity commonly is associated with environmental factors such as infections, which have been reported to increase the risk of developing autoimmune diseases. Occasionally, similarities between infectious non-self and self-tissue antigens may contribute to immunological cross-reactivity in autoimmune diseases. These reactions may be interpreted as molecular mimicry, which describes cross-reactivity between foreign pathogens and self-antigens that have been reported to cause tissue damage and to contribute to the development of autoimmunity. By focusing on the nature of antibodies, cross-reactivity in general, and antibody-antigen interactions, this review aims to characterize the nature of potential cross-reactive immune reactions between infectious non-self and self-tissue antigens which may be associated with autoimmunity but may not actually be the cause of disease onset.

Numbers and odds: TCR repertoire size and its age changes impacting on T cell functions

A vast array of αβ T cell receptors (TCRs) is generated during T cell development in the thymus through V(D)J recombination, which involves the rearrangement of multiple V, D, and J genes and the pairing of α and β chains. These diverse TCRs provide protection to the human body against a multitude of foreign pathogens and internal cancer cells. The entirety of TCRs present in an individual's T cells is referred to as the TCR repertoire. Despite an estimated 4 × 1011 T cells in the adult human body, the lower bound estimate for the TCR repertoire is 3.8 × 108. While the number of circulating T cells may slightly decrease with age, the changes in the diversity of the TCR repertoire is more apparent. Here, I review recent advancements in TCR repertoire studies, the methods used to measure it, how richness and diversity change as humans age, and some of the known consequences associated with these changes.