Human mucosal tissue-resident memory T cells in health and disease

Lipid nanoparticles encapsulating both adjuvant and antigen mRNA improve influenza immune cross-protection in mice

The rapid approval of SARS-CoV-2 mRNA lipid nanoparticle (LNP) vaccines indicates the versatility of mRNA LNPs in an urgent vaccine need. However, the mRNA vaccines do not induce mucosal cellular responses or broad protection against recent variants. To improve cross-protection of mRNA vaccines, here we engineered a pioneered mRNA LNP encapsulating with mRNA constructs encoding cytokine adjuvant and influenza A hemagglutinin (HA) antigen for intradermal vaccination. The adjuvant mRNA encodes a novel fusion cytokine GIFT4 comprising GM-CSF and IL-4. We found that the adjuvanted mRNA LNP vaccine induced high levels of humoral antibodies and systemic T cell responses against heterologous influenza antigens and protected immunized mice against influenza A viral infections. Also, the adjuvanted mRNA LNP vaccine elicited early germinal center reactions in draining lymph nodes and promoted antibody-secreting B cell responses. In addition, we generated another adjuvant mRNA encoding CCL27, which enhanced systemic immune responses. We found the two adjuvant mRNAs both showed effective adjuvanticity in enhancing humoral and cellular responses in mice. Interestingly, intradermal immunizations of GIFT4 or CCL27 mRNA adjuvanted mRNA LNP vaccines induced significant lung tissue-resident T cells. Our findings demonstrate that the cytokine mRNA can be a promising adjuvant flexibly formulated into mRNA LNP vaccines to provoke strong immunity against viral variants.

Deep profiling deconstructs features associated with memory CD8+ T cell tissue residence

Tissue-resident memory CD8+ T (Trm) cells control infections and cancer and are defined by their lack of recirculation. Because migration is difficult to assess, residence is usually inferred by putative residence-defining phenotypic and gene signature proxies. We assessed the validity and universality of residence proxies by integrating mouse parabiosis, multi-organ sampling, intravascular staining, acute and chronic infection models, dirty mice, and single-cell multi-omics. We report that memory T cells integrate a constellation of inputs-location, stimulation history, antigen persistence, and environment-resulting in myriad differentiation states. Thus, current Trm-defining methodologies have implicit limitations, and a universal residence-specific signature may not exist. However, we define genes and phenotypes that more robustly correlate with tissue residence across the broad range of conditions that we tested. This study reveals broad adaptability of T cells to diverse stimulatory and environmental inputs and provides practical recommendations for evaluating Trm cells.

Tissue-resident memory T cells in diseases and therapeutic strategies

Tissue-resident memory T (TRM) cells are crucial components of the immune system that provide rapid, localized responses to recurrent pathogens at mucosal and epithelial barriers. Unlike circulating memory T cells, TRM cells are located within peripheral tissues, and they play vital roles in antiviral, antibacterial, and antitumor immunity. Their unique retention and activation mechanisms, including interactions with local epithelial cells and the expression of adhesion molecules, enable their persistence and immediate functionality in diverse tissues. Recent advances have revealed their important roles in chronic inflammation, autoimmunity, and cancer, illuminating both their protective and their pathogenic potential. This review synthesizes current knowledge on TRM cells' molecular signatures, maintenance pathways, and functional dynamics across different tissues. We also explore the interactions of TRM cells with other immune cells, such as B cells, macrophages, and dendritic cells, highlighting the complex network that underpins the efficacy of TRM cells in immune surveillance and response. Understanding the nuanced regulation of TRM cells is essential for developing targeted therapeutic strategies, including vaccines and immunotherapies, to enhance their protective roles while mitigating adverse effects. Insights into TRM cells' biology hold promise for innovative treatments for infectious diseases, cancer, and autoimmune conditions.

Understanding Mucosal Physiology and Rationale of Formulation Design for Improved Mucosal Immunity

The oral and nasal cavities serve as critical gateways for infectious pathogens, with microorganisms primarily gaining entry through these routes. Our first line of defense against these invaders is the mucosal membrane, a protective barrier that shields the body's internal systems from infection while also contributing to vital functions like air and nutrient intake. One of the key features of this mucosal barrier is its ability to protect the physiological system from pathogens. Additionally, mucosal tolerance plays a crucial role in maintaining homeostasis by regulating the pH and water balance within the body. Recognizing the importance of the mucosal barrier, researchers have developed various mucosal formulations to enhance the immune response. Mucosal vaccines, for example, deliver antigens directly to mucosal tissues, triggering local immune stimulation and ultimately inducing systemic immunity. Studies have shown that lipid-based formulations such as liposomes and virosomes can effectively elicit both local and systemic immune responses. Furthermore, mucoadhesive polymeric particles, with their prolonged delivery to target sites, have demonstrated an enhanced immune response. This Review delves into the critical role of material selection and delivery approaches in optimizing mucosal immunity.

Immunological memory diversity in the human upper airway

The upper airway is an important site of infection, but immune memory in the human upper airway is poorly understood, with implications for COVID-19 and many other human diseases1-4. Here we demonstrate that nasal and nasopharyngeal swabs can be used to obtain insights into these challenging problems, and define distinct immune cell populations, including antigen-specific memory B cells and T cells, in two adjacent anatomical sites in the upper airway. Upper airway immune cell populations seemed stable over time in healthy adults undergoing monthly swabs for more than 1 year, and prominent tissue resident memory T (TRM) cell and B (BRM) cell populations were defined. Unexpectedly, germinal centre cells were identified consistently in many nasopharyngeal swabs. In subjects with SARS-CoV-2 breakthrough infections, local virus-specific BRM cells, plasma cells and germinal centre B cells were identified, with evidence of local priming and an enrichment of IgA+ memory B cells in upper airway compartments compared with blood. Local plasma cell populations were identified with transcriptional profiles of longevity. Local virus-specific memory CD4+ TRM cells and CD8+ TRM cells were identified, with diverse additional virus-specific T cells. Age-dependent upper airway immunological shifts were observed. These findings provide new understanding of immune memory at a principal mucosal barrier tissue in humans.

Immunity to Sexually Transmitted Bacterial Infections of the Female Genital Tract: Toward Effective Vaccines

Sexually transmitted infections (STIs) caused by bacterial pathogens Chlamydia trachomatis, Neisseria gonorrhoeae, and Treponema pallidum present significant public health challenges. These infections profoundly impact reproductive health, leading to pelvic inflammatory disease, infertility, and increased susceptibility to other infections. Prevention measures, including antibiotic treatments, are limited by the often-asymptomatic nature of these infections, the need for repetitive and continual screening of sexually active persons, antibiotic resistance for gonorrhea, and shortages of penicillin for syphilis. While vaccines exist for viral STIs like human papillomavirus (HPV) and hepatitis B virus (HBV), there are no vaccines available for bacterial STIs. This review examines the immune responses in the female genital tract to these bacterial pathogens and the implications for developing effective vaccines against bacterial STIs.

Intranasally Inoculated SARS-CoV-2 Spike Protein Combined with Mucoadhesive Polymer Induces Broad and Long-Lasting Immunity

Current mRNA vaccines against SARS-CoV-2 effectively induce systemic and cell-mediated immunity and prevent severe disease. However, they do not induce mucosal immunity that targets the primary route of respiratory infection, and their protective effects wane after a few months. Intranasal vaccines have some advantages, including their non-invasiveness and the additional ability to activate mucosal immunity. In this study, we aimed to explore the effectiveness of an intranasally inoculated spike protein of SARS-CoV-2 mixed with a carboxy-vinyl polymer (S-CVP), a viscous agent. Intranasally inoculated S-CVP strongly induced antigen-specific IgG, including neutralizing antibodies, in the mucosal epithelium and serum and cellular immunity compared to the spike protein mixed with aluminum potassium sulfate. Furthermore, IgA production was detected only with S-CVP vaccination. S-CVP-inoculation in mice significantly suppressed the viral load and inflammation in the lung and protected mice against SARS-CoV-2 challenges, including an early circulating strain and the Omicron BA.1 variant in a manner dependent on CD8+ cells and monocytes/neutrophils. Surprisingly, high antibody responses and protective effects against multiple variants of SARS-CoV-2, including Omicron BA.5, persisted for at least 15 months after the S-CVP immunization. Hence, we propose intranasal inoculation with S-CVP as a promising vaccine strategy against SARS-CoV-2.

A comprehensive meta-analysis of tissue resident memory T cells and their roles in shaping immune microenvironment and patient prognosis in non-small cell lung cancer

Tissue-resident memory T cells (TRM) are a specialized subset of long-lived memory T cells that reside in peripheral tissues. However, the impact of TRM-related immunosurveillance on the tumor-immune microenvironment (TIME) and tumor progression across various non-small-cell lung cancer (NSCLC) patient populations is yet to be elucidated. Our comprehensive analysis of multiple independent single-cell and bulk RNA-seq datasets of patient NSCLC samples generated reliable, unique TRM signatures, through which we inferred the abundance of TRM in NSCLC. We discovered that TRM abundance is consistently positively correlated with CD4+ T helper 1 cells, M1 macrophages, and resting dendritic cells in the TIME. In addition, TRM signatures are strongly associated with immune checkpoint and stimulatory genes and the prognosis of NSCLC patients. A TRM-based machine learning model to predict patient survival was validated and an 18-gene risk score was further developed to effectively stratify patients into low-risk and high-risk categories, wherein patients with high-risk scores had significantly lower overall survival than patients with low-risk. The prognostic value of the risk score was independently validated by the Cancer Genome Atlas Program (TCGA) dataset and multiple independent NSCLC patient datasets. Notably, low-risk NSCLC patients with higher TRM infiltration exhibited enhanced T-cell immunity, nature killer cell activation, and other TIME immune responses related pathways, indicating a more active immune profile benefitting from immunotherapy. However, the TRM signature revealed low TRM abundance and a lack of prognostic association among lung squamous cell carcinoma patients in contrast to adenocarcinoma, indicating that the two NSCLC subtypes are driven by distinct TIMEs. Altogether, this study provides valuable insights into the complex interactions between TRM and TIME and their impact on NSCLC patient prognosis. The development of a simplified 18-gene risk score provides a practical prognostic marker for risk stratification.

Vedolizumab Efficacy Is Associated With Decreased Intracolonic Dendritic Cells, Not Memory T Cells

BACKGROUND

Vedolizumab, an antibody blocking integrin α4β7, is a safe and effective therapy for Crohn's disease and ulcerative colitis. Blocking α4β7 from binding its cognate addressin MAdCAM-1 on intestinal blood vessel endothelial cells prevents T cells from migrating to the gut mucosa in animal models. However, data supporting this mechanism of action in humans is limited.

METHODS

We conducted a cross-sectional case-control study to evaluate the effect of vedolizumab on intestinal immune cell populations while avoiding the confounding effect of resolving inflammation on the cellularity of the colonic mucosa in treatment-responsive patients. Colon biopsies from 65 case subjects receiving vedolizumab were matched with biopsies from 65 control individuals, similar in disease type, medications, anatomic location, and inflammation. Biopsies were analyzed by flow cytometry and full messenger RNA transcriptome sequencing of sorted T cells.

RESULTS

No difference was seen between vedolizumab recipients and control individuals in the quantity of any antigen-experienced T lymphocyte subset or in the quality of the transcriptome in any experienced T cell subset. Fewer naïve colonic B and T cells were seen in vedolizumab recipients than control individuals, regardless of response. However, the most striking finding was a marked reduction in CD1c+ (BDCA1+) dendritic cells exclusively in vedolizumab-responsive patients. In blood, these dendritic cells ubiquitously express high levels of α4β7, which is rapidly downregulated upon vedolizumab exposure.

CONCLUSIONS

The clinical effects of vedolizumab reveal integrin α4β7-dependent dendritic cell migration to the intestinal mucosa to be central to inflammatory bowel disease pathogenesis.

Tissue-resident memory T cell signatures from single-cell analysis associated with better melanoma prognosis

Tissue-resident memory T cells (TRM) are a specialized T cell population residing in peripheral tissues. The presence and potential impact of TRM in the tumor immune microenvironment (TIME) remain to be elucidated. Here, we systematically investigated the relationship between TRM and melanoma TIME based on multiple clinical single-cell RNA-seq datasets and developed signatures indicative of TRM infiltration. TRM infiltration is associated with longer overall survival and abundance of T cells, NK cells, M1 macrophages, and memory B cells in the TIME. A 22-gene TRM-derived risk score was further developed to effectively classify patients into low- and high-risk categories, distinguishing overall survival and immune activation, particularly in T cell-mediated responses. Altogether, our analysis suggests that TRM abundance is associated with melanoma TIME activation and patient survival, and the TRM-based machine learning model can potentially predict prognosis in melanoma patients.

Tissue-Resident Memory T Cells in Allergy

Tissue-resident memory T (TRM) cells constitute a distinct subset within the memory T cell population, serving as the vanguard against invading pathogens and antigens in peripheral non-lymphoid tissues, including the respiratory tract, intestines, and skin. Notably, TRM cells adapt to the specific microenvironment of each tissue, predominantly maintaining a sessile state with distinctive phenotypic and functional attributes. Their role is to ensure continuous immunological surveillance and protection. Recent findings have highlighted the pivotal contribution of TRM cells to the modulation of adaptive immune responses in allergic disorders such as allergic rhinitis, asthma, and dermatitis. A comprehensive understanding of the involvement of TRM cells in allergic diseases bears profound implications for allergy prevention and treatment. This review comprehensively explores the phenotypic characteristics, developmental mechanisms, and functional roles of TRM cells, focusing on their intricate relationship with allergic diseases.

Understanding the molecular mechanisms of anti-trafficking therapies and their clinical relevance in inflammatory bowel disease

In patients with inflammatory bowel disease (IBD), a combination of dysbiosis, increased intestinal permeability, and insufficient regulatory responses facilitate the development of chronic inflammation, which is driven by a complex interplay between the mucosal immune system and the environment and sustained by immune priming and ongoing cellular recruitment to the gut. The localization of immune cells is mediated by their expression of chemokine receptors and integrins, which bind to chemokines and adhesion molecules, respectively. In this article, we review the mechanisms of action of anti-trafficking therapies for IBD and consider clinical observations in the context of the different mechanisms of action. Furthermore, we discuss the evolution of molecular resistance to anti-cytokines, in which the composition of immune cells in the gut changes in response to treatment, and the potential implications of this for treatment sequencing. Lastly, we discuss the relevance of mechanism of action to combination therapy for IBD.

Egress of resident memory T cells from tissue with neoadjuvant immunotherapy: Implications for systemic anti-tumor immunity

INTRODUCTION

Resident memory T (TRM) cells are embedded in peripheral tissue and capable of acting as sentinels that can respond quickly to repeat pathogen exposure as part of an endogenous anti-microbial immune response. Recent evidence suggests that chronic antigen exposure and other microenvironment cues may promote the development of TRM cells within solid tumors as well, and that this TRM phenotype can sequester tumor-specific T cells into tumors and out of circulation resulting in limited systemic antitumor immunity. Here, we perform a review of the published English literature and describe tissue-specific mediators of TRM cell differentiation in states of infection and malignancy with special focus on the role of TGF-β and how targeting TGF-β signaling could be used as a therapeutical approach to promote tumor systemic immunity.

DISCUSSION

The presence of TRM cells with antigen specificity to neoepitopes in tumors associates with positive clinical prognosis and greater responsiveness to immunotherapy. Recent evidence indicates that solid tumors may act as reservoirs for tumor specific TRM cells and limit their circulation - possibly resulting in impaired systemic antitumor immunity. TRM cells utilize specific mechanisms to egress from peripheral tissues into circulation and other peripheral sites, and emerging evidence indicates that immunotherapeutic approaches may initiate these processes and increase systemic antitumor immunity.

CONCLUSIONS

Reversing tumor sequestration of tumor-specific T cells prior to surgical removal or radiation of tumor may increase systemic antitumor immunity. This finding may underlie the improved recurrence free survival observed with neoadjuvant immunotherapy in clinical trials.

Interaction of an α-synuclein epitope with HLA-DRB1∗15:01 triggers enteric features in mice reminiscent of prodromal Parkinson's disease

Enteric symptoms are hallmarks of prodromal Parkinson's disease (PD) that appear decades before the onset of motor symptoms and diagnosis. PD patients possess circulating T cells that recognize specific α-synuclein (α-syn)-derived epitopes. One epitope, α-syn32-46, binds with strong affinity to the HLA-DRB1∗15:01 allele implicated in autoimmune diseases. We report that α-syn32-46 immunization in a mouse expressing human HLA-DRB1∗15:01 triggers intestinal inflammation, leading to loss of enteric neurons, damaged enteric dopaminergic neurons, constipation, and weight loss. α-Syn32-46 immunization activates innate and adaptive immune gene signatures in the gut and induces changes in the CD4+ TH1/TH17 transcriptome that resemble tissue-resident memory (TRM) cells found in mucosal barriers during inflammation. Depletion of CD4+, but not CD8+, T cells partially rescues enteric neurodegeneration. Therefore, interaction of α-syn32-46 and HLA-DRB1∗15:0 is critical for gut inflammation and CD4+ T cell-mediated loss of enteric neurons in humanized mice, suggesting mechanisms that may underlie prodromal enteric PD.

Phase I and II randomized clinical trial of an oral therapeutic vaccine targeting human papillomavirus for treatment of cervical intraepithelial neoplasia 2 and 3

BACKGROUND

Although many human papillomavirus (HPV)-targeted therapeutic vaccines have been examined for efficacy in clinical trials, none have been translated into clinical use. These previous agents were mostly administered by intramuscular or subcutaneous injection to induce systemic immunity. We investigated the safety and therapeutic efficacy of an HPV-16 E7-expressing lacticaseibacillus-based oral vaccine.

METHODS

In a double-blind, placebo-controlled, randomized trial, a total of 165 patients with HPV-16-positive high-grade cervical intraepithelial neoplasia 2 and 3 were assigned to orally administered placebo or low, intermediate, or high doses of IGMKK16E7 (lacticaseibacillus paracasei expressing cell surface, full-length HPV-16 E7). In the 4 groups, IGMKK16E7 or placebo was administered orally at weeks 1, 2, 4, and 8 postenrollment. The primary outcomes included histopathological regression and IGMKK16E7 safety.

RESULTS

In per-protocol analyses, histopathological regression to normal (complete response) occurred in 13 (31.7%) of 41 high-dose recipients and in 5 (12.5%) of 40 placebo recipients (rate difference = 19.2, 95% confidence interval [CI] = 0.5 to 37.8). In patients positive for HPV-16 only, the clinical response rate was 40.0% (12 of 30) in high-dose recipients and 11.5% (3 of 26) in recipients of placebo (rate difference = 28.5, 95% CI = 4.3 to 50.0). There was no difference in adverse events that occurred in the high-dose and placebo groups (P = .83). The number of HPV-16 E7-specific interferon-γ producing cells within peripheral blood increased with level of response (stable disease, partial, and complete responses; P = .004). The regression to normal (complete response) rates among recipients with high levels of immune response were increased in a dose-dependent manner.

CONCLUSION

This trial demonstrates safety of IGMKK16E7 and its efficacy against HPV-16-positive cervical intraepithelial neoplasia 2 and 3. IGMKK16E7 is the first oral immunotherapeutic vaccine to show antineoplastic effects.

TRIAL REGISTRATION

jRCT2031190034.

Integrative transcriptomic and metabolomic analysis in mice reveals the mechanism by which ginseng stem-leaf saponins enhance mucosal immunity induced by a porcine epidemic diarrhea virus vaccination

Porcine epidemic diarrhea virus (PEDV) is a main cause of severe enteric disease in piglets, leading to millions of dollars lost annually in the global pig industry. Parenteral vaccination is limited in generating sufficient mucosal immunity, which is crucial for early defense against PEDV. Here, we orally administered ginseng stem-leaf saponins (GSLS) to mice before parenteral vaccination and found that GSLS significantly enhanced the phagocytosis of dendritic cells, promoted the activities of CD4+ T cells and increased PEDV-specific IgA antibodies in the intestinal mucosa. Transcriptomic results showed that the altered genes following GSLS treatment were mostly related to the immune response and metabolism. In addition, integrated analysis of the transcriptome and metabolome revealed that the mechanism by which GSLS enhances mucosal immunity may be associated with progesterone-related pathways. Further studies are needed to explore the detailed molecular mechanisms.

Assessing the generation of tissue resident memory T cells by vaccines

Vaccines have been a hugely successful public health intervention, virtually eliminating many once common diseases of childhood. However, they have had less success in controlling endemic pathogens including Mycobacterium tuberculosis, herpesviruses and HIV. A focus on vaccine-mediated generation of neutralizing antibodies, which has been a successful approach for some pathogens, has been complicated by the emergence of escape variants, which has been seen for pathogens such as influenza viruses and SARS-CoV-2, as well as for HIV-1. We discuss how vaccination strategies aimed at generating a broad and robust T cell response may offer superior protection against pathogens, particularly those that have been observed to mutate rapidly. In particular, we consider here how a focus on generating resident memory T cells may be uniquely effective for providing immunity to pathogens that typically infect (or become reactivated in) the skin, respiratory mucosa or other barrier tissues.

Guardians of the oral barriers

The oral mucosa serves as a frontline defense against many infections. Stolley et al. (2023. J. Exp. Med.https://doi.org/10.1084/jem.20221853) discovered that the oral mucosa houses CD8+ CD103+ resident memory T cells, which are important for protecting against local viral infections in mice.

Comprehensive immune landscape of lung-resident memory CD8+ T cells after influenza infection and reinfection in a mouse model

Background

Resident phenotypic memory CD8⁺ T cells are crucial for immune defense against pathogens. However, little is known about the potential transitions and regulation mechanisms of their function after influenza virus infection and reinfection. In this study, we utilized integrated transcriptome data and in vivo experiments to investigate the key characteristics behind it.

Methods

Two single-cell RNA sequencing (scRNA-seq) datasets of lung CD8⁺ T cells and one RNA-seq dataset of lung tissue after infection or reinfection were included. After Seurat procedures classifying CD8⁺ T subsets, the scCODE algorithm was used to identify the differentially expressed genes for GSVA, GO, and KEGG pathway enrichment. Monocle 3 and CellChat were used to infer pseudotime cell trajectory and cell interactions. The ssGSEA method was used to estimate the relative proportions of immune cells. The findings were confirmed with a mouse model via flow cytometry and RT-PCR analysis.

Results

Our study refined the landscape of CD8⁺ T-cell subsets in the lung, showing that CD8⁺ Trm cells accumulated in the lung within 14 days after influenza infection. The classical CD8⁺ Trm cells co-expressed a high level of CD49a and even maintained 90 days after primary infection. The ratio of CD8⁺ Trm cells decreased 1 day after influenza reinfection, which may be parallel with their potential transition into effector types, as observed in trajectory inference analysis. KEGG analysis suggested that PD-L1 expression and PD-1 checkpoint pathway were upregulated in CD8⁺ Trm cells on day 14 after infection. GO and GSVA analyses revealed that PI3K-Akt-mTOR and type I interferon signaling pathways were enriched in CD8⁺ Tem and Trm cells after reinfection. Additionally, CCL signaling pathways were involved in cell interaction between CD8⁺ Trm cells and other cells, with Ccl4-Ccr5 and Ccl5-Ccr5 ligand/receptor pairs being important between CD8⁺ Trm and other memory subsets after infection and reinfection.

Conclusion

Our data suggest that resident memory CD8⁺ T cells with CD49a co-expression account for a large proportion after influenza infection, and they can be rapidly reactivated against reinfection. Function differences exist in CD8⁺ Trm and Tem cells after influenza infection and reinfection. Ccl5-Ccr5 ligand/receptor pair is important in cell interactions between CD8⁺ Trm and other subsets.

Innovative biomaterials for the treatment of periodontal disease

Periodontitis is a multifactorial disease that involves the destruction of hard and soft tissues surrounding the tooth. Routine periodontal treatment includes mechanical debridement (surgical and non-surgical) and the systemic administration of antibiotics. In contrast, severe and chronic periodontitis involves aggressive tissue destruction and bone resorption, and the damage is usually irreversible. In these severe cases, bone grafts, the delivery of growth hormones, and guided tissue regeneration can all be used to stimulate periodontal regeneration. However, these approaches do not result in consistent and predictable treatment outcomes. As a result, advanced biomaterials have evolved as an adjunctive approach to improve clinical performance. These novel biomaterials are designed to either prolong the release of antibacterial agents or osteogenic molecules, or to act as immunomodulators to promote healing. The first half of this review briefly summarizes the key immune cells and their underlying cellular pathways implicated in periodontitis. Advanced biomaterials designed to promote periodontal regeneration will be highlighted in the second half. Finally, the limitations of the current experimental design and the challenges of translational science will be discussed.

SIRT2 inhibition by AGK2 enhances mycobacteria-specific stem cell memory responses by modulating beta-catenin and glycolysis

Bacille Calmette-Guerin (BCG) generates limited long-lasting adaptive memory responses leading to short-lived protection against adult pulmonary tuberculosis (TB). Here, we show that host sirtuin 2 (SIRT2) inhibition by AGK2 significantly enhances the BCG vaccine efficacy during primary infection and TB recurrence through enhanced stem cell memory (T_SCM) responses. SIRT2 inhibition modulated the proteome landscape of CD4⁺ T cells affecting pathways involved in cellular metabolism and T-cell differentiation. Precisely, AGK2 treatment enriched the IFNγ-producing T_SCM cells by activating β-catenin and glycolysis. Furthermore, SIRT2 specifically targeted histone H3 and NF-κB p65 to induce proinflammatory responses. Finally, inhibition of the Wnt/β-catenin pathway abolished the protective effects of AGK2 treatment during BCG vaccination. Taken together, this study provides a direct link between BCG vaccination, epigenetics, and memory immune responses. We identify SIRT2 as a key regulator of memory T cells during BCG vaccination and project SIRT2 inhibitors as potential immunoprophylaxis against TB.

Memory T cells possess an innate-like function in local protection from mucosal infection

Mucosal infections pose a significant global health burden. Antigen-specific tissue-resident T cells are critical to maintaining barrier immunity. Previous studies in the context of systemic infection suggest that memory CD8+ T cells may also provide innate-like protection against antigenically unrelated pathogens independent of T cell receptor engagement. Whether bystander T cell activation is also an important defense mechanism in the mucosa is poorly understood. Here, we investigated whether innate-like memory CD8+ T cells could protect against a model mucosal virus infection, herpes simplex virus 2 (HSV-2). We found that immunization with an irrelevant antigen delayed disease progression from lethal HSV-2 challenge, suggesting that memory CD8+ T cells may mediate protection despite the lack of antigen specificity. Upon HSV-2 infection, we observed an early infiltration, rather than substantial local proliferation, of antigen-nonspecific CD8+ T cells, which became bystander-activated only within the infected mucosal tissue. Critically, we show that bystander-activated CD8+ T cells are sufficient to reduce early viral burden after HSV-2 infection. Finally, local cytokine cues within the tissue microenvironment after infection were sufficient for bystander activation of mucosal tissue memory CD8+ T cells from mice and humans. Altogether, our findings suggest that local bystander activation of CD8+ memory T cells contributes a fast and effective innate-like response to infection in mucosal tissue.

Intranasal COVID-19 vaccine induces respiratory memory T cells and protects K18-hACE mice against SARS-CoV-2 infection

Current COVID-19 vaccines prevent severe disease, but do not induce mucosal immunity or prevent infection with SARS-CoV-2, especially with recent variants. Furthermore, serum antibody responses wane soon after immunization. We assessed the immunogenicity and protective efficacy of an experimental COVID-19 vaccine based on the SARS-CoV-2 Spike trimer formulated with a novel adjuvant LP-GMP, comprising TLR2 and STING agonists. We demonstrated that immunization of mice twice by the intranasal (i.n.) route or by heterologous intramuscular (i.m.) prime and i.n. boost with the Spike-LP-GMP vaccine generated potent Spike-specific IgG, IgA and tissue-resident memory (TRM) T cells in the lungs and nasal mucosa that persisted for at least 3 months. Furthermore, Spike-LP-GMP vaccine delivered by i.n./i.n., i.m./i.n., or i.m./i.m. routes protected human ACE-2 transgenic mice against respiratory infection and COVID-19-like disease following lethal challenge with ancestral or Delta strains of SARS-CoV-2. Our findings underscore the potential for nasal vaccines in preventing infection with SARS-CoV-2 and other respiratory pathogen.

Nanoparticle-based immunotherapeutics: from the properties of nanocores to the differential effects of administration routes

The engagement with the immune system is one of the main cornerstones in the development of nanotechnologies for therapy and diagnostics. Recent advances have made possible the tuning of features like size, shape and biomolecular modifications that influence such interactions, however, the capabilities for immune modulation of nanoparticles are still not well defined and exploited. This review focuses on recent advances made in preclinical research for the application of nanoparticles to modulate immune responses, and the main features making them relevant for such applications. We review and discuss newest evidence in the field, which include in vivo experiments with an extensive physicochemical characterization as well as detailed study of the induced immune response. We emphasize the need of incorporating knowledge about immune response development and regulation in the design and application of nanoparticles, including the effect by parameters such as the administration route and the differential interactions with immune subsets.

T-Cell Immunity in COVID-19-Recovered Individuals and Individuals Vaccinated with the Combined Vector Vaccine Gam-COVID-Vac

The COVID-19 pandemic has required extensive research on the new coronavirus SARS-CoV-2 and the creation of new highly effective vaccines. The presence of T-cells in the body that respond to virus antigens suggests adequate antiviral immunity. We investigated T-cell immunity in individuals who recovered from mild and moderate COVID-19 and in individuals vaccinated with the Gam-COVID-Vac combined vector vaccine. The ELISPOT method was used to determine the number of T-cells responding with IFN-γ synthesis to stimulation by peptides containing epitopes of the S-protein or N-, M-, ORF3, and ORF7 proteins, using peripheral blood mononuclear cells (PBMCs). At the same time, the multiplex method was used to determine the accumulation of IFN-γ and other cytokines in the culture medium. According to the data obtained, the proportion of positive conclusions about the T-cell immune response to SARS-CoV-2 antigens in control, recovered, and vaccinated individuals was 12%, 70%, and 52%, respectively. At the same time, more than half of the vaccinated individuals with a T-cell response were sensitized to the antigens of N-, M-, ORF3, and ORF7 proteins not produced by Gam-COVID-Vac, indicating a high likelihood of asymptomatic SARS-CoV-2 infection. Increased IFN-γ release by single sensitized T-cells in response to specific stimulation in recovered and vaccinated individuals did not result in the accumulation of this and other cytokines in the culture medium. These findings suggest a balance between cytokine production and utilization by immunocompetent cells as a prerequisite for providing a controlled cytokine signal and avoiding a "cytokine storm".

Tissue-resident memory T cells in gastrointestinal tumors: turning immune desert into immune oasis

Tissue-resident memory T cells (Trm) are a particular type of T cell subgroup, which stably reside in tissues and have been revealed to be the most abundant memory T cell population in various tissues. They can be activated in the local microenvironment by infection or tumor cells and rapidly clean them up to restore homeostasis of local immunity in gastrointestinal tissues. Emerging evidence has shown that tissue-resident memory T cells have great potential to be mucosal guardians against gastrointestinal tumors. Therefore, they are considered potential immune markers for immunotherapy of gastrointestinal tumors and potential extraction objects for cell therapy with essential prospects in clinical translational therapy. This paper systematically reviews the role of tissue-resident memory T cells in gastrointestinal tumors and looks to the future of their prospect in immunotherapy to provide a reference for clinical application.

Activation of mucosal immunity as a novel therapeutic strategy for combating brucellosis

Brucellosis is a disease of livestock that is commonly asymptomatic until an abortion occurs. Disease in humans results from contact of infected livestock or consumption of contaminated milk or meat. Brucella zoonosis is primarily caused by one of three species that infect livestock, Bacillus abortus in cattle, B. melitensis in goats and sheep, and B. suis in pigs. To aid in disease prophylaxis, livestock vaccines are available, but are only 70% effective; hence, improved vaccines are needed to mitigate disease, particularly in countries where disease remains pervasive. The absence of knowing which proteins confer complete protection limits development of subunit vaccines. Instead, efforts are focused on developing new and improved live, attenuated Brucella vaccines, since these mimic attributes of wild-type Brucella, and stimulate host immune, particularly T helper 1-type responses, required for protection. In considering their development, the new mutants must address Brucella's defense mechanisms normally active to circumvent host immune detection. Vaccination approaches should also consider mode and route of delivery since disease transmission among livestock and humans is believed to occur via the naso-oropharyngeal tissues. By arming the host's mucosal immune defenses with resident memory T cells (TRMs) and by expanding the sources of IFN-γ, brucellae dissemination from the site of infection to systemic tissues can be prevented. In this review, points of discussion focus on understanding the various immune mechanisms involved in disease progression and which immune players are important in fighting disease.

[Advances in the Study of Tissue-resident Memory T Cells in Lung Cancer]

Immune checkpoint inhibitors (ICIs) have been widely used in the treatment of lung cancer, but the benefit population is limited and there is a lack of effective predictive markers of efficacy. Tissue-resident memory T cells (TRM) reside in tissues and exert anti-tumor effects by expressing the integrins CD103, CD49a or C-type lectin CD69 and immune checkpoint receptors. TRM expressing programmed cell death 1 (PD-1) is enriched with transcriptional products associated with cytotoxicity and enhances T cell (antigen) receptor (TCR)-mediated cytotoxicity. TRM is a promising biomarker for predicting the efficacy and prognosis of immunotherapy in lung cancer patients. This review will describe the progress of TRM research in lung cancer.
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Immunization of preterm infants: current evidence and future strategies to individualized approaches

Preterm infants are at particularly high risk for infectious diseases. As this vulnerability extends beyond the neonatal period into childhood and adolescence, preterm infants benefit greatly from infection-preventive measures such as immunizations. However, there is an ongoing discussion about vaccine safety and efficacy due to preterm infants' distinct immunological features. A significant proportion of infants remains un- or under-immunized when discharged from primary hospital stay. Educating health care professionals and parents, promoting maternal immunization and evaluating the potential of new vaccination tools are important means to reduce the overall burden from infectious diseases in preterm infants. In this narrative review, we summarize the current knowledge about vaccinations in premature infants. We discuss the specificities of early life immunity and memory function, including the role of polyreactive B cells, restricted B cell receptor diversity and heterologous immunity mediated by a cross-reactive T cell repertoire. Recently, mechanistic studies indicated that tissue-resident memory (Trm) cell populations including T cells, B cells and macrophages are already established in the fetus. Their role in human early life immunity, however, is not yet understood. Tissue-resident memory T cells, for example, are diminished in airway tissues in neonates as compared to older children or adults. Hence, the ability to make specific recall responses after secondary infectious stimulus is hampered, a phenomenon that is transcriptionally regulated by enhanced expression of T-bet. Furthermore, the microbiome establishment is a dominant factor to shape resident immunity at mucosal surfaces, but it is often disturbed in the context of preterm birth. The proposed function of Trm T cells to remember benign interactions with the microbiome might therefore be reduced which would contribute to an increased risk for sustained inflammation. An improved understanding of Trm interactions may determine novel targets of vaccination, e.g., modulation of T-bet responses and facilitate more individualized approaches to protect preterm babies in the future.

Role and Limits of COVID-19 Vaccines in the Delicate Transition from Pandemic Mitigation to Endemic Control

The recent surge of COVID-19 related to the Omicron variant emergence has thrown a harsh light upon epidemic control in the near future. This should lead the scientific and medical community to question the long-term vaccine strategy for SARS-CoV-2 control. We provide here a critical point of view regarding the virological evolution, epidemiological aspects, and immunological drivers for COVID-19 control, including a vaccination strategy. Overall, we need more innovations in vaccine development to reduce the COVID-19 burden long term. The most adequate answer might be better cooperation between universities, biotech and pharmaceutical companies

Duodenal CD8+ T resident memory cell apoptosis contributes to gut barrier dysfunction and microbial translocation in early alcohol-associated liver disease in humans

BACKGROUND

Intestinal T cells are key in gut barrier function. Their role in early stages of alcohol-associated liver disease (ALD) remain unknown.

AIM

To explore the links between intestinal T cells, microbial translocation and ALD METHODS: Patients with alcohol use disorder (AUD) following a rehabilitation programme were compared to subjects with non-alcoholic fatty liver disease (NAFLD) and healthy controls. Clinical and laboratory data (liver stiffness, controlled attenuation parameter, AST, ALT, K18-M65) served to identify AUD patients with isolated steatosis (minimal liver disease) or steatohepatitis/fibrosis (ALD). Serum microbial translocation markers were measured by ELISA, duodenal and plasma levels of sphingolipids by targeted LC-MS. T lymphocytes in duodenal biopsies were characterised by immunohistochemistry, flow cytometry and RNA sequencing on FACS-sorted cells. Mechanisms for T-cell alterations were assessed in vitro.

RESULTS

Patients with ALD, but not those with minimal liver disease, showed reduced numbers of duodenal CD8+ T resident memory (TRM) cells compared to controls or patients with NAFLD. TRM transcriptomic analysis, in vitro analyses and pharmacological inhibition of cathepsin B confirmed TRM apoptosis driven by lysosomal membrane permeabilisation and cathepsin B release into the cytosol. Altered lipid metabolism and increased duodenal and plasma sphingolipids correlated with apoptosis. Dihydroceramide dose-dependently reduced viability of TRM. Duodenal TRM phenotypic changes, apoptosis and transcriptomic alterations correlated with increased levels of microbial translocation markers. Short-term abstinence did not reverse TRM cell death in patients with ALD.

CONCLUSIONS

Duodenal CD8+ TRM apoptosis related to functional changes in lysosomes and lipid metabolism points to impaired gut adaptive immunity specifically in patients with AUD who developed early ALD.

Human Pulmonary Tuberculosis: Understanding the Immune Response in the Bronchoalveolar System

Mycobacterium tuberculosis, the causal agent of one of the most devastating infectious diseases worldwide, can evade or modulate the host immune response and remain dormant for many years. In this review, we focus on identifying the local immune response induced in vivo by M. tuberculosis in the lungs of patients with active tuberculosis by analyzing data from untouched cells from bronchoalveolar lavage fluid (BALF) or exhaled breath condensate (EBC) samples. The most abundant resident cells in patients with active tuberculosis are macrophages and lymphocytes, which facilitate the recruitment of neutrophils. The cellular response is characterized by an inflammatory state and oxidative stress produced mainly by macrophages and T lymphocytes. In the alveolar microenvironment, the levels of cytokines such as interleukins (IL), chemokines, and matrix metalloproteinases (MMP) are increased compared with healthy patients. The production of cytokines such as interferon (IFN)-γ and IL-17 and specific immunoglobulin (Ig) A and G against M. tuberculosis indicate that the adaptive immune response is induced despite the presence of a chronic infection. The role of epithelial cells, the processing and presentation of antigens by macrophages and dendritic cells, as well as the role of tissue-resident memory T cells (Trm) for in situ vaccination remains to be understood.

The Effect of the Long-Term Calcipotriol/Betamethasone Dipropionate Local Therapy on Tissue Resident Memory Cells Markers in Psoriatic Eruptions

Background: The natural course of psoriasis is characterized by the long-term persistence of lesions and a predilection for relapse in the same area. It is caused by the inherence of TRM (tissue resident memory T cells) in apparently healthy skin. These cells are able to initiate an inflammatory cascade and induce relapse of the disease. These cells are characterized by high resistance to damaging factors and apoptosis, which determines their longevity. Aim: The aim of our study was to evaluate the presence of TRM in psoriatic plaques before, during and after 12 weeks of therapy in patients treated with topical calcipotriol and betamethasone dipropionate (Cal/BD) foam. Methods: TRM markers (CD4, CD8, CD103, CD69, CD49, CXCR6) and tissue expression of cytokines (IL-17A, IL-22) in the lesional psoriatic skin from 10 patients compared to 10 healthy skin samples were estimated by immunohistochemistry. Biopsy samples from the area of the same psoriatic plaque were collected three times: before the initiation of therapy, 4 and 12 weeks after its initiation. Results: The presence of TRM markers in the epidermis and dermis of psoriatic lesions was significantly higher when compared to the skin of control group patients. A reduction in the expression of the characteristic TRM markers (CD8, CD4, CD103, CD69, CXCR6, IL-17A and IL-22) was observed in the epidermis on week 12 of therapy, while a depletion in the expression of TRM in the dermis was demonstrated only in CD4 and IL-22. Conclusions: Topical treatment with Cal/BD foam significantly decreased the expression of TRM markers mainly in the epidermis, and to a lesser extent in the dermis, during the 12-week observation period. It probably results from a worse penetration of the drug into the dermis and the effect of the preparation mainly on the epidermis. The persistence of a high expression of TRM markers in the dermis may result in the rapid recurrence of lesions after discontinuation of topical treatment.

The unfulfilled potential of mucosal immunization

Recent events involving the global coronavirus pandemic have focused attention on vaccination strategies. Although tremendous advances have been made in subcutaneous and intramuscular vaccines during this time, one area that has lagged in implementation is mucosal immunization. Mucosal immunization provides several potential advantages over subcutaneous and intramuscular routes, including protection from localized infection at the site of entry, clearance of organisms on mucosal surfaces, induction of long-term immunity through establishment of central and tissue-resident memory cells, and the ability to shape regulatory responses. Despite these advantages, significant barriers remain to achieving effective mucosal immunization. The epithelium itself provides many obstacles to immunization, and the activation of immune recognition and effector pathways that leads to mucosal immunity has been difficult to achieve. This review will highlight the potential advantages of mucosal immunity, define the barriers to mucosal immunization, examine the immune mechanisms that need to be activated on mucosal surfaces, and finally address recent developments in methods for mucosal vaccination that have shown promise in generating immunity on mucosal surfaces in human trials.

Research Advances for Virus-vectored Tuberculosis Vaccines and Latest Findings on Tuberculosis Vaccine Development

Tuberculosis (TB), caused by respiratory infection with Mycobacterium tuberculosis, remains a major global health threat. The only licensed TB vaccine, the one-hundred-year-old Bacille Calmette-Guérin has variable efficacy and often provides poor protection against adult pulmonary TB, the transmissible form of the disease. Thus, the lack of an optimal TB vaccine is one of the key barriers to TB control. Recently, the development of highly efficacious COVID-19 vaccines within one year accelerated the vaccine development process in human use, with the notable example of mRNA vaccines and adenovirus-vectored vaccines, and increased the public acceptance of the concept of the controlled human challenge model. In the TB vaccine field, recent progress also facilitated the deployment of an effective TB vaccine. In this review, we provide an update on the current virus-vectored TB vaccine pipeline and summarize the latest findings that might facilitate TB vaccine development. In detail, on the one hand, we provide a systematic literature review of the virus-vectored TB vaccines are in clinical trials, and other promising candidate vaccines at an earlier stage of development are being evaluated in preclinical animal models. These research sharply increase the likelihood of finding a more effective TB vaccine in the near future. On the other hand, we provide an update on the latest tools and concept that facilitating TB vaccine research development. We propose that a pre-requisite for successful development may be a better understanding of both the lung-resident memory T cell-mediated mucosal immunity and the trained immunity of phagocytic cells. Such knowledge could reveal novel targets and result in the innovative vaccine designs that may be needed for a quantum leap forward in vaccine efficacy. We also summarized the research on controlled human infection and ultra-low-dose aerosol infection murine models, which may provide more realistic assessments of vaccine utility at earlier stages. In addition, we believe that the success in the ongoing efforts to identify correlates of protection would be a game-changer for streamlining the triage of multiple next-generation TB vaccine candidates. Thus, with more advanced knowledge of TB vaccine research, we remain hopeful that a more effective TB vaccine will eventually be developed in the near future.