Memory CD8+ T cells vary in differentiation phenotype in different persistent virus infections

Immune Monitoring after Cell Therapy and Hematopoietic Cell Transplantation: Guidelines by the ISCT Stem Cell Engineering Committee

Allogeneic hematopoietic cell transplantation and cell therapy (TCT) are potentially lifesaving treatments for patients with high-risk hematologic malignancies and life-threatening acquired and genetic hematologic disorders. However, these treatments face significant challenges, particularly in the risks of relapse and severe toxicity, leading to both relapse-related and non-relapse mortality (NRM). The immune system plays a critical role in controlling these risks, but predictive immune biomarkers for relapse and toxicity have yet to be fully established. To better understand factors driving outcomes in TCT recipients, researchers are increasingly relying on minimally invasive specimens for analysis, such as peripheral blood. These liquid biopsies provide a cost-effective and rapid means to evaluate parameters such as minimal residual disease and genomic mutation profiles. The evolution of these techniques opens new possibilities for monitoring immune reconstitution, including tracking immune cell development and the diversity of surface and secreted biomarkers. This review presents a practical guideline for establishing an immune monitoring program tailored to the TCT environment. By adopting a proactive, harmonized approach, such programs can enhance prognosis prediction and enable early relapse detection, potentially surpassing traditional diagnostic methods. While recent advancements are promising, considerable progress is still needed to make liquid biopsies a routine component of clinical practice. © 2025 International Society for Cell & Gene Therapy. Published by Elsevier Inc.

Epstein-Barr virus pathogenesis and emerging control strategies

Sixty years after its discovery as the first human tumour virus, Epstein-Barr virus (EBV)-specific therapies and vaccines have entered clinical trials. These might not only be applicable for EBV-associated malignancies, where the virus was originally discovered, but also to immunopathologies, including the autoimmune disease multiple sclerosis, which might be triggered in susceptible individuals by primary EBV infection. This Review discusses the surprisingly large spectrum of diseases that EBV seems to cause, as well as which of these might be treated by the therapeutic approaches that are currently being developed or are already clinically applied. New pharmacological inhibitors, antibody therapies, adoptive T cell therapies and active vaccinations are beginning to offer possibilities to target the various EBV infection programmes that are associated with different diseases. These novel developments might allow us to specifically target EBV rather than its host cells in virus-associated pathologies.

Enhancing immunity during ageing by targeting interactions within the tissue environment

Immunity declines with age. This results in a higher risk of age-related diseases, diminished ability to respond to new infections and reduced response to vaccines. The causes of this immune dysfunction are cellular senescence, which occurs in both lymphoid and non-lymphoid tissue, and chronic, low-grade inflammation known as 'inflammageing'. In this Review article, we highlight how the processes of inflammation and senescence drive each other, leading to loss of immune function. To break this cycle, therapies are needed that target the interactions between the altered tissue environment and the immune system instead of targeting each component alone. We discuss the relative merits and drawbacks of therapies that are directed at eliminating senescent cells (senolytics) and those that inhibit inflammation (senomorphics) in the context of tissue niches. Furthermore, we discuss therapeutic strategies designed to directly boost immune cell function and improve immune surveillance in tissues.

Peripheral lymphocyte phenotypic characteristics in healthy populations across the lifespan, from infancy to older adults

INTRODUCTION

Lymphocyte compartment undergoes dramatic changes during childhood and adulthood. Changes in lymphocyte subtypes with age, from infancy to senescence, are rare.

METHODS

A total of 364 healthy individuals were included in this study. The population was divided into 2 groups: children and adults.

RESULTS

The proportion of naive CD4 T cells decreased gradually in the children group (P < .001), and this decrease was significantly negatively correlated with the adult group (P = .008). Conversely, the percentage of memory CD4 T cells increased, with central memory CD4 T cells showing an increase in both groups and effector memory CD4 T cells especially increasing in the children group (P < .001). A similar pattern of changes was observed in naive CD8 T cells, memory CD8 T cells, and CD45RA-positive regulatory T cells. There was a negative correlation between age and the proportion of naive B cells in the children group (P < .001) as well as plasma B cells in the adult group (P < .001). Sex had no influence on the fluctuation of lymphocyte subsets. Furthermore, positive correlations were observed between the expression of T cells and B cells during the developmental process.

DISCUSSION

The observed trends in the distribution of naive and memory lymphocyte subsets offer valuable insights that can help physicians understand patients' immune state and assess prognostic conditions.

The Reduced Immunogenicity of Zoster Vaccines in CMV-Seropositive Older Adults Correlates with T Cell Imprinting

Background: Cytomegalovirus (CMV) infection and age impact immune responses to vaccines. The effect of sex remains controversial. We investigated the relationship between cytomegalovirus-seropositivity, age, and sex and the immunogenicity of the recombinant (RZV) and live (ZVL) zoster vaccines in adults ≥50 years of age. Methods: Varicella zoster virus (VZV) glycoprotein E (gE)-specific antibody, antibody avidity, and cell-mediated immunity (CMI) were measured pre-vaccination and at regular intervals over 5 years post-vaccination in 80 RZV and 79 ZVL recipients, including 91 cytomegalovirus-seropositive and 90 female participants. Results: Differences associated with CMV-seropositivity: lower VZV-gE-CMI in RZV recipients after the first dose of vaccine, but no differences after the 2nd dose; lower VZV-gE-specific antibody avidity in ZVL recipients; and more abundant Th1 and senescent T cells (Tsen) and less abundant regulatory (Treg) and tissue-resident memory T cells (Trm). Differences associated with older age: lower antibody responses in RZV recipients and lower Th1 cells. Differences associated with sex: none for immunogenicity of either vaccine. Differences associated with T cell subset abundance: higher Tsens and lower Tregs or Trms were associated with lower post-dose 1 VZV-gE-specific CMI in RZV recipients, and higher Th1s were associated with higher antibody concentrations. Conclusions: The correlation of CMV- and age-associated T cell subsets with the immunogenicity of ZVLs and RZVs suggests that T cell imprinting contributes to the effect of age and CMV on vaccine responses.

Advanced disease and CD8+ TEMRA cells predict severe infections in multiple myeloma

Introduction

Infections are a major cause of early morbidity and mortality in patients with multiple myeloma (MM) who are characterized by immunodeficiency secondary to disease. However, prospectively collected data on infection risk in this population are scarce. We aimed at identifying parameters in monoclonal gammopathy of undetermined significance (MGUS) and newly diagnosed MM (NDMM) patients with predictive power for early severe infections (SI).

Methods

We conducted a prospective study with newly diagnosed MGUS and NDMM patients. Besides clinical and laboratory data, immune parameters were collected at initial diagnosis before therapy initiation. Primary endpoint was the occurrence of SI within 12 months after diagnosis.

Results

45% of patients developed infection, 26% with SI. Four main risk factors for SI were identified: ECOG ≥ 2 (p < 0.001), ISS stage II/III (p = 0.002), therapeutic intervention (p < 0.001), and elevated CD8+ TEMRA cells (p = 0.027). A risk score was compiled, enabling the stratification of patients with low or high risk for SI with a sensitivity of 92.9% and a specificity of 80%.

Conclusion

We developed a straightforward risk score that considers the relevance of T cell fitness in MGUS and NDMM patients and can help physicians to identify patients at risk of infection, thus enabling the implementation of timely and individualized prevention strategies.

Acute Myeloid Leukemia Skews Therapeutic WT1-specific CD8 TCR-T Cells Towards an NK-like Phenotype that Compromises Function and Persistence

Acute myeloid leukemia (AML) that is relapsed and/or refractory post-allogeneic hematopoietic cell transplantation (HCT) is usually fatal. In a prior study, we demonstrated that AML relapse in high-risk patients was prevented by post-HCT immunotherapy with Epstein-Barr virus (EBV)-specific donor CD8+ T cells engineered to express a high-affinity Wilms Tumor Antigen 1 (WT1)-specific T-cell receptor (TTCR-C4). However, in the present study, infusion of EBV- or Cytomegalovirus (CMV)-specific TTCR-C4 did not clearly improve outcomes in fifteen patients with active disease post-HCT. TCRC4-transduced EBV-specific T cells persisted longer post-transfer than CMV-specific T cells. Persisting TTCR-C4 skewed towards dysfunctional natural killer-like terminal differentiation, distinct from the dominant exhaustion programs reported for T-cell therapies targeting solid tumors. In one patient with active AML post-HCT, a sustained TTCR-C4 effector-memory profile correlated with long-term TTCR-C4 persistence and disease control. These findings reveal complex mechanisms underlying AML-induced T-cell dysfunction, informing future therapeutic strategies for addressing post-HCT relapse.

Memory inflation: Beyond the acute phase of viral infection

Memory inflation is confirmed as the most commonly dysregulation of host immunity with antigen-independent manner in mammals after viral infection. By generating large numbers of effector/memory and terminal differentiated effector memory CD8+ T cells with diminished naïve subsets, memory inflation is believed to play critical roles in connecting the viral infection and the onset of multiple diseases. Here, we reviewed the current understanding of memory inflated CD8+ T cells in their distinct phenotypic features that different from exhausted subsets; the intrinsic and extrinsic roles in regulating the formation of memory inflation; and the key proteins in maintaining the expansion and proliferation of inflationary populations. More importantly, based on the evidences from both clinic and animal models, we summarized the potential mechanisms of memory inflation to trigger autoimmune neuropathies, such as Guillain-Barré syndrome and multiple sclerosis; the correlations of memory inflation between tumorigenesis and resistance of tumour immunotherapies; as well as the effects of memory inflation to facilitate vascular disease progression. To sum up, better understanding of memory inflation could provide us an opportunity to beyond the acute phase of viral infection, and shed a light on the long-term influences of CD8+ T cell heterogeneity in dampen host immune homeostasis.

Epstein-Barr virus infection induces tissue-resident memory T cells in mucosal lymphoid tissues

EBV contributes to around 2% of all tumors worldwide. Simultaneously, more than 90% of healthy human adults persistently carry EBV without clinical symptoms. In most EBV carriers, it is thought that virus-induced tumorigenesis is prevented by cell-mediated immunity. Specifically, memory CD8+ T cells recognize EBV-infected cells during latent and lytic infection. Using a symptomatic primary infection model, similar to infectious mononucleosis (IM), we found EBV-induced CD8+ tissue resident memory T cells (TRMs) in mice with a humanized immune system. These human TRMs were preferentially established after intranasal EBV infection in nasal-associated lymphoid tissues (NALT), equivalent to tonsils, the primary site of EBV infection in humans. They expressed canonical TRM markers, including CD69, CD103, and BLIMP-1, as well as granzyme B, CD107a, and CCL5. Despite cytotoxic activity and cytokine production ex vivo, these TRMs demonstrated reduced CD27 expression and proliferation and failed to control EBV viral loads in the NALT during infection, although effector memory T cells (TEMs) controlled viral titers in spleen and blood. Overall, TRMs are established in mucosal lymphoid tissues by EBV infection, but primarily, systemic CD8+ T cell expansion seems to control viral loads in the context of IM-like infection.

Late-life Attenuation of Cytomegalovirus-mediated CD8 T Cell Memory Inflation: Shrinking of the Cytomegalovirus Latency Niche

CMV drives the accumulation of virus-specific, highly differentiated CD8 memory T cells (memory inflation [MI]). In mice, MI was shown to directly correlate with the CMV infection dose, yet the CMV-associated CD8 MI plateaus over time. It is unclear how MI is regulated with aging. We infected young mice with 102, 104, and 106 PFU of murine CMV and confirmed that MI magnitude was directly proportional to the infectious dose, reaching a setpoint by midlife. By old age, MI subsided, most prominently in mice infected with 106 PFU, and reached statistical parity between groups in 26-mo-old mice. This corresponded to an age-related loss in lymphatic endothelial cells in lymph nodes, recently shown to be sufficient to drive MI in mice. We propose that MI size and persistence over the lifespan is controlled by the size of the lymphatic endothelial cell niche, whose shrinking leads to reduced MI with aging.

Identification of different functions of CD8+ T cell subpopulations by a novel monoclonal antibody

The explicit identification of CD8+ T cell subpopulation is important for deciphering the role of CD8+ T cells for protecting our body against invading pathogens and cancer. Our generated monoclonal antibody (mAb), named FE-1H10, recognized two novel subpopulations of peripheral blood CD8+ T cells, FE-1H10+ and FE-1H10- CD8+ T cells. The molecule recognized by mAb FE-1H10 (FE-1H10 molecules) had a higher distribution on effector memory CD8+ T cell subsets. The functions of FE-1H10- and FE-1H10+ CD8+ T cells were investigated. T cell proliferation assays revealed that FE-1H10- CD8+ T cells exhibited a higher proliferation rate than FE-1H10+ CD8+ T cells, whereas FE-1H10+ CD8+ T cells produced higher levels of IFN-γ and TNF-α than FE-1H10- CD8+ T cells. In T cell cytotoxicity assays, FE-1H10+ CD8+ T cells were able to kill target cells better than FE-1H10- CD8+ T cells. RNA-sequencing analysis confirmed that these subpopulations were distinct: FE-1H10+ CD8+ T cells have higher expression of genes involved in effector functions (IFNG, TNF, GZMB, PRF1, GNLY, FASL, CX3CR1) while FE-1H10- CD8+ T cells have greater expression of genes related to memory CD8+ T cell populations (CCR7, SELL, TCF7, CD40LG). The results suggested that mAb FE-1H10 identifies two novel distinctive CD8+ T cell subpopulations. The FE-1H10+ CD8+ T cells carried a superior functionality in response to tumour cells. The uncover of these novel CD8+ T cell subpopulations may be the basis knowledge of an optional immunotherapy for the selection of potential CD8+ T cells in cancer treatment.

Viral Infection in Endometritis: Is There an Important Role or Not?

Chronic endometritis (CE) is a frequent pathological condition that is defined as localized inflammation in the endometrium. Some adverse fertility consequences such as recurrent miscarriage and failure of implantation are associated with chronic endometritis. On the one hand, inflammation plays an important role in the pathogenesis of endometritis, and on the other hand, the role of viral infections in inducing inflammation can make this review strongly attractive and practical. We set out to provide an overview of viral infections as a potential etiology of CE pathophysiology through the alteration of an endometrial microenvironment and its association with infertility. To the best of our knowledge, this is the first review to demonstrate the role of viral infection in chronic endometritis, and whether or not infection ultimately plays a role..

The effect of early life cytomegalovirus infection on the immune profile of children

Cytomegalovirus (CMV) infection has a life-long impact on the immune system, particularly on memory T cells. However, the effect of early life CMV infection on the phenotype and functionality of T cells in infants and especially longitudinal changes occurring during childhood have not been explored in detail. The phenotype and functionality of peripheral blood CD8+ and CD4+ T cells from children infected with CMV in early life (< 6 months of age) was analyzed using high-dimensional flow cytometry. Samples from CMV IgG-seropositive (CMV+) children were collected at 6 months and 6 years of age and compared to samples from CMV-seronegative (CMV-) children. Early life CMV infection caused multiple alterations within T cells. These include downregulation of CD28 expression and upregulation of CD57 expression within both CD27+ early and CD27- late effector memory CD8+ and CD4+ T-cells at 6 months of age. Of these changes, only alterations within the highly differentiated late effector memory compartment persisted at the age of 6 years. Early life CMV-infection has a distinct impact on developing CD8+ and CD4+ memory T cell compartments. It appears to induce both temporary as well as longer-lasting alterations, which may affect the functionality of the immune system throughout life.

Low-level HIV-1 viremia affects T-cell activation and senescence in long-term treated adults in the INSTI era

BACKGROUND

Around 10% of people with HIV (PWH) exhibit a low-level viremia (LLV) under antiretroviral therapy (ART). However, its origin and clinical significance are largely unknown, particularly at viremias between 50 and 200 copies/mL and under modern ART based on integrase strand transfer inhibitors (INSTIs). Our aim was to characterize their poor immune response against HIV in comparison to individuals with suppressed viremia (SV) and non-HIV controls (NHC).

METHODS

Transversal observational study in 81 matched participants: 27 PWH with LLV, 27 PWH with SV, and 27 NHC. Activation (CD25, HLA-DR, and CD38) and senescence [CD57, PD1, and HAVCR2 (TIM3)] were characterized in peripheral T-cell subsets by spectral flow cytometry. 45 soluble biomarkers of systemic inflammation were evaluated by immunoassays. Differences in cell frequencies and plasma biomarkers among groups were evaluated by a generalized additive model for location, scale, and shape (GAMLSS) and generalized linear model (GLM) respectively, adjusted by age, sex at birth, and ART regimen.

RESULTS

The median age was 53 years and 77.8% were male. Compared to NHC, PWH showed a lower CD4+/CD8+ ratio and increased activation, senescence, and inflammation, highlighting IL-13 in LLV. In addition, LLV showed a downtrend in the frequency of CD8+ naive and effector memory (EM) type 1 compared to SV, along with higher activation and senescence in CD4+ and CD8+ EM and terminally differentiated effector memory RA+ (TEMRA) subpopulations. No significant differences in systemic inflammation were observed between PWH groups.

CONCLUSION

LLV between 50 and 200 copies/mL leads to reduced cytotoxic activity and T-cell dysfunction that could affect cytokine production, being unable to control and eliminate infected cells. The increase in senescence markers suggests a progressive loss of immunological memory and a reduction in the proliferative capacity of immune cells. This accelerated immune aging could lead to an increased risk of developing future comorbidities. These findings strongly advocate for heightened surveillance of these PWH to promptly identify potential future complications.

Innate and adaptive effector immune drivers of cytomegalovirus disease in lung transplantation: a double-edged sword

Up to 90% of the global population has been infected with cytomegalovirus (CMV), a herpesvirus that remains latent for the lifetime of the host and drives immune dysregulation. CMV is a critical risk factor for poor outcomes after solid organ transplant, though lung transplant recipients (LTR) carry the highest risk of CMV infection, and CMV-associated comorbidities compared to recipients of other solid organ transplants. Despite potent antivirals, CMV remains a significant driver of chronic lung allograft dysfunction (CLAD), re-transplantation, and death. Moreover, the extended utilization of CMV antiviral prophylaxis is not without adverse effects, often necessitating treatment discontinuation. Thus, there is a critical need to understand the immune response to CMV after lung transplantation. This review identifies key elements of each arm of the CMV immune response and highlights implications for lung allograft tolerance and injury. Specific attention is paid to cellular subsets of adaptive and innate immune cells that are important in the lung during CMV infection and reactivation. The concept of heterologous immune responses is reviewed in depth, including how they form and how they may drive tissue- and allograft-specific immunity. Other important objectives of this review are to detail the emerging role of NK cells in CMV-related outcomes, in addition to discussing perturbations in CMV immune function stemming from pre-existing lung disease. Finally, this review identifies potential mechanisms whereby CMV-directed treatments may alter the cellular immune response within the allograft.

TB and HIV induced immunosenescence: where do vaccines play a role?

This paper tackles the complex interplay between Human Immunodeficiency virus (HIV-1) and Mycobacterium tuberculosis (M. tuberculosis) infections, particularly their contribution to immunosenescence, the age-related decline in immune function. Using the current literature, we discuss the immunological mechanisms behind TB and HIV-induced immunosenescence and critically evaluate the BCG (Bacillus Calmette-Guérin) vaccine's role. Both HIV-1 and M. tuberculosis demonstrably accelerate immunosenescence: M. tuberculosis through DNA modification and heightened inflammation, and HIV-1 through chronic immune activation and T cell production compromise. HIV-1 and M. tuberculosis co-infection further hastens immunosenescence by affecting T cell differentiation, underscoring the need for prevention and treatment. Furthermore, the use of the BCG tuberculosis vaccine is contraindicated in patients who are HIV positive and there is a lack of investigation regarding the use of this vaccine in patients who develop HIV co-infection with possible immunosenescence. As HIV does not currently have a vaccine, we focus our review more so on the BCG vaccine response as a result of immunosenescence. We found that there are overall limitations with the BCG vaccine, one of which is that it cannot necessarily prevent re-occurrence of infection due to effects of immunosenescence or protect the elderly due to this reason. Overall, there is conflicting evidence to show the vaccine's usage due to factors involving its production and administration. Further research into developing a vaccine for HIV and improving the BCG vaccine is warranted to expand scientific understanding for public health and beyond.

B7-H3-Targeting Chimeric Antigen Receptors Epstein-Barr Virus-specific T Cells Provides a Tumor Agnostic Off-The-Shelf Therapy Against B7-H3-positive Solid Tumors

Encouraged by the observations of significant B7-H3 protein overexpression in many human solid tumors compared to healthy tissues, we directed our focus towards targeting B7-H3 using chimeric antigen receptor (CAR) T cells. We utilized a nanobody as the B7-H3-targeting domain in our CAR construct to circumvent the stability issues associated with single-chain variable fragment-based domains. In efforts to expand patient access to CAR T-cell therapy, we engineered our nanobody-based CAR into human Epstein-Barr virus-specific T cells (EBVST), offering a readily available off-the-shelf treatment. B7H3.CAR-armored EBVSTs demonstrated potent in vitro and in vivo activities against multiple B7-H3-positive human tumor cell lines and patient-derived xenograft models. Murine T cells expressing a murine equivalent of our B7H3.CAR exhibited no life-threatening toxicities in immunocompetent mice bearing syngeneic tumors. Further in vitro evaluation revealed that while human T, B, and natural killer cells were unaffected by B7H3.CAR EBVSTs, monocytes were targeted because of upregulation of B7-H3. Such targeting of myeloid cells, which are key mediators of cytokine release syndrome (CRS), contributed to a low incidence of CRS in humanized mice after B7H3.CAR EBVST treatment. Notably, we showed that B7H3.CAR EBVSTs can target B7-H3-expressing myeloid-derived suppressor cells (MDSC), thereby mitigating MDSC-driven immune suppression. In summary, our data demonstrate that our nanobody-based B7H3.CAR EBVSTs are effective as an off-the-shelf therapy for B7-H3-positive solid tumors. These cells also offer an avenue to modulate the immunosuppressive tumor microenvironment, highlighting their promising clinical potential in targeting solid tumors.

SIGNIFICANCE

Clinical application of EBVSTs armored with B7-H3-targeting CARs offer an attractive solution to translate off-the-shelf CAR T cells as therapy for solid tumors.

Abrogation and homeostatic restoration of IgE responses by a universal IgE allergy CTL vaccine-The three signal self/non-self/self (S/NS/S) theory

Natural IgE cytotoxic peptides (nECPs), which are derived from the constant domain of the heavy chain of human IgE producing B cells via endoplasmic reticulum (ER) stress, are decorated onto MHC class 1a molecules (MHCIa) as unique biomarkers for CTL (cytotoxic T lymphocyte)-mediated immune surveillance. Human IgE exhibits only one isotype and lacks polymorphisms; IgE is pivotal in mediating diverse, allergen-specific allergies. Therefore, by disrupting self-IgE tolerance via costimulation, the CTLs induced by nECPs can serve as universal allergy vaccines (UAVs) in humans to dampen IgE production mediated by diverse allergen-specific IgE-secreting B cells and plasma cells expressing surface nECP-MHCIa as targets. The study herein has enabled the identification of nECPs, A32 and SP-1/SP-2 nonameric natural peptides produced through the correspondence principle. Vaccination using nECP induced nECP-specific CTL that profoundly suppressed human IgE production in vitro as well as chimeric human IgE production in human IgE/HLA-A2.01/HLA-B7.02 triple transgenic rodents. Furthermore, nECP-tetramer-specific CTLs were found to be converted into CD4 Tregs that restored IgE competence via the homeostatic principle, mediatepred by SREBP-1c suppressed DCs. Thus, nECPs showed causal efficacy and safety as UAVs for treating categorically type I hypersensitivity IgE-mediated allergies. The applied vaccination concept presented provides the foundation to unify, integrate through a singular class of tetramer-specific TCR clonotypes for regulaing human IgE production. The three signal theory pertains to mechanisms of three cells underlying central tolerance (S), breaking self tolerance (NS) and regaining peripheral tolerance (S) via homeostasis concerning nECP as an efficacious and safe UAV to treat type I IgE-mediated hypersensitivity. The three signal theory impirically extended, may be heuritic for immuno-regulation of adaptive immune repertoire in general.

Extrinsic and intrinsic drivers of natural killer cell clonality

Clonal expansion of antigen-specific lymphocytes is the fundamental mechanism enabling potent adaptive immune responses and the generation of immune memory. Accompanied by pronounced epigenetic remodeling, the massive proliferation of individual cells generates a critical mass of effectors for the control of acute infections, as well as a pool of memory cells protecting against future pathogen encounters. Classically associated with the adaptive immune system, recent work has demonstrated that innate immune memory to human cytomegalovirus (CMV) infection is stably maintained as large clonal expansions of natural killer (NK) cells, raising questions on the mechanisms for clonal selection and expansion in the absence of re-arranged antigen receptors. Here, we discuss clonal NK cell memory in the context of the mechanisms underlying clonal competition of adaptive lymphocytes and propose alternative selection mechanisms that might decide on the clonal success of their innate counterparts. We propose that the integration of external cues with cell-intrinsic sources of heterogeneity, such as variegated receptor expression, transcriptional states, and somatic variants, compose a bottleneck for clonal selection, contributing to the large size of memory NK cell clones.

Excess of body weight is associated with accelerated T-cell senescence in hospitalized COVID-19 patients

BACKGROUND

Several risk factors have been involved in the poor clinical progression of coronavirus disease-19 (COVID-19), including ageing, and obesity. SARS-CoV-2 may compromise lung function through cell damage and paracrine inflammation; and obesity has been associated with premature immunosenescence, microbial translocation, and dysfunctional innate immune responses leading to poor immune response against a range of viruses and bacterial infections. Here, we have comprehensively characterized the immunosenescence, microbial translocation, and immune dysregulation established in hospitalized COVID-19 patients with different degrees of body weight.

RESULTS

Hospitalised COVID-19 patients with overweight and obesity had similarly higher plasma LPS and sCD14 levels than controls (all p < 0.01). Patients with obesity had higher leptin levels than controls. Obesity and overweight patients had similarly higher expansions of classical monocytes and immature natural killer (NK) cells (CD56+CD16-) than controls. In contrast, reduced proportions of intermediate monocytes, mature NK cells (CD56+CD16+), and NKT were found in both groups of patients than controls. As expected, COVID-19 patients had a robust expansion of plasmablasts, contrasting to lower proportions of major T-cell subsets (CD4 + and CD8+) than controls. Concerning T-cell activation, overweight and obese patients had lower proportions of CD4+CD38+ cells than controls. Contrasting changes were reported in CD25+CD127low/neg regulatory T cells, with increased and decreased proportions found in CD4+ and CD8+ T cells, respectively. There were similar proportions of T cells expressing checkpoint inhibitors across all groups. We also investigated distinct stages of T-cell differentiation (early, intermediate, and late-differentiated - TEMRA). The intermediate-differentiated CD4 + T cells and TEMRA cells (CD4+ and CD8+) were expanded in patients compared to controls. Senescent T cells can also express NK receptors (NKG2A/D), and patients had a robust expansion of CD8+CD57+NKG2A+ cells than controls. Unbiased immune profiling further confirmed the expansions of senescent T cells in COVID-19.

CONCLUSIONS

These findings suggest that dysregulated immune cells, microbial translocation, and T-cell senescence may partially explain the increased vulnerability to COVID-19 in subjects with excess of body weight.

Dual CAR-T Cells Targeting CD19 and CD37 Are Effective in Target Antigen Loss B-cell Tumor Models

Chimeric antigen receptor T (CAR-T) cells targeting multiple antigens (Ag), may reduce the risk of immune escape following the loss of the target Ag and further increase the efficacy of treatment. We developed dual-targeting CAR-T cells that target CD19 and CD37 Ags and evaluated their antitumor effects. CD19/CD37 dual CAR-T cells were generated using cotransduction and simultaneous gene transfer of two types of lentiviral vectors transferring CD19CAR or CD37CAR genes, including the intracellular domains of CD28 and CD3ζ signaling domains. These dual CAR-T cells contained three fractions: CD19/CD37 bispecific CAR-T cells, single CD19CAR-T cells, and single CD37CAR-T cells. In the functional evaluation of CAR-T cells in vitro, CD19/CD37 dual CAR-T cells showed adequate proliferation and cytokine production in response to CD19 and CD37 antigen stimulation alone or in combination. Evaluation of intracellular signaling revealed that dual CAR-T cell-mediated signals were comparable with single CAR-T cells in response to CD19- and CD37-positive B-cell tumors. Although the cytotoxicity of CD19/CD37 dual CAR-T cells in both CD19- and CD37-positive B-cell tumors was similar to that of single CD19 and CD37CAR-T cells, against CD19 and CD37 Ag-heterogeneous tumor, dual CAR-T cells demonstrated significantly superior tumor lysis compared with single CAR-T cells. Furthermore, CD19/CD37 dual CAR-T cells effectively suppressed Ag-heterogeneous Raji cells in a xenograft mouse model. Collectively, these results suggest that CD19/CD37 dual CAR-T cells may be effective target-Ag-loss B-cell tumor models in vitro and in vivo, which represents a promising treatment for patients with relapsed/refractory B-cell malignancies.

Patients with ankylosing spondylitis present a distinct CD8 T cell subset with osteogenic and cytotoxic potential

OBJECTIVES

Ankylosing spondylitis (AS) is a chronic inflammatory rheumatic disease affecting mainly the axial skeleton. Peripheral involvement (arthritis, enthesitis and dactylitis) and extra-musculoskeletal manifestations, including uveitis, psoriasis and bowel inflammation, occur in a relevant proportion of patients. AS is responsible for chronic and severe back pain caused by local inflammation that can lead to osteoproliferation and ultimately spinal fusion. The association of AS with the human leucocyte antigen-B27 gene, together with elevated levels of chemokines, CCL17 and CCL22, in the sera of patients with AS, led us to study the role of CCR4+ T cells in the disease pathogenesis.

METHODS

CD8+CCR4+ T cells isolated from the blood of patients with AS (n=76) or healthy donors were analysed by multiparameter flow cytometry, and gene expression was evaluated by RNA sequencing. Patients with AS were stratified according to the therapeutic regimen and current disease score.

RESULTS

CD8+CCR4+ T cells display a distinct effector phenotype and upregulate the inflammatory chemokine receptors CCR1, CCR5, CX3CR1 and L-selectin CD62L, indicating an altered migration ability. CD8+CCR4+ T cells expressing CX3CR1 present an enhanced cytotoxic profile, expressing both perforin and granzyme B. RNA-sequencing pathway analysis revealed that CD8+CCR4+ T cells from patients with active disease significantly upregulate genes promoting osteogenesis, a core process in AS pathogenesis.

CONCLUSIONS

Our results shed light on a new molecular mechanism by which T cells may selectively migrate to inflammatory loci, promote new bone formation and contribute to the pathological ossification process observed in AS.

NFAT signaling is indispensable for persistent memory responses of MCMV-specific CD8+ T cells

Cytomegalovirus (CMV) induces a unique T cell response, where antigen-specific populations do not contract, but rather inflate during viral latency. It has been proposed that subclinical episodes of virus reactivation feed the inflation of CMV-specific memory cells by intermittently engaging T cell receptors (TCRs), but evidence of TCR engagement has remained lacking. Nuclear factor of activated T cells (NFAT) is a family of transcription factors, where NFATc1 and NFATc2 signal downstream of TCR in mature T lymphocytes. We show selective impacts of NFATc1 and/or NFATc2 genetic ablations on the long-term inflation of MCMV-specific CD8+ T cell responses despite largely maintained responses to acute infection. NFATc1 ablation elicited robust phenotypes in isolation, but the strongest effects were observed when both NFAT genes were missing. CMV control was impaired only when both NFATs were deleted in CD8+ T cells used in adoptive immunotherapy of immunodeficient mice. Transcriptome analyses revealed that T cell intrinsic NFAT is not necessary for CD8+ T cell priming, but rather for their maturation towards effector-memory and in particular the effector cells, which dominate the pool of inflationary cells.

Cytomegalovirus Infection Facilitates the Costimulation of CD57+CD28- CD8 T Cells in HIV Infection and Atherosclerosis via the CD2-LFA-3 Axis

CD8 T cells are emerging as important mediators in atherosclerosis and cardiovascular disease (CVD). Immune activation may play a particular role in people with HIV (PWH) who are at an increased risk of CVD, even after controlling for known CVD risk factors. Latent CMV infection is associated with increased CVD risk for both PWH and people without HIV, and human CMV-specific CD4 and CD8 T cells are enriched for an immunosenescent phenotype. We previously showed that CMV coinfection in PWH promotes vascular homing and activation of inflammatory CD4 T cells through the CD2-LFA-3 axis. However, the role of CD2/LFA3 costimulation of CD8 T cells in PWH with CMV has yet to be described. In the present study, we demonstrate that CD2 expression on CX3CR1+CD57+CD28- inflammescent CD8 T cells is increased on cells from CMV-seropositive PWH. In vitro CD2/LFA-3 costimulation enhances TCR-mediated activation of these inflammatory CD8 memory T cells. Finally, we show that LFA-3 is highly expressed in aortas of SIV-infected rhesus macaques and in atherosclerotic plaques of people without HIV. Our findings are consistent with a model in which CMV infection enhances CD2 expression on highly proinflammatory CD8 T cells that can then be stimulated by LFA-3 expressed in the vasculature, even in the absence of CD28 costimulation. This model, in which CMV infection exacerbates toxic cytokine and granzyme production by CD8 T cells within the vasculature, highlights a potential therapeutic target in atherosclerosis development and progression, especially for PWH.

Multiparameter Flow Cytometry Monitoring of T Cell Responses

Multiparameter flow cytometry is a common tool for assessing responses of T, B, and other cells to pathogens or vaccines. Such responses are likely to be important for predicting the efficacy of an HIV vaccine, despite the elusive findings in HIV vaccine trials to date. Fortunately, flow cytometry has evolved to be capable of readily measuring 30-40 parameters, providing the ability to dissect detailed phenotypes and functions that may be correlated with disease protection. Nevertheless, technical hurdles remain, and standardization of assays is still largely lacking. Here an optimized protocol for antigen-specific T cell monitoring is presented, with specific variations for particular markers. It covers the analysis of multiple cytokines, cell surface proteins, and other functional markers such as CD107, CD154, CD137, etc. References are given to published panels of 8-28 colors.

A Novel Biallelic LCK Variant Resulting in Profound T-Cell Immune Deficiency and Review of the Literature

Lymphocyte-specific protein tyrosine kinase (LCK) is an SRC-family kinase critical for initiation and propagation of T-cell antigen receptor (TCR) signaling through phosphorylation of TCR-associated CD3 chains and recruited downstream molecules. Until now, only one case of profound T-cell immune deficiency with complete LCK deficiency [1] caused by a biallelic missense mutation (c.1022T>C, p.L341P) and three cases of incomplete LCK deficiency [2] caused by a biallelic splice site mutation (c.188-2A>G) have been described. Additionally, deregulated LCK expression has been associated with genetically undefined immune deficiencies and hematological malignancies. Here, we describe the second case of complete LCK deficiency in a 6-month-old girl born to consanguineous parents presenting with profound T-cell immune deficiency. Whole exome sequencing (WES) revealed a novel pathogenic biallelic missense mutation in LCK (c.1393T>C, p.C465R), which led to the absence of LCK protein expression and phosphorylation, and a consecutive decrease in proximal TCR signaling. Loss of conventional CD4+ and CD8+ αβT-cells and homeostatic T-cell expansion was accompanied by increased γδT-cell and Treg percentages. Surface CD4 and CD8 co-receptor expression was reduced in the patient T-cells, while the heterozygous mother had impaired CD4 and CD8 surface expression to a lesser extent. We conclude that complete LCK deficiency is characterized by profound T-cell immune deficiency, reduced CD4 and CD8 surface expression, and a characteristic TCR signaling disorder. CD4 and CD8 surface expression may be of value for early detection of mono- and/or biallelic LCK deficiency.

Sicilian semi- and supercentenarians: identification of age-related T-cell immunophenotype to define longevity trait

The immunophenotype of oldest centenarians, i.e. semi- and supercentenarians, could provide important information about their ability to adapt to factors associated with immune changes, including ageing per se and chronic Cytomegalovirus infection. We investigated, by flow cytometry, variations in percentages and absolute numbers of immune cell subsets, focusing on T cells, and pro-inflammatory parameters in a cohort of 28 women and 26 men (age range 19-110 years). We observed variability in hallmarks of immunosenescence related to age and Cytomegalovirus serological status. The eight oldest centenarians showed the lowest percentages of naïve T cells, due to their age, and the highest percentages of T-effector memory cells re-expressing CD45RA (TEMRA), according to their cytomegalovirus status, and high levels of serum pro-inflammatory parameters, although their means were lower than that of remaining 90+ donors. Some of them showed CD8 naïve and TEMRA percentages, and exhaustion/pro-inflammatory markers comparable to the younger ones. Our study supports the suggestion that immune ageing, especially of oldest centenarians, exhibits great variability that is not only attributable to a single contributor but should also be the full result of a combination of several factors. Everyone ages differently because he/she is unique in genetics and experience of life and this applies even more to the immune system; everybody has had a different immunological history. Furthermore, our findings on inflammatory markers, TEMRA and CMV seropositivity in centenarians, discussed in the light of the most recent literature, suggest that these changes might be not unfavourable for centenarians, and in particular for the oldest ones.

Modulation of Epstein-Barr-Virus (EBV)-Associated Cancers by Co-Infections

The oncogenic and persistent Epstein Barr virus (EBV) is carried by more than 95% of the human adult population. While asymptomatic in most of these, EBV can cause a wide variety of malignancies of lymphoid or epithelial cell origin. Some of these are also associated with co-infections that either increase EBV-induced tumorigenesis or weaken its immune control. The respective pathogens include Kaposi-sarcoma-associated herpesvirus (KSHV), Plasmodium falciparum and human immunodeficiency virus (HIV). In this review, I will discuss the respective tumor entities and possible mechanisms by which co-infections increase the EBV-associated cancer burden. A better understanding of the underlying mechanisms could allow us to identify crucial features of EBV-associated malignancies and defects in their immune control. These could then be explored to develop therapies against the respective cancers by targeting EBV and/or the respective co-infections with pathogen-specific therapies or vaccinations.

Early-to-mid stage idiopathic Parkinson's disease shows enhanced cytotoxicity and differentiation in CD8 T-cells in females

Neuroinflammation in the brain contributes to the pathogenesis of Parkinson's disease (PD), but the potential dysregulation of peripheral immunity has not been systematically investigated for idiopathic PD (iPD). Here we showed an elevated peripheral cytotoxic immune milieu, with more terminally-differentiated effector memory (TEMRA) CD8 T, CD8+ NKT cells and circulating cytotoxic molecules in fresh blood of patients with early-to-mid iPD, especially females, after analyzing > 700 innate and adaptive immune features. This profile, also reflected by fewer CD8+FOXP3+ T cells, was confirmed in another subcohort. Co-expression between cytotoxic molecules was selectively enhanced in CD8 TEMRA and effector memory (TEM) cells. Single-cell RNA-sequencing analysis demonstrated the accelerated differentiation within CD8 compartments, enhanced cytotoxic pathways in CD8 TEMRA and TEM cells, while CD8 central memory (TCM) and naïve cells were already more-active and transcriptionally-reprogrammed. Our work provides a comprehensive map of dysregulated peripheral immunity in iPD, proposing candidates for early diagnosis and treatments.

Overall avidity declines in TCR repertoires during latent CMV but not EBV infection

Introduction

The avidity of the T-cell receptor (TCR) for antigenic peptides presented by the MHC (pMHC) on cells is an essential parameter for efficient T cell-mediated immunity. Yet, whether the TCR-ligand avidity can drive the clonal evolution of virus antigen-specific CD8 T cells, and how this process is determined in latent Cytomegalovirus (CMV)- against Epstein-Barr virus (EBV)-mediated infection remains largely unknown.

Methods

To address these issues, we quantified monomeric TCR-pMHC dissociation rates on CMV- and EBV-specific individual TCRαβ clonotypes and polyclonal CD8 T cell populations in healthy donors over a follow-up time of 15-18 years. The parameters involved during the long-term persistence of virus-specific T cell clonotypes were further evaluated by gene expression profiling, phenotype and functional analyses.

Results

Within CMV/pp65-specific T cell repertoires, a progressive contraction of clonotypes with high TCR-pMHC avidity and low CD8 binding dependency was observed, leading to an overall avidity decline during long-term antigen exposure. We identified a unique transcriptional signature preferentially expressed by high-avidity CMV/pp65-specific T cell clonotypes, including the inhibitory receptor LILRB1. Interestingly, T cell clonotypes of high-avidity showed higher LILRB1 expression than the low-avidity ones and LILRB1 blockade moderately increased T cell proliferation. Similar findings were made for CD8 T cell repertoires specific for the CMV/IE-1 epitope. There was a gradual in vivo loss of high-avidity T cells with time for both CMV specificities, corresponding to virus-specific CD8 T cells expressing enhanced LILRB1 levels. In sharp contrast, the EBV/BMFL1-specific T cell clonal composition and distribution, once established, displayed an exceptional stability, unrelated to TCR-pMHC binding avidity or LILRB1 expression.

Conclusions

These findings reveal an overall long-term avidity decline of CMV- but not EBV-specific T cell clonal repertoires, highlighting the differing role played by TCR-ligand avidity over the course of these two latent herpesvirus infections. Our data further suggest that the inhibitor receptor LILRB1 potentially restricts the clonal expansion of high-avidity CMV-specific T cell clonotypes during latent infection. We propose that the mechanisms regulating the long-term outcome of CMV- and EBV-specific memory CD8 T cell clonotypes in humans are distinct.

Human virome profiling identified CMV as the major viral driver of a high accumulation of senescent CD8+ T cells in patients with advanced NSCLC

Circulating senescent CD8+ T (T8sen) cells are characterized by a lack of proliferative capacities but retain cytotoxic activity and have been associated to resistance to immunotherapy in patients with advanced non-small cell lung cancer (aNSCLC). We aimed to better characterize T8sen and to determine which factors were associated with their accumulation in patients with aNSCLC. Circulating T8sen cells were characterized by a higher expression of SA-βgal and the transcription factor T-bet, confirming their senescent status. Using whole virome profiling, cytomegalovirus (CMV) was the only virus associated with T8sen. CMV was necessary but not sufficient to explain high accumulation of T8sen (T8senhigh status). In CMV+ patients, the proportion of T8sen cells increased with cancer progression. Last, CMV-induced T8senhigh phenotype but not CMV seropositivity itself was associated with worse progression-free and overall survival in patients treated with anti-PD-(L)1 therapy but not with chemotherapy. Overall, CMV is the unique viral driver of T8sen-driven resistance to anti-PD-(L)1 antibodies in patients with aNSCLC.

Cytomegalovirus Cell-Mediated Immunity: Ready for Routine Use?

Utilizing assays that assess specific T-cell-mediated immunity against cytomegalovirus (CMV) holds the potential to enhance personalized strategies aimed at preventing and treating CMV in organ transplantation. This includes improved risk stratification during transplantation compared to relying solely on CMV serostatus, as well as determining the optimal duration of antiviral prophylaxis, deciding on antiviral therapy when asymptomatic replication occurs, and estimating the risk of recurrence. In this review, we initially provide an overlook of the current concepts into the immune control of CMV after transplantation. We then summarize the existent literature on the clinical experience of the use of immune monitoring in organ transplantation, with a particular interest on the outcomes of interventional trials. Current evidence indicates that cell-mediated immune assays are helpful in identifying patients at low risk for replication for whom preventive measures against CMV can be safely withheld. As more data accumulates from these and other clinical scenarios, it is foreseeable that these assays will likely become part of the routine clinical practice in organ transplantation.

Baseline immune states (BIS) associated with vaccine responsiveness and factors that shape the BIS

Vaccines are among the greatest inventions in medicine, leading to the elimination or control of numerous diseases, including smallpox, polio, measles, rubella, and, most recently, COVID-19. Yet, the effectiveness of vaccines varies among individuals. In fact, while some recipients mount a robust response to vaccination that protects them from the disease, others fail to respond. Multiple clinical and epidemiological factors contribute to this heterogeneity in responsiveness. Systems immunology studies fueled by advances in single-cell biology have been instrumental in uncovering pre-vaccination immune cell types and genomic features (i.e., the baseline immune state, BIS) that have been associated with vaccine responsiveness. Here, we review clinical factors that shape the BIS, and the characteristics of the BIS associated with responsiveness to frequently studied vaccines (i.e., influenza, COVID-19, bacterial pneumonia, malaria). Finally, we discuss potential strategies to enhance vaccine responsiveness in high-risk groups, focusing specifically on older adults.

Abrogation and Homeostatic Restoration of IgE Responses by a Universal IgE Allergy CTL Vaccine-The Three Signal Self/Non-Self/Self (S/NS/S) Model

Natural IgE cytotoxic peptides (nECPs), which are derived from the constant domain of the heavy chain of human IgE producing B cells via endoplasmic reticulum (ER) stress, are decorated onto MHC class 1a molecules (MHCIa) as unique biomarkers for CTL (cytotoxic T lymphocyte)-mediated immune surveillance. Human IgE exhibits only one isotype and lacks polymorphisms; IgE is pivotal in mediating diverse, allergen-specific allergies. Therefore, by disrupting self-IgE tolerance via costimulation, the cytotoxic T lymphocytes (CTLs) induced by nECPs can serve as universal allergy vaccines (UAVs) in humans to dampen IgE production mediated by diverse allergen-specific IgE- secreting B cells and plasma cells expressing surface nECP-MHCIa as targets. The study herein has enabled the identification of nECPs produced through the correspondence principle 1, 2 . Furthermore, nECP-tetramer-specific CTLs were found to be converted into CD4 Tregs that restored IgE competence via the homeostatic principle, mediated by SREBP-1c suppressed DCs. Thus, nECPs showed causal efficacy and safety as UAVs for treating type I hypersensitivity IgE-mediated allergies. The applied vaccination concept presented provides the foundation to unify, integrate through a singular class of tetramer-specific TCR clonotypes. The three signal model is proposed on the mechanisms underlying central tolerance, breaking tolerance and regaining peripheral tolerance via homeostasis concerning nECP as an efficacious and safe UAV to treat type I IgE-mediated hypersensitivity.

One Sentence Summary

Human IgE self-peptides are identified as universal allergy vaccines that inhibit IgE synthesis while allowing homeostatic IgE recovery.Graphic abstract textThree cell S/NS/S model of Universal Allergy Vaccines (UAV): Natural IgE peptides (nECPs) presented by enabler DCs break central IgE tolerance (Self), leading to CTLs that inhibit IgE production (Non-self). Generative DCs converted by the metabolic milieu transform the pre-existing nECP-specific CTLs into nECP-specific Tregs leading to homeostatic recovery of IgE competence (S).

Relevance of tissue-resident memory CD8 T cells in the onset of Parkinson's disease and examination of its possible etiologies: infectious or autoimmune?

Tissue-resident memory CD8 T cells are responsible for local immune surveillance in different tissues, including the brain. They constitute the first line of defense against pathogens and cancer cells and play a role in autoimmunity. A recently published study demonstrated that CD8 T cells with markers of residency containing distinct granzymes and interferon-γ infiltrate the parenchyma of the substantia nigra and contact dopaminergic neurons in an early premotor stage of Parkinson's disease. This infiltration precedes α-synuclein aggregation and neuronal loss in the substantia nigra, suggesting a relevant role for CD8 T cells in the onset of the disease. To date, the nature of the antigen that initiates the adaptive immune response remains unknown. This review will discuss the role of tissue-resident memory CD8 T cells in brain immune homeostasis and in the onset of Parkinson's disease and other neurological diseases. We also discuss how aging and genetic factors can affect the CD8 T cell immune response and how animal models can be misleading when studying human-related immune response. Finally, we speculate about a possible infectious or autoimmune origin of Parkinson's disease.

Estimating the contribution of CD4 T cell subset proliferation and differentiation to HIV persistence

Persistence of HIV in people living with HIV (PWH) on suppressive antiretroviral therapy (ART) has been linked to physiological mechanisms of CD4+ T cells. Here, in the same 37 male PWH on ART we measure longitudinal kinetics of HIV DNA and cell turnover rates in five CD4 cell subsets: naïve (TN), stem-cell- (TSCM), central- (TCM), transitional- (TTM), and effector-memory (TEM). HIV decreases in TTM and TEM but not in less-differentiated subsets. Cell turnover is ~10 times faster than HIV clearance in memory subsets, implying that cellular proliferation consistently creates HIV DNA. The optimal mathematical model for these integrated data sets posits HIV DNA also passages between CD4 cell subsets via cellular differentiation. Estimates are heterogeneous, but in an average participant's year ~10 (in TN and TSCM) and ~104 (in TCM, TTM, TEM) proviruses are generated by proliferation while ~103 proviruses passage via cell differentiation (per million CD4). In simulations, therapies blocking proliferation and/or enhancing differentiation could reduce HIV DNA by 1-2 logs over 3 years. In summary, HIV exploits cellular proliferation and differentiation to persist during ART but clears faster in more proliferative/differentiated CD4 cell subsets and the same physiological mechanisms sustaining HIV might be temporarily modified to reduce it.

Identification of T cell responses to the nonstructural glycoproteins in survivors of Crimean-Congo hemorrhagic fever in South Africa

Crimean-Congo hemorrhagic fever orthonairovirus (CCHFV) is listed as a priority pathogen by the World Health Organization due to the severity of disease, propensity for spread to nonendemic regions, and absence of a vaccine or specific treatment. The immune correlates of protection are not clearly defined and hence the importance of investigating host immune responses in survivors. We have previously shown that survivors generate memory T cell responses that are long-lived and this study aimed to further define specific viral proteins targeted by the T cell response. The NSM , GP38, highly variable mucin-like domain, and N-terminus of GC regions in CCHFV are considered immunogenic regions and were investigated using peptide libraries representing regions of interest. An interferon gamma ELISpot assay was used to identify responses in peripheral blood mononuclear cells isolated from 12 survivors of laboratory confirmed CCHFV infections. IFN-γ responses were detected from eight survivors, against nine peptides, including four peptides located in the NSM region and five peptides located in the GP38 protein. No response was detected against peptides representing the mucin-like domain. In conclusion, the results suggest the presence of a long-lasting T cell memory response upon stimulation with viral epitopes in survivors of infection.

SARS-CoV-2 reservoir in post-acute sequelae of COVID-19 (PASC)

Millions of people are suffering from Long COVID or post-acute sequelae of COVID-19 (PASC). Several biological factors have emerged as potential drivers of PASC pathology. Some individuals with PASC may not fully clear the coronavirus SARS-CoV-2 after acute infection. Instead, replicating virus and/or viral RNA-potentially capable of being translated to produce viral proteins-persist in tissue as a 'reservoir'. This reservoir could modulate host immune responses or release viral proteins into the circulation. Here we review studies that have identified SARS-CoV-2 RNA/protein or immune responses indicative of a SARS-CoV-2 reservoir in PASC samples. Mechanisms by which a SARS-CoV-2 reservoir may contribute to PASC pathology, including coagulation, microbiome and neuroimmune abnormalities, are delineated. We identify research priorities to guide the further study of a SARS-CoV-2 reservoir in PASC, with the goal that clinical trials of antivirals or other therapeutics with potential to clear a SARS-CoV-2 reservoir are accelerated.

Analyses of human immune responses to Francisella tularensis identify correlates of protection

Francisella tularensis is the etiological agent of the potentially severe infection tularemia. An existing F: tularensis vaccine, the live vaccine strain (LVS), has been used to protect at-risk personnel, but it is not licensed in any country and it has limited efficacy. Therefore, there is a need of a new, efficacious vaccine. The aim of the study was to perform a detailed analysis of the characteristics of the human immune response to F. tularensis, since this will generate crucial knowledge required to develop new vaccine candidates. Nine individuals were administered the LVS vaccine and peripheral blood mononuclear cells (PBMC) were collected before and at four time points up to one year after vaccination. The properties of the PBMC were characterized by flow cytometry analysis of surface markers and intracellular cytokine staining. In addition, the cytokine content of supernatants from F. tularensis-infected PBMC cultures was determined and the protective properties of the supernatants investigated by adding them to cultures with infected monocyte-derived macrophages (MDM). Unlike before vaccination, PBMC collected at all four time points after vaccination demonstrated F. tularensis-specific cell proliferation, cytokine secretion and cytokine-expressing memory cells. A majority of 17 cytokines were secreted at higher levels by PBMC collected at all time points after vaccination than before vaccination. A discriminative analysis based on IFN-γ and IL-13 secretion correctly classified samples obtained before and after vaccination. Increased expression of IFN-γ, IL-2, and MIP-1β were observed at all time points after vaccination vs. before vaccination and the most significant changes occurred among the CD4 transient memory, CD8 effector memory, and CD8 transient memory T-cell populations. Growth restriction of the highly virulent F. tularensis strain SCHU S4 in MDM was conferred by supernatants and protection correlated to levels of IFN-γ, IL-2, TNF, and IL-17. The findings demonstrate that F. tularensis vaccination induces long-term T-cell reactivity, including TEM and TTM cell populations. Individual cytokine levels correlated with the degree of protection conferred by the supernatants. Identification of such memory T cells and effector mechanisms provide an improved understanding of the protective mechanisms against F. tularensis. mechanisms against F. tularensis.

Regulation of CD8+ T memory and exhaustion by the mTOR signals

CD8+ T cells are the key executioners of the adaptive immune arm, which mediates antitumor and antiviral immunity. Naïve CD8+ T cells develop in the thymus and are quickly activated in the periphery after encountering a cognate antigen, which induces these cells to proliferate and differentiate into effector cells that fight the initial infection. Simultaneously, a fraction of these cells become long-lived memory CD8+ T cells that combat future infections. Notably, the generation and maintenance of memory cells is profoundly affected by various in vivo conditions, such as the mode of primary activation (e.g., acute vs. chronic immunization) or fluctuations in host metabolic, inflammatory, or aging factors. Therefore, many T cells may be lost or become exhausted and no longer functional. Complicated intracellular signaling pathways, transcription factors, epigenetic modifications, and metabolic processes are involved in this process. Therefore, understanding the cellular and molecular basis for the generation and fate of memory and exhausted CD8+ cells is central for harnessing cellular immunity. In this review, we focus on mammalian target of rapamycin (mTOR), particularly signaling mediated by mTOR complex (mTORC) 2 in memory and exhausted CD8+ T cells at the molecular level.

Omicron infection following vaccination enhances a broad spectrum of immune responses dependent on infection history

Pronounced immune escape by the SARS-CoV-2 Omicron variant has resulted in many individuals possessing hybrid immunity, generated through a combination of vaccination and infection. Concerns have been raised that omicron breakthrough infections in triple-vaccinated individuals result in poor induction of omicron-specific immunity, and that prior SARS-CoV-2 infection is associated with immune dampening. Taking a broad and comprehensive approach, we characterize mucosal and blood immunity to spike and non-spike antigens following BA.1/BA.2 infections in triple mRNA-vaccinated individuals, with and without prior SARS-CoV-2 infection. We find that most individuals increase BA.1/BA.2/BA.5-specific neutralizing antibodies following infection, but confirm that the magnitude of increase and post-omicron titres are higher in the infection-naive. In contrast, significant increases in nasal responses, including neutralizing activity against BA.5 spike, are seen regardless of infection history. Spike-specific T cells increase only in infection-naive vaccinees; however, post-omicron T cell responses are significantly higher in the previously-infected, who display a maximally induced response with a highly cytotoxic CD8+ phenotype following their 3rd mRNA vaccine dose. Responses to non-spike antigens increase significantly regardless of prior infection status. These findings suggest that hybrid immunity induced by omicron breakthrough infections is characterized by significant immune enhancement that can help protect against future omicron variants.

Dysregulated Lymphocyte Antigen Receptor Signaling in Common Variable Immunodeficiency with Granulomatous Lymphocytic Interstitial Lung Disease

PURPOSE

A subset of common variable immunodeficiency (CVID) patients either presents with or develops autoimmune and lymphoproliferative complications, such as granulomatous lymphocytic interstitial lung disease (GLILD), a major cause of morbidity and mortality in CVID. While a myriad of phenotypic lymphocyte derangements has been associated with and described in GLILD, defects in T and B cell antigen receptor (TCR/BCR) signaling in CVID and CVID with GLILD (CVID/GLILD) remain undefined, hindering discovery of biomarkers for disease monitoring, prognostic prediction, and personalized medicine approaches.

METHODS

To identify perturbations of immune cell subsets and TCR/BCR signal transduction, we applied mass cytometry analysis to peripheral blood mononuclear cells (PBMCs) from healthy control participants (HC), CVID, and CVID/GLILD patients.

RESULTS

Patients with CVID, regardless of GLILD status, had increased frequency of HLADR+CD4+ T cells, CD57+CD8+ T cells, and CD21lo B cells when compared to healthy controls. Within these cellular populations in CVID/GLILD patients only, engagement of T or B cell antigen receptors resulted in discordant downstream signaling responses compared to CVID. In CVID/GLILD patients, CD21lo B cells showed perturbed BCR-mediated phospholipase C gamma and extracellular signal-regulated kinase activation, while HLADR+CD4+ T cells and CD57+CD8+ T cells displayed disrupted TCR-mediated activation of kinases most proximal to the receptor.

CONCLUSION

Both CVID and CVID/GLILD patients demonstrate an activated T and B cell phenotype compared to HC. However, only CVID/GLILD patients exhibit altered TCR/BCR signaling in the activated lymphocyte subsets. These findings contribute to our understanding of the mechanisms of immune dysregulation in CVID with GLILD.

Cytomegalovirus and Epstein-Barr virus co-infected young and middle-aged adults can have an aging-related T-cell phenotype

Cytomegalovirus (CMV) is known to alter circulating effector memory or re-expressing CD45RA⁺ (TemRA) T-cell numbers, but whether Epstein-Barr virus (EBV) does the same or this is amplified during a CMV and EBV co-infection is unclear. Immune cell numbers in blood of children and young, middle-aged, and senior adults (n = 336) were determined with flow cytometry, and additional multivariate linear regression, intra-group correlation, and cluster analyses were performed. Compared to non-infected controls, CMV-seropositive individuals from all age groups had more immune cell variance, and CMV⁺ EBV^- senior adults had more late-differentiated CD4⁺ and CD8⁺ TemRA and CD4⁺ effector memory T-cells. EBV-seropositive children and young adults had a more equal immune cell composition than non-infected controls, and CMV^- EBV⁺ senior adults had more intermediate/late-differentiated CD4⁺ TemRA and effector memory T-cells than non-infected controls. CMV and EBV co-infected young and middle-aged adults with an elevated BMI and anti-CMV antibody levels had a similar immune cell composition as senior adults, and CMV⁺ EBV⁺ middle-aged adults had more late-differentiated CD8⁺ TemRA, effector memory, and HLA-DR⁺ CD38^- T-cells than CMV⁺ EBV^- controls. This study identified changes in T-cell numbers in CMV- or EBV-seropositive individuals and that some CMV and EBV co-infected young and middle-aged adults had an aging-related T-cell phenotype.

Senescent T cells: Beneficial and detrimental roles

As the thymus involutes during aging, the T-cell pool has to be maintained by the periodic expansion of preexisting T cells during adulthood. A conundrum is that repeated episodes of activation and proliferation drive the differentiation of T cells toward replicative senescence, due to telomere erosion. This review discusses mechanisms that regulate the end-stage differentiation (senescence) of T cells. Although these cells, within both CD4 and CD8 compartments, lose proliferative activity after antigen-specific challenge, they acquire innate-like immune function. While this may confer broad immune protection during aging, these senescent T cells may also cause immunopathology, especially in the context of excessive inflammation in tissue microenvironments.

Human circulating and tissue-resident memory CD8+ T cells

Our current knowledge of human memory CD8⁺ T cells is derived largely from studies of the intravascular space. However, emerging data are starting to challenge some of the dogmas based on this work, suggesting that a conceptual revision may be necessary. In this review, we provide a brief history of the field and summarize the biology of circulating and tissue-resident memory CD8⁺ T cells, which are ultimately responsible for effective immune surveillance. We also incorporate recent findings into a biologically integrated model of human memory CD8⁺ T cell differentiation. Finally, we address how future innovative human studies could improve our understanding of anatomically localized CD8⁺ T cells to inform the development of more effective immunotherapies and vaccines, the need for which has been emphasized by the global struggle to contain severe acute respiratory syndrome coronavirus 2.

Adenoid lymphocyte heterogeneity in pediatric adenoid hypertrophy and obstructive sleep apnea

Introduction

Adenoid hypertrophy is the main cause of obstructive sleep apnea in children. Previous studies have suggested that pathogenic infections and local immune system disorders in the adenoids are associated with adenoid hypertrophy. The abnormalities in the number and function of various lymphocyte subsets in the adenoids may play a role in this association. However, changes in the proportion of lymphocyte subsets in hypertrophic adenoids remain unclear.

Methods

To identify patterns of lymphocyte subsets in hypertrophic adenoids, we used multicolor flow cytometry to analyze the lymphocyte subset composition in two groups of children: the mild to moderate hypertrophy group (n = 10) and the severe hypertrophy group (n = 5).

Results

A significant increase in naïve lymphocytes and a decrease in effector lymphocytes were found in severe hypertrophic adenoids.

Discussion

This finding suggests that abnormal lymphocyte differentiation or migration may contribute to the development of adenoid hypertrophy. Our study provides valuable insights and clues into the immunological mechanism underlying adenoid hypertrophy.

The effects of exercise training for eight weeks on immune cell characteristics among breast cancer survivors

Methods

This study examined the effects of exercise training for 8 weeks on blood immune cell characteristics among 20 breast cancer survivors (age 56 ± 6 years, Body Mass Index 25.4 ± 3.0 kg m2) within two years of treatment. Participants were randomly allocated to a partly-supervised or a remotely-supported exercise group (n = 10 each). The partly supervised group undertook 2 supervised (laboratory-based treadmill walking and cycling) and 1 unsupervised session per week (outdoor walking) progressing from 35 to 50 min and 55% to 70% V˙O2max. The remotely-supported group received weekly exercise/outdoor walking targets (progressing from 105 to 150 min per week 55% to 70% V˙O2max) via weekly telephone calls discussing data from a fitness tracker. Immune cell counts were assessed using flow cytometry: CD4+ and CD8+ T cells (Naïve, NA; Central memory, CM; and Effector cells, EM and EMRA; using CD27/CD45RA), Stem cell-like memory T cells (TSCMs; using CD95/CD127), B cells (plasmablasts, memory, immature and naïve cells using CD19/CD27/CD38/CD10) and Natural Killer cells (effector and regulatory cells, using CD56/CD16). T cell function was assessed by unstimulated HLA-DR expression or interferon gamma (IFN-γ) production with Enzyme-linked ImmunoSpot assays following stimulation with virus or tumour-associated antigens.

Results

Total leukocyte counts, lymphocytes, monocytes and neutrophils did not change with training (p > 0.425). Most CD4+ and CD8+ T cell subtypes, including TSCMs, and B cell and NK cell subtypes did not change (p > 0.127). However, across groups combined, the CD4+ EMRA T cell count was lower after training (cells/µl: 18 ± 33 vs. 12 ± 22, p = 0.028) and these cells were less activated on a per cell basis (HLA-DR median fluorescence intensity: 463 ± 138 vs. 420 ± 77, p = 0.018). Furthermore, the partly-supervised group showed a significant decrease in the CD4+/CD8+ ratio (3.90 ± 2.98 vs. 2.54 ± 1.29, p = 0.006) and a significant increase of regulatory NK cells (cells/µl: 16 ± 8 vs. 21 ± 10, p = 0.011). T cell IFN-γ production did not change with exercise training (p > 0.515).

Discussion

In summary, most immune cell characteristics are relatively stable with 8 weeks of exercise training among breast cancer survivors. The lower counts and activation of CD4+ EMRA T cells, might reflect an anti-immunosenescence effect of exercise.

Deletion of MIF gene from live attenuated LdCen-/- parasites enhances protective CD4+ T cell immunity

Vaccination with live attenuated Leishmania parasites such as centrin deleted Leishmania donovani (LdCen^-/-) against visceral leishmaniasis has been reported extensively. The protection induced by LdCen^-/- parasites was mediated by both CD4⁺ and CD8⁺ T cells. While the host immune mediators of protection are known, parasite determinants that affect the CD4⁺ and CD8⁺ T cell populations remain unknown. Parasite encoded inflammatory cytokine MIF has been shown to modulate the T cell differentiation characteristics by altering the inflammation induced apoptosis during contraction phase in experimental infections with Leishmania or Plasmodium. Neutralization of parasite encoded MIF either by antibodies or gene deletion conferred protection in Plasmodium and Leishmania studies. We investigated if the immunogenicity and protection induced by LdCen^-/- parasites is affected by deleting MIF genes from this vaccine strain. Our results showed that LdCen^-/-MIF^-/- immunized group presented higher percentage of CD4⁺ and CD8⁺ central memory T cells, increased CD8⁺ T cell proliferation after challenge compared to LdCen^-/- immunization. LdCen^-/-MIF^-/- immunized group presented elevated production of IFN-γ⁺ and TNF-α⁺ CD4⁺ T cells concomitant with a reduced parasite load in spleen and liver compared to LdCen^-/-group following challenge with L. infantum. Our results demonstrate the role of parasite induced factors involved in protection and long-term immunity of vaccines against VL.

CD38: an ecto-enzyme with functional diversity in T cells

CD38, a nicotinamide adenine dinucleotide (NAD)+ glycohydrolase, is considered an activation marker of T lymphocytes in humans that is highly expressed during certain chronic viral infections. T cells constitute a heterogeneous population; however, the expression and function of CD38 has been poorly defined in distinct T cell compartments. We investigated the expression and function of CD38 in naïve and effector T cell subsets in the peripheral blood mononuclear cells (PBMCs) from healthy donors and people with HIV (PWH) using flow cytometry. Further, we examined the impact of CD38 expression on intracellular NAD+ levels, mitochondrial function, and intracellular cytokine production in response to virus-specific peptide stimulation (HIV Group specific antigen; Gag). Naïve T cells from healthy donors showed remarkably higher levels of CD38 expression than those of effector cells with concomitant reduced intracellular NAD+ levels, decreased mitochondrial membrane potential and lower metabolic activity. Blockade of CD38 by a small molecule inhibitor, 78c, increased metabolic function, mitochondrial mass and mitochondrial membrane potential in the naïve T lymphocytes. PWH exhibited similar frequencies of CD38+ cells in the T cell subsets. However, CD38 expression increased on Gag-specific IFN-γ and TNF-α producing cell compartments among effector T cells. 78c treatment resulted in reduced cytokine production, indicating its distinct expression and functional profile in different T cell subsets. In summary, in naïve cells high CD38 expression reflects lower metabolic activity, while in effector cells it preferentially contributes to immunopathogenesis by increasing inflammatory cytokine production. Thus, CD38 may be considered as a therapeutic target in chronic viral infections to reduce ongoing immune activation.

Extremely Differentiated T Cell Subsets Contribute to Tissue Deterioration During Aging

There is a dramatic remodeling of the T cell compartment during aging. The most notorious changes are the reduction of the naive T cell pool and the accumulation of memory-like T cells. Memory-like T cells in older people acquire a phenotype of terminally differentiated cells, lose the expression of costimulatory molecules, and acquire properties of senescent cells. In this review, we focus on the different subsets of age-associated T cells that accumulate during aging. These subsets include extremely cytotoxic T cells with natural killer properties, exhausted T cells with altered cytokine production, and regulatory T cells that gain proinflammatory features. Importantly, all of these subsets lose their lymph node homing capacity and migrate preferentially to nonlymphoid tissues, where they contribute to tissue deterioration and inflammaging.