Jain, Abhinav

Abstract Introduction The ability of the adaptive immune system to have memory of previous pathogen encounters is the basis for vaccination as one of the most successful medical interventions. With increasing age, the ability to develop protective immunity after vaccination declines. Differentiation into T memory cells is at least in part determined during the early cell divisions after activation when cells undergo assymmetric cell division (ACD). Fate decisions depend on the uneven distribution of signaling molecules and transcription factors with accumulation of mTORC1 activity biasing for an effector and TCF1 for a memory state. We explored whether ACD of naïve CD4 T cells is impaired in older adults. Methods We used human primary cells from young and older adults. Human naive CD4 T cells were isolated and cultured in RPMI, 10% FBS and antibiotics on plates coated with anti-CD3 Ab, anti-CD28 Ab and huICAM1 for 3 days. We used transfection by electroporation to modify gene expression. Read out systems included confocal microscopy, flow cytometry and lysosome function assays. Results were compared by t-test with values of p < 0.05 considered significant. Results Naive CD4 T cell responses from older adults is characterized by increased activation of the AKT-mTORC1 pathway and reduced ACD of mTORC1 activity. Increased RICTOR expression resulting in increased mTORC2 activity in naive CD4 T cells from older individuals accounted for the activation of the AKT-mTORC1 pathway. AKT inhibition or silencing of RICTOR restores ACD of mTORC1 activity as well as of TCF1. Conversely, ACD was also improved through inducing WNT signaling by GSK3β inhibition irrespective of RICTOR expression. Conclusion Our data show that increased RICTOR expression in naïve T cells from older adults at least in part accounts for defective memory cell generation. Silencing of RICTOR or downstream AKT inhibition can enforce both mTORC1 ACD and TCF1 ACD suggesting that mTORC2 is a promising target to improve vaccine responses. Funding Source n/a Topic Categories Lymphocyte Differentiation and Peripheral Maintenance (LYM)

Older adults are susceptible to infections in part due to waning of immune memory. To uncover mechanisms of a long-lasting immune memory, we contrasted varicella zoster virus antigen–specific memory T cell responses in adults vaccinated at young (<20 years) or older age (>50 years) with a live-attenuated vaccine conferring durable protection only when given at young age or with an adjuvanted component vaccine eliciting long-lasting immunity in older adults. Unlike VZV-specific CD4 + T cells, CD8 + T cells exhibited profound age-sensitive changes including memory subset shifts, reduced T cell receptor diversity, and loss of stem-like features. Vaccination of older adults with the adjuvanted vaccine did not restore CD8 + defects but selectively enhanced T helper 17 (T H 17) CD4 + T cells and prevented their conversion into regulatory T cells, likely through lipid metabolic regulation. Thus, durable vaccine efficacy with aging relies on antigen-specific T H 17 cells that compensate for CD8 + T cell defects.

Abstract Description The two key determinants of successful vaccines are the ability to induce a protective immune response and a long-lived immune memory. The mechanism determining durability and its contribution to the lower vaccine efficacy in older adults is elusive. We use varicella zoster virus (VZV) vaccination as a model that relies on cellular, not humoral immunity. We compared long-lived antigen-specific memory T cells in adults who were vaccinated at young (&lt;20 years) or older age (&gt;50 years) with a life-attenuated vaccine that confers sustained protection only in young age, or who received an adjuvanted subunit vaccine that is protective at older age. We stimulated PBMCs of vaccine recipients years after vaccination and collected VZV-reactive T cells for spectral flow cytometry and single-cell sequencing. While CD4 T cells were resilient to aging, VZV-specific CD8 T cells lost diversity and lacked stem-like features while gaining end-differentiated, NK-like signatures. These age-associated changes in CD8 T cells were not reversed with the effective subunit vaccine. Instead, this vaccine induced pro-inflammatory VZV-specific TH17 cells. TH17 cells in the less efficient vaccine response, albeit present, were skewed towards a FOXP3+ regulatory phenotype and deficient in TH1 polyfunctionality – a phenotypic shift that is in part controlled by lipid metabolic pathways. Our study uncovers traits of T cell dysfunction with age and informs vaccination efforts tailored towards healthy aging. Funding Sources NIH U19AI057266, R01AG045779, R01AI108891, R01AI129191, T32AG049672, Glenn Foundation for Medical Research Postdoctoral Fellowship, Robert and Arlene Kogod Center on Aging Career Development Award. Topic Categories Lymphocyte Differentiation and Peripheral Maintenance (LYM)

ABSTRACT Older adults are susceptible to infections, in part due to waning of immune memory. To determine mechanisms that determine long-lasting versus short-term immunity, we examined varicella zoster virus (VZV) vaccination as a model system. We contrasted VZV antigen-specific T cells several years after vaccination in adults who had been vaccinated at young (<20 years) or older age (>50 years) with a live-attenuated vaccine that confers durable protection only when given at young age, or with an adjuvanted VZV component vaccine that elicits effective, long-lasting immunity in older adults. CD8 + T cells were highly sensitive to age-related changes showing T cell subset shifts, loss in TCR diversity and reduced stem-like features while gaining NK-like signatures without evidence for cellular senescence or exhaustion. VZV-specific CD4 + T cells were largely resilient to age and maintained phenotypic and TCR diversity. Immunization of older adults with the adjuvanted VZV vaccine did not reverse age-associated defects in CD8 + T cells. Instead, it selectively improved the functionality of VZV-specific Th17 CD4 + T cells and prevented their acquisition of Treg features, likely as consequence of lipid metabolic pathways. Collectively, our data indicate that effective vaccination in older adults is supported by the generation of a durable, antigen-specific CD4 + Th17 population that resists mis-differentiation into Tregs and that compensates for age-related defects in CD8 + T cells. One sentence summary Aging primarily impairs the CD8 + T cell VZV vaccine response, while effective VZV vaccination in older adults induces antigen-specific Th17 CD4 + T cells to compensate for aging defects.

Abstract Generation of a protective and long-lasting immune memory is central to effective vaccination strategies and healthy aging. However, age-associated changes in immune cells, particularly T cells, impair immune memory generation and maintenance rendering older adults vulnerable to infectious diseases. Here, we investigated signatures of age-related memory T cell dysfunction and uncovered molecular determinants of a protective, persistent T cell memory in older individuals. We leveraged the contrasting T cell memory elicited in younger (&lt;30 years) and older adults (&gt;55 years) by vaccination against varicella zoster virus (VZV). Using ex vivo peptide stimulation of peripheral blood mononuclear cells of vaccine recipients several years after vaccination, we collected antigen-specific CD4+ and CD8+ T cells for high-dimensional spectral flow cytometry and tri-modal single-cell sequencing analyses. We found that older vaccine recipients predominantly suffer from a quantitatively and qualitatively impaired CD8+ T cell memory response compared to younger adults receiving the same vaccine type. Conversely, comparisons of two VZV vaccine strategies with contrasting efficacies in older adults demonstrated that a CD4+ T cell response rich in self-renewing Th17-like and low in regulatory T cells overcomes the age-associated T cell memory defect and associates with a durable, protective T cell memory. Collectively, we propose that vaccine strategies targeted towards older adults benefit from a Th17-focused CD4+ T cell memory response. Our results not only uncover traits of immune cell dysfunction with aging, but also inform vaccination efforts tailored towards healthy aging.

IgG4-related disease (IgG4-RD) is a systemic immune-mediated fibroinflammatory disease whose pathomechanisms remain poorly understood. Here, we identified gene variants in familial IgG4-RD and determined their functional consequences. All 3 affected members of the family shared variants of the transcription factor IKAROS, encoded by IKZF1 , and the E3 ubiquitin ligase UBR4. The IKAROS variant increased binding to the FYN promoter, resulting in higher transcription of FYN in T cells. The UBR4 variant prevented the lysosomal degradation of the phosphatase CD45. In the presence of elevated FYN, CD45 functioned as a positive regulatory loop, lowering the threshold for T cell activation. Consequently, T cells from the affected family members were hyperresponsive to stimulation. When transduced with a low-avidity, autoreactive T cell receptor, their T cells responded to the autoantigenic peptide. In parallel, high expression of FYN in T cells biased their differentiation toward Th2 polarization by stabilizing the transcription factor JunB. This bias was consistent with the frequent atopic manifestations in patients with IgG4-RD, including the affected family members in the present study. Building on the functional consequences of these 2 variants, we propose a disease model that is not only instructive for IgG4-RD but also for atopic diseases and autoimmune diseases associated with an IKZF1 risk haplotype.

The human adult immune system maintains normal T cell counts and compensates for T cell loss throughout life, mainly through peripheral homeostatic proliferation after the ability of the thymus to generate new T cells has rapidly declined at adolescence. This process is mainly driven by STAT5-activating cytokines, most importantly IL-7, and is very effective in maintaining a large naive CD4 + T cell compartment into older age. Here, we describe that naive CD4 + T cells undergo adaptations to optimize IL-7 responses by upregulating the guanine-nucleotide exchange factor PREX1 in older age. PREX1 promotes nuclear translocation of phosphorylated STAT5, thereby supporting homeostatic proliferation in response to IL-7. Through the same mechanism, increased expression of PREX1 also biases naive cells to differentiate into effector T cells. These findings are consistent with the concept that primarily beneficial adaptations during aging, i.e., improved homeostasis, account for unfavorable functions of the aged immune system, in this case biased differentiation.

Autoimmune vasculitis of the medium and large elastic arteries can cause blindness, stroke, aortic arch syndrome, and aortic aneurysm. The disease is often refractory to immunosuppressive therapy and progresses over decades as smoldering aortitis. How the granulomatous infiltrates in the vessel wall are maintained and how tissue-infiltrating T cells and macrophages are replenished are unknown. Single-cell and whole-tissue transcriptomic studies of immune cell populations in vasculitic arteries identified a CD4 + T cell population with stem cell–like features. CD4 + T cells supplying the tissue-infiltrating and tissue-damaging effector T cells survived in tertiary lymphoid structures around adventitial vasa vasora, expressed the transcription factor T cell factor 1 (TCF1), had high proliferative potential, and gave rise to two effector populations, Eomesodermin (EOMES) + cytotoxic T cells and B cell lymphoma 6 (BCL6) + T follicular helper-like cells. TCF1 hi CD4 + T cells expressing the interleukin 7 receptor (IL-7R) sustained vasculitis in serial transplantation experiments. Thus, TCF1 hi CD4 + T cells function as disease stem cells and promote chronicity and autonomy of autoimmune tissue inflammation. Remission-inducing therapies will require targeting stem-like CD4 + T cells instead of only effector T cells.