Mu, Yunmei

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 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.

The ectonucleotidase CD39 functions as a checkpoint in purinergic signaling on effector T cells. By depleting eATP and initiating the generation of adenosine, it impairs memory cell development and contributes to T cell exhaustion, thereby causing defective tumor immunity and deficient T cell responses in older adults who have increased CD39 expression. Tuning enzymatic activity of CD39 and targeting the transcriptional regulation of ENTPD1 can be used to modulate purinergic signaling. Here, we describe that STAT6 phosphorylation downstream of IL-4 signaling represses CD39 expression on activated T cells by inducing a transcription factor network including GATA3, GFI1, and YY1. GATA3 suppresses ENTPD1 transcription through prevention of RUNX3 recruitment to the ENTPD1 promoter. Conversely, pharmacological STAT6 inhibition decreases T cell effector functions via increased CD39 expression, resulting in the defective signaling of P2X receptors by ATP and stimulation of A2A receptors by adenosine. Our studies suggest that inhibiting the STAT6 pathway to increase CD39 expression has the potential to treat autoimmune disease while stimulation of the pathway could improve T cell immunity.