National Institute on Aging's 50th anniversary: Advancing aging research and the health and well-being of older adults.

The National Institute on Aging (NIA), part of the National Institutes of Health (NIH), was founded in 1974 to support and conduct research on aging and the health and well-being of older adults. Fifty years ago, the concept of studying aging generated much skepticism. Early NIA-funded research findings helped establish the great value of aging research and provided the foundation for significant science advances that have improved our understanding of the aging process, diseases and conditions associated with aging, and the effects of health inequities, as well as the need to promote healthy aging lifestyles. Today, we celebrate the many important contributions to aging research made possible by NIA, as well as opportunities to continue to make meaningful progress. NIA emphasizes that the broad aging research community must continue to increase and expand our collective efforts to recruit and train a diverse next generation of aging researchers.

TRAF6 and TRAF2/3 Binding Motifs in CD40 Differentially Regulate B Cell Function in T-Dependent Antibody Responses and Dendritic Cell Function in Experimental Autoimmune Encephalomyelitis.

Expression of the costimulatory molecule CD40 on both B cells and dendritic cells (DCs) is required for induction of experimental autoimmune encephalomyelitis (EAE), and cell-autonomous CD40 expression on B cells is required for primary T-dependent (TD) Ab responses. We now ask whether the function of CD40 expressed by different cell types in these responses is mediated by the same or different cytoplasmic domains. CD40 has been reported to possess multiple cytoplasmic domains, including distinct TRAF6 and TRAF2/3 binding motifs. To elucidate the in vivo function of these motifs in B cells and DCs involved in EAE and TD germinal center responses, we have generated knock-in mice containing distinct CD40 cytoplasmic domain TRAF-binding site mutations and have used these animals, together with bone marrow chimeric mice, to assess the roles that these motifs play in CD40 function. We found that both TRAF2/3 and TRAF6 motifs of CD40 are critically involved in EAE induction and demonstrated that this is mediated by a role of both motifs for priming of pathogenic T cells by DCs. In contrast, the TRAF2/3 binding motif, but not the TRAF6 binding motif, is required for B cell CD40 function in TD high-affinity Ab responses. These data demonstrate that the requirements for expression of specific TRAF-binding CD40 motifs differ for B cells or DCs that function in specific immune responses and thus identify targets for intervention to modulate these responses.

CD40 Drives Central Nervous System Autoimmune Disease by Inducing Complementary Effector Programs via B Cells and Dendritic Cells.

Costimulatory CD40 plays an essential role in autoimmune diseases, including experimental autoimmune encephalomyelitis (EAE), a murine model of human multiple sclerosis (MS). However, how CD40 drives autoimmune disease pathogenesis is not well defined. Here, we used a conditional knockout approach to determine how CD40 orchestrates a CNS autoimmune disease induced by recombinant human myelin oligodendrocyte glycoprotein (rhMOG). We found that deletion of CD40 in either dendritic cells (DCs) or B cells profoundly reduced EAE disease pathogenesis. Mechanistically, CD40 expression on DCs was required for priming pathogenic Th cells in peripheral draining lymph nodes and promoting their appearance in the CNS. By contrast, B cell CD40 was essential for class-switched MOG-specific Ab production, which played a crucial role in disease pathogenesis. In fact, passive transfer of MOG-immune serum or IgG into mice lacking CD40 on B cells but not DCs reconstituted autoimmune disease, which was associated with inundation of the spinal cord parenchyma by Ig and complement. These data demonstrate that CD40 supports distinct effector programs in B cells and DCs that converge to drive a CNS autoimmune disease and identify targets for intervention.

Antigen-presenting T cells provide critical B7 co-stimulation for thymic iNKT cell development via CD28-dependent trogocytosis.

Invariant natural killer T (iNKT) cell development in the thymus depends on T cell receptor recognition of CD1d ligand on CD4/CD8 double-positive thymocytes. We previously reported that B7-CD28 co-stimulation is required for thymic iNKT cell development, but the cellular and molecular mechanisms underlying this co-stimulatory requirement are not understood. Here we report that CD28 expression on CD1d-expressing antigen-presenting T cells is required for thymic iNKT cell development. Mechanistically, antigen-presenting T cells provide co-stimulation through an unconventional mechanism, acquiring B7 molecules via CD28-dependent trogocytosis from B7-expressing thymic epithelial cells, dendritic cells, and B cells and providing critical B7 co-stimulation to developing iNKT cells. Thus, the present study demonstrates a mechanism of B7 co-stimulation in thymic T cell development by antigen-presenting T cells.

Needs Assessment and Best Practices for Digital Trainings for Health Professionals in Ethiopia Using the RE-AIM Framework: COVID-19, Case Study.

OBJECTIVES: This study is aimed to assess the implementation science outcomes of the coronavirus disease (COVID-19) e-health educational intervention in Ethiopia targeting health care workers via the RE-AIM (Reach, Effectiveness, Adaption, Implementation, Maintenance) framework. METHODS: A series of three 1-hour medical seminars focused on COVID-19 prevention and treatment education were conducted between May and August 2020. Educational content was built from medical sites previously impacted by COVID-19. Post-seminar evaluation information was collected from physician and other participants by a survey instrument. Cross-sectional evaluation results are reported here by RE-AIM constructs. RESULTS: The medical seminars reached 324 participants. Key success metrics include that 90% reporting the information delivered in a culturally sensitive/tailored manner (effectiveness), 80% reporting that they planned to share the information presented with someone else (adoption and implementation), and 64% reporting using information presented in their daily clinical responsibilities 6 months after the first medical seminars (maintenance). CONCLUSION: Grounded in a theoretical framework and following evidence-based best practices, this intervention advances the field of dissemination and implementation science by demonstrating how to transition health care training and delivery from an in-person to digital medium in low-resource settings like Ethiopia.

B7-CD28 co-stimulation modulates central tolerance via thymic clonal deletion and Treg generation through distinct mechanisms.

The molecular and cellular mechanisms mediating thymic central tolerance and prevention of autoimmunity are not fully understood. Here we show that B7-CD28 co-stimulation and B7 expression by specific antigen-presenting cell (APC) types are required for clonal deletion and for regulatory T (Treg) cell generation from endogenous tissue-restricted antigen (TRA)-specific thymocytes. While B7-CD28 interaction is required for both clonal deletion and Treg induction, these two processes differ in their CD28 signaling requirements and in their dependence on B7-expressing dendritic cells, B cells, and thymic epithelial cells. Meanwhile, defective thymic clonal deletion due to altered B7-CD28 signaling results in the accumulation of mature, peripheral TRA-specific T cells capable of mediating destructive autoimmunity. Our findings thus reveal a function of B7-CD28 co-stimulation in shaping the T cell repertoire and limiting autoimmunity through both thymic clonal deletion and Treg cell generation.

A Blueprint for Characterizing Senescence.

Given the heterogeneity of senescent cells, our knowledge of both the drivers and consequences of cellular senescence in tissues and organs remains limited, as is our understanding of how this process could be harnessed for human health. Here we identified five broad areas that would help propel the field forward.

National Institutes of Health social and behavioral research in response to the SARS-CoV2 Pandemic.

The COVID-19 pandemic has been mitigated primarily using social and behavioral intervention strategies, and these strategies have social and economic impacts, as well as potential downstream health impacts that require further study. Digital and community-based interventions are being increasingly relied upon to address these health impacts and bridge the gap in health care access despite insufficient research of these interventions as a replacement for, not an adjunct to, in-person clinical care. As SARS-CoV-2 testing expands, research on encouraging uptake and appropriate interpretation of these test results is needed. All of these issues are disproportionately impacting underserved, vulnerable, and health disparities populations. This commentary describes the various initiatives of the National Institutes of Health to address these social, behavioral, economic, and health disparities impacts of the pandemic, the findings from which can improve our response to the current pandemic and prepare us better for future infectious disease outbreaks.

TCR Repertoires of Thymic Conventional and Regulatory T Cells: Identification and Characterization of Both Unique and Shared TCR Sequences.

Thymic regulatory T cells (tTreg) are critical in the maintenance of normal T cell immunity and tolerance. The role of TCR in tTreg selection remains incompletely understood. In this study, we assessed TCRα and TCRß sequences of mouse tTreg and thymic conventional CD4+ T cells (Tconv) by high-throughput sequencing. We identified αß TCR sequences that were unique to either tTreg or Tconv and found that these were distinct as recognized by machine learning algorithm and by preferentially used amino acid trimers in αß CDR3 of tTreg. In addition, a proportion of αß TCR sequences expressed by tTreg were also found in Tconv, and machine learning classified the great majority of these shared αß TCR sequences as characteristic of Tconv and not tTreg. These findings identify two populations of tTreg, one in which the regulatory T cell fate is associated with unique properties of the TCR and another with TCR properties characteristic of Tconv for which tTreg fate is determined by factors beyond TCR sequence.

Transient induction of telomerase expression mediates senescence and reduces tumorigenesis in primary fibroblasts.

Telomerase is an enzymatic ribonucleoprotein complex that acts as a reverse transcriptase in the elongation of telomeres. Telomerase activity is well documented in embryonic stem cells and the vast majority of tumor cells, but its role in somatic cells remains to be understood. Here, we report an unexpected function of telomerase during cellular senescence and tumorigenesis. We crossed Tert heterozygous knockout mice (mTert+/- ) for 26 generations, during which time there was progressive shortening of telomeres, and obtained primary skin fibroblasts from mTert+/+ and mTert-/- progeny of the 26th cross. As a consequence of insufficient telomerase activities in prior generations, both mTert+/+ and mTert-/- fibroblasts showed comparable and extremely short telomere length. However, mTert-/- cells approached cellular senescence faster and exhibited a significantly higher rate of malignant transformation than mTert+/+ cells. Furthermore, an evident up-regulation of telomerase reverse-transcriptase (TERT) expression was detected in mTert+/+ cells at the presenescence stage. Moreover, removal or down-regulation of TERT expression in mTert+/+ and human primary fibroblast cells via CRISPR/Cas9 or shRNA recapitulated mTert-/- phenotypes of accelerated senescence and transformation, and overexpression of TERT in mTert-/- cells rescued these phenotypes. Taking these data together, this study suggests that TERT has a previously underappreciated, protective role in buffering senescence stresses due to short, dysfunctional telomeres, and preventing malignant transformation.

Telomere Shortening, Inflammatory Cytokines, and Anti-Cytomegalovirus Antibody Follow Distinct Age-Associated Trajectories in Humans.

A number of biological parameters have been cited as hallmarks of immune aging. However, it is not clear whether these multiple biological changes are the result of common underlying aging processes and follow correlated trajectories, or whether the patterns of change for multiple parameters vary across individuals and reflect heterogeneity in the aging process. Here, we have studied parameters of immune system aging through longitudinal analysis of telomere length, inflammatory cytokines, and antibody titer to cytomegalovirus (CMV) in 465 subjects ranging in age from 21 to 88 years at the first visit, with an average of 13 years (7-19 years) follow-up. We observed a highly variable rate of change in telomere length of PBMCs with a relatively slow average rate of telomere shortening (-16 bp/year). Similarly, there were significant increases with age in vivo in three inflammation-related cytokines (interferon gamma, IL-6, and IL-10) and in anti-CMV IgG titer, which varied widely across individuals as well. We further observed positive correlative changes among different inflammatory cytokines. However, we did not find significant correlations among the rate of changes in telomere length, inflammatory cytokines, and anti-CMV IgG titers. Our findings thus reveal that age-related trajectories of telomere attrition, elevated circulating inflammatory cytokines, and anti-CMV IgG are independent and that aging individuals do not show a uniform pattern of change in these variables. Immune aging processes are complex and vary across individuals, and the use of multiple biomarkers is essential to evaluation of biological aging of the immune system.

Aging Research: Collaborations Forge a Promising Future.

The National Institute on Aging (NIA), one of 27 institutes and centers at the National Institutes of Health (NIH), was founded in 1974 to conduct and support research on aging and the health and well-being of older people. The Institute's interests span the fundamental processes that contribute to aging and their impact on systems; diseases and conditions for which aging is a risk factor; and interventions that may prevent, delay, or treat these conditions or otherwise contribute to an extension of healthy, active years of life. Multiple fruitful research collaborations within and outside the federal government, spanning the breadth of the Institute's research activities, have marked NIA's growth over the past 40 years, as well as its current areas of ongoing research. This article discusses several highlights of these collaborations, including the Health and Retirement Study, geroscience research, falls injury prevention in elderly adults, and implementation of the National Plan to Address Alzheimer's Disease, from the perspective of past accomplishments and trends for the future.