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Open Access Publications from the University of California

Scholarly Works (13 results)

  • Article
  • Peer Reviewed
UCLA Previously Published Works (2016)
Human cytomegalovirus (CMV), the prototypical β-herpervirus, is a widespread pathogen that establishes a lifelong latent infection in myeloid progenitor, and possibly other cells as well. Although immunocompetent individuals show mild or no symptoms despite periodic reactivation during myeloid cell differentiation, CMV is responsible for considerable morbidity and mortality in older adults and in persons chronically infected with HIV. Indeed, in these individuals, reactivation of CMV can cause serious complications. This review will focus of the effects of CMV during aging and HIV/AIDS, with particular attention to the cellular immunity and age-related pathology outcomes from this persistent infection. The impact of the long-term chronic exposure to CMV antigens on the expansion of CD8 T cells with features of replicative senescence will be highlighted.
    Cover page: The silent war of CMV in aging and HIV infection
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2005)
    Roy Walford died on April 27, 2004, at the age of 79. His contributions to gerontological research in such diverse areas as caloric restriction, genetics of lifespan, immunosenescence, DNA repair and replicative senescence were truly remarkable in their depth and innovation. Significantly, most of the areas that he pioneered during his illustrious research career remain the "hot" areas of current gerontological research. In this sense, he has achieved the most important type of immortality. His death was a major personal and professional loss to numerous scientists within the gerontological community. In launching this new journal on Immunity and Ageing, it is highly fitting, therefore, to remember him on the anniversary of his death by briefly reviewing the contributions of Roy Walford to this important facet of gerontology. Indeed, it was Roy who actually first coined the commonly used term "immunosenescence".
      Cover page: Roy Walford and the immunologic theory of aging
      • Thesis
      • Peer Reviewed
      UCLA Electronic Theses and Dissertations (2014)

      A hallmark of age-related immunosenescence is the accumulation of late-differentiated memory CD8 T cells in peripheral blood with features of replicative senescence, such as inability to proliferate, absence of CD28 expression, shortened telomeres, loss of telomerase activity, enhanced activation, and increased secretion of inflammatory cytokines. Oligoclonal expansions of these late-differentiated memory CD8 T cells in peripheral blood are correlated with increased risk of morbidity and mortality in elderly humans. The studies described in this thesis focus on furthering our understanding of CD8 T cell replicative senescence in humans and its relationship to aging and HIV disease, with special emphasis on immune features of gut-associated lymphoid tissue (GALT), which contains 40-65% of lymphocytes (as opposed to peripheral blood, which houses only 2%) and is an area of high antigenic exposure.

      We first review the data for CD8 T cell replicative senescence in peripheral blood. This includes a comprehensive discussion of experiments defining the phenotype and function of senescent cells in vitro. We then present evidence that CD8 T cell replicative senescence occurs in vivo, and discuss how senescent cells contribute to, and are affected by, dysregulated immunity in aging and HIV disease, ultimately contributing towards "inflammaging" and an immune risk phenotype (IRP) predictive of morbidity and mortality. We next move the focus of our studies to the GALT and compare blood and gut (specifically rectosigmoid colon) CD8 T cells, focusing on age-related phenotypic and functional alterations previously linked to senescence in peripheral blood. Overall, our results support the hypothesis that gut CD8 T cells have profiles suggestive of greater "aging" than those in peripheral blood. These results include a significant increase in RA-CD8+ (memory), CD28-CD8+ (differentiated), RA-CD28-CD8+ (differentiated memory), DR+CD38+CD8+ (activated), CD8 &alpha/&alpha, RO+PD-1+CD8+, and a (non-significant) decrease in baseline telomerase activity. However, other criteria from this study (lower levels of CD57 expression, lack of inverted CD4:CD8 ratio, increase in KI-67 (proliferation) expression, and proliferative potential that is similar to blood) suggest that gut CD8 T cells may not be more senescent than peripheral blood. Our data suggest that additional work (such as looking at CD4 cells, other regions of the gut, and CD8 T cell gut senescence in aging and HIV disease) is needed to further elucidate this relationship. We then describe the development and optimization of a novel protocol to test our hypothesis of compartment-specific differences of in vitro proliferative dynamics of CD8 T cells. The protocol involves a 5 day culture of mononuclear leukocyte populations from blood and gut, respectively, labeled with CFSE and BrdU and stimulated with anti-CD2/3/28-linked microbeads. The specific experimental variables we have optimized include: mode of T cell stimulation, CFSE concentration, inclusion of second proliferation marker BrdU, culture duration, initial cell concentration and inclusion of autologous irradiated feeder cells. Finally, we transition back to peripheral blood in order to examine a link between peripheral blood T cell senescence and a mild presentation of Kaposi's sarcoma in treated HIV-infected subjects with long-term suppression of HIV replication. This study indicates these subjects exhibit some features of immunosenescence relative to treated controls without sarcoma (increased frequency of CD57+ and CD28- CD4 and CD8 T cells, decreased proportion of naïve CD27+CD28+CD45RA+ CD4 and CD8 cells, increased expression of CCR5 in CD4 and CD8 T cells), indicating immunologic perturbations associated with immune senescence might be casually associated with development of this disease. Together, results from this research further our understanding of CD8 T cell senescence, especially in the rectosigmoid colon region of the GALT, and pave the way for further research elucidating the relationship of CD8 T cell immunosenescence and pathologies such as aging, HIV disease and Kaposi's sarcoma.

        Cover page: Beyond blood: expanding immune studies to the human gut
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2010)
        CD28 costimulatory signal transduction in T lymphocytes is essential for optimal telomerase activity, stabilization of cytokine mRNAs, and glucose metabolism. During aging and chronic infection with HIV-1, there are increased proportions of CD8 T lymphocytes that lack CD28 expression and show additional features of replicative senescence. Moreover, the abundance of these cells correlates with decreased vaccine responsiveness, early mortality in the very old, and accelerated HIV disease progression. Here, we show that sustained expression of CD28, via gene transduction, retards the process of replicative senescence, as evidenced by enhanced telomerase activity, increased overall proliferative potential, and reduced secretion of pro-inflammatory cytokines. Nevertheless, the transduced cultures eventually do reach senescence, which is associated with increased CTLA-4 gene expression and a loss of CD28 cell surface expression. These findings further elucidate the central role of CD28 in the replicative senescence program, and may ultimately lead to novel therapies for diseases associated with replicative senescence.
          Cover page: Sustained CD28 Expression Delays Multiple Features of Replicative Senescence in Human CD8 T Lymphocytes
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2013)
          Clinical evaluation of immune reconstitution and health status during HIV-1 infection and anti-retroviral therapy (ART) is largely based on CD4+ T cell counts and viral load, measures that fail to take into account the CD8+ T cell subset, known to show features of accelerated aging in HIV disease. Here, we compare adenosine deaminase (ADA), glucose uptake receptor 1 (GLUT1), and leucine-rich repeat neuronal 3 (LRRN3) to CD38 expression and telomerase activity, two strong predictors of HIV disease progression. Our analysis revealed that reduced ADA, telomerase activity and LRRN3 gene expression were significantly associated with high CD38 and HLA-DR in CD8+ T cells, with % ADA+ cells being the most robust predictor of CD8+ T cell activation. Our results suggest that ADA, LRRN3 and telomerase activity in CD8+ T cells may serve as novel, clinically relevant biomarkers of immune status in HIV-1 infection, specifically by demonstrating the degree to which CD8+ T cells have progressed to the end stage of replicative senescence. Since chronological aging itself leads to the accumulation of senescent CD8+ T cells, the prolonged survival and resultant increased age of the HIV+ population may synergize with the chronic immune activation to exacerbate both immune decline and age-associated pathologies. The identification and future validation of these new biomarkers may lead to fresh immune-based HIV treatments.
            Cover page: Accelerated Aging in HIV/AIDS: Novel Biomarkers of Senescent Human CD8+ T Cells
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2017)
            The accumulation of peripheral blood late-differentiated memory CD8 T cells with features of replicative (cellular) senescence, including inability to proliferate in vitro, has been extensively studied. Importantly, the abundance of these cells is directly correlated with increased morbidity and mortality in older persons. Of note, peripheral blood contains only 2% of the total body lymphocyte population. By contrast, the gut-associated lymphoid tissue (GALT) is the most extensive lymphoid organ, housing up to 60% of total body lymphocytes, but has never been assessed with respect to senescence profiles. We report here the development of a method for measuring and comparing proliferative capacity of peripheral blood and gut colorectal mucosa-derived CD8 T cells. The protocol involves a 5-day culture of mononuclear leukocyte populations, from blood and gut colorectal mucosa respectively, labeled with 5-(and 6)-carboxyfluorescein diacetate succinimidyl ester (CFSE) and 5-bromo-2'-deoxyuridine (BrdU) and stimulated with anti-CD2/3/28-linked microbeads. Variables tested and optimized as part of the protocol development include: mode of T cell stimulation, CFSE concentration, inclusion of a second proliferation marker, BrdU, culture duration, initial culture concentration, and inclusion of autologous irradiated feeder cells. Moving forward, this protocol demonstrates a significant advance in the ability of researchers to study compartment-specific differences of in vitro proliferative dynamics of CD8 T cells, as an indicator of replicative senescence and immunological aging. The study's two main novel contributions are (1) Optimization and adaptation of standard proliferative dynamics blood T cell protocols for T cells within the mucosal immune system. (2) Introduction of the novel technique of combining CFSE and BrdU staining to do so.
              Cover page: Human immune compartment comparisons: Optimization of proliferative assays for blood and gut T lymphocytes
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2014)
              Prostaglandin E2 (PGE2), a pleiotropic immunomodulatory molecule, and its free radical catalyzed isoform, iso-PGE2, are frequently elevated in the context of cancer and chronic infection. Previous studies have documented the effects of PGE2 on the various CD4+ T cell functions, but little is known about its impact on cytotoxic CD8+ T lymphocytes, the immune cells responsible for eliminating virally infected and tumor cells. Here we provide the first demonstration of the dramatic effects of PGE2 on the progression of human CD8+ T cells toward replicative senescence, a terminal dysfunctional state associated multiple pathologies during aging and chronic HIV-1 infection. Our data show that exposure of chronically activated CD8+ T cells to physiological levels of PGE2 and iso-PGE2 promotes accelerated acquisition of markers of senescence, including loss of CD28 expression, increased expression of p16 cell cycle inhibitor, reduced telomerase activity, telomere shortening and diminished production of key cytotoxic and survival cytokines. Moreover, the CD8+ T cells also produced higher levels of reactive oxygen species, suggesting that the resultant oxidative stress may have further enhanced telomere loss. Interestingly, we observed that even chronic activation per se resulted in increased CD8+ T cell production of PGE2, mediated by higher COX-2 activity, thus inducing a negative feedback loop that further inhibits effector function. Collectively, our data suggest that the elevated levels of PGE2 and iso-PGE2, seen in various cancers and HIV-1 infection, may accelerate progression of CD8+ T cells towards replicative senescence in vivo. Inhibition of COX-2 activity may, therefore, provide a strategy to counteract this effect.
                Cover page: Prostaglandin E2 Promotes Features of Replicative Senescence in Chronically Activated Human CD8+ T Cells
                • Article
                • Peer Reviewed
                UCLA Previously Published Works (2010)
                Osteoporosis, which contributes to morbidity and mortality, often coexists with cardiovascular disease, especially atherosclerosis. We have reported recently that in vitro exposure of human T-lymphocytes to oxidized lipids induced expression of a key osteoclastogenic cytokine, receptor activator of NF-κB ligand (RANKL). Our previous studies have shown that mice fed an atherogenic high-fat diet developed osteopenia and that bone marrow preosteoclasts from these hyperlipidemic mice have increased osteoclastic potential. To investigate the role of T-lymphocytes in the diet-induced bone loss, C57BL/6 mice were fed either chow or a high-fat diet, and bone parameters and T-lymphocyte activation were assessed at 6 and 11 months. Consistent with our previous findings, peripheral quantitative computed tomographic (pQCT) analysis showed that mice in the high-fat group had lower bone mineral content than mice in the chow group. Furthermore, histomorphometric analysis showed decreased structural parameters in the high-fat group. Coculture studies showed that bone marrow cells isolated from the high-fat group, which contained increased levels of activated memory T-lymphocytes compared with bone marrow cells from the chow mice, supported osteoclastic differentiation of RAW 264.7 cells. Additionally, RANKL expression was upregulated significantly in the T-lymphocytes isolated from the bone marrow of the high-fat group. Splenic T-lymphocytes isolated from the high-fat group also had increased expression of transcripts for the receptor for oxidized lipids (LOX-1) as well as for inflammatory and osteoclastogenic cytokines, including RANKL, interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), IL-1β, and interferon γ (IFN-γ). Together these findings suggest that T-lymphocytes play a key role in the osteoclastogenesis induced by a high-fat diet and may contribute to the bone loss associated with diet-induced osteopenia.
                  Cover page: Bone density and hyperlipidemia: The T‐lymphocyte connection
                  • Article
                  • Peer Reviewed
                  UCLA Previously Published Works (2016)

                  Study objectives

                  Insomnia, particularly in later life, may raise the risk for chronic diseases of aging and mortality through its effect on cellular aging. The current study examines the effects of insomnia on telomere length, a measure of cellular aging, and tests whether insomnia interacts with chronological age to increase cellular aging.

                  Methods

                  A total of 126 males and females (60-88 y) were assessed for insomnia using the Diagnostic and Statistical Manual IV criterion for primary insomnia and the International Classification of Sleep Disorders, Second Edition for general insomnia (45 insomnia cases; 81 controls). Telomere length in peripheral blood mononuclear cells (PBMC) was determined using real-time quantitative polymerase chain reaction (qPCR) methodology.

                  Results

                  In the analysis of covariance model adjusting for body mass index and sex, age (60-69 y versus 70-88 y) and insomnia diagnosis interacted to predict shorter PBMC telomere length (P = 0.04). In the oldest age group (70-88 y), PBMC telomere length was significantly shorter in those with insomnia, mean (standard deviation) M(SD) = 0.59(0.2) compared to controls with no insomnia M(SD) = 0.78(0.4), P = 0.04. In the adults aged 60-69 y, PBMC telomere length was not different between insomnia cases and controls, P = 0.44.

                  Conclusions

                  Insomnia is associated with shorter PBMC telomere length in adults aged 70-88 y, but not in those younger than 70 y, suggesting that clinically severe sleep disturbances may increase cellular aging, especially in the later years of life. These findings highlight insomnia as a vulnerability factor in later life, with implications for risk for diseases of aging.
                    Cover page: Insomnia and Telomere Length in Older Adults
                    • Article
                    • Peer Reviewed
                    UCLA Previously Published Works (2017)
                    A hallmark of human immunosenescence is the accumulation of late-differentiated memory CD8+ T cells with features of replicative senescence, such as inability to proliferate, absence of CD28 expression, shortened telomeres, loss of telomerase activity, enhanced activation, and increased secretion of inflammatory cytokines. Importantly, oligoclonal expansions of these cells are associated with increased morbidity and mortality risk in elderly humans. Currently, most information on the adaptive immune system is derived from studies using peripheral blood, which contains approximately only 2% of total body lymphocytes. However, most lymphocytes reside in tissues. It is not clear how representative blood changes are of the total immune status. This is especially relevant with regard to the human gastrointestinal tract (GALT), a major reservoir of total body lymphocytes (approximately 60%) and an anatomical region of high antigenic exposure. To assess how peripheral blood T cells relate to those in other locations, we compare CD8+ T cells from peripheral blood and the GALT, specifically rectosigmoid colon, in young/middle age, healthy donors, focusing on phenotypic and functional alterations previously linked to senescence in peripheral blood. Overall, our results indicate that gut CD8+ T cells show profiles suggestive of greater differentiation and activation than those in peripheral blood. Specifically, compared to blood from the same individual, the gut contains significantly greater proportions of CD8+ T cells that are CD45RA- (memory), CD28-, CD45RA-CD28+ (early memory), CD45RA-CD28- (late memory), CD25-, HLA-DR+CD38+ (activated) and Ki-67+ (proliferating); ex vivo CD3+ telomerase activity levels are greater in the gut as well. However, gut CD8+ T cells may not necessarily be more senescent, since they expressed significantly lower levels of CD57 and PD-1 on CD45RO+ memory cells, and had in vitro proliferative dynamics similar to that of blood cells. Compartment-specific age-effects in this cohort were evident as well. Blood cells showed a significant increase with age in proportion of HLA-DR+38+, Ki-67+ and CD25+ CD8+ T cells; and an increase in total CD3+ ex-vivo telomerase activity that approached significance. By contrast, the only age-effect seen in the gut was a significant increase in CD45RA- (memory) and concurrent decrease in CD45RA+CD28+ (naïve) CD8+ T cells. Overall, these results indicate dynamics of peripheral blood immune senescence may not hold true in the gut mucosa, underscoring the importance for further study of this immunologically important tissue in evaluating the human immune system, especially in the context of chronic disease and aging.
                      Cover page: Distinct aging profiles of CD8+ T cells in blood versus gastrointestinal mucosal compartments
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