The impact of exercise, adiposity and persistent viral infection on blood T-Cell phenotype and function

Human ageing is associated with a progressive decline in the function of the immune system, commonly referred as immunosenescence. This is characterized by the shrinkage of the naïve T-cell repertoire and a concomitant accumulation of highly differentiated effector-memory cells and dysfunctional senescent T-cells. These systemic immune alterations have clinical implications and have been associated with increased morbidity and mortality in the elderly. However chronological ageing may not be the only factor influencing immunosenescence and certain lifestyle factors may moderate or potentiate the rate at which immune alterations occur. The studies comprised within this thesis investigated the effects of lifestyle factors such as physical activity or obesity, along with latent viral infections on the proportions of highly differentiated and senescent T-cells. Data were gathered from individuals of various age, physical activity, body composition and latent viral infection status to assess the effects of a wide range of lifestyle factors on T-cell proportions. The different levels of T-cell differentiation were assessed by four-colour flow cytometry using monoclonal antibodies specific to cell surface markers associated with T-cell phenotypes. The role played by leptin on T-cell activation was assessed by in vitro stimulation assays followed by cell surface phenotype and gene expression analysis. The effects of acute bouts of exercise on T-cells subsets were characterized using a submaximal cycling protocol. Aerobic fitness was associated with lower proportions of senescent and higher proportions of naïve T-cells, particularly within the CD8+ T-cell compartment in healthy adult men. The beneficial impact of aerobic fitness, and consequently of regular physical activity, on the ageing immune system was independent of age, latent viral infection status and body composition. Furthermore, the moderating effect of higher estimated VO2max on the proportions of senescent T-cells suggested that a transition from low physical activity, characterized as having an estimated VO2max below average, to regular physical activity, characterized as having a VO2max above average, could prevent the age-associated accumulation of senescent T-cells during decades. Obesity and excess serum leptin in adolescents were shown to be associated with changes in T-cell subsets associated with immunosenescence, such as reduced proportions of naïve and early T-cell and increased proportions of effector-memory and senescent T-cells. In addition, high physiological concentrations of leptin enhanced the mitogen-induced T-cell activation in vitro suggesting a potential role in the accumulation of senescent T-cells observed in obese individuals. Latent CMV infection was also associated with similar reductions in naïve T-cell proportions and increased proportions of highly differentiated and senescent T-cells in young adults. Although CMV infection appeared to be associated with an amplified exercise-induced preferential mobilization of highly differentiated and senescent T-cells in blood, those cells may not have been specific for CMV. It is concluded from this work, therefore, that chronological ageing is not the only factor associated with the accumulation of senescent T-cells in the elderly. By preventing obesity, and by potentially inducing senescent T-cells frequent mobilization and subsequent deletion via apoptosis, regular physical activity may prevent the accumulation of highly differentiated and senescent T-cells in the elderly, and consequently reduce morbidity and mortality in later life.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The impact of exercise, adiposity and persistent viral infection on blood T-Cell phenotype and function

Human ageing is associated with a progressive decline in the function of the immune system, commonly referred as immunosenescence. This is characterized by the shrinkage of the naïve T-cell repertoire and a concomitant accumulation of highly differentiated effector-memory cells and dysfunctional senescent T-cells. These systemic immune alterations have clinical implications and have been associated with increased morbidity and mortality in the elderly. However chronological ageing may not be the only factor influencing immunosenescence and certain lifestyle factors may moderate or potentiate the rate at which immune alterations occur. The studies comprised within this thesis investigated the effects of lifestyle factors such as physical activity or obesity, along with latent viral infections on the proportions of highly differentiated and senescent T-cells.Data were gathered from individuals of various age, physical activity, body composition and latent viral infection status to assess the effects of a wide range of lifestyle factors on T-cell proportions. The different levels of T-cell differentiation were assessed by four-colour flow cytometry using monoclonal antibodies specific to cell surface markers associated with T-cell phenotypes. The role played by leptin on T-cell activation was assessed by in vitro stimulation assays followed by cell surface phenotype and gene expression analysis. The effects of acute bouts of exercise on T-cells subsets were characterized using a submaximal cycling protocol.Aerobic fitness was associated with lower proportions of senescent and higher proportions of naïve T-cells, particularly within the CD8+ T-cell compartment in healthy adult men. The beneficial impact of aerobic fitness, and consequently of regular physical activity, on the ageing immune system was independent of age, latent viral infection status and body composition. Furthermore, the moderating effect of higher estimated VO2max on the proportions of senescent T-cells suggested that a transition from low physical activity, characterized as having an estimated VO2max below average, to regular physical activity, characterized as having a VO2max above average, could prevent the age-associated accumulation of senescent T-cells during decades. Obesity and excess serum leptin in adolescents were shown to be associated with changes in T-cell subsets associated with immunosenescence, such as reduced proportions of naïve and early T-cell and increased proportions of effector-memory and senescent T-cells. In addition, high physiological concentrations of leptin enhanced the mitogen-induced T-cell activation in vitro suggesting a potential role in the accumulation of senescent T-cells observed in obese individuals. Latent CMV infection was also associated with similar reductions in naïve T-cell proportions and increased proportions of highly differentiated and senescent T-cells in young adults. Although CMV infection appeared to be associated with an amplified exercise-induced preferential mobilization of highly differentiated and senescent T-cells in blood, those cells may not have been specific for CMV.It is concluded from this work, therefore, that chronological ageing is not the only factor associated with the accumulation of senescent T-cells in the elderly. By preventing obesity, and by potentially inducing senescent T-cells frequent mobilization and subsequent deletion via apoptosis, regular physical activity may prevent the accumulation of highly differentiated and senescent T-cells in the elderly, and consequently reduce morbidity and mortality in later life

The impact of latent CMV infection on NK-cell mobilization and expression of KLRG1 and CD57 in response to acute exercise.

Natural killer (NK) cells are cytotoxic effectors of the innate immune system that are able to distinguish healthy autologous cells from tumors and virally infected cells. NK-cells kill the targeted cells by releasing cytotoxic proteins, a process that is governed by inhibitory surface receptors, such as KLRG1. Additionally, activated NK-cells are able to proliferate in response to immunological stimuli, a process that is inhibited in NK-cells expressing the senescence marker CD57. Acute bouts of exercise are known to mobilize NK cells into the blood compartment, which could alter immunity; however, whether or not exercise alters NK-cell KLRG1 and CD57 expression has not been fully elucidated. Furthermore, as latent CMV infection is associated with an increased frequency of inhibitory NK cells, it is not known if CMV status influences NK-cell mobilization in response to acute exercise. PURPOSE: To examine the impact of latent CMV infection on the mobilization of NK-cells and their expression of KLRG1 and CD57 in response to acute exercise. METHODS: Otherwise healthy CMV seropositive (CMV+) and CMV seronegative (CMV-) males (age 23-35 years) completed a 30-min cycling protocol at 85% of maximum power. Lymphocytes isolated from whole blood before, immediately after, and one hour after exercise were surface-stained with monoclonal antibodies against CD3, CD56, KLRG1 and CD57 and analyzed by 4-color flow cytometry. RESULTS: Preliminary analysis of the data show a prodigious increase in the number of CD56 dim (mature, highly cytotoxic subset) NK-cells immediately after exercise in all subjects, which subsequently fell below pre-exercise values 1 hour later. In CMV- subjects, the proportion of CD56 bright (immature, mildly cytotoxic) NK cells was considerably higher 1 hour post-exercise than before exercise, but the number of cells changed very little suggesting that the increased proportion was due merely to the egress of CD56 dim NK cells. Interestingly, CMV seropositivity was associated with a near complete absence of CD56 bright NK cells that was unaffected by exercise. Neither exercise nor CMV status influenced the proportion of NK-cells expressing KLRG1 or CD57. CONCLUSION: Preliminary analysis of this data indicates that acute exercise preferentially mobilizes CD56 dim NK cells without altering KLRG1 and CD57 expression. Latent CMV infection is associated with a lowered proportion of CD56 bright NK-cells; however, the NK-cell response to exercise was not influenced by CMV status. Future work will examine the role of aging on NK-cell response to exercise and CMV status

The Impact of Latent Herpesvirus Infections on the Mobilization of Recent Thymic Emigrants and Extrathymic T-cells in Response to Acute Aerobic Exercise in Man

T-cells typically mature in the thymus gland, which eventually succumbs to age-related atrophy, resulting in a decreased naïve T-cell repertoire in middle to later years. Aged individuals and those with persistently reactivating herpesvirus infections have an increased reliance on the extrathymic maturation of T-cells due to the shrinking effects that age and latent viral infection has on the naïve T-cell repertoire. Acute bouts of aerobic exercise are known to mobilize T-cells that exhibit both a naïve and late-stage differentiation phenotype into the blood compartment; however, it is not known if recent thymic emigrants (RTE) or extrathymic T-cells contribute to the lymphocytosis associated with exercise. PURPOSE: To examine the impact of latent cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infection on the mobilization of RTE and extrathymic T-cells in response to acute exercise. METHODS: Otherwise healthy CMV or EBV seropositive (CMV+ or EBV+) and CMV or EBV seronegative (CMV- or EBV-) males (age 23-35y) completed a 30-min cycling protocol at 85% of maximum power. Lymphocytes isolated from whole blood before, immediately after, and one hour after exercise were surface stained with monoclonal antibodies to identify phenotypes of RTE (CD103+/CD62L-) and extrathymic T-cells believed to mature in the liver (CD3+/CD25-/CD122+) and the epithelium of the small intestine (CD3+/CD4-/CD8-; TCRγδ+/ CD8αα+; CD3-/CD2+/CD7+). Cell populations were analyzed by flow cytometry and antibodies against CMV and EBV were determined in serum by ELISA. RESULTS: Preliminary analyses show that the proportion of RTE among the total CD3+/CD4+ or CD3+/CD8+ T-cell subsets did not change immediately after exercise, but was elevated above baseline 1h later due to the preferential egress of late stage differentiated T-cells. Neither CMV nor EBV status influenced the proportions of RTE in blood in response to exercise. T-cells mainly found in intestinal mucosa (i.e. CD3+/CD4-/CD8- and CD3-/CD2+/CD7+) were found to increase in blood immediately after exercise; an effect that appeared to be more pronounced in EBV but not CMV-infected subjects. CONCLUSION: An acute bout of aerobic exercise elicits the mobilization of T-cells exhibiting phenotype characteristics of extrathymically matured T-cells, suggesting that extrathymic T-cell mobilization contributes to the lymphocytosis associated with acute exercise. This effect appears to be amplified in subjects carrying a latent EBV but not CMV infection. Future research should attempt to establish the impact of long-term exercise and latent herpesvirus infections on the frequency of RTE and extrathymic T-cells in the aged, as this could have significant implications for age-associated immune dysfunction

A single exercise bout enhances the manufacture of viral-specific T-cells from healthy donors: implications for allogeneic adoptive transfer immunotherapy

Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infections remain a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). The adoptive transfer of donor-derived viral-specific cytotoxic T-cells (VSTs) is an effective treatment for controlling CMV and EBV infections after HSCT; however, new practical methods are required to augment the ex vivo manufacture of multi-VSTs from healthy donors. This study investigated the effects of a single exercise bout on the ex vivo manufacture of multi-VSTs. PBMCs isolated from healthy CMV/EBV seropositive participants before (PRE) and immediately after (POST) 30-minutes of cycling exercise were stimulated with CMV (pp65 and IE1) and EBV (LMP2A and BMLF1) peptides and expanded over 8 days. The number (fold difference from PRE) of T-cells specific for CMV pp65 (2.6), EBV LMP2A (2.5), and EBV BMLF1 (4.4) was greater among the VSTs expanded POST. VSTs expanded PRE and POST had similar phenotype characteristics and were equally capable of MHC-restricted killing of autologous target cells. We conclude that a single exercise bout enhances the manufacture of multi-VSTs from healthy donors without altering their phenotype or function and may serve as a simple and economical adjuvant to boost the production of multi-VSTs for allogeneic adoptive transfer immunotherapy

No impact of CMV or EBV seropositivity on the frequency of highly differentiated T-cells in Mexican-American adolescents

Recurring activations of the prevalent latent herpes viruses Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) induces immune cell division leading to the premature terminal differentiation of T-cells. Terminally differentiated T-cells are known to accumulate with age causing a reduction in the naïve T-cell repertoire, which compromises the ability of the adaptive immune system to respond to novel pathogens. Although CMV and EBV seropositivity are hallmarks of the “immune risk profile” and are known to influence the frequency of terminally differentiated T-cells and increase infection risk in adults, it is not known if CMV or EBV impacts on the frequency of these cells in a young subject cohort. PURPOSE: To examine the impact of CMV and EBV seropositivity on the frequency of highly differentiated blood T-cells in Mexican-American adolescents. METHODS: Fasted resting blood samples were obtained from 77 adolescents consisting of both males and females. The presence of antibodies against CMV and EBV was determined in serum by ELISA. Lymphocytes isolated from peripheral blood were assessed for a combination of cell surface markers to determine their stage of differentiation. Monoclonal antibodies and four-color flow cytometry were used to identify senescent (CD27-, CD28-, CD57+), naïve (CCR7+, CD45RA+), memory (CCR7-, CD45RA-) and effector memory (CCD7-, CD45RA+) T-cell markers on pan CD3+ T-cells, CD4+ T-cells and CD8+ T-cells. Differences in T-cell phenotype between the CMV/EBV seropositive and seronegative participants were compared using independent Student t-tests. RESULTS: The prevalence of latent CMV and EBV infection among the subject cohort was 16% and 44% respectively, while 7% of all participants were carrying a latent infection for both. No differences in senescent and memory phenotypes were found between the CMV or EBV seropositive and seronegative groups. CONCLUSION: Despite the known influence of latent CMV and EBV infection on the frequency of senescent T-cells in adults, these preliminary data indicate that CMV and EBV seropositivity has no impact on the frequency of senescent T-cells in adolescents. These data suggest that the increased frequency of terminally differentiated T-cells that are associated with CMV and EBV seropositivity in adults is probably due to long-term infections. Future studies will assess the impact of CMV and EBV seropositivity on immunosenescence in association with other factors known to have an effect on T-cells differentiation, such as BMI and physical activity status

T-Lymphocyte Activation is Not Affected by the Mobilization of Senescent T-Cells into the Peripheral Blood Following an Acute Bout of Exercise

It is well recognized that individuals are at an increased risk of illness following an arduous exercise regime. Exercise may affect activation status of cells and play a pivotal role in defense against pathogenic invasion. CD69 is the earliest known expressed cell surface antigen of T-cell activation and is a reliable marker of cell activation status (Green et al. Med. Sci. Sports Exerc. 35, 582-588: 2003). Exercise is known to alter the frequency of senescent cells in the blood expressing the cell surface glycoprotein killer cell lectin-like receptor G1 (KLRG1), and are antigen-experienced and unable to clonally expand upon further antigenic stimulation (Simpson et al. J. Appl. Phys. 103, 396-401:2007), PURPOSE: To examine the contribution of senescent T-cells mobilized by exercise on the overall activation status of the peripheral blood T-cell pool following an acute bout of exercise. METHODS: Ten moderately trained males (age: 24.6 ± 4.8; height: 183.1 ± 6.7cm; mass: 72.8 ± 7.9kg; ; 61.3 ± 5.9 ml.kg-1.min-1) ran at speeds corresponding to 80% until volitional exhaustion (time: 36.1 ± 5.8 minutes). Blood lymphocytes isolated before (PRE), immediately after (POST) and 1 hour after (1HrPOST) exercise were stimulated for 4 hours in culture with and without the mitogen PMA and assessed for KLRG1 and CD69 expression and co-expression on CD3+, CD3+/CD4+ (CD4+) and CD3+/CD8+ (CD8+) lymphocyte subsets using 4-colour flow cytometry. RESULTS: No changes in CD69 GMFI were observed on total CD3+, CD4+ and CD8+ T-cells POST or 1HrPOST exercise. The proportions of KLRG1+ cells among the total CD3+, CD4+ and CD8+ T-cell populations increased by 172%, 107% and 169% respectively POST exercise and fell below baseline values 1h later (p\u3c0.05). At all sample time points, CD69 GMFI was greater on stimulated KLRG1+ T-cells compared to KLRG1- cells (p\u3c0.05). CONCLUSION: We conclude that exercise does not affect the activation status of the total T-cell pool. Instead, the number of senescent cells expressing CD69 is greater than those that are not senescent at all times. This suggests that upon pathogenic invasion post-exercise

Boost your brain: a simple 100% normobaric oxygen treatment improves human motor learning processes

IntroductionHuman motor learning processes are a fundamental part of our daily lives and can be adversely affected by neurologic conditions. Motor learning largely depends on successfully integrating cognitive and motor-related sensory information, and a simple, easily accessible treatment that could enhance such processes would be exciting and clinically impactful. Normobaric 100% oxygen treatment (NbOxTr) is often used as a first-line intervention to improve survival rates of brain cells in neurological trauma, and recent work indicates that improvements in elements crucial for cognitive-motor-related functions can occur during NbOxTr. However, whether NbOxTr can enhance the motor learning processes of healthy human brains is unknown. Here, we investigated whether a brief NbOxTr administered via nasal cannula improves motor learning processes during a visuomotor adaptation task where participants adapt to a visual distortion between visual feedback and hand movements.Methods40 healthy young adults (M = 21 years) were randomly assigned to a NbOxTr (N = 20; 100% oxygen) or air (N = 20; regular air) group and went through four typical visuomotor adaptation phases (Baseline, Adaptation, After-Effect, Refresher). Gas treatment (flow rate 5 L/min) was only administered during the Adaptation phase of the visuomotor experiment, in both groups.ResultsThe NbOxTr provided during the Adaptation phase led to significantly faster and about 30% improved learning (p < 0.05). Notably, these motor learning improvements consolidated into the subsequent experiment phases, i.e., after the gas treatment was terminated (p < 0.05).DiscussionWe conclude that this simple and brief NbOxTr dramatically improved fundamental human motor learning processes and may provide promising potential for neurorehabilitation and skill-learning approaches. Further studies should investigate whether similar improvements exist in elderly and neurologically impaired individuals, other motor learning tasks, and also long-lasting effects