Cytomegalovirus Infection Minimally Affects the Frequencies of B-Cell Phenotypes in Peripheral Blood of Younger and Older Adults

Potential relationship between cytomegalovirus and immunosenescence: Evidence from observational studies

Immunosenescence (IS) occurs as a natural outcome of ageing and may be described as a decline in immune system flexibility and adaptability to sufficiently respond to new, foreign antigens. Potential factors that may precipitate IS include persistent herpesvirus infections, such as cytomegalovirus (CMV). Here, we conducted a review of the literature evaluating the potential association between CMV and IS. Twenty-seven epidemiologic studies that included direct comparisons between CMV-seropositive and CMV-seronegative immunocompetent individuals were analysed. The majority of these studies (n = 20) were conducted in European populations. The strength of evidence supporting a relationship between CMV, and various IS-associated immunologic endpoints was assessed. T-cell population restructuring was the most prominently studied endpoint, described in 21 studies, most of which reported a relationship between CMV and reduced CD4:CD8 T-cell ratio or modified CD8+ T-cell levels. Telomere length (n = 4) and inflammageing (n = 3) were less frequently described in the primary literature, and the association of these endpoints with CMV and IS was less pronounced. An emergent trend from our review is the potential effect modification of the CMV-IS relationship with both sex and age, indicating the importance of considering various effector variables when evaluating associations between CMV and IS. Our analysis revealed plausible mechanisms that may underlie the larger epidemiologic trends seen in the literature that support the indirect effect of CMV on IS. Future studies are needed to clarify CMV-associated and IS-associated immunologic endpoints, as well as in more diverse global and immunocompromised populations.

Circulating immune cell phenotypes are associated with age, sex, CMV, and smoking status in the Framingham Heart Study offspring participants

Understanding the composition of circulating immune cells with aging and the underlying biologic mechanisms driving aging may provide molecular targets to slow the aging process and reduce age-related disease. Utilizing cryopreserved cells from 996 Framingham Heart Study (FHS) Offspring Cohort participants aged 40 and older (mean 62 years, 48% female), we report on 116 immune cell phenotypes including monocytes, T-, B-, and NK cells and their subtypes, across age groups, sex, cytomegalovirus (CMV) exposure groups, smoking and other cardiovascular risk factors. The major cellular differences with CMV exposure were higher Granzyme B+ cells, effector cells, and effector-memory re-expressing CD45RA (TEMRA) cells for both CD4+ and CD8+. Older age was associated with lower CD3+ T cells, lower naïve cells and naïve/memory ratios for CD4+ and CD8+. We identified many immune cell differences by sex, with males showing lower naïve cells and higher effector and effector memory cells. Current smokers showed lower pro-inflammatory CD8 cells, higher CD8 regulatory type cells and altered B cell subsets. No significant associations were seen with BMI and other cardiovascular risk factors. Our cross-sectional observations of immune cell phenotypes provide a reference to further the understanding of the complexity of immune cells in blood, an easily accessible tissue.

T cell phenotypes associated with insulin resistance: results from the Berlin Aging Study II

Background

Obesity is associated with chronic low-grade inflammation leading to metabolic and cardiovascular diseases, but a subset of obese individuals is considered insulin sensitive (IS). The underlying pathophysiologic mechanisms remain elusive and clinical studies on the relationship between inflammatory markers and metabolically healthy obesity (MHO) are scarce.

Methods

In this cross-sectional analysis, we included a sample of 437 older participants (60–84 years) from the Berlin Aging Study II (BASE-II). Peripheral blood mononuclear cells were isolated, immune cell subsets were analyzed with multiparameter flow cytometry and systemic cytokine levels were measured. Immune cell parameters were correlated with metabolic measures and multiple linear regression analysis was conducted and adjusted for various demographic and clinical factors.

Results

We found that frequencies of naïve and memory CD4⁺ and CD8⁺ T cells inversely correlated with measures for insulin sensitivity in the older population. Moreover, the percentages of naïve CD4⁺ and CD8⁺ T cells were significantly higher, whereas activated T cells and IL-6 levels were lower in IS compared to insulin resistant (IR) obese individuals. The percentages of naïve CD4⁺ and CD8⁺ T cells were predictive for impaired insulin sensitivity (ß = 0.16, p = 0.01 and ß = 0.11, p = 0.04), and the association of naïve CD4⁺ T cells with insulin sensitivity persisted after multivariate adjustment (ß = 0.14, p = 0.02).

Conclusions

These findings support the hypothesis that parameters of systemic inflammation can differentiate IS from IR obese individuals that are at higher risk for cardiometabolic diseases and may have clinical implications with regard to obesity treatment stratification.

Trial registration

DRKS00009277. Registered 31 August 2015 - Retrospectively registered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12979-020-00211-y.

'From immunosenescence to immune modulation': a re-appraisal of the role of cytomegalovirus as major regulator of human immune function

In the year 2000, cytomegalovirus was identified as a risk factor for mortality in a seminal study of octogenarian residents in Sweden. This finding triggered a wave of additional epidemiological investigations, some of which supported this association whilst others observed no such effect. In addition, this increased risk of death in CMV-seropositive people was correlated with observed changes within the T-cell repertoire such that accelerated 'immunosenescence' became a de facto explanation, without strong evidence to this effect. Recent years have seen a re-appraisal of these findings. Interestingly, many studies show that cytomegalovirus acts to improve immune function, most clearly in younger donors. In addition, the excess mortality in older people that is observed in CMV-seropositive cohorts appears to be related primarily to an excess of vascular disease rather than impairment of immune function. CMV is an important member of the natural 'virome' of Homo sapiens and has an important, and generally positive, modulatory influence on human immune function throughout most of life. However, within certain populations, this influence can become negative and age, co-morbidity and environment all act as determinants of this effect. As such, it is important that new interventions are developed that can mitigate the damaging influence of CMV on human health in populations at risk.

Do human B-lymphocytes avoid aging until 60 years?

Broad changes in human innate and adaptive immunity are associated with advanced age. The age-related alteration of gene expression was reported for both T and B lymphocytes. We analysed the genome-wide expression profiles (n=20) of naive and whole B cell populations from young and early aged healthy donors under 60 years. We revealed large homogeneity of all analysed genome-wide expression profiles but did not identified any significant gene deregulation between young (30-45 years) and early aged healthy donors (50-60 years). We argue that B cells avoid the aging program on molecular level until 60 years of age. Our results demonstrate the potential of hematopoietic stem cells to generate uncompromised lymphocytes in early elderly. These are very encouraging findings for the general health and the immunity maintenance would not need any intervention to naive B cells. Rather, a suitable immune stimulation in healthy body environment warrants further research into aging of older elderly.

Long-term maintenance of diphtheria-specific antibodies after booster vaccination is hampered by latent infection with Cytomegalovirus

Many currently used vaccines are less immunogenic in the elderly compared to young adults. The impact of latent infection with Cytomegalovirus (CMV) on vaccine-induced antibody responses has been discussed controversially. We have demonstrated that recall responses to diphtheria vaccination are frequently insufficient in elderly persons and that antibody concentrations decline substantially within 5 years. In the current study we show that within a cohort of healthy elderly (n = 87; median age 71 years, range 66–92) antibody responses to a booster vaccination against diphtheria do not differ between CMV-negative and CMV-positive individuals 4 weeks after vaccination.. However, the goal of diphtheria-vaccination is long-term protection and this is achieved by circulating anti-toxin antibodies. Diphtheria-specific antibody concentrations decline faster in CMV-positive compared to CMV-negative older adults leading to an increased proportion of persons without protective antibody concentrations 5 years after booster vaccination and endangering long-term protection. This finding could be relevant for vaccination schedules.

Changes in Circulating B Cell Subsets Associated with Aging and Acute SIV Infection in Rhesus Macaques

Aging and certain viral infections can negatively impact humoral responses in humans. To further develop the nonhuman primate (NHP) model for investigating B cell dynamics in human aging and infectious disease, a flow cytometric panel was developed to characterize circulating rhesus B cell subsets. Significant differences between human and macaque B cells included the proportions of cells within IgD+ and switched memory populations and a prominent CD21-CD27+ unswitched memory population detected only in macaques. We then utilized the expanded panel to analyze B cell alterations associated with aging and acute simian immunodeficiency virus (SIV) infection in the NHP model. In the aging study, distinct patterns of B cell subset frequencies were observed for macaques aged one to five years compared to those between ages 5 and 30 years. In the SIV infection study, B cell frequencies and absolute number were dramatically reduced following acute infection, but recovered within four weeks of infection. Thereafter, the frequencies of activated memory B cells progressively increased; these were significantly correlated with the magnitude of SIV-specific IgG responses, and coincided with impaired maturation of anti-SIV antibody avidity, as previously reported for HIV-1 infection. These observations further validate the NHP model for investigation of mechanisms responsible for B cells alterations associated with immunosenescence and infectious disease.

Editorial

Human aging is characterized by large differences between and within older adults. Numerous factors are known to contribute to these differences, including genetic and immunological, somatic and medical, cognitive and behavioral, psychosocial and experiential, as well as socioeconomic and geospatial conditions. Continuing and expanding the scientific objectives of the Berlin Aging Study, the Berlin Aging Study II (BASE-II) seeks to comprehensively describe phenomena associated with aging and old age and to better understand the multiple different underlying factors and their interactions. To this end, BASE-II was established as a multi-institutional project combining and integrating interdisciplinary perspectives ranging from molecular genetics and immunology, geriatric medicine and psychology, to sociology and economics. In this Special Issue, we have compiled seven empirical analyses that feature examples of interdisciplinary insights that BASE-II provides by linking data across multiple levels of analyses at which human functioning and development occur in old age. Here, we provide an overview of the study, note commonalities between BASE-II and earlier studies, and highlight some of its unique qualities.