Aging down-regulates the transcription factor E2A, activation-induced cytidine deaminase, and Ig class switch in human B cells

The Impact of Immune System Aging on Infectious Diseases

Immune system aging is becoming a field of increasing public health interest because of prolonged life expectancy, which is not paralleled by an increase in health expectancy. As age progresses, innate and adaptive immune systems undergo changes, which are defined, respectively, as inflammaging and immune senescence. A wealth of available data demonstrates that these two conditions are closely linked, leading to a greater vulnerability of elderly subjects to viral, bacterial, and opportunistic infections as well as lower post-vaccination protection. To face this novel scenario, an in-depth assessment of the immune players involved in this changing epidemiology is demanded regarding the individual and concerted involvement of immune cells and mediators within endogenous and exogenous factors and co-morbidities. This review provides an overall updated description of the changes affecting the aging immune system, which may be of help in understanding the underlying mechanisms associated with the main age-associated infectious diseases.

Tobacco exposure, but not aging, shifts the frequency of peripheral blood B cell subpopulations

Several disturbances in T-cell mediated immunity have been described during aging, but immunosenescence of the B-cell compartment is less well elucidated. The peripheral blood B-cell compartment (CD19+) can be split into six main subpopulations according to the cell surface markers IgD, CD27, CD24, and CD38: Transitional, naïve, unswitched, switched, double negative and plasmablasts. We thus aimed to verify whether shifts in these subsets occur during healthy and pathological aging. We recruited three groups of aged people (> 60 years old), healthy, COPD patients, and smokers without altered pulmonary function test, and a fourth group of individuals 18-40 years old (youngs). Total B-cells percentage and absolute number were similar among the healthy aged, COPD patients, and youngs, but the smokers showed significantly higher absolute numbers. While all six B-cell subset percentages were comparable among the healthy aged, COPD patients, and youngs, smokers showed significantly higher percentages of switched B-cells and reduced naïve B-cells than the other three groups, resulting in an inverted naive:switched ratio. Analysis of the cell subset absolute numbers showed a similar trend. Overall, our results suggest that aging drives milder alterations in the distribution of peripheral blood B-cell subpopulations than in the T-cell compartment. We suggest that it is the T-cell immunosenescence that most contributes to the poor humoral immune responses in the elderly, vaccine responses included. Surprisingly it was the smokers who showed significant alterations when compared with the youngs, healthy aged, and aged COPD patients, probably as a result of the chronic immune stimulation described in active smoking subjects.

Regulatory RNAs in immunosenescence

BACKGROUND

Immunosenescence is a multifactorial stress response to different intrinsic and extrinsic insults that cause immune deterioration and is accompanied by genomic or epigenomic perturbations. It is now widely recognized that genes and proteins contributing in the process of immunosenescence are regulated by various noncoding (nc) RNAs, including microRNAs (miRNAs), long ncRNAs, and circular RNAs.

AIMS

This review article aimed to evaluate the regulatore RNAs roles in the process of immunosenescence.

METHODS

We analyzed publications that were focusing on the different roles of regulatory RNAs on the several aspects of immunosenescence.

RESULTS

In the immunosenescence setting, ncRNAs have been found to play regulatory roles at both transcriptional and post-transcriptional levels. These factors cooperate to regulate the initiation of gene expression programs and sustaining the senescence phenotype and proinflammatory responses.

CONCLUSION

Immunosenescence is a complex process with pivotal alterations in immune function occurring with age. The extensive network that drive immunosenescence-related features are are mainly directed by a variety of regulatory RNAs such as miRNAs, lncRNAs, and circRNAs. Latest findings about regulation of senescence by ncRNAs in the innate and adaptive immune cells as well as their role in the immunosenescence pathways, provide a better understanding of regulatory RNAs function in the process of immunosenescence.

B Cells Dynamic in Aging and the Implications of Nutritional Regulation

Aging negatively affects B cell production, resulting in a decrease in B-1 and B-2 cells and impaired antibody responses. Age-related B cell subsets contribute to inflammation. Investigating age-related alterations in the B-cell pool and developing targeted therapies are crucial for combating autoimmune diseases in the elderly. Additionally, optimal nutrition, including carbohydrates, amino acids, vitamins, and especially lipids, play a vital role in supporting immune function and mitigating the age-related decline in B cell activity. Research on the influence of lipids on B cells shows promise for improving autoimmune diseases. Understanding the aging B-cell pool and considering nutritional interventions can inform strategies for promoting healthy aging and reducing the age-related disease burden.

Ocrelizumab associates with reduced cerebrospinal fluid B and CD20dim CD4+ T cells in primary progressive multiple sclerosis

The anti-CD20 monoclonal antibody ocrelizumab reduces disability progression in primary progressive multiple sclerosis. CD20 is a prototypical B-cell marker; however, subpopulations of CD4+ and CD8+ T cells in peripheral blood and cerebrospinal fluid also express low levels of CD20 (CD20dim). Therefore, direct targeting and depletion of these CD20dim T-cell subpopulations may contribute to the therapeutic effect of ocrelizumab. The aim of this observational cohort study was to compare CD20+ B-cell and CD20dim T-cell distributions between peripheral blood and cerebrospinal fluid of ocrelizumab-treated or ocrelizumab-untreated people with primary progressive multiple sclerosis. Ocrelizumab treatment was associated with depletion of circulating B cells and CD20dim CD4+ and CD20dim CD8+ T cells (P < 0.0001, P = 0.0016 and P = 0.0008, respectively) but, in cerebrospinal fluid, only with lower proportions of B cells and CD20dim memory CD4+ T cells (P < 0.0001 and P = 0.0043, respectively). The proportional prevalence of cerebrospinal fluid CD20dim memory CD8+ T cells was not significantly reduced (P = 0.1333). Only in cerebrospinal fluid, the proportions of CD20dim cells within CD4+ and not CD8+ T cells positive for CCR5, CCR6 and CXCR3 were reduced in ocrelizumab-treated participants. The proportion of CD20dim CD4+ T cells and abundance of CD4+ relative to CD8+ T cells in cerebrospinal fluid correlated positively with age (R = 0.6799, P = 0.0150) and Age-Related Multiple Sclerosis Severity score (R = 0.8087, P = 0.0014), respectively. We conclude that, in contrast to cerebrospinal fluid CD20dim CD8+ T cells, B cells and CD20dim CD4+ T cells are reduced in cerebrospinal fluid of people with primary progressive multiple sclerosis with an ocrelizumab-associated depletion of circulating B cells and CD20dim T cells. Therefore, these cells are likely to contribute to the therapeutic effects of ocrelizumab in people with primary progressive multiple sclerosis.

Nanovaccines for Advancing Long-Lasting Immunity against Infectious Diseases

Infectious diseases, particularly life-threatening pathogens such as small pox and influenza, have substantial implications on public health and global economies. Vaccination is a key approach to combat existing and emerging pathogens. Immunological memory is an essential characteristic used to evaluate vaccine efficacy and durability and the basis for the long-term effects of vaccines in protecting against future infections; however, optimizing the potency, improving the quality, and enhancing the durability of immune responses remains challenging and a focus for research involving investigation of nanovaccine technologies. In this review, we describe how nanovaccines can address the challenges for conventional vaccines in stimulating adaptive immune memory responses to protect against reinfection. We discuss protein and nonprotein nanoparticles as useful antigen platforms, including those with highly ordered and repetitive antigen array presentation to enhance immunogenicity through cross-linking with multiple B cell receptors, and with a focus on antigen properties. In addition, we describe how nanoadjuvants can improve immune responses by providing enhanced access to lymph nodes, lymphnode targeting, germinal center retention, and long-lasting immune response generation. Nanotechnology has the advantage to facilitate vaccine induction of long-lasting immunity against infectious diseases, now and in the future.

Systemic immunometabolism and responses to vaccines: insights from T and B cell perspectives

Vaccination stands as the cornerstone in the battle against infectious diseases, and its efficacy hinges on several host-related factors like genetics, age, and metabolic status. Vulnerable populations, such as malnourished individuals, the obese, and the elderly, commonly exhibit diminished vaccine responses and efficacy. While the specific factors contributing to this impairment may vary, these individuals typically display a degree of metabolic dysregulation, thereby underscoring its potential significance as a fundamental determinant of suboptimal vaccine responses. The emerging field of immunometabolism aims to unravel the intricate interplay between immune regulation and metabolic pathways, and recent research has revealed diverse metabolic signatures linked to various vaccine responses and outcomes. In this review, we summarize the major metabolic pathways utilized by B and T cells during vaccine responses, their complex and varied metabolic requirements, and the impact of micronutrients and metabolic hormones on vaccine outcomes. Furthermore, we examine how systemic metabolism influences vaccine responses and the evidence suggesting that metabolic dysregulation in vulnerable populations can lead to impaired vaccine responses. Lastly, we reflect on the challenge of proving causality with respect to the contribution of metabolic dysregulation to poor vaccine outcomes, and highlight the need for a systems biology approach that combines multimodal profiling and mathematical modelling to reveal the underlying mechanisms of such complex interactions.

Antibody responses after BNT162b2 vaccination in Japanese geriatric intermediate care facilities

Background

To evaluate antibody responses against the primary series of vaccination of severe acute respiratory syndrome coronavirus-2 [SARS-CoV-2] vaccines in the staff and residents of Japanese geriatric intermediate care facilities.

Methods

All subjects (159 staff and 96 residents) received two doses of the BNT162b2 mRNA vaccine 3 weeks apart. Baseline data of subject were collected using a structured form. Serum samples were collected three times: before vaccination, 3 weeks after the first dose, and 4 weeks after the second dose, and anti-receptor binding domain of the spike protein of SARS-CoV-2 [anti-RBD] IgG was measured using two immunoassays.

Results

After the second dose, geometric mean titers [GMT] of anti-RBD with both the Abbott and Roche assay were significantly lower in residents than staff (2282 AU/mL vs. 8505 AU/mL, and 258 U/mL vs. 948 U/mL, respectively). Multivariate analysis of characteristics affecting antibody responses (≥1280 AU/mL for Abbott and > 210 U/mL for Roche) showed lower odds ratios [ORs] for older age (adjusted OR per 10 year increase [aOR] = 0.62, 95 % confidence interval [95 %CI]; 0.38-1.02), steroid usage (aOR = 0.09, 95 %CI; 0.01-0.60) and regular nonsteroidal anti-inflammatory drugs [NSAIDs] usage (aOR = 0.16, 95 %CI; 0.03-0.88).

Conclusions

Elderly people and steroid and NSAID users had lower antibody responses following the second vaccine dose.

Baseline immune states (BIS) associated with vaccine responsiveness and factors that shape the BIS

Vaccines are among the greatest inventions in medicine, leading to the elimination or control of numerous diseases, including smallpox, polio, measles, rubella, and, most recently, COVID-19. Yet, the effectiveness of vaccines varies among individuals. In fact, while some recipients mount a robust response to vaccination that protects them from the disease, others fail to respond. Multiple clinical and epidemiological factors contribute to this heterogeneity in responsiveness. Systems immunology studies fueled by advances in single-cell biology have been instrumental in uncovering pre-vaccination immune cell types and genomic features (i.e., the baseline immune state, BIS) that have been associated with vaccine responsiveness. Here, we review clinical factors that shape the BIS, and the characteristics of the BIS associated with responsiveness to frequently studied vaccines (i.e., influenza, COVID-19, bacterial pneumonia, malaria). Finally, we discuss potential strategies to enhance vaccine responsiveness in high-risk groups, focusing specifically on older adults.

Immunosenescence and multiple sclerosis: inflammaging for prognosis and therapeutic consideration

Aging is associated with a progressive decline of innate and adaptive immune responses, called immunosenescence. This phenomenon links to different multiple sclerosis (MS) disease courses among different age groups. While clinical relapse and active demyelination are mainly related to the altered adaptive immunity, including invasion of T- and B-lymphocytes, impairment of innate immune cell (e.g., microglia, astrocyte) function is the main contributor to disability progression and neurodegeneration. Most patients with MS manifest the relapsing-remitting phenotype at a younger age, while progressive phenotypes are mainly seen in older patients. Current disease-modifying therapies (DMTs) primarily targeting adaptive immunity are less efficacious in older patients, suggesting that immunosenescence plays a role in treatment response. This review summarizes the recent immune mechanistic studies regarding immunosenescence in patients with MS and discusses the clinical implications of these findings.

Functions of double-negative B cells in autoimmune diseases, infections, and cancers

Most mature B cells can be divided into four subtypes based on the expression of the surface markers IgD and CD27: IgD+ CD27- naïve B cells, IgD+ CD27+ unswitched memory B cells, IgD- CD27+ switched memory B cells, and IgD- CD27- double-negative (DN) B cells. Despite their small population size in normal peripheral blood, DN B cells play integral roles in various diseases. For example, they generate autoimmunity in autoimmune conditions, while these cells may generate both autoimmune and antipathogenic responses in COVID-19, or act in a purely antipathogenic capacity in malaria. Recently, DN B cells have been identified in nasopharyngeal carcinoma and non-small-cell lung cancers, where they may play an immunosuppressive role. The distinct functions that DN B cells play in different diseases suggest that they are a heterogeneous B-cell population. Therefore, further study of the mechanisms underlying the involvement of DN B cells in these diseases is essential for understanding their pathogenesis and the development of therapeutic strategies. Further research is thus warranted to characterize the DN B-cell population in detail.

Human immune phenotyping reveals accelerated aging in type 1 diabetes

The proportions and phenotypes of immune cell subsets in peripheral blood undergo continual and dramatic remodeling throughout the human life span, which complicates efforts to identify disease-associated immune signatures in type 1 diabetes (T1D). We conducted cross-sectional flow cytometric immune profiling on peripheral blood from 826 individuals (stage 3 T1D, their first-degree relatives, those with ≥2 islet autoantibodies, and autoantibody-negative unaffected controls). We constructed an immune age predictive model in unaffected participants and observed accelerated immune aging in T1D. We used generalized additive models for location, shape, and scale to obtain age-corrected data for flow cytometry and complete blood count readouts, which can be visualized in our interactive portal (ImmScape); 46 parameters were significantly associated with age only, 25 with T1D only, and 23 with both age and T1D. Phenotypes associated with accelerated immunological aging in T1D included increased CXCR3+ and programmed cell death 1-positive (PD-1+) frequencies in naive and memory T cell subsets, despite reduced PD-1 expression levels on memory T cells. Phenotypes associated with T1D after age correction were predictive of T1D status. Our findings demonstrate advanced immune aging in T1D and highlight disease-associated phenotypes for biomarker monitoring and therapeutic interventions.

The impact of age-related syndromes on ICU process and outcomes in very old patients

In this narrative review, we describe the most important age-related "syndromes" found in the old ICU patients. The syndromes are frailty, comorbidity, cognitive decline, malnutrition, sarcopenia, loss of functional autonomy, immunosenescence and inflam-ageing. The underlying geriatric condition, together with the admission diagnosis and the acute severity contribute to the short-term, but also to the long-term prognosis. Besides mortality, functional status and quality of life are major outcome variables. The geriatric assessment is a key tool for long-term qualitative outcome, while immediate severity accounts for acute mortality. A poor functional baseline reduces the chances of a successful outcome following ICU. This review emphasises the importance of using a geriatric assessment and considering the older patient as a whole, rather than the acute illness in isolation, when making decisions regarding intensive care treatment.

Obesity accelerates age defects in B cells, and weight loss improves B cell function

BACKGROUND

We have previously shown that obesity accelerates age-associated defects in B cell function and antibody production leading to decreased secretion of protective antibodies and increased autoimmunity. We wanted to evaluate if obese adults enrolled in a voluntary weight reduction program had higher protective and lower autoimmune antibody responses similar to those observed in lean adults.

METHODS

Experiments were performed using blood isolated from an established cohort of female lean adult and elderly individuals, as well as from the blood of female adults with obesity, before and after a voluntary weight reduction program in which their Body Mass Index (BMI) was reduced 10-34% in 12 months. All participants were vaccinated with the Trivalent Inactivated Influenza vaccine. Serum samples were evaluated for the presence of pro-inflammatory cytokines and adipokines, vaccine-specific antibodies and autoimmune antibodies. We evaluated the composition of the B cell pool by flow cytometry, the expression of RNA for class switch transcription factors and pro-inflammatory markers by qPCR, the in vitro secretion of pro- and anti-inflammatory cytokines and their capacity to induce pro-inflammatory T cells.

RESULTS

Obesity, similar to aging, induced increased serum levels of pro-inflammatory cytokines and autoimmune antibodies, while vaccine-specific antibodies were reduced. In agreement with the serum results, the B cell pool of obese adults and elderly individuals was enriched in pro-inflammatory B cell subsets and was characterized by higher expression of markers associated with cell senescence, higher levels of T-bet, the transcription factor for autoimmune antibodies and lower levels of E47, the transcription factor associated with protective responses to the influenza vaccine. B cells from obese adults and elderly individuals were also able to secrete inflammatory cytokines and support the generation of inflammatory T cells. All these pro-inflammatory characteristics of B cells from obese individuals were significantly attenuated, but not completely reversed, by weight loss.

CONCLUSIONS

Although the results from our small observational study show that obesity-induced dysfunctional B cell responses, similar to those occurring during aging, are ameliorated in some but not all obese individuals after weight loss, the effects of body weight loss on mechanistic pathways are largely missing and deserve further investigation.

The link between lymphocyte subpopulations in peripheral blood and metabolic variables in patients with severe obesity

Background

Obesity, a public health problem, is a state of metainflammation that influences the development of chronic degenerative diseases, particularly in patients with severe obesity.

Objective

The objective of this study was to evidence immunometabolic differences in patients with different degrees of obesity, including severe obesity, by determining correlations between lymphocyte subpopulations and metabolic, body composition, and clinical variables.

Methods

Peripheral blood immune cells (CD4+, CD8+ memory and effector T lymphocytes) were analyzed, and measures of body composition, blood pressure, and biochemical composition (glucose, glycated hemoglobin (HbA1c), insulin, C-reactive protein (CRP), and the lipid profile) were carried out in patients with different degrees of obesity.

Results

The patients were classified according to total body fat (TBF) percentage as normal body fat, class 1 and 2 obesity, class 3 obesity, and class 4 obesity. The greater the TBF percentage, the more pronounced the differences in body composition (such as a decrease in the fat-free mass (FFM) that is defined as sarcopenic obesity) and the immunometabolic profile. There was an increase of CD3+ T lymphocytes (mainly CD4+, CD4+CD62-, and CD8+CD45RO+ T lymphocytes) and an increase in the TBF percentage (severity of obesity).

Conclusions

The correlations between lymphocyte subpopulations and metabolic, body composition, and clinical variables demonstrated the existence of a chronic, low-intensity inflammatory process in obesity. Therefore, measuring the immunometabolic profile by means of lymphocyte subpopulations in patients with severe obesity could be useful to determine the severity of the disease and the increased risk of presenting obesity-associated chronic degenerative diseases.

COVID-19: A Comprehensive Review on Cardiovascular Alterations, Immunity, and Therapeutics in Older Adults

Here, we present a review focusing on three relevant issues related to COVID-19 and its impact in older adults (60 years and older). SARS-CoV-2 infection starts in the respiratory system, but the development of systemic diseases accompanied by severe clinical manifestations has also been reported, with cardiovascular and immune system dysfunction being the major ones. Additionally, the presence of comorbidities and aging represent major risk factors for the severity and poor prognosis of the disease. Since aging-associated decline has been largely related to immune and cardiovascular alterations, we sought to investigate the consequences and the underlying mechanisms of these pathologies to understand the severity of the illness in this population. Understanding the effects of COVID-19 on both systems should translate into comprehensive and improved medical care for elderly COVID-19 patients, preventing cardiovascular as well as immunological alterations in this population. Approved therapies that contribute to the improvement of symptoms and a reduction in mortality, as well as new therapies in development, constitute an approach to managing these disorders. Among them, we describe antivirals, cytokine antagonists, cytokine signaling pathway inhibitors, and vaccines.

B cells from old mice induce the generation of inflammatory T cells through metabolic pathways

We have measured the capacity of B cells from young and old mice to induce the differentiation of naïve CD4 + T cells from young mice into pro-inflammatory subsets. We found that only B cells from old mice are inflammatory and induce in vitro secretion of the pro-inflammatory cytokines IL-17A and IFN-γ by T cells. In co-culture experiments, B cells from old mice showed a strong helper function on T cells from young mice, making them pro-inflammatory, and this effect is regulated by metabolic pathways, mainly anaerobic glycolysis, leading to increased RNA expression of the enzyme lactate dehydrogenase (LDHA) and increased secretion of lactate. These results have indicated that lactate is a crucial player of the B cell-induced polarization of T cells. When we measured the effects of lactate on isolated CD4 + T cells from young mice, we found that lactate increases RNA expression of LDHA, secretion of pro-inflammatory cytokines and NF-kB activation. Moreover, lactate effects in culture can be abrogated in the presence of the specific inhibitor of LDHA, FX11. These results altogether may have relevant clinical implications and suggest novel targets for therapeutic interventions in patients with inflammatory conditions and diseases.

How aging impacts vaccine efficacy: known molecular and cellular mechanisms and future directions

Aging leads to a gradual dysregulation of immune functions, one consequence of which is reduced vaccine efficacy. In this review, we discuss several key contributing factors to the age-related decline in vaccine efficacy, such as alterations within the lymph nodes where germinal center (GC) reactions take place, alterations in the B cell compartment, alterations in the T cell compartment, and dysregulation of innate immune pathways. Additionally, we discuss several methods currently used in vaccine development to bolster vaccine efficacy in older adults. This review highlights the multifactorial defects that impair vaccine responses with aging.

Comparison of the deep immune profiling of B cell subsets between healthy adults and Sjögren's syndrome

OBJECTIVES

Detailed analysis targeting B cell subgroups was considered crucial in monitoring autoimmune diseases and treatment responses. Thus, precisely describing the phenotypes of B cell differentiation and their variation in primary Sjögren's syndrome (pSS) is particularly needed.

METHODS

To characterize the proportions and absolute counts of B cell subsets, peripheral blood from 114 healthy adults of China (age range: 19-73 years) and 55 patients with pSS were performed by flow cytometry and CD19, CD20, CD24, CD27, CD38 and IgD were used as surface markers to identify B cell mature process. Age- and gender-stratified analyses were then carried out to improve the interpretation of B cell subsets.

RESULTS

The assessments from healthy adults showed that the proportion of naive B cells presented a significant increase with age. A reversal trend was noted that the percentage of B10 decreased markedly with age. In addition, analysis based on gender showed that the relative percentage and number of naive B cells were higher in females than in males whereas the proportions of switched memory B cells and B10 cells were decreased in female. Patients with pSS exhibited a significant expansion in naïve B cells and unswitched memory B cells, accompanied with decreased switched memory B cells and B10 cells, which were identified to be associated with autoantibody production.

CONCLUSIONS

Our study presented a reliable analysis by flow cytometry to cover the principal B cell subtypes. These different stages of B lymphocytes may have implications for evaluating the activation of pSS and other autoimmune diseases and treatment efficacy.KEY MESSAGESB cell subsets play a pivotal role in the pathogenesis of primary Sjögren's syndrome (pSS) and other autoimmune diseases. A practical and accurate flow cytometry method to profile B cell phenotypes in peripheral blood of healthy adults is especially essential.Additionally, we presented reliable reference ranges for B cell subsets in regards to the local population. Age- and gender-related analyses are available to better understand their influence in immune status and treatment outcome.The distribution of B-cell subsets is found substantially altered in patients with pSS, bringing novel avenues for pSS research in the future.

Modeling interaction networks between host, diet, and bacteria predicts obesogenesis in a mouse model

Host-microbiome interactions are known to have substantial effects on human health, but the diversity of the human microbiome makes it difficult to definitively attribute specific microbiome features to a host phenotype. One approach to overcoming this challenge is to use animal models of host-microbiome interaction, but it must be determined that relevant aspects of host-microbiome interactions are reflected in the animal model. One such experimental validation is an experiment by Ridura et al. In that experiment, transplanting a microbiome from a human into a mouse also conferred the human donor’s obesity phenotype. We have aggregated a collection of previously published host-microbiome mouse-model experiments and combined it with thousands of sequenced and annotated bacterial genomes and metametabolomic pathways. Three computational models were generated, each model reflecting an aspect of host-microbiome interactions: 1) Predict the change in microbiome community structure in response to host diet using a community interaction network, 2) Predict metagenomic data from microbiome community structure, and 3) Predict host obesogenesis from modeled microbiome metagenomic data. These computationally validated models were combined into an integrated model of host-microbiome-diet interactions and used to replicate the Ridura experiment in silico. The results of the computational models indicate that network-based models are significantly more predictive than similar but non-network-based models. Network-based models also provide additional insight into the molecular mechanisms of host-microbiome interaction by highlighting metabolites and metabolic pathways proposed to be associated with microbiome-based obesogenesis. While the models generated in this study are likely too specific to the animal models and experimental conditions used to train our models to be of general utility in a broader understanding of obesogenesis, the approach detailed here is expected to be a powerful tool of investigating multiple types of host-microbiome interactions.

Aging, inflammaging and immunosenescence as risk factors of severe COVID-19

Coronavirus disease 2019 (COVID-19) is a respiratory infectious disease caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is characterized by having a heterogeneous disease course, ranging from asymptomatic and mild symptoms to more severe and critical cases. In most cases the severity of COVID-19 is related to host factors, especially deregulation of the immune response in patients. Even if COVID-19 indiscriminately affects individuals of different age group, ethnicity and economic status; most severe cases and disproportional mortality occur in elderly individuals. This point out that aging is one risk factor for unfavourable clinical outcomes among COVID-19 patients. The biology of aging is a complex process; Aging can alter the structure and function of cells, tissues, and organs resulting in impaired response to stress. Alongside with other systems, the immune system is also affected with the aging process. Immunosenescence is an age associated change in the immune system that affects the overall response to immunological challenges in the elderly. Similarly, apart from the normal inflammatory process, aging is associated with a low grade, sterile, chronic inflammation which is termed as inflammaging. We hypothesized that inflammaging and immunosenescence could play an important role in SARS-CoV-2 pathogenesis and poor recovery from COVID-19 in elderly individuals. This review summarizes the changes in the immune system with age and how these changes play part in the pathogenesis of SARS-CoV-2 and clinical outcome of COVID-19 which could add to the understanding of age associated targeted immunotherapy in the elderly.

B cell-intrinsic changes with age do not impact antibody-secreting cell formation but delay B cell participation in the germinal centre reaction

Vaccines typically protect against (re)infections by generating pathogen-neutralising antibodies. However, as we age, antibody-secreting cell formation and vaccine-induced antibody titres are reduced. Antibody-secreting plasma cells differentiate from B cells either early post-vaccination through the extrafollicular response or from the germinal centre (GC) reaction, which generates long-lived antibody-secreting cells. As the formation of both the extrafollicular antibody response and the GC requires the interaction of multiple cell types, the impaired antibody response in ageing could be caused by B cell intrinsic or extrinsic factors, or a combination of the two. Here, we show that B cells from older people do not have intrinsic defects in their proliferation and differentiation into antibody-secreting cells in vitro compared to those from the younger donors. However, adoptive transfer of B cells from aged mice to young recipient mice showed that differentiation into extrafollicular plasma cells was favoured at the expense of B cells entering the GC during the early stages of GC formation. In contrast, by the peak of the GC response, GC B cells derived from the donor cells of aged mice had expanded to the same extent as those from the younger donors. This indicates that age-related intrinsic B cell changes delay the GC response but are not responsible for the impaired antibody-secreting response or smaller peak GC response in ageing. Collectively, this study shows that B cells from aged individuals are not intrinsically defective in responding to stimulation and becoming antibody-secreting cells, implicating B cell-extrinsic factors as the primary cause of age-associated impairment in the humoral immunity.

Cellular senescence is a key mediator of lung aging and susceptibility to infection

Aging results in systemic changes that leave older adults at much higher risk for adverse outcomes following respiratory infections. Much work has been done over the years to characterize and describe the varied changes that occur with aging from the molecular/cellular up to the organismal level. In recent years, the systemic accumulation of senescent cells has emerged as a key mediator of many age-related declines and diseases of aging. Many of these age-related changes can impair the normal function of the respiratory system and its capability to respond appropriately to potential pathogens that are encountered daily. In this review, we aim to establish the effects of cellular senescence on the disruption of normal lung function with aging and describe how these effects compound to leave an aged respiratory system at great risk when exposed to a pathogen. We will also discuss the role cellular senescence may play in the inability of most vaccines to confer protection against respiratory infections when administered to older adults. We posit that cellular senescence may be the point of convergence of many age-related immunological declines. Enhanced investigation into this area could provide much needed insight to understand the aging immune system and how to effectively ameliorate responses to pathogens that continue to disproportionately harm this vulnerable population.

Investigating population-level immunosenescence: From bench to bedside

The immune response is remodeled with aging in a process called immunosenescence. Some immunologists conceive immunosenescence as an adaptation of immunity to the aged immune-environment rather than a merely collapsed reactivity of immune cells against microbes and tumor cells. Others believe on an uninterrupted activation of the innate immune system with aging, leading to a low grade, sterile and chronic proinflammatory state called inflammaging. For instance, it is possible that chronic infection by cytomegalovirus leads to persistent production of viral load. This phenomenon offers periodic stimuli to the immune system that ultimately contribute to the remodeling of the immune response. If investigating immunosenescence at the cellular level is already a difficult task, considering the population level is much more complex. However, by studying immunosenescence at the population level, we can extract valuable results with viable applications. While studies with animal models allow scientists to deepen their understanding of the mechanisms of immunosenescence, studying large populations can bring practical innovations to medicine and the health system. Many researchers and funders have dedicated themselves to producing methods for the evaluation of immunosenescence on a large scale, aiming to elucidate new mechanisms by which diseases are established in the elderly. The description of how the immune response is remodeled with aging emerges as a new tool to identify the subset of subjects in which unhealthy aging is a matter of time, to help better individualize clinical management and select patients who may benefit. of early interventions. This review focuses on functional assays as valuable methods for measuring the remodeling of the immune response with aging and discuss their clinical impact. We also recall fundamental concepts for understanding the aging process of the immune response. In addition, we highlight future prospects for immunosenescence research.

Immunosenescence, aging and successful aging

Aging induces a series of immune related changes, which is called immunosenescence, playing important roles in many age-related diseases, especially neurodegenerative diseases, tumors, cardiovascular diseases, autoimmune diseases and coronavirus disease 2019(COVID-19). However, the mechanism of immunosenescence, the association with aging and successful aging, and the effects on diseases are not revealed obviously. In order to provide theoretical basis for preventing or controlling diseases effectively and achieve successful aging, we conducted the review and found that changes of aging-related phenotypes, deterioration of immune organ function and alterations of immune cell subsets participated in the process of immunosenescence, which had great effects on the occurrence and development of age-related diseases.

Metformin Enhances B Cell Function and Antibody Responses of Elderly Individuals With Type-2 Diabetes Mellitus

Our previous work has shown that young and elderly patients with Type-2 Diabetes Mellitus (T2DM) treated with Metformin have optimal B cell function and serum antibodies specific for the seasonal influenza vaccine. In this paper, we have evaluated B cell function and the metabolic requirements of B cell antibody responses in elderly T2DM patients (E_T2DM) taking or not Metformin, and compared to those of healthy elderly (E_H) and healthy young (Y_H) individuals. Results show that Metformin significantly increases in vivo B cell function, measured by influenza vaccine-specific serum antibodies, in E_T2DM patients to the levels observed in E_H and more importantly in Y_H individuals. Metformin also decreases the frequencies of pro-inflammatory B cell subsets, as well as intrinsic inflammation and metabolic requirements of peripheral B cells from E_T2DM. This hyper-metabolic phenotype of B cells from E_T2DM is needed to support intrinsic inflammation, measured by the expression of transcripts for markers of the senescence-associated secretory phenotype (SASP), and the secretion of autoimmune antibodies. Importantly, B cell function in E_T2DM patients taking Metformin is not only increased as compared to that in E_T2DM patients not taking Metformin, but is comparable to B cell function measured in Y_H individuals. These results altogether strongly support the anti-aging effects of Metformin on humoral immunity.

Lifelong cytomegalovirus and early-LIFE irradiation synergistically potentiate age-related defects in response to vaccination and infection

While whole-body irradiation (WBI) can induce some hallmarks of immune aging, (re)activation of persistent microbial infection also occurs following WBI and may contribute to immune effects of WBI over the lifespan. To test this hypothesis in a model relevant to human immune aging, we examined separate and joint effects of lifelong latent murine cytomegalovirus (MCMV) and of early-life WBI over the course of the lifespan. In late life, we then measured the response to a West Nile virus (WNV) live attenuated vaccine, and lethal WNV challenge subsequent to vaccination. We recently published that a single dose of non-lethal WBI in youth, on its own, was not sufficient to accelerate aging of the murine immune system, despite widespread DNA damage and repopulation stress in hematopoietic cells. However, 4Gy sub-lethal WBI caused manifest reactivation of MCMV. Following vaccination and challenge with WNV in the old age, MCMV-infected animals experiencing 4Gy, but not lower, dose of sub-lethal WBI in youth had reduced survival. By contrast, old irradiated mice lacking MCMV and MCMV-infected, but not irradiated, mice were both protected to the same high level as the old non-irradiated, uninfected controls. Analysis of the quality and quantity of anti-WNV immunity showed that higher mortality in MCMV-positive WBI mice correlated with increased levels of MCMV-specific immune activation during WNV challenge. Moreover, we demonstrate that infection, including that by WNV, led to MCMV reactivation. Our data suggest that MCMV reactivation may be an important determinant of increased late-life mortality following early-life irradiation and late-life acute infection.

Aging and Microbiome in the Modulation of Vaccine Efficacy

From infancy through to old age, the microbiome plays an important role in modulating the host-immune system. As we age, our immune system and our gut microbiota change significantly in composition and function, which is linked to an increased vulnerability to infectious diseases and a decrease in vaccine responses. Our microbiome remains largely stable throughout adulthood; however, aging causes a major shift in the composition and function of the gut microbiome, as well as a decrease in diversity. Considering the critical role of the gut microbiome in the host-immune system, it is important to address, prevent, and ameliorate age-related dysbiosis, which could be an effective strategy for preventing/restoring functional deficits in immune responses as we grow older. Several factors, such as the host’s genetics and nutritional state, along with the gut microbiome, can influence vaccine efficacy or reaction. Emerging evidence suggests that the microbiome could be a significant determinant of vaccine immunity. Physiological mechanisms such as senescence, or the steady loss of cellular functions, which affect the aging process and vaccination responses, have yet to be comprehended. Recent studies on several COVID-19 vaccines worldwide have provided a considerable amount of data to support the hypothesis that aging plays a crucial role in modulating COVID-19 vaccination efficacy across different populations.

Competent immune responses to SARS-CoV-2 variants in older adults following two doses of mRNA vaccination

Aging is associated with a reduced magnitude of primary immune responses to vaccination. mRNA-based SARS-CoV-2 vaccines have shown efficacy in older adults but virus variant escape is still unclear. Here we analyze humoral and cellular immunity against an early-pandemic viral isolate and compare that to the P.1 (Gamma) and B.1.617.2 (Delta) variants in two cohorts (<50 and >55 age) of mRNA vaccine recipients. We further measure neutralizing antibody titers for B.1.617.1 (Kappa) and B.1.595, with the latter SARS-CoV-2 isolate bearing the spike mutation E484Q. Robust humoral immunity is measured following second vaccination, and older vaccinees manifest cellular immunity comparable to the adult group against early-pandemic SARS-CoV-2 and more recent variants. More specifically, the older cohort has lower neutralizing capacity at 7-14 days following the second dose but equilibrates with the younger cohort after 2-3 months. While long-term vaccination responses remain to be determined, our results implicate vaccine-induced protection in older adults against SARS-CoV-2 variants and inform thinking about boost vaccination.

Breakthrough COVID-19 Infections in the US: Implications for Prolonging the Pandemic

The incidence of COVID-19 breakthrough infections-an infection that occurs after you have been vaccinated-has increased in frequency since the Delta and now Omicron variants of the SARS-CoV-2 coronavirus have become the dominant strains transmitted in the United States (US). Evidence suggests that individuals with breakthrough infections, though rare and expected, may readily transmit COVID-19 to unvaccinated populations, posing a continuing threat to the unvaccinated. Here, we examine factors contributing to breakthrough infections including a poor immune response to the vaccines due to the fact of advanced age and underlying comorbidities, the natural waning of immune protection from the vaccines over time, and viral variants that escape existing immune protection from the vaccines. The rise in breakthrough infections in the US and how they contribute to new infections, specifically among the unvaccinated and individuals with compromised immune systems, will create the need for additional booster vaccinations or development of modified vaccines that directly target current variants circulating among the general population. The need to expedite vaccination among the more than 49.8 million unvaccinated eligible people in the US is critical.

Analysis of Immune and Inflammation Characteristics of Atherosclerosis from Different Sample Sources

Background

Atherosclerosis is the predominant cause of cardiovascular diseases. Existing studies suggest that the development of atherosclerosis is closely related to inflammation and immunity, but whether there are differences and similarities between atherosclerosis occurring at different sites is still unknown. We elucidated the pathological characteristics of peripheral vascular diseases by using bioinformatic analyses on immune cells and inflammation-related gene expression in atherosclerotic arteries and plaques.

Methods

Eight data sets regarding atherosclerosis were downloaded from the Gene Expression Omnibus database. Human immune genes were obtained from the IMMPORT website. The samples were scored and divided into high- and low-immune groups. Then the samples were analysed using weighted gene co-expression network analysis, while the modules were analysed using functional enrichment. The protein–protein interaction network was constructed using the STRING and Cytoscape databases. The hub immune genes were screened, and the correlation between hub immune genes and immune cells was analysed.

Results

Immune cells and their functions were significantly different during atherosclerosis development. The infiltration proportion of immune cells was approximately similar in samples from different sources of patients with carotid atherosclerosis. However, the sensitivity of lower extremity atherosclerosis samples to immune cells is lower than that of carotid atherosclerosis samples.The samples from the plaque and artery were mainly infiltrated by macrophages, T cells and mast cells. After immune cells were assessed, resting NK cells, activated mast cells and M0 macrophages were found to be key immune cells in atherosclerosis and plaque formation. In addition, CCL4, TLR2, IL1B and PTPRC were considered to be immune marker genes in atherosclerosis development. Conclusion. Bioinformatic data analysis confirms the essential role of immune cells in cardiovascular diseases, and also indicates some differences of immune and inflammation characteristics of atherosclerosis between carotid and lower extremity arteries.

An old problem with new solutions: Strategies to improve vaccine efficacy in the elderly

Vaccination is the most effective measure to protect against infections. However, with increasing age, there is a progressive decline in the ability of the immune system to both protect against infection and develop protective immunity from vaccination. This age-related decline of the immune system is due to age-related changes in both the innate and adaptive immune systems. With an aging world population and increased risk of pandemics, there is a need to continue to develop strategies to increase vaccine responses in the elderly. Here, the major age-related changes that occur in both the innate and adaptive immune responses that impair the response to vaccination in the elderly will be highlighted. Existing and future strategies to improve vaccine efficacy in the elderly will then be discussed, including adjuvants, delivery methods, and formulation. These strategies provide mechanisms to improve the efficacy of existing vaccines and develop novel vaccines for the elderly.

Analysis of R848 as an Adjuvant to Improve Inactivated Influenza Vaccine Immunogenicity in Elderly Nonhuman Primates

Elderly individuals are highly susceptible to developing severe outcomes as a result of influenza A virus (IAV) infection. This can be attributed to alterations that span the aged immune system, which also result in reduced responsiveness to the seasonal inactivated vaccine. Given the rapidly increasing number of individuals in this age group, it is imperative that we develop strategies that can better protect this population from IAV-associated disease. Based on our previous findings that the TLR7/8 agonist resiquimod (R848) could efficiently boost responses in the newborn, another population with decreased vaccine responsiveness, we evaluated this adjuvant in an elderly African green monkey (AGM) model. AGM aged 16-24 years old (equivalent to 64-96 in human years) were primed and boosted with inactivated A/PuertoRico/8/1934 (H1N1) (IPR8) alone or directly linked to R848 (IPR8-R848). We observed increases in the level of circulating virus-specific IgM antibody 10 days following primary vaccination in AGM that were vaccinated with IPR8-R848, but not IPR8 alone. In addition, there were significant increases in virus-specific IgG after boosting selectively in the IPR8-R848 vaccinated animals. These findings provide insights into the ability of R848 to modulate the aged immune system in the context of IAV vaccination.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Rebalancing the unbalanced aged immune system - A special focus on zinc

Nowadays, aging is understood as a dynamic and multifaceted dysregulation process that spares almost no human organ or cell. The immune system being among the most affected, it has been shown predominantly that its integrity determines the tightrope walk between the difference of escaping or suffering from age-related diseases. Next to drug-based anti-aging strategies, micronutrient intervention may represent an emerging but less radical way to slow immune aging. While a sufficient supply of a variety of micronutrients is undeniably important, adequate intake of the trace element zinc appears to tower over others in terms of reaching old age. Inconveniently, zinc deficiency prevalence among the elderly is high, which in turn contributes to increased susceptibility to infection, decreased anti-tumor immunity as well as attenuated response to vaccination. Driven by this research, this review aims to provide a comprehensive and up-to-date overview of the various rebalancing capabilities of zinc in the unbalanced immune system of the elderly. This includes an in-depth and cell type-centered discussion on the role of zinc in immunosenescence and inflammaging. We further address upcoming translational aspects e.g. how zinc deficiency promotes the flourishing of certain pathogenic taxa of the gut microbiome and how zinc supply counteracts such alterations in a manner that may contribute to longevity. In the light of the ongoing COVID-19 pandemic, we also briefly review current knowledge on the interdependency between age, zinc status, and respiratory infections. Based on two concrete examples and considering the latest findings in the field we conclude our remarks by outlining tremendous parallels between suboptimal zinc status and accelerated aging on the one hand and an optimized zinc status and successful aging on the other hand.

Mechanisms underpinning poor antibody responses to vaccines in ageing

Vaccines are a highly effective intervention for conferring protection against infections and reducing the associated morbidity and mortality in vaccinated individuals. However, ageing is often associated with a functional decline in the immune system that results in poor antibody production in older individuals after vaccination. A key contributing factor of this age-related decline in vaccine efficacy is the reduced size and function of the germinal centre (GC) response. GCs are specialised microstructures where B cells undergo affinity maturation and diversification of their antibody genes, before differentiating into long-lived antibody-secreting plasma cells and memory B cells. The GC response requires the coordinated interaction of many different cell types, including B cells, T follicular helper (Tfh) cells, T follicular regulatory (Tfr) cells and stromal cell subsets like follicular dendritic cells (FDCs). This review discusses how ageing affects different components of the GC reaction that contribute to its limited output and ultimately impaired antibody responses in older individuals after vaccination. An understanding of the mechanisms underpinning the age-related decline in the GC response is crucial in informing strategies to improve vaccine efficacy and extend the healthy lifespan amongst older people.

Patho-Physiology of Aging and Immune-Senescence: Possible Correlates With Comorbidity and Mortality in Middle-Aged and Old COVID-19 Patients

During the last 2 years, the entire world has been severely devastated by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic (COVID-19) as it resulted in several million deaths across the globe. While the virus infects people indiscriminately, the casualty risk is higher mainly in old, and middle-aged COVID-19 patients. The incidences of COVID-19 associated co-morbidity and mortality have a great deal of correlation with the weakened and malfunctioning immune systems of elderly people. Presumably, due to the physiological changes associated with aging and because of possible comorbidities such as diabetes, hypertension, obesity, cardiovascular, and lung diseases, which are more common in elderly people, may be considered as the reason making the elderly vulnerable to the infection on one hand, and COVID-19 associated complications on the other. The accretion of senescent immune cells not only contributes to the deterioration of host defense, but also results in elevated inflammatory phenotype persuaded immune dysfunction. In the present review, we envisage to correlate functioning of the immune defense of older COVID-19 patients with secondary/super infection, increased susceptibility or aggravation against already existing cancer, infectious, autoimmune, and other chronic inflammatory diseases. Moreover, we have discussed how age-linked modulations in the immune system affect therapeutic response against administered drugs as well as immunological response to various prophylactic measures including vaccination in the elderly host. The present review also provides an insight into the intricate pathophysiology of the aging and the overall immune response of the host to SARS-CoV-2 infection. A better understanding of age-related immune dysfunction is likely to help us in the development of targeted preemptive strategies for deadly COVID-19 in elderly patients.

The Dynamics of B Cell Aging in Health and Disease

Aging is considered to be an important risk factor for several inflammatory diseases. B cells play a major role in chronic inflammatory diseases by antibody secretion, antigen presentation and T cell regulation. Different B cell subsets have been implicated in infections and multiple autoimmune diseases. Since aging decreases B cell numbers, affects B cell subsets and impairs antibody responses, the aged B cell is expected to have major impacts on the development and progression of these diseases. In this review, we summarize the role of B cells in health and disease settings, such as atherosclerotic disease. Furthermore, we provide an overview of age-related changes in B cell development and function with respect to their impact in chronic inflammatory diseases.

The influences of α-hemolytic Streptococcus on class switching and complement activation of human tonsillar cells in IgA nephropathy

While β-hemolytic streptococcus (β-HS) infections are known to predispose patients to acute poststreptococcal glomerulonephritis, there is evidence that implicates α-hemolytic streptococcus (α-HS) in IgA nephropathy (IgAN). The alternative pathway of the complement system has also been implicated in IgAN. We aimed to explore the association between α-HS and complement activation in human tonsillar mononuclear cells (TMCs) in IgAN. In our study, α-HS induced higher IgA levels than IgG levels, while β-HS increased higher IgG levels than IgA levels with more activation-induced cytidine deaminase, in TMCs in the IgAN group. Aberrant IgA1 O-glycosylation levels were higher in IgAN patients with α-HS. C3 and C3b expression was decreased in IgAN patients, but in chronic tonsillitis control patients, the expression decreased only after stimulation with β-HS. Complement factor B and H (CFH) mRNA increased, but the CFH concentration in culture supernatants decreased with α-HS. The percentage of CD19 + CD35 + cells/complement receptor 1 (CR1) decreased with α-HS more than with β-HS, while CD19 + CD21 + cells/complement receptor 2 (CR2) increased more with β-HS than with α-HS. The component nephritis-associated plasmin receptor (NAPlr) of α-HS was not detected on tonsillar or kidney tissues in IgAN patients and was positive on cultured TMCs and mesangial cells. We concluded that α-HS induced the secretion of aberrantly O-glycosylated IgA while decreasing the levels of the inhibitory factor CFH in culture supernatants and CR1 + B cells. These findings provide testable mechanisms that relate α-HS infection to abnormal mucosal responses involving the alternative complement pathway in IgAN.

Immune response to COVID-19 in older adults

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the third highly pathogenic coronavirus to emerge in the human population in last two decades. SARS-CoV-2 spread from Wuhan, China, across the globe, causing an unprecedented public healthcare crisis. The virus showed remarkable age dependent pathology, with symptoms resembling common cold in most adults and children while causing more severe respiratory distress and significant mortality in older and frail humans. Even before the SARS-CoV-2 outbreak infectious diseases represented one of the major causes of death of older adults. Loss of immune function and reduced protection from infectious agents with age - immunosenescence - is a result of complex mechanisms affecting production and maintenance of immune cells as well as the initiation, maintenance and termination of properly directed immune responses. Here we briefly discuss the current knowledge on how this process affects age-dependent outcomes of SARS-CoV-2 infection.

Review of Influenza Virus Vaccines: The Qualitative Nature of Immune Responses to Infection and Vaccination Is a Critical Consideration

Influenza viruses have affected the world for over a century, causing multiple pandemics. Throughout the years, many prophylactic vaccines have been developed for influenza; however, these viruses are still a global issue and take many lives. In this paper, we review influenza viruses, associated immunological mechanisms, current influenza vaccine platforms, and influenza infection, in the context of immunocompromised populations. This review focuses on the qualitative nature of immune responses against influenza viruses, with an emphasis on trained immunity and an assessment of the characteristics of the host–pathogen that compromise the effectiveness of immunization. We also highlight innovative immunological concepts that are important considerations for the development of the next generation of vaccines against influenza viruses.

B Cell Immunosenescence

Innate and adaptive immune responses decline with age, leading to greater susceptibility to infectious diseases and reduced responses to vaccines. Diseases are more severe in old than in young individuals and have a greater impact on health outcomes such as morbidity, disability, and mortality. Aging is characterized by increased low-grade chronic inflammation, so-called inflammaging, that represents a link between changes in immune cells and a number of diseases and syndromes typical of old age. In this review we summarize current knowledge on age-associated changes in immune cells with special emphasis on B cells, which are more inflammatory and less responsive to infections and vaccines in the elderly. We highlight recent findings on factors and pathways contributing to inflammaging and how these lead to dysfunctional immune responses. We summarize recent published studies showing that adipose tissue, which increases in size with aging, contributes to inflammaging and dysregulated B cell function.

Surviving older patients show preserved cellular and humoral immunological memory several months after SARS-CoV-2 infection

Understanding how older people respond to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical if we are to confront the coronavirus disease 2019 (COVID-19) pandemic and establish effective vaccination strategies. Immunosenescence reduces the ability to respond to neoantigens and may compromise the life of infected individuals. Here, we analyzed the immunological memory to SARS-CoV-2 in 102 recovered patients aged over 60 years several months after the infection had been resolved. Specific memory T lymphocytes against the virus were measured by interferon-γ (IFN-γ) and granzyme B release by ELISpot; memory B-lymphocyte responses were quantified by detection of anti-S IgG1 producer cells by ELISpot and anti-S and anti-N antibodies were determined by enzyme-linked immunosorbent assay (ELISA). Memory T lymphocytes were found in peripheral blood of most of the studied donors, more than 7 months after the infection in some of them. Fewer patients maintained memory B lymphocytes, but antibodies, mainly anti-S, were highly durable and positively correlated with T responses. More robust humoral responses were found in patients who had more severe symptoms and had been admitted to hospital. We concluded that specific immunity against SARS-CoV-2 is effectively preserved regardless of age, despite the great heterogeneity of their immune responses, and that memory T lymphocytes and anti-S IgG might be more durable than memory B cells and anti-N IgG.

"An Intrinsic Program Determines Key Age-Associated Changes in Adaptive Immunity that Limit Response to Non-Pathogens."

As mice age their adaptive immune system changes dramatically, leading to weakened responses to newly encountered antigens and poor efficacy of vaccines. A shared pattern emerges in the aged, with both CD4 T and B cell responses requiring higher levels of pathogen recognition. Moreover, in aged germ-free mice we find accumulation of the same novel age-associated T and B cell subsets that we and others have previously identified using mice maintained in normal laboratory animal housing conditions, suggesting that their development follows an intrinsic program.

Aging and respiratory viral infection: from acute morbidity to chronic sequelae

The altered immune response in aged hosts play a vital role in contributing to their increased morbidity and mortality during respiratory virus infections. The aged hosts display impaired antiviral immune response as well as increased risk for long-term pulmonary sequelae post virus clearance. However, the underlying cellular and molecular mechanisms driving these alterations of the immune compartment have not been fully elucidated. During the era of COVID-19 pandemic, a better understanding of such aspects is urgently needed to provide insight that will benefit the geriatric patient care in prevention as well as treatment. Here, we review the current knowledge about the unique immune characteristics of aged hosts during homeostasis and respiratory virus infections.

B and T Lymphocyte Densities Remain Stable With Age in Human Cortex

One hallmark of human aging is increased brain inflammation represented by glial activation. With age, there is also diminished function of the adaptive immune system, and modest decreases in circulating B- and T-lymphocytes. Lymphocytes traffic through the human brain and reside there in small numbers, but it is unknown how this changes with age. Thus we investigated whether B- and T-lymphocyte numbers change with age in the normal human brain. We examined 16 human subjects in a pilot study and then 40 human subjects from a single brain bank, ranging in age from 44–96 years old, using rigorous criteria for defining neuropathological changes due to age alone. We immunostained post-mortem cortical tissue for B- and T-lymphocytes using antibodies to CD20 and CD3, respectively. We quantified cell density and made a qualitative assessment of cell location in cortical brain sections, and reviewed prior studies. We report that density and location of both B- and T-lymphocytes do not change with age in the normal human cortex. Solitary B-lymphocytes were found equally in intravascular, perivascular, and parenchymal locations, while T-lymphocytes appeared primarily in perivascular clusters. Thus, any change in number or location of lymphocytes in an aging brain may indicate disease rather than normal aging.

B Cell Responses against Influenza Viruses: Short-Lived Humoral Immunity against a Life-Long Threat

Antibodies are critical for providing protection against influenza virus infections. However, protective humoral immunity against influenza viruses is limited by the antigenic drift and shift of the major surface glycoproteins, hemagglutinin and neuraminidase. Importantly, people are exposed to influenza viruses throughout their life and tend to reuse memory B cells from prior exposure to generate antibodies against new variants. Despite this, people tend to recall memory B cells against constantly evolving variable epitopes or non-protective antigens, as opposed to recalling them against broadly neutralizing epitopes of hemagglutinin. In this review, we discuss the factors that impact the generation and recall of memory B cells against distinct viral antigens, as well as the immunological limitations preventing broadly neutralizing antibody responses. Lastly, we discuss how next-generation vaccine platforms can potentially overcome these obstacles to generate robust and long-lived protection against influenza A viruses.

Biomarkers of Senescence during Aging as Possible Warnings to Use Preventive Measures

Human life expectancy is increasing significantly over time thanks to the improved possibility for people to take care of themselves and the higher availability of food, drugs, hygiene, services, and assistance. The increase in the average age of the population worldwide is, however, becoming a real concern, since aging is associated with the rapid increase in chronic inflammatory pathologies and degenerative diseases, very frequently dependent on senescent phenomena that occur alongside with senescence. Therefore, the search for reliable biomarkers that can diagnose the possible onset or predict the risk of developing a disease associated with aging is a crucial target of current medicine. In this review, we construct a synopsis of the main addressable biomarkers to study the development of aging and the associated ailments.

The aging lung: Physiology, disease, and immunity

The population is aging at a rate never seen before in human history. As the number of elderly adults grows, it is imperative we expand our understanding of the underpinnings of aging biology. Human lungs are composed of a unique panoply of cell types that face ongoing chemical, mechanical, biological, immunological, and xenobiotic stress over a lifetime. Yet, we do not fully appreciate the mechanistic drivers of lung aging and why age increases the risk of parenchymal lung disease, fatal respiratory infection, and primary lung cancer. Here, we review the molecular and cellular aspects of lung aging, local stress response pathways, and how the aging process predisposes to the pathogenesis of pulmonary disease. We place these insights into context of the COVID-19 pandemic and discuss how innate and adaptive immunity within the lung is altered with age.

Analysis of the heterogeneity of the BCR H-CDR3 repertoire in the bone marrow and spleen of 3-, 12-, and 20-month old mice

The number of central and peripheral B cells and their responsiveness are decreased in aged mice. The diversity of mice central and peripheral B cell repertoires with increasing age has not been elucidated. In this study, we demonstrated that there were significant differences in the usage of some V, D, and J genes in the BCR H-CDR3 repertoire of bone marrow B cells, spleen B cells and spleen memory B cells in 3-, 12-, and 20-month-old mice. In the productive, pseudogene, and out-of-frame sequences, bone marrow B cells had significant differences in 5′J trimming with age; peripheral spleen B cells and memory B cells had significant differences in N1 insertion, N2 insertion, P5’D insertion, and 5’D trimming with age. The BCR H-CDR3 repertoire diversity of mice bone marrow B cells, spleen B cells and spleen memory B cells decreased with increasing age. The proportion of overlap in bone marrow and spleen B cells, but not spleen memory B cells, of mice at different ages was lower at 3 months than at 12 and 20 months. This study is the first to report the homogeneity and heterogeneity of the CDR3 repertoire of central and peripheral B cells change as mice age, to further investigation of the decline and response of B cell immunity in young/middle/old-aged mice.