Ageing and infection

Significance of radio-pathological correlations: differentiating severe central nervous system infection from acute embolic infarction

We describe two educational autopsy cases of severe central nervous system (CNS) infection and septic emboli, such cases having been difficult to differentiate from acute infarctions via emergency MR imaging studies. We briefly discuss the pathology and MR findings along with radiopathological correlation.

Micronutrient deficiencies are associated with impaired immune response and higher burden of respiratory infections in elderly Ecuadorians

The proportion of the Latin American population above age 65 y is expected to rise substantially. To better define the prevalence of infectious diseases and micronutrient deficiencies, assess immunological status, and evaluate associations between nutritional status and infection, we performed a cross-sectional study of elderly Ecuadorians in a low-income peri-urban community in Quito, Ecuador. Culturally adapted questionnaires, delayed type hypersensitivity (DTH) skin response, micronutrient, and immunological assays were performed in randomly selected Ecuadorians aged > or = 65 y. Multiple linear and logistic regression models were developed to assess relationships between micronutrient concentrations and history of infection, DTH, and immune function. Participants (n = 352; mean age +/- SD, 74.4 +/- 6.4 y) recalled recent episodes of colds/influenza-like syndromes (62.8%), cough (61.0%), urinary tract infection (37.9%), diarrhea (32.2%), fever (24.1%), and pneumonia (3.5%). A prospective substudy of respiratory infections (RI) in 203 elderly revealed similar findings. Colds and pneumonia occurred in 42.8 and 7.9% of participants, respectively, during 737 person-weeks of observation (3.6 +/- 1.1 wk per person). Anemia and micronutrient deficiencies, especially for vitamins C, D, B-6, and B-12 and folic acid and zinc, were common. Plasma vitamin C was associated with interferon-gamma (IFNgamma) (P < 0.01) and zinc with IFNgamma and interleukin-2 (each P < 0.0001). RI history was associated with any micronutrient deficiency (P < 0.001). The burden of infectious diseases, micronutrient deficiencies, and anemia was substantial in this elderly Ecuadorian population. Deficiencies of essential vitamins and minerals place these elderly adults at risk for infections through their negative impact on immune function.

Non-regulatory CD8+CD45RO+CD25+ T-lymphocytes may compensate for the loss of antigen-inexperienced CD8+CD45RA+ T-cells in old age

The age-related decline in immune system functions is responsible for the increased prevalence of infectious diseases and the low efficacy of vaccination in elderly individuals. In particular, the number of peripheral naive T-cells declines throughout life and they exhibit severe functional defects at advanced age. However, we have recently identified a non-regulatory CD8+CD45RO+ CD25+ T-cell subset that occurs in a subgroup of healthy elderly individuals, who still exhibit an intact humoral immune response following influenza vaccination. Here, we demonstrate that CD8+CD45RO+CD25+ T-cells share phenotypic and functional characteristics with naive CD8+CD45RA+CD28+ T-cells from young individuals, despite their expression of CD45RO. CD8+CD45RO+ CD25+ T-cells also have long telomeres and upon antigenic challenge, they efficiently expand in vitro and differentiate into functional effector cells. The expanded population also maintains a diverse T-cell receptor repertoire. In conclusion, CD8+CD45RO+CD25+ T-cells from elderly individuals compensate for the loss of functional naive T-cells and may therefore be used as a marker of immunological competence in old age.

Age-related appearance of a CMV-specific high-avidity CD8+ T cell clonotype which does not occur in young adults

Old age is associated with characteristic changes of the immune system contributing to higher incidence and severity of many infectious diseases. Particularly within the T cell compartment latent infection with human Cytomegalovirus (CMV) is contributing to and accelerating immunosenescence. However, latent CMV infection and reactivation usually does not cause overt symptoms in immunocompetent elderly persons indicating immunological control of disease. Little is still known about the clonal composition of CMV-specific T cell responses in donors of different age. We therefore analyzed CD8⁺ T cells specific for an immunodominant pp65-derived nonamer-peptide (NLVPMVATV; CMV_NLV) in different age-groups. Independent of donor age CMV_NLV-specific CD8⁺ T cells preferentially use the V beta family 8. This family has monoclonal expansions in the majority of donors after stimulation of CD8⁺ T cells with the peptide. By sequencing the CDR3 region of the T cell receptor we demonstrated that CMV_NLV-specific, BV8⁺ CD8⁺ T cells share the conserved CDR3-sequence motif SANYGYT in donors of all age groups. Interestingly, a second conserved clonotype with the CDR3-sequence motif SVNEAF appears in middle-aged and elderly donors. This clonotype is absent in young individuals. The age-related clonotype SVNEAF binds to the pMHC-complex with higher avidity than the clonotype SANYGYT, which is predominant in young adults. The dominance of this high avidity clonotype may explain the lack of overt CMV-disease in old age.

Renal transplantation in the elderly

Elderly patients are increasingly being considered for kidney transplantation due to a global explosion of the aging population with end-stage renal disease (ESRD). However, mounting scarcity of available organs for transplant has led to a wider disparity between organ supply and demand. Consequently, the criteria for accepting kidneys for transplantation have been extended in an attempt to allow the use of organs from elderly donors or those with significant co-morbidities, so-called "expanded criteria donor" (ECD) kidneys. Excellent outcomes have been achieved from ECD kidneys with appropriate donor and recipient profiling and selection. With increasing recovery efforts directed at older donors, the concept of age-matching is becoming more accepted as a method of optimizing utilization of organs in elderly donors and recipients. Utilization of pulsatile perfusion has further improved ECD outcomes and helped the decision-making process for the UNOS (United Network for Organ Sharing) offer. However, age-related immune dysfunction and associated co-morbidities make the elderly transplant recipients ever more susceptible to complications associated with immunosuppressive agents. Consequently, the elderly population is at a higher risk to develop infections and malignancy in the post-transplant period notwithstanding improved transplant outcomes. Appropriate immunosuppressive agents and dosages should be selected to minimize adverse events while reducing the risk of acute rejections and maximizing patient and renal allograft survival.

Differences between naive and memory T cell phenotype in Malawian and UK adolescents: a role for Cytomegalovirus?

Background

Differences in degree of environmental exposure to antigens in early life have been hypothesized to lead to differences in immune status in individuals from different populations, which may have implications for immune responses in later years.

Methods

Venous blood from HIV-negative adolescents and blood from the umbilical cords of babies, born to HIV-negative women, post-delivery was collected and analysed using flow cytometry. T cell phenotype was determined from peripheral blood lymphocytes and cytomegalovirus (CMV) seropositivity was assessed by ELISA in adolescents.

Results

HIV-negative Malawian adolescents were shown to have a lower percentage of naïve T cells (CD45RO^-CD62L^hi CD11a^lo), a higher proportion of memory T cells and a higher percentage of CD28^- memory (CD28^-CD45RO⁺) T cells compared to age-matched UK adolescents. Malawian adolescents also had a lower percentage of central memory (CD45RA^-CCR7⁺) T cells and a higher percentage of stable memory (CD45RA⁺CCR7^-) T cells than UK adolescents. All of the adolescents tested in Malawi were seropositive for CMV (59/59), compared to 21/58 (36%) of UK adolescents. CMV seropositivity in the UK was associated with a reduced percentage of naïve T cells and an increased percentage of CD28^- memory T cells in the periphery. No differences in the proportions of naïve and memory T cell populations were observed in cord blood samples from the two sites.

Conclusion

It is likely that these differences between Malawian and UK adolescents reflect a greater natural exposure to various infections, including CMV, in the African environment and may imply differences in the ability of these populations to induce and maintain immunological memory to vaccines and natural infections.

Functional regulatory T cells accumulate in aged hosts and promote chronic infectious disease reactivation

Declines in immune function are well described in the elderly and are considered to contribute significantly to the disease burden in this population. Regulatory T cells (T(regs)), a CD4(+) T cell subset usually characterized by high CD25 expression, control the intensity of immune responses both in rodents and humans. However, because CD25 expression does not define all T(regs), especially in aged hosts, we characterized T(regs) by the expression of FOXP3, a transcription factor crucial for T(reg) differentiation and function. The proportion of FOXP3(+)CD4(+) T(regs) increased in the blood of the elderly and the lymphoid tissues of aged mice. The expression of functional markers, such as CTLA-4 and GITR, was either preserved or increased on FOXP3(+) T(regs) from aged hosts, depending on the tissue analyzed. In vitro depletion of peripheral T(regs) from elderly humans improves effector T cell responses in most subjects. Importantly, T(regs) from old FoxP3-GFP knock-in mice were suppressive, exhibiting a higher level of suppression per cell than young T(regs). The increased proportion of T(regs) in aged mice was associated with the spontaneous reactivation of chronic Leishmania major infection in old mice, likely because old T(regs) efficiently suppressed the production of IFN-gamma by effector T cells. Finally, in vivo depletion of T(regs) in old mice attenuated disease severity. Accumulation of functional T(regs) in aged hosts could therefore play an important role in the frequent reactivation of chronic infections that occurs in aging. Manipulation of T(reg) numbers and/or activity may be envisioned to enhance the control of infectious diseases in this fragile population.

Age-associated changes in immune and inflammatory responses: impact of vitamin E intervention

Aging is associated with dysregulated immune and inflammatory responses. Declining T cell function is the most significant and best-characterized feature of immunosenescence. Intrinsic changes within T cells and extrinsic factors contribute to the age-associated decline in T cell function. T cell defect seen in aging involves multiple stages from early receptor activation events to clonal expansion. Among extrinsic factors, increased production of T cell-suppressive factor PGE(2) by macrophages (Mphi) is most recognized. Vitamin E reverses an age-associated defect in T cells, particularly naïve T cells. This effect of vitamin E is also reflected in a reduced rate of upper respiratory tract infection in the elderly and enhanced clearance of influenza infection in a rodent model. The T cell-enhancing effect of vitamin E is accomplished via its direct effect on T cells and indirectly by inhibiting PGE(2) production in Mphi. Up-regulated inflammation with aging has attracted increasing attention as a result of its implications in the pathogenesis of diseases. Increased PGE(2) production in old Mphi is a result of increased cyclooxygenase 2 (COX-2) expression, leading to higher COX enzyme activity, which in turn, is associated with the ceramide-induced up-regulation of NF-kappaB. Similar to Mphi, adipocytes from old mice have a higher expression of COX-2 as well as inflammatory cytokines IL-1beta, IL-6, and TNF-alpha, which might also be related to elevated levels of ceramide and NF-kappaB activation. This review will discuss the above age-related immune and inflammatory changes and the effect of vitamin E as nutritional intervention with a focus on the work conducted in our laboratory.

An age-old paradigm challenged: old baboons generate vigorous humoral immune responses to LcrV, a plague antigen

Immune senescence in the elderly results in decreased immunity with a concomitant increase in susceptibility to infection and diminished efficacy of vaccination. Nonhuman primate models have proven critical for testing of vaccines and therapeutics in the general population, but a model using old animals has not been established. Toward that end, immunity to LcrV, a protective Ag from Yersinia pestis, was tested in young and old baboons. Surprisingly, there was no age-associated loss in immune competence; LcrV elicited high-titer, protective Ab responses in the older individuals. The primary responses in the younger baboons were lower, but they did show boosting upon secondary immunization to the levels achieved in the old animals. The LcrV Ag was also tested in mice and, as expected, age-associated loss of immunity was seen; older animals responded with lower-titer Abs and, as a result, were more susceptible to Yersinia challenge. Thus, although age-related loss in immune function has been observed in humans, rodents, and some nonhuman primates, baboons appear to be unusual; they age without losing immune competence.

Age-related changes in eosinophil function in human subjects

BACKGROUND

Aging results in changes in immune cell function that have been described for T-cells, macrophage, neutrophils, and dendritic cells but not for eosinophils. We sought to define age-related changes in eosinophil function and their potential implications for asthma.

METHODS

We recruited human subjects with asthma in two age groups: a younger group (20 to 40 years), and an older group (55 to 80 years). Lung function, induced sputum, and peripheral blood were obtained from each subject. Eosinophils isolated from the peripheral blood were examined for in vitro functional activities including degranulation, superoxide anion production, adhesion, and chemotaxis.

RESULTS

Eosinophil degranulation in response to interleukin-5 stimulation was significantly decreased in the older group (p = 0.025). Eosinophil production of superoxide anions in response to phorbol myristate acetate was lower in the older group but did not achieve statistical significance (p = 0.097). Eosinophil adhesion, eosinophil chemotaxis, lung function, and the percentage of sputum eosinophils were similar in the two groups.

CONCLUSION

Airway eosinophilia is comparable in younger and older asthma subjects. However, there are age-related changes in peripheral blood eosinophil "effector" functions. Diseases such as asthma, in which eosinophils are thought to play a pathophysiologic role, may exhibit important clinical differences in the elderly due to age-related changes in inflammatory cell function that affect the manifestations of the disease and/or responsiveness to specific classes of medications.

T cell subset-specific susceptibility to aging

With increasing age, the competence of the immune system to fight infections and tumors declines. Age-dependent changes have been mostly described for human CD8 T cells, raising the question of whether the response patterns for CD4 T cells are different. Gene expression arrays of memory CD4 T cells yielded a similar age-induced fingerprint as has been described for CD8 T cells. In cross-sectional studies, the phenotypic changes were not qualitatively different for CD4 and CD8 T cells, but occurred much more frequently in CD8 T cells. Homeostatic stability partially explained this lesser age sensitivity of CD4 T cells. With aging, naïve and central memory CD8 T cells were lost at the expense of phenotypically distinct CD8 effector T cells, while effector CD4 T cells did not accumulate. However, phenotypic shifts on central memory T cells were also more pronounced in CD8 T cells. This distinct stability in cell surface marker expression can be reproduced in vitro. The data show that CD8 T cells are age sensitive by at least two partially independent mechanisms: fragile homeostatic control and gene expression instability in a large set of regulatory cell surface molecules.

Immunosupportive therapies in aging

The primary role of the immune system is to protect the organism against pathogens, but age-associated alterations to immunity increase the susceptibility of the elderly to infectious disease. The exact nature of these changes is still controversial, but the use of screening procedures, such as the SENIEUR protocol to exclude underlying illness, helped to better characterize the changes actually related to physiological aging rather than pathology. It is generally agreed that the most marked changes occur in the cellular immune response reflecting profound alterations in T cells. Much of this is due to thymic involution as well as changes in the proportions of T cell subpopulations resulting from antigen exposure, and altered T cell activation pathways. However, a body of data indicates that innate immune responses, including the critical bridge between innate and adaptive immunity, and antigen presenting capacity are not completely resistant to senescence processes. The consequences of all these alterations are an increased incidence of infections, as well as possibly cancers, autoimmune disorders, and chronic inflammatory diseases. The leading question is what, if anything, can we do to prevent these deleterious changes without dangerously dysregulating the precarious balance of productive immunity versus immunopathology? There are many potential new therapeutic means now available to modulate immunosenescence and many others are expected to be available shortly. One main problem in applying these experimental therapies is ethical: there is a common feeling that as ageing is not a disease; the elderly are not sick and therefore do not require adventurous therapies with unpredictable side-effects in mostly frail individuals. Animal models are not helpful in this context. In this chapter we will first briefly review what we think we know about human immunosenescence and its consequences for the health status of elderly individuals. We will then discuss possible interventions that might one day become applicable in an appropriate ethical environment.

Infection in the elderly

Many functional, demographic, and immunologic changes associated with aging are responsible for increasing the incidence and severity of infectious diseases in the elderly. Management is complicated by age-related organ system changes. Because many of the elderly are on multiple medications for underlying illnesses, antimicrobial therapy needs to be chosen keeping drug interactions and adverse events in mind. Common infections seen in the elderly are infections of skin and soft tissue, urinary tract, respiratory tract, and gastrointestinal tract. Organized and well-funded programs to address infectious disease issues in the elderly are the only way to improve care.

Challenges for vaccination in the elderly

The increased susceptibility of the elderly to infection presents a major challenge to public health services. An aging immune system is well documented as the cause of increased infection rates in elderly people. Such immunosenescence is multi-factorial and incompletely understood. Immunosenescent changes include malfunctioning of innate immune system cellular receptors; involution of the thymus, with consequent reduction of the naïve T cell population; alteration of the T cell population composition; modified phenotypes of individual T cells; and replicative senescence of memory cells expressing naïve markers. Unfortunately, immunosenescence also renders vaccination less effective in the elderly. It is therefore important that the vaccines used against common but preventable diseases, such as influenza, are specifically enhanced to overcome the reduced immune responsiveness of this vulnerable population.

Non-human primate models of T-cell reconstitution

Non-human primates (NHP) have become an indispensable model in studying the common and dangerous human chronic infections, including HIV/SIV, Hepatitis C virus, and tuberculosis. More recently, we and others have used aged NHP to model human immune aging. Chronic infections and aging are both characterized by a significant depletion of defined lymphocyte subsets and the compensatory attempts to regenerate the immune system. As the efficacious antiviral drugs and novel methods to improve and boost the immune system emerge, therapeutic immune regeneration has become a realistic goal in both the physiologic and pathologic settings. This article will summarize our current knowledge on this topic and will discuss future research directions as well as the potential and power of translational studies in non-human primate models of infection, aging and bone marrow transplantation.

Effectiveness of MF59-adjuvanted subunit influenza vaccine in preventing hospitalisations for cardiovascular disease, cerebrovascular disease and pneumonia in the elderly

Annual circulation of influenza virus coincides with a peak in cardiovascular and pneumonia mortality/morbidity. This study aimed to determine the effectiveness of MF59-adjuvanted subunit influenza vaccine in preventing hospitalisation due to acute coronary syndrome (ACS), cerebrovascular accident (CVA) and pneumonia in the elderly. Three case-control studies were performed during the 2004-2005 influenza season in three health districts in Valencia, Spain (total elderly [>64 years of age] population: n=105,454). Controls were patients admitted for an acute surgical process or trauma within 10 days of case admission. In total, 159 patients were hospitalised for ACS, 148 for CVA and 242 for pneumonia. The risk of hospitalisation after the start of the influenza season was significantly lower in vaccinated patients compared with non-vaccinated patients (adjusted odds ratios: 0.13 [P=0.013] for ACS; 0.07 [P=0.007] for CVA; 0.31 [P=0.005] for pneumonia). During peak virus circulation, vaccination with MF59-adjuvanted subunit influenza vaccine was associated with an 87% relative risk reduction in hospitalisation for ACS, 93% for CVA, and 69% for pneumonia.

Coxiella burnetiiinfection in C57BL/6 mice aged 1 or 14 months

The objective of this study was to investigate the effects of age on infection with Coxiella burnetii, the agent of Q fever. Bacterial burden and granuloma number were increased in the spleens of 14-month-old as compared with 1-month-old mice. This increase was not the result of an anti-inflammatory macrophage response, because inflammatory and anti-inflammatory cytokines were induced in macrophages from young mice but were repressed in mature mice. In addition, macrophage microbicidal competence was similar in mature and young mice. These results suggest the importance of individual host factors in the pathophysiology of an infectious disease such as Q fever.

Characteristics of elderly tuberculosis patients in Recife, Brazil: a contribution to the tuberculosis control program

OBJECTIVE

To describe the demographic characteristics, everyday habits, socio-economic conditions, clinico-epidemiological profiles and access to health care services among the elderly patients with tuberculosis diagnosed and treated in the city of Recife, Brazil, comparing them to those observed in young adults with tuberculosis.

METHODS

A case-control type strategy was used to evaluate a cohort of patients with tuberculosis, all of whom were treated in public health care facilities in Recife between May of 2001 and July of 2003.

RESULTS

The final cohort consisted of 1127 patients: 136 elderly patients (cases) and 991 young adults (controls). In both groups, males predominated, and the most common form of tuberculosis was the pulmonary form. Alcoholism was more common in the control group, whereas illiteracy was more common in the case group. There were fewer complaints of cough, sweats and chest pain among the patients in the case group than among those in the control group. Serological testing for the human immunodeficiency virus was performed in only 29 patients (2.6%). The percentage of positive sputum smear microscopy results, as well as that of positive cultures, was higher in the controls. Prior to being diagnosed with the disease, patients in both groups had sought treatment at more than two health care facilities and had waited more than two months (after first seeking treatment). The elderly patients presented higher indices of cure and were more often compliant with the treatment regimen, yet presented higher mortality rates.

CONCLUSION

In the population studied, the elderly presented less cough, fewer episodes of night sweats and less chest pain, as well as less often presenting positivity on complementary exams. Nevertheless, the mortality rate was higher among the elderly patients than among the young adult patients. Elderly patients with tuberculosis constitute a population that should be given special attention in public health care facilities.

Anti-tumor necrosis factor alpha therapy and the risk of serious bacterial infections in elderly patients with rheumatoid arthritis

OBJECTIVE

To assess the association between the initiation of anti-tumor necrosis factor alpha (anti-TNFalpha) therapy and the risk of serious bacterial infections in routine care.

METHODS

This was a cohort study of patients with rheumatoid arthritis (RA) in whom specific disease-modifying antirheumatic drugs (DMARDs) were initiated. Patients were Medicare beneficiaries ages 65 years and older (mean age 76.5 years) who were concurrently enrolled in the Pharmaceutical Assistance Contract for the Elderly provided by the state of Pennsylvania. A total of 15,597 RA patients in whom a DMARD was initiated between January 1, 1995 and December 31, 2003 were identified using linked data on all prescription drug dispensings, physician services, and hospitalizations. Initiation of anti-TNFalpha therapy, cytotoxic agents other than methotrexate (MTX), noncytotoxic agents, and glucocorticoids was compared with initiation of MTX. The main outcome measure was serious bacterial infections that required hospitalization.

RESULTS

The incidence of serious bacterial infections was, on average, 2.2 per 100 patient-years in this population (95% confidence interval [95% CI] 2.0-2.4). Glucocorticoid use doubled the rate of serious bacterial infections as compared with MTX use, independent of previous DMARD use (rate ratio [RR] 2.1 [95% CI 1.5-3.1]), with a clear dose-response relationship for dosages >5 mg/day (for < or = 5 mg/day, RR 1.34; for 6-9 mg/day, RR 1.53; for 10-19 mg/day, RR 2.97; and for > or = 20 mg/day, RR 5.48 [P for trend < 0.0001]). Adjusted models showed no increase in the rate of serious infections among initiators of anti-TNFalpha therapy (RR 1.0 [95% CI 0.6-1.7]) or other DMARDs as compared with initiators of MTX.

CONCLUSION

In a large cohort of patients with RA, we found no increase in serious bacterial infections among users of anti-TNFalpha therapy compared with users of MTX. Glucocorticoid use was associated with a dose-dependent increase in such infections.

[Relationship between eating dysfunction and life span and mortality in institutionalized elderly people]

AIM

The aim of this study was to evaluate the relationship between eating disorders and anticipated life span stage and mortality in institutionalized elderly people.

METHODS

Ninety-eight elderly residents (mean 86.3 +/- 5.9 years) at a nursing home were selected for investigation of the date and cause of death. Inclusion was limited to those who died within one week from admission to the institution/hospital. Data on 11 potential prognostic factors were analyzed: underlying disease, activity of daily living (ADL), disorder of anticipatory stage, swallowing function, need for feeding assistance, weight decrease rate in the part 6 months, body mass index (BMI), minimum nutritional assessment (MNA), occlusal status, age and sex. These 11 factors were analyzed by Kaplan-Meier survival curve, and either the log-rank or Wilcoxon test was used to analyze significant differences in survival days in subjects with and without the factors listed above. Moreover, the regression analysis was made using Cox proportional-hazards model, a nonlinear multivariate analysis, to extract factors contributing greatly to short survival days.

RESULTS

The survival days showed significant differences in six factors; ADL, disorder of anticipatory stage, swallowing function, need for feeding assistance, BMI and MNA. Three factors were shown to be related to a significantly shorter mortality by the Cox proportional-hazards model: disorder of anticipatory stage (hazard rate = 2.85, 95% CI = 1.04-7.83), swallowing function (hazard rate = 2.90, 95% CI = 1.06-7.91) and BMI (hazard rate = 2.54, 95% CI = 1.00-6.44) were involved in.

CONCLUSION

This study speculated that an appropriate response with a focus on feeding training may possibly contribute to prolong the mortality of elderly people.

Immunodominant peptides from conserved influenza proteins – A tool for more efficient vaccination in the elderly?

Influenza-specific CD8+ T cells are important for the clearance of infection especially in high risk groups such as elderly persons. Activation of these cells by immunization might therefore be a useful tool for a better protection of this specific age group. We therefore analyzed the frequency, phenotype and function of CD8+ T cells with specificity to the influenza M1(58-66) peptide in young, middle-aged and elderly persons ex vivo and after in vitro stimulation. Significantly lower numbers of M1(58-66)-specific CD8+ T cells were detected in the middle-aged and elderly compared to young donors. M1(58-66)-specific CD8+ T cells were either CD45RA(low)CD45RO(low) or CD45RA-CD45RO+, expressed CD28 and CD62L and did not produce perforin. There was no difference in the phenotype of influenza-specific CD8+ T cells between the three age groups. Despite the initially low numbers of M1(58-66)-specific CD8+ T cells in the older age groups, these cells could be expanded in vitro following peptide stimulation. They also acquired a CD45RO+CD28+ CD62L(+/-) phenotype and produced perforin. Our results demonstrate that although initially low in number, M1(58-66)-specific CD8+ T cells from elderly persons can be propagated and differentiated into perforin producing effector cells upon appropriate stimulation. M1(58-66) peptide or other immunodominant peptides derived from conserved influenza proteins could therefore be useful in future influenza vaccines in order to render elderly persons better protected against disease, in particular in the case of an influenza pandemic.

The Efficacy of Vaccines to Prevent Infectious Diseases in the Elderly

Infectious diseases still represent a major challenge to human progress and survival. Especially elderly persons are more frequently and severely affected by infectious diseases and they display distinct features with respect to clinical presentation and treatment. Although vaccinations are considered a vital medical procedure for preventing morbidity and mortality caused by infectious diseases, the protective effect of vaccinations is abrogated in elderly persons. This is due to a decline in the functions of the immune system referred to as immunosenescence. The first part of this chapter will therefore summarize the status quo of the efficacy of vaccines in preventing morbidity and mortality caused by typical infectious diseases in the elderly, such as influenza, pneumonia and tuberculosis. The second part will then elucidate the underlying age-related mechanisms which may contribute to the decreased efficacy of vaccines. Based on the complex mechanisms involved in immunosenescence, strategies will be outlined which may be succesfful in enhancing protective immune responses following vaccination in elderly persons.

Healthy aging and latent infection with CMV lead to distinct changes in CD8+ and CD4+ T-cell subsets in the elderly

Despite general acceptance that immunologic changes are associated with aging and latent infection with Cytomegalovirus (CMV), no clear-cut distinction has so far been made between strictly age-related and CMV-induced changes. We therefore compared CD4+ and CD8+ naïve (CD45RA+CD28+), memory (CD45RA-CD28+), and effector (CD28-) T cells in CMV-positive (n = 164) and CMV-negative (n = 87) elderly persons and correlated CD8+ and CD4+ effector T cells with other T-cell subpopulations. Percentages of CD8+ as well as CD4+ effector T cells were higher, but percentages of naïve and memory cells were lower in CMV-positive compared to CMV-negative elderly persons. Negative correlations within CD8+ T-cell subsets were found to be present in both CMV-positive and CMV-negative elderly individuals. In contrast, correlations within CD4+ T-cell subpopulations and a positive correlation between CD8+ and CD4+ effector T cells were found in CMV-positive individuals only. Our results demonstrate that (a) in the elderly different T-cell subsets compete for space within the CD8+, but not the CD4+ T-cell population; (b) CMV induces changes in the CD4+ compartment that differ from the solely age-related changes seen in CMV-negative elderly population; and (c) the CMV-status of a population has to be taken into account before a conclusion on the effect of aging on the composition of the T-cell pool can be reached.

Booster vaccination in the elderly: Their success depends on the vaccine type applied earlier in life as well as on pre-vaccination antibody titers

BACKGROUND

Recent retrospective studies demonstrate that elderly persons have a shortened protection period following vaccination with recall antigens.

METHODS

We now analysed the effect of booster vaccination with a multivalent vaccine containing tetanus, dipththeria, pertussis and polio antigens in 252 healthy elderly persons. The magnitude of the humoral immune response was assessed by antibody measurements.

RESULTS

Comparison with a small control group of 21 younger persons demonstrates that pre- and post-vaccination antibody concentrations are lower in elderly persons for all antigens except polio, for which higher pre- and similar post-vaccination antibody levels are observed. Using multiple linear regression analysis we also show that the magnitude of the humoral immune response in elderly persons greatly depends on pre-vaccination antibody concentrations in the case of tetanus, diphtheria and pertussis, but much less so in the case of polio, against which priming and preceding booster immunizations were performed with attenuated live vaccine.

CONCLUSION

Regular booster vaccinations throughout life are of clinical importance to maintain the ability to respond to recall antigens in old age. Longer lasting protection and good responsiveness to boosting in spite of low antibody titres can be expected following exposure to live vaccine earlier in life.

Immunizations in the elderly: do they live up to their promise?

In the 21st century, public health is not only challenged by newly emerging and re-emerging infectious diseases but also by demographic developments that are taking place in many countries. Importantly, infections in the elderly are more frequent, more severe and have distinct features with respect to clinical presentation and treatment. This is due to a decline in the functions of the immune system referred to as immunosenescence. The most important age-related changes affect the T cell system. Although this derogates the protective effect of some vaccines, vaccinations are still considered the most cost-effective medical procedure for preventing morbidity and mortality caused by infectious diseases. The present article aims at outlining the impact of infectious diseases on the elderly and summarizing the progress made in the field of vaccinations of the elderly and how age-related changes within the immune system contribute to the decreased efficacy of vaccines.

Age dependent increase in early resistance of mice to Mycobacterium tuberculosis is associated with an increase in CD8 T cells that are capable of antigen independent IFN-gamma production

The lungs of naïve 18-month-old mice contain an abundant resident population of CD8 T cells that express typical markers of memory, express elevated levels of Th1 cytokine receptors on their surface, and are capable of non-specific IFN-gamma production in response to a Th1 cytokine cocktail. In this study we characterize this population of CD8 T cells in the lungs and spleens of mice with increasing age. In general, the proportion of CD8 T cells expressing markers of memory and Th1 cytokine receptors increased with age. The enhanced ability of CD8 T cells to produce IFN-gamma in an antigen independent manner followed this pattern as well, beginning to increase between 6 and 12 months of age. Interestingly, the phenotypic and functional age-related changes in CD8 T cells were also associated with a progressive age-related increase in early resistance to Mycobacterium tuberculosis. Taken together, these data suggest that as mice age a population of memory CD8 T cells, that are capable of contributing to innate immune responses to M. tuberculosis, gradually emerges and could be relevant for developing strategies to enhance immunity in the elderly.

High frequencies cytomegalovirus pp65(495-503)-specific CD8+ T cells in healthy young and elderly Chinese donors: characterization of their phenotypes and TCR Vbeta usage

Human cytomegalovirus (HCMV) is a ubiquitous beta-herpesvirus which persists lifelong after primary infection and can lead to a significant disease in the immunocompromised individuals. CD8(+) T cells are believed to play a crucial role in both the elimination of active infection and maintenance of HCMV latency. Large expansions of CD8(+) T cells specific for a single epitope of HCMV have been well documented in Caucasoid population. To date, no similar study has been performed in Chinese populations. Here we report the characteristics of HCMV-specific CD8(+) T cells in healthy young and elderly Chinese donors using pp65(495-503)-loaded HLA-A*0201 tetramers. Cells were stained with a combination of the tetramers and antibodies for CD28 and CD57 or a panel of TCR Vbeta and analyzed by three-color flow cytometry. The frequencies of pp65(495-503)-specific T cells within total CD8(+) T cell population were between 0.14 and 6.84% (mean 2.45%) in the young donors and were from 0.33 to 6.89% (mean 1.95%) in the elderly donors, respectively. There was no significant difference between the two groups. The expression of CD28 was decreased whereas CD57 expression was increased in tetramer-negative CD8(+) T cells in the elderly when compared with the young group. However, neither of these changes was found within tetramer-positive cell populations. Moreover, TCR Vbeta usage within tetramer-positive population was predominated by certain TCR Vbeta subsets. These results demonstrate that large expansions of HCMV-specific CD8(+) T cells with certain subsets TCR Vbeta exist both in the healthy young and in the elderly Chinese individuals, which may play a role in the maintenance of virus latency but have potential detrimental influence on the immune responses to other pathogens or vaccinations.

Age-associated changes within CD4+ T cells

As individuals age their ability to respond and clear pathogens declines, leading to a greater incidence and severity of infectious diseases. Additionally, the efficacy of vaccines is frequently decreased in elderly persons. Increased susceptibility to infections and reduced protection after vaccination reflect the impact of age-related changes on the immune system. The immune system undergoes a wide range of changes with increasing age. The aim of this review is to summarize cellular and molecular aspects of aging CD4(+) T cells. CD4(+) T cells play an essential role in mediating both humoral and cellular immune responses. Therefore, age-associated dysfunctions within CD4(+) T cells have a strong clinical impact. Improving our understanding of the aged CD4(+) T cells, in particular but also of the aged immune system in general, is crucial for developing effective prevention and treatment programs which will facilitate healthy aging and improve the quality of life of the elderly population.

Dysregulation of T-cell function in the elderly : scientific basis and clinical implications

The function of the immune system is to maintain body integrity by defending against infections, cancers, autoimmune diseases and inflammation-related chronic diseases. The immune response is known to become defective with aging, leading to decreased longevity and appearance of age-related disease. The most important changes occur in T-cell immunity, and are manifested particularly as altered clonal expansion of cells of limited antigen specificity. The causes of these alterations are multifactorial, and include thymic involution, T-cell subset changes and signal transduction alterations. The clinical consequences of these changes are not well defined, except for their extremely important negative impact on defence against infections, especially by new pathogens, and decreased responses to vaccination. Considering the public health consequences of decreased immune competence in old age, strategies for immune response modulation are desirable to decrease the health burden for the elderly and improve their quality of life.

[Results from biomedical aging research. Trends and current examples from immunology]

The public health of our society is challenged by a continuous increase in life expectancy. Hence, biomedical aging research is enjoying a steadily increasing popularity but also enlightens our understanding of age-related diseases by a number of striking results from basic research. One of the most striking changes that occurs during normal human aging is an overall diminution of immune functions, a phenomenon often termed immunosenescence. Starting from some highly exciting examples from basic immunological research, this article sheds light on which impact normal human aging has on several immune defence mechanisms. In addition, clinical consequences in view of Alzheimer's disease, immunogenicity of vaccines and autoimmune diseases are discussed.

Effects of oral functional training for nutritional improvement in Japanese older people requiring long-term care

OBJECTIVES

The aim of this study was to evaluate the effect of oral functional training and nutrient supplements to improve the nutrition of malnourished elderly people in a nursing home.

BACKGROUND

Malnutrition is a frequent problem in the elderly requiring long-tem care; however, it is not clear whether oral functional training can be effective to improve nutrition.

SUBJECTS AND METHODS

Fourteen subjects of 82 residents (mean age 85.7+or-6.2 years) in a nursing home, who had a serum albumin level of <or=3.8 g/dl and understood the purpose of this study, were randomly divided into two groups of seven: one group served as the supplement group (mean age 87.0+/- 4.9 years) to which a high-calorie and high-protein diet was provided, and the other as the oral training plus supplement group (mean age 84.6+/- 10.1 years) to which oral functional training was given by a dental hygienist once a week as well as the above diet. Nutritional status was evaluated using serum biochemical values as indices at 4 months after the start of the intervention.

RESULTS

In the supplement group, serum albumin was 3.44+/- 0.36 g/dl at the start of the study (before intervention) and 3.24+/- 0.45 g/dl at 4 months after intervention. In the oral training plus supplement group, it was 3.56+/- 0.22 g/dl before intervention and significantly increased to 3.70+/- 0.33 g/dl after intervention (p<0.05: Wilcoxon signed-rank test).

CONCLUSION

Nutritional supplements alone were not adequate, but with oral functional training to maintain and improve feeding function, nutritional improvement in the elderly could be observed.

Geriatric neurologic emergencies

Geriatrics is an important subspecialty within the field of emergency medicine and represents a burgeoning area of practice. The special vulnerability of elderly patients to neurologic disease and injury and the comparative subtlety of clinical presentation mean that physicians should have a lower threshold for laboratory studies, radiologic imaging, consultation, and admission. Transferring appropriate patients to tertiary centers that offer specialized trauma and neurologic and neurosurgical care greatly enhances survival and functional outcomes.

Infectious Emergencies in the Elderly

As life expectancy continues to rise, the number of geriatric patients will increase and the percentages of geriatric patients seen in the emergency department will reflect those numbers. Emergency physicians are responsible for making immediate diagnoses and initiating expeditious treatment. Infectious diseases in the elderly are more prevalent, challenging to diagnose, and are associated with greater morbidity and mortality than with the younger patient population.

Geriatric neutrophils: implications for older adults

OBJECTIVES

To review the intersection of immunosenescence and neutropenia, focusing on innate immunity, and implications for research and practice for neutropenic older adults with cancer.

DATA SOURCES

Research studies, journal articles, and web sites.

CONCLUSION

Immunosenescence, age-related changes within the immune system renders older adults more vulnerable to infection. This vulnerability is magnified by cancer and its treatment. Unfortunately, there has been little consideration of immunosenescence as it relates to supportive care for this population.

IMPLICATIONS FOR NURSING PRACTICE

Studies detailing the impact of immunosenescence on neutropenia and outcomes for neutropenic older adults are necessary to advance clinical research and practice.

Mice and flies and monkeys too: caloric restriction rejuvenates the aging immune system of non-human primates

Humanity has been obsessed with extending life span and reversing the aging process throughout recorded history and this quest most likely preceded the invention of the written word. The search for eternal youth has spurred holy wars and precipitated the discovery of the new world (the 'Fountain of youth'). It therefore comes as no surprise that an increasingly greater amount of research effort is dedicated to improve our understanding of the aging process and finding interventions to moderate its impact on health. Caloric restriction (CR) is the only intervention in biology that consistently extends maximal and median life span in a variety of short-lived species. Several theories to explain the mechanisms of action of CR have been put forth, including the possibility that CR acts by retarding immune senescence. The question remains, however, whether CR will have the same beneficial impact on human aging, and, if so, how long does CR need to last to produce beneficial effects. To address this question, several groups initiated long-term studies in Rhesus macaques (RM) in the 1980s. Here, we review published data describing the impact of CR on the aging immune system of mice and primates, and discuss our unpublished data that delineate similarities and differences in the effects of CR upon T cell aging and homeostasis between these two models.

Procalcitonin and Infection in Elderly Patients

OBJECTIVES

To compare the usefulness of procalcitonin (PCT) in detecting infection in elderly patients with that of other clinical and biological markers.

DESIGN

Prospective observational study to compare PCT levels in infected and uninfected patients.

SETTING

Geriatric teaching hospital in Switzerland.

PARTICIPANTS

Two hundred eighteen elderly patients aged 75 and older admitted to an acute geriatric care unit.

MEASUREMENTS

Demographic characteristics, comorbidities, Charlson index, general signs (respiratory rate, temperature, pulse rate, confusion, falls, shivering), presence of systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, septic shock, functional score (Functional Independence Measurement (FIM)) biological parameters (PCT, C-reactive protein (CRP), leukocytes, albumin), and definite diagnosis at admission were collected prospectively for each patient.

RESULTS

Long-term corticotherapy, chronic immune diseases, fever of 38 degrees C or higher, white blood cell count, pulse rate, FIM, SIRS, sepsis, CRP of 3 mg/mL or higher, and PCT of 0.5 ng/mL or higher were associated with an infection at admission. In multivariate analysis, only sepsis and CRP of 3 mg/mL or higher were still associated with an infection; PCT levels do not show any significant association in the multivariate analysis. In addition, when PCT had good specificity (94%), it had low sensitivity (24%). False-negative PCT was related to lower severity of infection (lower inflammatory reaction and lower acute renal failure) than true-positive PCT. This finding may also be related to aging per se.

CONCLUSION

PCT may be useful to identify severely ill elderly patients admitted to an acute geriatric ward but not to discriminate patients with infection from those without.

CD25-Expressing CD8+T Cells Are Potent Memory Cells in Old Age

We have recently described an IL-2/IL-4-producing CD8+CD25+ non-regulatory memory T cell population that occurs in a subgroup of healthy elderly persons who characteristically still have a good humoral response after vaccination. The present study addresses this specific T cell subset and investigates its origin, clonal composition, Ag specificity, and replicative history. We demonstrate that CD8+CD25+ memory T cells frequently exhibit a CD4+CD8+ double-positive phenotype. The expression of the CD8 alphabeta molecule and the occurrence of signal-joint TCR rearrangement excision circles suggest a thymic origin of these cells. They also have longer telomeres than their CD8+CD25- memory counterparts, thus indicating a shorter replicative history. CD8+CD25+ memory T cells display a polyclonal TCR repertoire and respond to IL-2 as well as to a panel of different Ags, whereas the CD8+CD25- memory T cell population has a more restricted TCR diversity, responds to fewer Ags, and does not proliferate in response to stimulation with IL-2. Molecular tracking of specific clones with clonotypic primers reveals that the same clones occur in CD8+CD25+ and CD8+CD25- memory T cell populations, demonstrating a lineage relationship between CD25+ and CD25- memory CD8+ T cells. Our results suggest that CD25-expressing memory T cells represent an early stage in the differentiation of CD8+ cells. Accumulation of these cells in elderly persons appears to be a prerequisite of intact immune responsiveness in the absence of naive T cells in old age.

Longitudinal trends in antimicrobial susceptibilities across long-term-care facilities: emergence of fluoroquinolone resistance

BACKGROUND

Antibiotic resistance in the longterm-care facility (LTCF) setting is of increasing concern due to both the increased morbidity and mortality related to infections in this debilitated population and the potential for transfer of resistant organisms to other healthcare settings. Longitudinal trends in antibiotic resistance in LTCFs have not been well described.

DESIGN

Correlational longitudinal survey study.

SETTING

Four LTCFs in Pennsylvania.

SUBJECTS

All clinical cultures of residents of the participating LTCFs (700 total beds) from 1998 through 2003. We assessed the annual prevalence of resistance to various antimicrobials of interest for the following organisms: Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus aureus, and enterococcus species.

RESULTS

A total of 4,954 clinical isolates were obtained during the study. A high prevalence of antimicrobial resistance was noted for many organism-drug combinations. This was especially true for fluoroquinolone susceptibility among the Enterobacteriaceae (susceptibility range, 51.3% to 92.2%). In addition, the prevalence of resistance to various agents differed significantly across study sites. Finally, significant increasing trends in resistance were noted over time and were most pronounced for fluoroquinolone susceptibility among the Enterobacteriaceae.

CONCLUSIONS

The prevalence of antimicrobial resistance has increased significantly in LTCFs, although trends have varied substantially across different institutions. These trends have been particularly pronounced for fluoroquinolone resistance among the Enterobacteriaceae. These findings demonstrate that antimicrobial resistance is widespread and increasing in LTCFs, highlighting the need for future studies to more clearly elucidate the risk factors for, and potential interventions against, emerging resistance in these settings.

Insufficient protection for healthy elderly adults by tetanus and TBE vaccines

Little information is available on post-vaccination antibody concentrations and the duration of protection in persons of more than 20 years of age. We, therefore, measured antibodies specific for tetanus (TT) or tick-borne encephalitis (TBE) virus in 734 adults (age 18-93 years, 382 females and 352 males) and evaluated these data in connection with the time point of the last vaccination against tetanus or TBE and age. This analysis revealed that the time of the last vaccination as well as age had highly significant effects on tetanus and TBE titers (p < 0.001). Our results show a strong decline in post-vaccination antibody concentrations with age, which sets in at the age of 40 in the case of tetanus, and is observed right throughout adult life in the case of TBE. Persons over 60 years of age frequently do not have protective antibody concentrations. We conclude that immunological responsiveness to vaccination decreases throughout adult life, and that conventional vaccination strategies designed for children and young adults cannot be uncritically applied in the elderly.

Long-term cytomegalovirus infection leads to significant changes in the composition of the CD8+ T-cell repertoire, which may be the basis for an imbalance in the cytokine production profile in elderly persons

In spite of the present belief that latent cytomegalovirus (CMV) infection drives CD8+ T-cell differentiation and induces premature immune senescence, no systematic studies have so far been performed to compare phenotypical and functional changes in the CD8+ T-cell repertoire in CMV-infected and noninfected persons of different age groups. In the present study, number, cytokine production, and growth potential of naive (CD45RA+ CD28+), memory (CD45RA- CD28+), and effector (CD45RA+ CD28- or CD45RA- CD28-) CD8+ T cells were analyzed in young, middle-aged, and elderly clinically healthy persons with a positive or negative CMV antibody serology. Numbers and functional properties of CMVpp65(495-503)-specific CD8+ T cells were also studied. We demonstrate that aging as well as CMV infection lead to a decrease in the size of the naive CD8+ T-cell pool but to an increase in the number of CD8+ effector T cells, which produce gamma interferon but lack substantial growth potential. The size of the CD8+ memory T-cell population, which grows well and produces interleukin-2 (IL-2) and IL-4, also increases with aging, but this increase is missing in CMV carriers. Life-long latent CMV infection seems thus to diminish the size of the naive and the early memory T-cell pool and to drive a Th1 polarization within the immune system. This can lead to a reduced diversity of CD8 responses and to chronic inflammatory processes which may be the basis of severe health problems in elderly persons.

Age and immune response in organ transplantation

The immune system undergoes a complex and continuous remodeling as the result of aging. These changes have a major impact on allorecognition and alloresponse. In addition, immunosuppression in the elderly is challenging as a consequence of an increased incidence of associated comorbidities and altered pharmacokinetics. Both advanced donor and recipient age should be considered independent risk factors for poor patient and graft survival rates, albeit acting in a synergistic manner. Consequently, modifications of the immune system because of aging may request an age-adapted allocation and immunosuppression in parallel with close patient monitoring. Interventions to selectively target changes associated with the senescence process seem to be promising therapeutic strategies to improve transplantation outcome. Here, we are going to review the immunologic changes associated with the aging process relevant for transplantation and their impact on immunosuppressive protocols, organ allocation policies, and transplantation outcome.

The role of the MAPK pathway alterations in GM-CSF modulated human neutrophil apoptosis with aging

Background

Neutrophils represent the first line of defence against aggressions. The programmed death of neutrophils is delayed by pro-inflammatory stimuli to ensure a proper resolution of the inflammation in time and place. The pro-inflammatory stimuli include granulocyte-macrophage colony-stimulating factor (GM-CSF). Recently, we have demonstrated that although neutrophils have an identical spontaneous apoptosis in elderly subjects compared to that in young subjects, the GM-CSF-induced delayed apoptosis is markedly diminished. The present study investigates whether an alteration of the GM-CSF stimulation of MAPKs play a role in the diminished rescue from apoptosis of PMN of elderly subjects.

Methods

Neutrophils were separated from healthy young and elderly donors satisfying the SENIEUR protocol. Neutrophils were stimulated with GM-CSF and inhibitors of the MAPKinase pathway. Apoptosis commitment, phosphorylation of signaling molecules, caspase-3 activities as well as expression of pro- and anti-apoptotic molecules were performed in this study. Data were analyzed using Student's two-tailed t-test for independent means. Significance was set for p ≤ 0.05 unless stated otherwise.

Results

In this paper we present evidence that an alteration in the p42/p44 MAPK activation occurs in PMN of elderly subjects under GM-CSF stimulation and this plays a role in the decreased delay of apoptosis of PMN in elderly. We also show that p38 MAPK does not play a role in GM-CSF delayed apoptosis in PMN of any age-groups, while it participates to the spontaneous apoptosis. Our results also show that the alteration of the p42/p44 MAPK activation contributes to the inability of GM-CSF to decrease the caspase-3 activation in PMN of elderly subjects. Moreover, GM-CSF converts the pro-apoptotic phenotype to an anti-apoptotic phenotype by modulating the bcl-2 family members Bax and Bcl-xL in PMN of young subjects, while this does not occur in PMN of elderly. However, this modulation seems MAPK independent.

Conclusion

Our results show that the alteration of p42/p44 MAPK activation contributes to the GM-CSF induced decreased PMN rescue from apoptosis in elderly subjects. The modulation of MAPK activation in PMN of elderly subjects might help to restore the functionality of PMN with aging.