Impact of aging on gastrointestinal mucosal immunity

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.

Evolution of Human Memory B Cells From Childhood to Old Age

High quality medical assistance and preventive strategies, including pursuing a healthy lifestyle, result in a progressively growing percentage of older people. The population and workforce is aging in all countries of the world. It is widely recognized that older individuals show an increased susceptibility to infections and a reduced response to vaccination suggesting that the aged immune system is less able to react and consequently protect the organism. The SARS-CoV-2 pandemic is dramatically showing us that the organism reacts to novel pathogens in an age-dependent manner. The decline of the immune system observed in aging remains unclear. We aimed to understand the role of B cells. We analyzed peripheral blood from children (4-18 years); young people (23-60 years) and elderly people (65-91 years) by flow cytometry. We also measured antibody secretion by ELISA following a T-independent stimulation. Here we show that the elderly have a significant reduction of CD27dull memory B cells, a population that bridges innate and adaptive immune functions. In older people, memory B cells are mostly high specialized antigen-selected CD27bright. Moreover, after in vitro stimulation with CpG, B cells from older individuals produced significantly fewer IgM and IgA antibodies compared to younger individuals. Aging is a complex process characterized by a functional decline in multiple physiological systems. The immune system of older people is well equipped to react to often encountered antigens but has a low ability to respond to new pathogens.

Clinical Features, Endoscopic Findings, and Predictive Factors for Mortality in Tissue-Invasive Gastrointestinal Cytomegalovirus Disease between Immunocompetent and Immunocompromised Patients

Background and Aims

Tissue-invasive gastrointestinal cytomegalovirus (TI-GI CMV) disease is common in immunocompromised patients, but the increasing prevalence in immunocompetent patients has been reported. This study compared the clinical manifestations, endoscopic features, treatment outcomes, and predictors for inhospital mortality of TI-GI CMV between immunocompromised and immunocompetent patients.

Methods

Patients with HIV infection, malignancy, or receiving immunosuppressive agents (chemotherapy, high dose, or long-term corticosteroids) were defined as the immunocompromised group. Demographic and inhospital mortality data were obtained and retrospectively analyzed.

Results

A total of 213 patients (89 immunocompetent) with histologically confirmed TI-GI CMV were enrolled. Immunocompetent patients were older (70 vs. 52 years; p < 0.001), had more GI bleeding as a presenting symptom (47.2% vs. 29.0%; p = 0.010), and shorter symptom onset (2 vs. 14 days, p = 0.018). Concomitant extra-GI involvement was only seen in the immunocompromised group (6.5% vs. 0%; p = 0.02). Diffuse GI tract (14.5% vs. 4.5%; p = 0.032) and esophageal involvement (14.5% vs. 5.6%; p = 0.046) were more frequent in the immunocompromised, while small bowel involvement was more frequent in the immunocompetent group (19.1% vs. 8.1%; p = 0.029). An overall inhospital mortality was 27.7%. There was no significant difference in inhospital survival probability between the two groups (Peto-Peto test, p = 0.65). ICU admission (hazard ratio [HR] 7.21; 95% CI 2.55-20.36), sepsis or shock (HR 1.98; 95% CI 1.08-3.66), malnutrition (HR 2.62; 95% CI 1.05-7.01), and receiving chemotherapy (HR 5.2; 95% CI 1.89-14.29) were independent factors for inhospital mortality. Antiviral treatment for more than 14 days was the only protective factor to improve survival (Peto-Peto test, p < 0.001).

Conclusions

Immunocompetent and immunocompromised patients with TI-GI CMV disease had distinct clinical and endoscopic characteristics. There was no significant difference in the inhospital mortality between the two groups. The factors for mortality were ICU admission, sepsis/shock, malnutrition, and receiving chemotherapy. Early diagnosis and initiation of antiviral treatment might improve the survival probability.

Cytomegalovirus ileitis with protein-losing enteropathy in an immunocompetent adult

Symptomatic cytomegalovirus (CMV) infection in immunocompetent hosts has traditionally been considered to have a benign, self-limited course, and those who need intensive therapy are rare. Moreover, there are few reports of CMV infection with protein-losing enteropathy (PLE). We present an immunocompetent 74-year-old woman with CMV ileitis with PLE, which was diagnosed due to severe hypoalbuminemia and edema of the lower extremities. The patient was not immunocompromised, because a human immunodeficiency virus (HIV) antibody test was negative and she had not been taking immunosuppressants. Imaging tests including colonoscopy revealed ileitis with shallow widespread ulcers. ^99mTc-human serum albumin (HAS-D) scintigraphy suggested a possibility of protein loss in the ileum based on selective accumulation of nuclides in the right abdomen. Histological findings of the biopsy showed ulcerative mucosa with abnormal cells, which had enlarged nuclei with intranuclear inclusion bodies, including typical Cowdry A type. In immunohistochemistry, these cells were positive for anti-CMV staining. She was successfully treated with medical treatments including intravenous injection of ganciclovir (GCV) (500 mg/day). We described an extremely rare case of CMV ileitis with PLE in an immunocompetent adult who was treated successfully with medical treatments, including GCV.

Endoscopic features and clinical outcomes of cytomegalovirus gastroenterocolitis in immunocompetent patients

We aimed to investigate the endoscopic features and clinical course of CMV gastroenterocolitis in immunocompetent patients. We reviewed the medical records and endoscopic images of 86 immunocompetent patients with CMV gastroenterocolitis. Immunocompetent patients were defined as those without congenital or acquired immunodeficiency syndrome, use of anti-cancer chemotherapeutic and immunosuppressive agents, and inflammatory bowel diseases. The mean age was 65.5 ± 11.8 years and 53 (61.6%) were male. Sixty-eight (79.1%) patients had comorbidities. Upper gastrointestinal-dominant, small bowel-dominant, and colon-dominant types were observed in 19, 7, and 60 patients, respectively. Endoscopic features could be classified into discrete ulcerative type with/without exudate and diffuse erythematous type with/without exudate. Antiviral treatment with ganciclovir was initiated in 51 patients (59.3%), 40 of whom improved and 1 improved after changing ganciclovir to foscarnet. Thirty-three patients (38.4%) improved without antiviral treatment. Surgery was necessary in two patients because of colon perforation before antiviral treatment. Another two patients underwent surgery because of sigmoid stricture and cecal perforation during antiviral treatment. Endoscopic type was not associated with clinical outcomes, such as surgery and death. CMV gastroenterocolitis in immunocompetent patients mostly occur in older patients with comorbidities, and the endoscopic features vary with no association with clinical outcomes.

Cytomegalovirus ileo-pancolitis presenting as toxic megacolon in an immunocompetent patient: A case report

BACKGROUND

Cytomegalovirus (CMV) enterocolitis presenting in the form of pancolitis or involving the small and large intestines in an immunocompetent patient is rarely encountered, and CMV enterocolitis presenting with a serious complication, such as toxic megacolon, in an immunocompetent adult has only been reported on a few occasions.

CASE SUMMARY

We describe the case of a 70-year-old male with no history of inflammatory bowel disease or immunodeficiency who presented with toxic megacolon and subsequently developed massive hemorrhage as a complication of CMV ileo-pancolitis. The patient was referred to our institute for abdominal pain and distension. Abdominal X-ray showed marked dilatation of ileum and whole colon without air-fluid level, and sigmoidoscopy with biopsy failed to reveal any specific finding. After 7 d of conservative treatment, massive hematochezia developed, and he was diagnosed to have CMV enterocolitis by colonoscopy with biopsy. Although the diagnosis of CMV enterocolitis was delayed, the patient was treated successfully by repeat colonoscopic decompression and antiviral therapy with intravenous ganciclovir.

CONCLUSION

This report cautions that CMV-induced colitis should be considered as a possible differential diagnosis in a patient with intractable symptoms of enterocolitis or megacolon of unknown cause, even when the patient is non-immunocompromised.

Rejuvenation of mucosal immunosenescence by adipose tissue-derived mesenchymal stem cells

Age-associated alterations in the mucosal immune system are generally termed mucosal immunosenescence. The major change seen in the aged mucosa is a failure to elicit an antigen-specific secretory IgA (SIgA) antibody response, which is a central player for host defense from various pathogens at mucosal surfaces. In this regard, it would be a first priority to compensate for mucosal dysregulation in the elderly in order to maintain their health in aging. We have successfully established antigen-specific SIgA antibody responses in aged (2 years old) mice, which provide protective immunity from Streptococcus pneumoniae and influenza virus infections, by using a new adjuvant system consisting of a plasmid encoding Flt3 ligand (pFL) and CpG ODN. In order to explore possible use of current mucosal vaccine strategies for the elderly, we have adoptively transferred adipose tissue-derived mesenchymal stem cells (AMSCs) to aged mice prior to mucosal vaccination. This immune therapy successfully resulted in protective antigen-specific antibody responses in the intestinal mucosa of aged mice that were comparable to those seen in young adult mice. In this regard, we postulate that adoptively transferred AMSCs could augment dendritic cell functions in aged mice. The potential cellular and molecular mechanisms whereby AMSCs restore mucosal immunity in immunosenescence are discussed in this short review. A stem cell transfer system could be an attractive and effective immunologic intervention strategy to reverse mucosal immunosenescence.

Distinct aging profiles of CD8+ T cells in blood versus gastrointestinal mucosal compartments

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

Cytomegalovirus colitis in a patient undergoing postoperative adjuvant chemotherapy for lung adenocarcinoma with uracil-tegafur

When we examine a patient with symptoms of acute enteritis in the course of chemotherapy with oral fluoropyrimidines such as uracil-tegafur (often referred to as UFT), we usually suspect 5-fluorouracil-induced enterocolitis. In case of persistent clinical symptoms despite discontinuation of chemotherapy, cytomegalovirus colitis should be considered in the differential diagnosis of chemotherapy-induced enterocolitis. We herein report the case of a patient who underwent surgery for lung adenocarcinoma followed by postoperative adjuvant chemotherapy with uracil-tegafur and was diagnosed as having cytomegalovirus colitis during the therapy. In the course of chemotherapy, cytomegalovirus colitis occasionally occurs even though the patient does not experience severe myelosuppression; thus, it is necessary that we recognize its potential occurrence.

Compartmentalization of immunosenescence: a deeper look at the mucosa

Developments in medical care and living conditions led to an astonishing increase in life-span perspective and subsequently a rise in the old population. This can be seen as a success for public health policies but it also challenges society to adapt, in order to cope with the potentially overwhelming cost for the healthcare system. A fast-growing number of older people lose their ability to live independently because of diseases and disabilities, frailty or cognitive impairment. Many require long-term care, including home-based nursing, communities and hospital-based care. Immunosenescence, an age-related deterioration in immune functions, is considered a major contributory factor for the higher prevalence and severity of infectious diseases and the poor efficacy of vaccination in the elderly. When compared with systemic immunosenescence, alterations in the mucosal immune system with age are less well understood. For this reason, this area deserves more extensive and intensive research and support. In this article, we provide an overview of age-associated changes occurring in systemic immunity and discuss the distinct features of mucosal immunosenescence.

Mucosal Immunosenescence in the Gastrointestinal Tract: A Mini-Review

It has been shown that pathogen-specific secretory IgA (SIgA) antibody (Ab) is the major player at mucosal surfaces for host defense. However, alterations in the mucosal immune system occur in advanced aging, which results in a failure of induction of SIgA Abs for the protection from infectious diseases. Signs of mucosal senescence first appear in the gut immune system. Further, changes in the intestinal microbiota most likely influence mucosal immunity. To overcome the immunological aging decline in mucosal immunity, several adjuvant systems including mucosal dendritic cell targeting have been shown to be attractive and effective immunological strategies. Similarly, microfold (M) cells involved in the antigen (Ag) uptake are ideal targets for facilitating Ag-specific mucosal immune responses. However, the numbers of M cells are reduced in aged mice. In this regard, Spi-B, an essential transcription factor for the functional and structural differentiation of M cells, could be a potent strategy for the induction of effective mucosal immunity in aging.

Analysis of HIV/AIDS epidemiology in Japan from 1985-2011-infection detection pattern for male homosexuals different from that for male heterosexuals but similar to that for females

This article reviews Japanese HIV/AIDS surveillance data from 1985 to 2011. It revealed that heterosexual males are more prone to be detected as "AIDS cases," whereas male homosexuals and females are more prone to be detected as "HIV cases," irrespective of the gender, age, infection route, residential area, and nationality. The probability of being detected as an "AIDS case" increased with advanced age, irrespective of the gender and infection route. Interpretation of the data requires further information on the clinical latency of AIDS that could differ depending on differences in infection routes, gender, age, nature of the acute-phase syndrome and factors enhancing it, e.g., route and dose of infection, and mucosal immunity involved in sexually transmitted HIV/AIDS infection and the influence of age and gender on it.

Cytomegalovirus proctitis mimicking rectal cancer in an immunocompetent elderly patient: a case report

Background

Cytomegalovirus infection is associated with significant morbidity and mortality in immunocompromised patients, but its impact on immunocompetent patients is still poorly understood. Furthermore, there is increasing evidence implying that chronic infection may contribute to a heightened cardiovascular risk.

Case presentation

We describe the case of incidental diagnosis of Cytomegalovirus proctitis in an immune-competent white British elderly gentleman, admitted following a stroke and investigated for rectal cancer following the development of bloody diarrhoea and persistent systemic inflammatory response.

Conclusion

This raised some several interesting points; firstly that we must revise our approach to investigating the immunocompetent elderly patient, secondly, could chronic Cytomegalovirus infection have contributed to the presentation of stroke in this patient and lastly what are the existing evidence for treatment in this population? We use this opportunity to try and address some of these questions and feel that this would be of benefit to the wider audience.

We discuss the risk factors for disease in immune-competent patients and also a brief overview of the benefits of treatment in this population.

Debilitating chronic diarrhea caused by generalized gastrointestinal cytomegalovirus infection in an immunocompetent adult

Gastrointestinal cytomegalovirus (CMV) infection is a common opportunistic infection in immunocompromised patients, especially patients with acquired immunodeficiency syndrome and transplant recipients. In contrast, CMV infection of the gastrointestinal tract is rare in immunocompetent individuals. We report a case of severe, protracted, and debilitating diarrhea caused by generalized CMV infection of the gastrointestinal tract in an elderly woman with no apparent immunosuppression. An extensive diagnostic investigation demonstrated CMV-associated disease affecting both the upper and lower gastrointestinal tracts (esophagus, small intestine, and colon). Such extensive simultaneous involvement of the alimentary tract in an immunocompetent patient is rare and presents a diagnostic and therapeutic challenge. The diagnosis was based on a combination of endoscopic, histopathological, serological, and polymerase chain reaction analysis findings and our patient was successfully treated with intravenous ganciclovir. Our case demonstrates that gastrointestinal CMV infection should be considered in the differential diagnosis of severe chronic diarrhea in immunocompetent patients and that antiviral treatment may be justified in this setting.

Mucosal adjuvants for vaccines to control upper respiratory infections in the elderly

Influenza virus and Streptococcus pneumoniae are two major pathogens that lead to significant morbidity and mortality in the elderly. Since both pathogens enter the host via the mucosa, especially the upper respiratory tract (URT), it is essential to elicit pathogen-specific secretory IgA (SIgA) antibody (Ab) responses at mucosal surfaces for defense of the elderly. However, as aging occurs, alterations in the mucosal immune system of older individuals result in a failure to induce SIgA Abs for protection from these infections. To overcome mucosal immunosenescence, we have developed a mucosal dendritic cell targeting, novel double adjuvant system which we show to be an attractive and effective immunological modulator. This system induces a more balanced Th1- and Th2-type cytokine response which supports both mucosal SIgA and systemic IgG1 and IgG2a Ab responses. Thus, adaptation of this adjuvant system to nasal vaccines for influenza virus and S. pneumoniae could successfully provide protection by supporting pathogen-specific SIgA Ab responses in the URT in the mouse model of aging. In summary, a double adjuvant system is considered to be an attractive and potentially important strategy for the future development of mucosal vaccines for the elderly.

Oral supplementation with Lactobacillus delbrueckii subsp. bulgaricus 8481 enhances systemic immunity in elderly subjects

Throughout life, there is an aging of the immune system that causes impairment of its defense capability. Prevention or delay of this deterioration is considered crucial to maintain general health and increase longevity. We evaluated whether dietary supplementation with Lactobacillus delbrueckii subsp. bulgaricus 8481 could enhance the immune response in the elderly. This multi-center, double-blind, and placebo controlled study enrolled 61 elderly volunteers who were randomly assigned to receive either placebo or probiotics. Each capsule of probiotics contained at least 3 × 10(7)  L. delbrueckii subsp. bulgaricus 8481. Individuals in the study were administered three capsules per day for 6 months. Blood samples were obtained at baseline (time 0), end of month 3, and month 6. We characterized cell subpopulations, measured cytokines by flow cytometry, quantified T cell receptor excision circle (TREC) by real-time PCR (RT-PCR), and determined human β-defensin-2 (hBD-2) concentrations and human cytomegalovirus (CMV) titers by enzyme-linked immunosorbent assay (ELISA). Elderly responded to the intake of probiotic with an increase in the percentage of NK cells, an improvement in the parameters defining the immune risk profile (IRP), and an increase in the T cell subsets that are less differentiated. The probiotic group also showed decreased concentrations of the pro-inflammatory cytokine IL-8 but increased antimicrobial peptide hBD-2. These effects disappeared within 6 months of stopping the probiotic intake. Immunomodulation induced by L. delbrueckii subsp. bulgaricus 8481 could favor the maintenance of an adequate immune response, mainly by slowing the aging of the T cell subpopulations and increasing the number of immature T cells which are potential responders to new antigens.

Characterization and optimization of bilosomes for oral vaccine delivery

Oral vaccines offer significant benefits due to the ease of administration, better patient compliance and non-invasive, needle-free administration. However, this route is marred by the harsh gastro intestinal environment which is detrimental to many vaccine formats. To address this, a range of delivery systems have been considered including bilosomes; these are bilayer vesicles constructed from non-ionic surfactants combined with the inclusion of bile salts which can stabilize the vesicles in the gastro intestinal tract by preventing membrane destabilization. The aim of this study was to investigate the effect of formulation parameters on bilosome carriers using Design of Experiments to select an appropriate formulation to assess in vivo. Bilosomes were constructed from monopalmitoylglycerol, cholesterol, dicetyl phosphate and sodium deoxycholate at different blends ratios. The optimized bilosome formulation was identified and the potential of this formulation as an oral vaccine delivery system were assessed in biodistribution and vaccine efficacy studies. Results showed that the larger bilosomes vesicles (~6 µm versus 2 µm in diameter) increased uptake within the Peyer's patches and were able to reduce median temperature differential change and promote a reduction in viral cell load in an influenza challenge study.

Isolated Lymphoid Follicles are Dynamic Reservoirs for the Induction of Intestinal IgA

IgA is one of the most important molecules in the regulation of intestinal homeostasis. Peyer's patches have been traditionally recognized as sites for the induction of intestinal IgA responses, however more recent studies demonstrate that isolated lymphoid follicles (ILFs) can perform this function as well. ILF development is dynamic, changing in response to the luminal microbial burden, suggesting that ILFs play an important role providing an expandable reservoir of compensatory IgA inductive sites. However, in situations of immune dysfunction, ILFs can over-develop in response to uncontrollable enteric flora, resulting in ILF hyperplasia. The ability of ILFs to expand and respond to help control the enteric flora makes this dynamic reservoir an important arm of IgA inductive sites in intestinal immunity.

Formulation design considerations for oral vaccines

Whilst oral vaccination is a potentially preferred route in terms of patient adherence and mass vaccination, the ability to formulate effective oral vaccines remains a challenge. The primary barrier to oral vaccination is effective delivery of the vaccine through the GI tract owing to the many obstacles it presents, including low pH, enzyme degradation and bile-salt solubilization, which can result in breakdown/deactivation of a vaccine. For effective immune responses after oral administration, particulates need to be taken up by the M cells however, these are few in number. To enhance M-cell uptake, particle characteristics can be optimized with particle size, surface charge, targeting groups and bioadhesive properties all being considerations. Yet improved uptake may not translate into enhanced immune responses and formulating particulates with inherent adjuvant properties can offer advantages. Within this article, we establish the options available for consideration when building effective oral particulate vaccines.

Aging impacts isolated lymphoid follicle development and function

BACKGROUND

Immunosenescence is the age-related decline and dysfunction of protective immunity leading to a marked increase in the risk of infections, autoimmune disease, and cancer. The majority of studies have focused on immunosenescence in the systemic immune system; information concerning the effect of aging on intestinal immunity is limited. Isolated lymphoid follicles (ILFs) are newly appreciated dynamic intestinal lymphoid structures that arise from nascent lymphoid tissues, or cryptopatches (CP), in response to local inflammatory stimuli. ILFs promote "homeostatic" responses including the production of antigen-specific IgA, thus playing a key role in mucosal immune protection. ILF dysfunction with aging could contribute to immunosenescence of the mucosal system, and accordingly we examined phenotypic and functional aspects of ILFs from young (2 month old) and aged (2 year old) mice.

RESULTS

We observed that aged mice have increased numbers of ILFs and increased numbers of structures corresponding to an early stage of CPs transforming into ILFs. The cellular composition of ILFs in aged mice is altered with a smaller B-lymphocyte population and an increased T-lymphocyte population. The ILF T-lymphocyte population is notable by the presence of CD4+ CD8αα+ T-lymphocytes, which are absent from the systemic compartment. The smaller B-lymphocyte population in ILFs from aged mice is directly correlated with decreased mRNA and protein expression of CCL20 and CXCL13, two chemokines that play crucial roles in recruiting B-lymphocytes into ILFs. Aged mice had elevated levels of serum and fecal immunoglobulins and despite the decreased B-lymphocyte population, ILFs from aged mice displayed increased IgA production. The immunoglobulin repertoire was skewed in aged mice, and ILFs demonstrated a repertoire usage similar to that of the systemic pool in both young and aged mice.

CONCLUSIONS

Here we observed that ILF development, cellular composition, and immunoglobulin production are altered with aging suggesting that ILF dysfunction contributes to mucosal immunosenescence.

Cytomegalovirus colitis in patients without inflammatory bowel disease: a single center study

OBJECTIVE

Cytomegalovirus (CMV) aggravates preexisting inflammatory bowel disease (IBD), and there are numerous reports of CMV colitis in IBD patients. However, little attention has been paid to CMV colitis in non-IBD patients. The aim was to determine the clinical manifestations, endoscopic appearance, and clinical course of CMV colitis in non-IBD patients.

MATERIAL AND METHODS

We reviewed medical records of patients diagnosed with CMV colitis based on immunohistochemical studies of biopsy specimens or surgical specimens between 1998 and 2009.

RESULTS

The medical records of 43 patients were reviewed. Subjects included individuals with AIDS, and those undergoing chemotherapy, steroid therapy, or transplantation, as well as individuals with other co-morbidities and individuals with no previous illnesses. Frequent symptoms were non-bloody diarrhea, abdominal pain, fever, and hematochezia. Macroscopically normal rectosigmoid mucosa was observed in eight of 21 patients who underwent full-length colonoscopy. Endoscopic findings were varied, and included macroscopically normal (n = 2), colitis alone (n = 12), ulcer alone (n = 5), and ulcer with colitis (n = 22). The ulcer margin was well-circumscribed in 12 of 21 patients. Thirty-six patients were administered antiviral agents and two patients died. All patients who were not treated with an antiviral agent recovered spontaneously while waiting for their biopsy results.

CONCLUSIONS

Colonoscopy is preferred to sigmoidoscopy for diagnosis of CMV colitis. Antiviral therapy should not be mandatory for a subset of patients with CMV colitis.

Recurrent cytomegalovirus colitis with megacolon in an immunocompetent elderly man

Gastrointestinal infection with cytomegalovirus (CMV) is uncommon in immunocompetent hosts. The case of a 70-year-old male with CMV colitis, who has no history of chronic inflammatory bowel disease or immunodeficiency is described. Diagnosis was aided by the identification of inclusion bodies that reacted positively for CMV by immunohistochemical testing in biopsy specimens from the colonic mucosa. His hospital course was characterized by poor improvement of his symptoms after the CMV infection was treated with ganciclovir, and the occurrence of megacolon. A repeat colonoscopy with biopsy revealed a recurrence of the CMV infection. Although CMV colitis is common in immunocompromised patients, we believe this is the first case of CMV colitis with megacolon and recurrent CMV infection in an immunocompetent patient. Colitis caused by CMV colitis should be considered in elderly people with diarrhea.

Ageing and its possible impact on mucosal immune responses

The development, structural diversification, and functional maturation of mammalian immunologic repertoire at mucosal surfaces and the systemic lymphoid tissue is a remarkably dynamic and continuous process, which begins in early fetal life and eventually culminates in variable degree of senescence or cellular death with advancing age. This brief overview will highlight the status of our current understanding of the ontogeny of mucosal immunologic response. The role of mucosal microflora and other environmental macromolecules in the regulation of mucosal immunity relative to the process of ageing will also be reviewed.

Recurrent lower gastrointestinal bleeding secondary to cytomegalovirus-associated colonic ulcer in a non human immunodeficiency virus infected patient: timely diagnosis and treatment averted surgery

Mr C, a 68-year-old Chinese male with diabetes mellitus, previous stroke and ischaemic cardiomyopathy on clopidogrel, presented with haematochezia. Colonoscopy showed a sigmoid ulcer, which was treated endoscopically. Histology of the biopsy from the ulcer revealed non-specific changes. However, he presented with recurrent bleeding from this non-healing sigmoid ulcer. A review of the histologic specimen revealed CMV intranuclear inclusion bodies. He was treated with intravenous ganciclovir, with no further hematochezia.

Effect of age on susceptibility to Salmonella Typhimurium infection in C57BL/6 mice

Ageing is associated with a decline in immune function, which predisposes the elderly to a higher incidence of infections. Information on the mechanism of the age-related increase in susceptibility to Salmonella enterica serovar Typhimurium (S. Typhimurium) is limited. In particular, little is known regarding the involvement of the immune response in this age-related change. We employed streptomycin (Sm)-pretreated C57BL/6 mice to develop a mouse model that would demonstrate age-related differences in susceptibility and immune response to S. Typhimurium. In this model, old mice inoculated orally with doses of 3 x 10(8) or 1 x 10(6) c.f.u. S. Typhimurium had significantly greater S. Typhimurium colonization in the ileum, colon, Peyer's patches, spleen and liver than young mice. Old mice had significantly higher weight loss than young mice on days 1 and 2 post-infection. In response to S. Typhimurium infection, old mice failed to increase ex vivo production of IFN-gamma and TNF-alpha in the spleen and mesenteric lymph node cells to the same degree as observed in young mice; this was associated with their inability to maintain the presence of neutrophils and macrophages at a 'youthful' level. These results indicate that Sm-pretreated C57BL/6 old mice are more susceptible to S. Typhimurium infection than young mice, which might be due to impaired IFN-gamma and TNF-alpha production as well as a corresponding change in the number of neutrophils and macrophages in response to S. Typhimurium infection compared to young mice.

A combination of Flt3 ligand cDNA and CpG ODN as nasal adjuvant elicits NALT dendritic cells for prolonged mucosal immunity

We explore cellular and molecular mechanisms of nasal adjuvant of a combination of a plasmid encoding the Flt3 ligand cDNA (pFL) and CpG oligodeoxynucleotides (CpG ODN). The double DNA adjuvant given with OVA maintained prolonged OVA-specific secretory IgA (S-IgA) Ab responses in external secretions for more than 25 weeks after the final immunization. Further, both Th1- and Th2-type cytokine responses were induced by this combined adjuvant regimen. The frequencies of plasmacytoid DCs (pDCs) and CD8(+) DCs were significantly increased in nasopharyngeal-associated lymphoreticular tissue (NALT) of mice given the combined adjuvant. Importantly, when we examined adjuvanticity of pFL plus CpG ODN in 2-year-old mice, significant levels of mucosal IgA Ab responses were also induced. These results demonstrate that nasal delivery of a combined DNA adjuvant offers an attractive possibility for the development of an effective mucosal vaccine for the elderly.

Aging and infectious diseases: workshop on HIV infection and aging: what is known and future research directions

Highly active antiretroviral treatment has resulted in dramatically increased life expectancy among patients with HIV infection who are now aging while receiving treatment and are at risk of developing chronic diseases associated with advanced age. Similarities between aging and the courses of human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome suggest that HIV infection compresses the aging process, perhaps accelerating comorbidities and frailty. In a workshop organized by the Association of Specialty Professors, the Infectious Diseases Society of America, the HIV Medical Association, the National Institute on Aging, and the National Institute on Allergy and Infectious Diseases, researchers in infectious diseases, geriatrics, immunology, and gerontology met to review what is known about HIV infection and aging, to identify research gaps, and to suggest high priority topics for future research. Answers to the questions posed are likely to help prioritize and balance strategies to slow the progression of HIV infection, to address comorbidities and drug toxicity, and to enhance understanding about both HIV infection and aging.

The clinical spectrum of cytomegalovirus colitis in adults

BACKGROUND

Colonic cytomegalovirus reactivation rarely occurs in adults without inflammatory bowel disease or a known immunosuppressive state.

AIM

To describe our experience with such patients.

METHODS

All consecutive admissions of patients with possible cytomegalovirus colitis, between 1995 and 2006, were reviewed retrospectively.

RESULTS

Nineteen patients were studied. Most of the patients were elderly with multiple co-morbidities. Three main forms of disease presentation were recognized: acute diarrhoea, chronic diarrhoea and lower gastrointestinal bleeding. Colonic mucosal intranuclear inclusion bodies were found in 12 patients. Thirteen patients had cytomegalovirus viraemia (either by polymerase chain reaction and/or by white blood cell-cytomegalovirus antigenaemia test). Ganciclovir therapy was given to only eight patients; only five of these patients survived. The other subgroup of 11 patients received only supportive therapy. Most of the patients from this subgroup had a prolonged and complicated hospital course; only nine patients survived. Follow-up colonoscopies were performed only in five patients (out of the 14 patients who survived). In four of these patients, chronic mucosal inflammatory changes were noted.

CONCLUSIONS

Cytomegalovirus colitis occurs rarely in adult individuals. The disease may have various and multiple acute and/or chronic clinical manifestations. Clinical awareness of this condition is needed.

Distribution of mast cell subtypes and immune cell populations in canine intestines: Evidence for age-related decline in T cells and macrophages and increase of IgA-positive plasma cells

The distribution and numbers of leucocytes and mast cells (MC) in the canine gastrointestinal tract of three different age groups was investigated immunhistochemically. In all age groups, CD3+ T cells were more prominent in the villus region than in the crypt areas without differences between intestinal segments, whereas macrophages were more randomly distributed. Kresylecht-violet and tryptase-positive MC were prominent in pericrypt regions with statistic significances. Chymase-bearing mast cells, IgA-, IgG- and IgM-containing cells did not show significant differences in their distribution but, except for IgG-positive cells, subjective trends with increasing numbers towards the crypts exist. The reasons for the distribution of T cells, macrophages, immunoglobulin-containing cells and mast cells are not clear. Lamina propria CD3+ T cells and macrophages significantly decreased whilst a significant increase of IgA-containing plasma cells with increasing age was found. For mast cell subtypes, IgG- and IgM-containing cells no significant changes in numbers with increasing age exist.

Outcomes of Clostridium difficile-associated disease treated with metronidazole or vancomycin before and after the emergence of NAP1/027

OBJECTIVE

To reassess the comparative efficacy of vancomycin versus metronidazole in the treatment of Clostridium difficile-associated disease (CDAD) after the emergence in 2003 of the hypervirulent NAP1/027 strain.

METHODS

A retrospective cohort study was conducted in a tertiary-care Canadian hospital among 1,616 patients treated initially with metronidazole (N=1,360), vancomycin (N=219), or both (N=37), between 1991 and 2006, and followed for 60 days after diagnosis. Primary outcome was severe/complicated CDAD (SC-CDAD) defined as any of: (a) death within 30 days, (b) septic shock, (c) megacolon, (d) perforation, or (e) emergency colectomy. Adjusted odds ratios (AOR) and their 95% confidence intervals (CI) were calculated, stratifying into pre-epidemic (1991-2002) and epidemic (2003-2006) periods. Secondary outcome was recurrence within 60 days.

RESULTS

Risk factors for SC-CDAD were the same in both periods: age>or=65 yr, male sex, immunosuppression, hospital acquisition, tube feeding, short duration of diarrhea, fever, elevated leukocytosis, or creatinine. Adjusting for confounders and using metronidazole therapy as baseline, vancomycin therapy was associated with a lower probability of developing SC-CDAD in 1991-2002 (AOR 0.21, 95% CI 0.05-0.99, P=0.048) but not during 2003-2006 (AOR 0.90, 95% CI 0.53-1.55, P=0.71). For both metronidazole and vancomycin, risk of recurrence increased in 2003-2004 but decreased in 2005-2006.

CONCLUSIONS

Loss of superiority of vancomycin over metronidazole coincided with the emergence of NAP1/027. Toxin hyperproduction by NAP1/027 might be such that the disease follows its natural course. Novel therapeutic approaches are needed. The higher risk of recurrence in 2003-2004 probably reflected reinfections rather than relapses.

Immunological responses to exogenous insulin

Regardless of purity and origin, therapeutic insulins continue to be immunogenic in humans. However, severe immunological complications occur rarely, and less severe events affect a small minority of patients. Insulin autoantibodies (IAAs) may be detectable in insulin-naive individuals who have a high likelihood of developing type 1 diabetes or in patients who have had viral disorders, have been treated with various drugs, or have autoimmune disorders or paraneoplastic syndromes. This suggests that under certain circumstances, immune tolerance to insulin can be overcome. Factors that can lead to more or less susceptibility to humoral responses to exogenous insulin include the recipient's immune response genes, age, the presence of sufficient circulating autologous insulin, and the site of insulin delivery. Little proof exists, however, that the development of insulin antibodies (IAs) to exogenous insulin therapy affects integrated glucose control, insulin dose requirements, and incidence of hypoglycemia, or contributes to beta-cell failure or to long-term complications of diabetes. Studies in which pregnant women with diabetes were monitored for glycemic control argue against a connection between IAs and fetal risk. Although studies have shown increased levels of immune complexes in patients with diabetic microangiopathic complications, these immune complexes often do not contain insulin or IAs, and insulin administration does not contribute to their formation. The majority of studies have shown no relationship between IAs and diabetic angiopathic complications, including nephropathy, retinopathy, and neuropathy. With the advent of novel insulin formulations and delivery systems, such as insulin pumps and inhaled insulin, examination of these issues is increasingly relevant.

Insulin antibodies with pulmonary delivery of insulin

BACKGROUND AND METHODS

Delivery of insulin to the deep lung presents unique challenges to the body's mucosal defense system. Pulmonary mucosal defense has the ability to discriminate between self and non-self antigens and has the potential for induction of immunologic tolerance. Published data concerning the immunogenicity of inhaled human insulin in drug trials will be reviewed, and data regarding the possible adverse effects of anti-insulin antibody development will be presented. Examination of the immunologic safety of inhaled human insulin will include discussion of comparator studies, factors affecting immunogenicity, the effects of insulin immunity on glycemic control and pulmonary function, and the relationship of insulin antibodies to dose requirements, pharmacodynamics, and hypoglycemia.

CONCLUSIONS

Inhaled human insulin, whether formulated as a powder or liquid, has been shown to be more immunogenic than comparator insulins given by subcutaneous routes; however, adverse effects of antibody formation have not been demonstrated.

A second generation of double mutant cholera toxin adjuvants: enhanced immunity without intracellular trafficking

Nasal application of native cholera toxin (nCT) as a mucosal adjuvant has potential toxicity for the CNS through binding to GM1 gangliosides in the olfactory nerves. Although mutants of cholera toxin (mCTs) have been developed that show mucosal adjuvant activity without toxicity, it still remains unclear whether these mCTs will induce CNS damage. To help overcome these concerns, in this study we created new double mutant CTs (dmCTs) that have two amino acid substitutions in the ADP-ribosyltransferase active center (E112K) and COOH-terminal KDEL (E112K/KDEV or E112K/KDGL). Confocal microscopic analysis showed that intracellular localization of dmCTs differed from that of mCTs and nCTs in intestinal epithelial T84 cells. Furthermore, both dmCTs exhibited very low toxicity in the Y1 cell assay and mouse ileal loop tests. When mucosal adjuvanticity was examined, both dmCTs induced enhanced OVA-specific immune responses in both mucosal and systemic lymphoid tissues. Interestingly, although both dmCT E112K/KDEV and dmCT E112K/KDGL showed high Th2-type and significant Th1-type cytokine responses by OVA-specific CD4+ T cells, dmCT E112K/KDEV exhibited significantly lower Th1-type cytokine responses than did nCT and dmCT E112K/KDGL. These results show that newly developed dmCTs retain strong biological adjuvant activity without CNS toxicity.

Mucosal immunity and tolerance in the elderly

Age-associated dysregulation of the immune system of the gastrointestinal (GI) tract has been well documented for both secretory (S)-IgA immunity and oral tolerance. Thus, impaired antigen-specific Ab responses in aged animals and the elderly have been reported. Further, it has been shown that gut-associated lymphoreticular tissue (GALT) mediated immune responses are more susceptible to aging than are lymphoid tissues involved in peripheral immunity. Aging also impairs oral tolerance, which may be of central importance for maintaining GI homeostasis. Thus, as early as 6-8-month-old mice failed to establish systemic unresponsiveness to orally introduced antigens. Despite these studies, the precise mechanisms for impaired GI tract immune system responses remain unclear. The evidence of reduced sizes of Peyer's patches through aging suggests that age-associated mucosal dysregulation may be the result of mucosal inductive tissue dysfunction. Indeed, the frequencies of naive CD4+ T cells and dendritic cells (DCs) in Peyer's patches of aged mice were reduced and this led to a lack of essential cytokine synthesis for the induction of either S-IgA immunity or oral tolerance.

Meta-analysis of outcome of cytomegalovirus colitis in immunocompetent hosts

There are only a few anecdotal reports of cytomegalovirus (CMV) colitis in immunocompetent hosts. The impact of the disease in this patient population remains poorly understood. The aim of this study was to perform a meta-analysis using individual patient data to determine outcomes of CMV colitis in immunocompetent patients and identify risk factors that might influence prognosis. A literature search was performed from 1980 to 2003 looking for immunocompetent patients with CMV colitis. Immunocompetence was defined as absence of congenital or acquired immune deficiency, transplant, or immunosuppressive medication. Patients were divided by age (<55 versus > or =55) and grouped according to coexisting illnesses. Kaplan-Meier curves were plotted to assess survival. Variables included age, sex, site of acquisition of infection, extent of disease, coexisting illnesses, and treatment modality. A total of 44 patients were identified, with an average age of 61.1. Only 10 were free of any comorbidity. The mean follow-up was 13.4 months. Spontaneous remission occurred in 31.8%, mostly individuals <55 years old. Fourteen deaths occurred, all of which were in patients >55. There was a higher mortality rate among male patients > or =55 (56.9%; P = 0.08), patients with immune-modulating diseases (75.2%; P = 0.10), and those having a colectomy (68.9%; P = 0.09). This analysis underlines the rarity of CMV colitis in patients with an intact immune system. Advanced age, male gender, presence of immune-modulating comorbidities, and need for surgical intervention are factors negatively influencing survival. Conversely, young healthy patients have a good prognosis with no intervention.

Effects of Bak Foong Pills and Menoease Pills on white blood cell distribution in old age female rats

This study examined the effects of Bak Foong Pills (BFP) and the new BFP-derived post-menopause formula, Menoease Pills (MBFP), on the distribution of peripheral white blood cells (WBC) between BFP/MBFP-treated and non-treated rats. Eighteen months old female SD rats were used to mimic post-menopausal and old age animal models. The percentage distribution of lymphocytes, monocytes and granulocytes were measured using flow cytometry with and without treatments of BFP or MBFP. Results showed that WBC distribution in old age rats were significantly different from that of adult rats, suggesting that as the animal aged, their WBC distributions were altered. Old age rats were observed to have much lower percentages of lymphocytes, but higher percentages of granulocytes when compared to the adult rats, indicating possible attenuated immunity. Following treatment with BFP or MBFP, WBC populations were found to be redistributed back into the ranges observed in adult animals. Furthermore, MBFP, was found to alter WBC distribution in a dose-dependent manner. When compared to estrogen (E(2)), a well documented regulator of immune function, results showed that MBFP was able to show significantly greater effects on WBC redistribution compared to E(2). However, in ovariectomised (ovx) old age rats, neither MBFP nor E(2) treated groups showed any changes in WBC redistribution. These results indicate that MBFP may share similarities to E(2). Indeed, the effect of MBFP and E(2) seems to require intact ovaries, which are believed to be necessary for the modulation of WBC distributions and immune functions. Overall, our findings suggest that BFP and MBFP may be able to regulate WBC population in old age female rats, and thus, indicate their potential role on improving the attenuated immunity evident in post-menopausal and elderly women.

Senescence-associated decline of lymphocyte migration in gut-associated lymphoid tissues of rat small intestine

Scenescence-induced changes in gut-associated lymphoid tissues may contribute largely to the impaired immune responses during aging. Age-related changes in lymphocyte recirculations were investigated in Peyer's patches of rat small intestine. Cell dynamics of labeled T lymphocytes were observed under an intravital fluorescence microscope and compared between young and aged rats. Lymphocyte transport through intestinal lymph was decreased in aged rats. The lymphocyte rolling and adherence in postcapillary venules (PCV) of Peyer's patches was also significantly impaired in aged rats, with decreased expression of L-selectin on lymphocyte surfaces. Immunohistochemical analysis revealed a significant decrease in the CD8-positive cell population in Peyer's patches of the aged group, although mucosal addressin cell adhesion molecule-1 (MAdCAM-1) expression in postcapillary venules was unaltered. Lymphocyte adoptive-transfer studies indicated that although both the donor and recipient factors influence the adherence of T cells, the former may play a predominant role in the age-related change. This study clearly demonstrated in situ that T cell migration into Peyer's patches is significantly decreased in the aged intestine, which may reflect the impaired immune responses in the aging process.

Oral Administration with Papillomavirus Pseudovirus Encoding IL-2 Fully Restores Mucosal and Systemic Immune Responses to Vaccinations in Aged Mice

Infectious diseases are one of the major threats for the elderly because their immune system is often compromised, and vaccinations to prevent these infections are not effective. A major defect in their immune system seems to be the inability of T cells to produce IL-2. We used papillomavirus (PV) pseudoviruses (PSVs) as a model vaccine and a gene delivery vector to address how to enhance immune responses to vaccinations. We found that oral immunization with PV PSV induced minimal mucosal and systemic Abs and CTLs specific for the PSVs in aged mice compared with young adult mice. In addition, fewer specific Th cells were generated in the aged mice. When aged mice were immunized with PV PSVs encoding human IL-2, specific Th cells were generated, producing murine IL-2, IL-4, and IFN-gamma. Further, specific Abs and CTLs were induced, resulting in protection against mucosal viral challenge. Thus, this study provided a basis for clinical trials using PV PSVs encoding IL-2 for vaccination of the elderly.

Nasal Flt3 ligand cDNA elicits CD11c+CD8+ dendritic cells for enhanced mucosal immunity

Nasal immunization is an effective way to induce both mucosal and systemic immune responses. In this study, we assessed a cDNA vector for Flt3 ligand (FL) for its potential to enhance mucosal immunity or tolerance. Interestingly, tolerance was avoided and elevated levels of OVA-specific Ab responses were induced in nasal washes, fecal extracts, and saliva as well as in plasma when compared with mice given nasal OVA plus DNA plasmid without the FL gene. In addition, significant levels of OVA-specific CD4+ T cell proliferative responses and OVA-induced IL-4 and IL-2 production were noted in spleen and cervical lymph nodes. Further, marked increases in FL protein occurred in the nasal lamina propria and submandibular glands and the frequencies of CD11c+CD8+ dendritic cells (DCs) significantly increased in the mucosal tissues. Moreover, these DCs expressed high levels of CD40, CD80, CD86, and MHC class II molecules. Nasal delivery of plasmid FL with OVA resulted in FL expression in both mucosal inductive and effector sites and resulted in expanded activated lymphoid DCs. Thus, nasal plasmid FL prevents mucosal tolerance and enhances active immunity when given by a mucosal route.

Protective mucosal immunity in aging is associated with functional CD4+ T cells in nasopharyngeal-associated lymphoreticular tissue

Our previous studies showed that mucosal immunity was impaired in 1-year-old mice that had been orally immunized with OVA and native cholera toxin (nCT) as mucosal adjuvant. In this study, we queried whether similar immune dysregulation was also present in mucosal compartments of mice immunized by the nasal route. Both 1-year-old and young adult mice were immunized weekly with three nasal doses of OVA and nCT or with a nontoxic chimeric enterotoxin (mutant cholera toxin-A E112K/B subunit of native labile toxin) from Brevibacillus choshinensis. Elevated levels of OVA-specific IgG Abs in plasma and secretory IgA Abs in mucosal secretions (nasal washes, saliva, and fecal extracts) were noted in both young adult and 1-year-old mice given nCT or chimeric enterotoxin as mucosal adjuvants. Significant levels of OVA-specific CD4(+) T cell proliferative and OVA-induced Th1- and Th2-type cytokine responses were noted in cervical lymph nodes and spleen of 1-year-old mice. In this regard, CD4(+), CD45RB(+) T cells were detected in greater numbers in the nasopharyngeal-associated lymphoreticular tissues of 1-year-old mice than of young adult mice, but the same did not hold true for Peyer's patches or spleen. One-year-old mice given nasal tetanus toxoid plus the chimeric toxin as adjuvant were protected from lethal challenge with tetanus toxin. This result reinforced our findings that age-associated immune alterations occur first in gut-associated lymphoreticular tissues, and thus nasal delivery of vaccines for nasopharyngeal-associated lymphoreticular tissue-based mucosal immunity offers an attractive possibility to protect the elderly.

Problems and solutions to the development of vaccines in the elderly

Scientists involved in vaccine research and development face the challenge of protecting the ever-increasing elderly population from a broad spectrum of infectious diseases. The optimal vaccine-induced immune response to confer protection is undefined for many pathogens, and the field of vaccine research is undergoing a gradual shift from the original focus on humoral immunity to a focus that incorporates cellular and innate immune components. The age-related changes in various aspects of immune function, including an increase in a population of T cells that shows signs of replicative senescence, underscore the need to enhance research aimed at designing vaccines to meet the unique requirements of the elderly population.