Interdisciplinary topics in gerontology and geriatrics最新文献

The collective loss of immune protection during aging leads to poor vaccine responses and an increased severity of infection for the elderly. Here, we review our current understanding of effects of aging on the cellular and molecular dysregulation of innate immune cells as well as the relevant tissue milieu which influences their functions. The innate immune system is composed of multiple cell types which provide distinct and essential roles in tissue surveillance and antigen presentation as well as early responses to infection or injury. Functional defects that arise during aging lead to a reduced dynamic range of responsiveness, altered cytokine dynamics, and impaired tissue repair. Heightened inflammation influences both the dysregulation of innate immune responses as well as surrounding tissue microenvironments which have a critical role in development of a functional immune response. In particular, age-related physical and inflammatory changes in the skin, lung, lymph nodes, and adipose tissue reflect disrupted architecture and spatial organization contributing to diminished immune responsiveness. Underlying mechanisms include altered transcriptional programming and dysregulation of critical innate immune signaling cascades. Further, we identify signaling functions of bioactive lipid mediators which address chronic inflammation and may contribute to the resolution of inflammation to improve innate immunity during aging.

Respiratory syncytial virus (RSV) causes infection throughout life, with infants, adults who are severely immunocompromised, and the elderly at special risk of developing lower respiratory tract disease, hospitalisation, and death. The burden of severe disease in the elderly is comparable to seasonal influenza, and there remains no effective anti-viral drugs or vaccine for any target population. The development of a vaccine to confer immunity against severe disease is a major global health priority. A multitude of safe and immunogenic vaccine candidates have failed to induce the protective immunity needed for licensure, and in recent years this has included the largest clinical trials of RSV vaccines in history. The obstacles to vaccine development in elderly populations include an incomplete understanding of the immune responses needed for protection, the effect of aging on induction and maintenance of immunity (natural and vaccine induced immunity), and the high rate of co-morbid disease in older adults. Recent advances in structural biology, new biological platforms for antigen delivery, and insights from experimental challenge models mark the latest developments in over 50 years of research. This continues to be an active and evolving field of scientific discovery with renewed hope for a vaccine in the future.

Immunization strategies for the elderly are frequently perceived as comprising only vaccines against influenza, Streptococcus pneumoniae, and herpes zoster. However, besides these vaccines, which are recommended specifically for the elderly, regular booster vaccinations against tetanus, diphtheria, and in some cases pertussis and polio, are recommended in many countries for adults including the elderly. Vaccination recommendations for adults differ greatly between individual countries and coverage data are scarce. A substantial proportion of adults, and particularly of the older age groups, do not have protective antibody concentrations against diphtheria, whereas tetanus-specific antibody concentrations are generally higher. Protection against pertussis is unsatisfactory in all adults, and development of improved vaccines is ongoing. Future vaccination strategies should include regular and well-documented booster shots throughout life, as post-booster antibody concentrations correlate with pre-booster antibody concentrations.

Vaccine development has traditionally been driven by the need to prevent high numbers of childhood deaths due to infectious disease. With few exceptions, vaccines for adults are the same as vaccines for infants, although it has long been apparent that they become less effective as age increases. It is only in the last few years that concerted efforts have commenced to develop life-long vaccination strategies through into older age. Impressive progress has been made in the field of vaccine technologies which, when they will be applied to vaccination of older adults, could change the landscape for disease prevention in this age group. The recently licensed adjuvanted herpes zoster vaccine shows that immunosenescence need not be a barrier to highly effective vaccination, and that highly effective vaccines for older adults can be achieved with good vaccine design. One of the greatest public health challenges of the 21st century is ensuring the health and well-being of the aged. New or improved vaccines targeting pathogens with a high disease burden in older adults have the potential to major contributions to the longevity and productivity of the older aged population.

Increased susceptibility to the serious complications of influenza is common in older adults. It is often ascribed to weakening of the immune system with age, and 90% of influenza-related deaths occur in older adults despite widespread vaccination programs. Common chronic conditions not only contribute to the loss of immune protection after vaccination and increase the risk for serious outcomes of influenza, but also increase the long-term consequences following hospitalization. Interactions of T and B cell ageing, chronic elevation of inflammatory cytokines (sometimes dubbed "inflammaging"), and dysregulated acute cytokine production pose major challenges to the development of new and more effective vaccines. However, these age-related problems are modifiable, as we have shown, and provide a clear margin for improvement. This chapter describes how an exclusive focus on developing influenza vaccines to stimulate strain-specific antibody responses against the hemagglutinin surface glycoprotein of the influenza virus, to the exclusion of other potentially important mechanisms, is missing the mark in terms of preventing the serious complications of influenza in older adults. Novel approaches are needed to enhance antibody-mediated protection against infection and stimulate cell-mediated immune responses to clear influenza virus from the lungs. These strategies for improving vaccine effectiveness will address the public health need for "vaccine prevention of disability" to mitigate the global pressures of aging populations on health and social care systems.

T lymphocytes follow three main stages of differentiation during their lifetime history - memory generation, memory homeostasis, and immunosenescence. Current definitions of T cell immunosenescence now include distinct aspects of both T cell senescence and exhaustion. Multiple studies have indicated a loss of vaccine efficacy in old age, and because this period coincides with the onset of T cell immunosenescence, the latter has often been implicated in the loss of vaccine responsiveness. This chapter examines changes in T cell homeostasis with age, and proposes mechanisms of how these changes, together with senescence and exhaustion, could affect the T cell contribution to the vaccine response.

Vaccine-preventable diseases represent a considerable burden on world health, and can have long-lasting consequences in those infected, especially in older adults, who can suffer functional decline, disability, and death. Vaccine uptake across the life course is desirable, but often suboptimal. A number of factors have been identified as contributors to low vaccine coverage, including sociodemographic characteristics, logistic factors such as ease of access and convenience, cultural attitudes including health literacy, and vaccine hesitancy. Strategies to improve vaccine uptake can target all the components underpinning low coverage, and include technology and communication-based strategies, physician-centered approaches, targeting healthcare workers for influenza vaccination, system-based factors, improved vaccine efficacy, and above all, political will and leadership.

Nosocomial infections represent a major global disease burden, and effective treatments are urgently needed, especially among older adult populations (≥65 years of age). With increasing age, risk factors for these infections increase due to underlying health conditions, immunosenescence, and increased contact with healthcare settings. In addition, many common nosocomial pathogens feature increasing rates of antibiotic resistance, compounding the problem and highlighting the need for prophylactic alternatives to antibiotic treatment, such as vaccines. In many cases, mortality rates associated with nosocomial pathogens that are antibiotic resistant are high. This chapter reviews the epidemiology of common nosocomial pathogens and diseases affecting older adult populations. Vaccines that are currently approved or in development for preventing disease caused by common nosocomial pathogens are also described. While important progress has been made in vaccine development for several pathogens such as Clostridium difficile and Staphylococcus aureus, there remains a crucial unmet need for vaccines to prevent the many common nosocomial infections, which disproportionately affect older adults.