Immune senescence and vaccines to prevent herpes zoster in older persons

Immunosuppressive medication use and risk of herpes zoster (HZ) in patients with systemic lupus erythematosus (SLE): A nationwide case-control study

BACKGROUND

The association between immunosuppressive medication use and herpes zoster (HZ) in patients with systemic lupus erythematosus (SLE) has not been clearly defined.

OBJECTIVE

We evaluated the risk of HZ in patients with SLE treated with different immunosuppressants.

METHODS

A nationwide population-based case-control study was conducted using the Taiwanese National Health Insurance Research Database. Cases (1555 patients with SLE who developed HZ) and controls (3049 age- and sex-matched patients with SLE but without HZ) were analyzed for use of various immunosuppressive medications in the preceding 3-month period, and dose-response relationships were determined. Logistic regression was performed to estimate the adjusted odds ratio for HZ development.

RESULTS

Medications associated with greater HZ risk in patients with SLE included oral corticosteroids, intravenous methylprednisolone, hydroxychloroquine, oral cyclophosphamide, intravenous cyclophosphamide, azathioprine, methotrexate, and mycophenolate mofetil. Combination immunosuppressive therapy was common in patients with SLE and was associated with greatly increased HZ risk. For oral corticosteroids and hydroxychloroquine, the risk of HZ was strongly dependent on the medication dose.

LIMITATIONS

This study is retrospective in nature.

CONCLUSION

Recent immunosuppressive medication use is associated with increased HZ risk in patients with SLE, particularly those receiving high-dose oral corticosteroids and multiagent immunosuppressive therapy.

Expression of CD39 on Activated T Cells Impairs their Survival in Older Individuals

In an immune response, CD4⁺ T cells expand into effector T cells and then contract to survive as long-lived memory cells. To identify age-associated defects in memory cell formation, we profiled activated CD4⁺ T cells and found an increased induction of the ATPase CD39 with age. CD39⁺ CD4⁺ T cells resembled effector T cells with signs of metabolic stress and high susceptibility to undergo apoptosis. Pharmacological inhibition of ATPase activity dampened effector cell differentiation and improved survival, suggesting that CD39 activity influences T cell fate. Individuals carrying a low-expressing CD39 variant responded better to vaccination with an increase in vaccine-specific memory T cells. Increased inducibility of CD39 after activation may contribute to the impaired vaccine response with age.

Long-term immunogenicity and safety of an investigational herpes zoster subunit vaccine in older adults

BACKGROUND

An investigational subunit vaccine containing the varicella-zoster virus (VZV) glycoprotein E (gE) and the AS01B adjuvant system is being evaluated for the prevention of herpes zoster (HZ) in older adults. A phase II trial evaluating different formulations of this vaccine (containing 25μg, 50μg, or 100μg gE) was conducted in adults ≥60 years of age and showed that all formulations elicited robust cellular and humoral immune responses for up to 3 years after vaccination. In this follow-up study in subjects who received two doses of the 50μg gE/AS01B formulation (HZ/su), we assessed the persistence of the immune responses for up to 6 years after vaccination.

METHODS

This phase II, open-label, multicenter, single-group trial conducted in the Czech Republic, Germany, Sweden, and the Netherlands followed 129 subjects who had received two doses (2 months apart) of HZ/su during the initial trial. Vaccine-induced immune responses (frequencies of gE-specific CD4(+) T cells expressing ≥2 activation markers and serum anti-gE antibody concentrations) were evaluated at 48, 60, and 72 months after the first HZ/su dose.

RESULTS

Six years after vaccination with HZ/su, gE-specific cell-mediated immune responses and anti-gE antibody concentrations had decreased by 20-25% from month 36, but remained higher than the prevaccination values. At month 72, the gE-specific cell-mediated immune response was 3.8 times higher than the prevaccination value (477.3 vs. 119.4 activated gE-specific CD4(+) T cells per 10(6) cells), and the anti-gE antibody concentration was 7.3 times higher than the prevaccination value (8159.0 vs. 1121.3mIU/mL). No vaccine-related serious adverse events were reported between months 36 and 72.

CONCLUSIONS

gE-specific cellular and humoral immune responses persisted for 6 years after two-dose vaccination with HZ/su in healthy older adults. No safety concerns were identified.

As we age: Does slippage of quality control in the immune system lead to collateral damage?

The vertebrate adaptive immune system is remarkable for its possession of a very broad range of antigen receptors imbuing the system with exquisite specificity, in addition to the phagocytic and inflammatory cells of the innate system shared with invertebrates. This system requires strict control both at the level of the generation the cells carrying these receptors and at the level of their activation and effector function mediation in order to avoid autoimmunity and mitigate immune pathology. Thus, quality control checkpoints are built into the system at multiple nodes in the response, relying on clonal selection and regulatory networks to maximize pathogen-directed effects and minimize collateral tissue damage. However, these checkpoints are compromised with age, resulting in poorer immune control manifesting as tissue-damaging autoimmune and inflammatory phenomena which can cause widespread systemic disease, paradoxically compounding the problems associated with increased susceptibility to infectious disease and possibly cancer in the elderly. Better understanding the reasons for slippage of immune control will pave the way for developing rational strategies for interventions to maintain appropriate immunity while reducing immunopathology.

A prospective study of the clinical characteristics of patients with herpes simplex and varicella zoster keratitis, presenting to a New Zealand emergency eye clinic

PURPOSE

To identify the demographic and clinical associations of patients presenting with herpetic keratitis in New Zealand compared with presentations of presumed microbial keratitis.

METHODS

A prospective, 6-month, observational case series of presumed microbial keratitis (including marginal keratitis), specifically identifying all cases of herpes simplex and varicella zoster keratitis attending an emergency eye clinic was conducted. Main outcome measures included demographics, presenting signs and symptoms, and medical, ocular, and drug history.

RESULTS

A total of 140 cases of herpetic keratitis were identified, which comprised 125 cases of herpes simplex virus (89%) and 15 cases of varicella zoster virus (11%). Herpes simplex keratitis was associated with a history of keratitis (n = 58, phi = 0.24, P < 0.0001), Maori ethnicity (n = 27, phi = 0.26, P < 0.0001), respiratory disease (n = 18, phi = 0.14, P = 0.009), corticosteroid use (n = 23, phi = 0.22, P < 0.0001), and cardiovascular disease (CVD) (n = 10, phi = 0.11, P = 0.03). Inverse association was observed between herpes simplex keratitis and ocular surface disease (n = 8, phi = -0.16, P < 0.002) and Asian ethnicity (n = 4, phi = -0.11, P = 0.04). Varicella zoster keratitis was associated with CVD (n = 3, phi = 0.15, P = 0.03).

CONCLUSIONS

Patients with asthma, CVD, on long-term corticosteroid inhalers or creams, or of Maori ethnicity need particular assessment to investigate herpes simplex as a possible cause of keratitis. Clinicians prescribing inhaled corticosteroids or topical corticosteroid creams should be aware of possible association with herpes simplex keratitis.

Naive T cell maintenance and function in human aging

In studies of immune aging, naive T cells frequently take center stage. Describing the complexity of the human naive T cell repertoire remains a daunting task; however, emerging data suggest that homeostatic mechanisms are robust enough to maintain a large and diverse CD4 T cell repertoire with age. Compartment shrinkage and clonal expansions are challenges for naive CD8 T cells. In addition to population aspects, identification of potentially targetable cellular defects is receiving renewed interest. The last decade has seen remarkable progress in identifying genetic and biochemical pathways that are pertinent for aging in general and that are instructive to understand naive T cell dysfunction. One hallmark sets naive T cell aging apart from most other tissues except stem cells: they initiate but do not complete differentiation programs toward memory cells. Maintaining quiescence and avoiding differentiation may be the ultimate challenge to maintain the functions unique for naive T cells.

Efficacy of an adjuvanted herpes zoster subunit vaccine in older adults

BACKGROUND

In previous phase 1-2 clinical trials involving older adults, a subunit vaccine containing varicella-zoster virus glycoprotein E and the AS01B adjuvant system (called HZ/su) had a clinically acceptable safety profile and elicited a robust immune response.

METHODS

We conducted a randomized, placebo-controlled, phase 3 study in 18 countries to evaluate the efficacy and safety of HZ/su in older adults (≥50 years of age), stratified according to age group (50 to 59, 60 to 69, and ≥70 years). Participants received two intramuscular doses of the vaccine or placebo 2 months apart. The primary objective was to assess the efficacy of the vaccine, as compared with placebo, in reducing the risk of herpes zoster in older adults.

RESULTS

A total of 15,411 participants who could be evaluated received either the vaccine (7698 participants) or placebo (7713 participants). During a mean follow-up of 3.2 years, herpes zoster was confirmed in 6 participants in the vaccine group and in 210 participants in the placebo group (incidence rate, 0.3 vs. 9.1 per 1000 person-years) in the modified vaccinated cohort. Overall vaccine efficacy against herpes zoster was 97.2% (95% confidence interval [CI], 93.7 to 99.0; P<0.001). Vaccine efficacy was between 96.6% and 97.9% for all age groups. Solicited reports of injection-site and systemic reactions within 7 days after vaccination were more frequent in the vaccine group. There were solicited or unsolicited reports of grade 3 symptoms in 17.0% of vaccine recipients and 3.2% of placebo recipients. The proportions of participants who had serious adverse events or potential immune-mediated diseases or who died were similar in the two groups.

CONCLUSIONS

The HZ/su vaccine significantly reduced the risk of herpes zoster in adults who were 50 years of age or older. Vaccine efficacy in adults who were 70 years of age or older was similar to that in the other two age groups. (Funded by GlaxoSmithKline Biologicals; ZOE-50 ClinicalTrials.gov number, NCT01165177.).

Multifunctional cytomegalovirus (CMV)-specific CD8(+) T cells are not restricted by telomere-related senescence in young or old adults

Antigen-specific multifunctional T cells that secrete interferon-γ, interleukin-2 and tumour necrosis factor-α simultaneously after activation are important for the control of many infections. It is unclear if these CD8⁺ T cells are at an early or late stage of differentiation and whether telomere erosion restricts their replicative capacity. We developed a multi-parameter flow cytometric method for investigating the relationship between differentiation (CD45RA and CD27 surface phenotype), function (cytokine production) and replicative capacity (telomere length) in individual cytomegalovirus (CMV) antigen-specific CD8⁺ T cells. This involves surface and intracellular cell staining coupled to fluorescence in situ hybridization to detect telomeres (flow-FISH). The end-stage/senescent CD8⁺ CD45RA⁺ CD27⁻ T-cell subset increases significantly during ageing and this is exaggerated in CMV immune-responsive subjects. However, these end-stage cells do not have the shortest telomeres, implicating additional non-telomere-related mechanisms in inducing their senescence. The telomere lengths in total and CMV (NLV)-specific CD8⁺ T cells in all four subsets defined by CD45RA and CD27 expression were significantly shorter in old compared with young individuals in both a Caucasian and an Asian cohort. Following stimulation by anti-CD3 or NLV peptide, similar proportions of triple-cytokine-producing cells are found in CD8⁺ T cells at all stages of differentiation in both age groups. Furthermore, these multi-functional cells had intermediate telomere lengths compared with cells producing only one or two cytokines after activation. Therefore, global and CMV (NLV)-specific CD8⁺ T cells that secrete interferon-γ, interleukin-2 and tumour necrosis factor-α are at an intermediate stage of differentiation and are not restricted by excessive telomere erosion.

Cellular signalling pathways in immune aging and regeneration

The thymus is one of the cornerstones of an effective immune system. It produces new T-cells for the naïve T-cell pool, thus refreshing the peripheral repertoire. As we age, the thymus atrophies and there is a decrease in the area of active T-cell production. A decline in the output of the thymus eventually leads to changes in the peripheral T-cell pool which includes increases in the number of cells at or near their replicative limit and contraction of the repertoire. Debate about the age-associated changes in the thymus leading to functional decline centres on whether this is due to problems with the environment provided by the thymus or with defects in the progenitor cell compartment. In mice, the evidence points towards problems in the epithelial component of the thymus and the production of IL-7 (interleukin 7). But there are discussions about how appropriate mouse models are for human aging. We have developed a simple system that utilizes both human keratinocyte and fibroblast cell lines arrayed on a synthetic tantalum-coated matrix to provide a permissive environment for the maturation of human CD34+ haemopoietic progenitor cells into mature CD4+ or CD8+ T-lymphocytes. We have characterized the requirements for differentiation within these cultures and used this system to compare the ability of CD34+ cells derived from different sources to produce mature thymocytes. The TREC (T-cell receptor excision circle) assay was used as a means of identifying newly produced thymocytes.

Comparison of intramuscular and subcutaneous administration of a herpes zoster live-attenuated vaccine in adults aged ≥50 years: a randomised non-inferiority clinical trial

Zostavax(®) is a live, attenuated varicella zoster virus (VZV) vaccine developed specifically for the prevention of HZ and PHN in individuals aged ≥50 years. During the clinical development of Zostavax, which was mainly in the US, the vaccine was administrated by the subcutaneous (SC) route. In Europe, many healthcare professionals prefer administering vaccines by the intramuscular (IM) route. This was an open-label, randomised trial conducted in 354 subjects aged ≥50 years. The primary objectives were to demonstrate that IM administration is both non-inferior to SC administration in terms of 4-week post-vaccination geometric mean titres (GMTs), and elicits an acceptable geometric mean fold-rise (GMFR) of antibody titres measured by glycoprotein enzyme-linked immunosorbent assay. Pre-specified non-inferiority was set as the lower bound of the 95% confidence interval (CI) of the GMT ratio (IM/SC) being >0.67. An acceptable GMFR for the IM route was pre-specified as the lower bound of its 95% CI being >1.4. Description of the VZV immune response using the interferon-gamma enzyme-linked immunospot (IFN-γ ELISPOT) assay and of the safety were secondary objectives. Participants were randomised to IM or SC administration (1:1). The baseline demographics were comparable between groups; mean age: 62.6 years (range: 50.0-90.5). The primary immunogenicity objectives were met (per protocol analysis): GMT ratio (IM/SC): 1.05 (95% CI: 0.93-1.18); GMFR: 2.7 (2.4-3.0). VZV immune response using IFN-γ ELISPOT were comparable between groups. Frequencies of systemic adverse events were comparable between groups. Injection-site reactions were less frequent with IM than SC route: erythema (15.9% versus 52.5%), pain (25.6% versus 39.5%) and swelling (13.6% versus 37.3%), respectively. In adults aged ≥50 years, IM administration of Zostavax elicited similar immune responses to SC administration and was well tolerated, with fewer injection-site reactions than with SC administration.

Vaccines for the elderly

The aging of the human population is posing serious challenges to research and to public health authorities in order to prevent diseases that more frequently affect the elderly, a portion of the population that will increase more and more in the coming years. While some vaccines exist and are used in the elderly to effectively fight against some infections (e.g. influenza, pneumococci, varicella-zoster virus, diphtheria, and tetanus), still a lot of work remains to be done to better adapt these vaccines and to develop new ones for this age group. The prevention of infectious diseases affecting the elderly can be successful only through a holistic approach. This approach will aim at the following: (1) a deeper understanding of the mechanisms leading to the senescence of the immune system, (2) a better and broader use of vaccines recommended for the elderly, (3) the use of vaccines currently considered only for other age groups and (4) actively priming the population when they are immunological competent, before the physiological waning of immune responsiveness may affect the beneficial effects of vaccination.

Vaccine responsiveness in the elderly: best practice for the clinic

The success of vaccines developed since the beginning of the 20th century, has enabled the conquest of several childhood diseases preventing death and or disability for millions of children. But, globally, the number of children will soon be surpassed by the number of adults over the age of 65. The active lifestyle of these older individuals, coupled with a degree of immune deficiency recognised within this population will lead to a change in the profile of diseases affecting the elderly. The challenge for policy makers and also those involved in primary healthcare is how to protect this population from communicable diseases and keep them healthy, autonomous and independent when vaccines in the main have been developed for use on children and young adults.

Cost-effectiveness of vaccination against herpes zoster and postherpetic neuralgia: a critical review

OBJECTIVE

The objective of this study was to systematically review cost-effectiveness studies of vaccination against herpes zoster (HZ) and postherpetic neuralgia (PHN).

METHODS

We searched MEDLINE and EMBASE databases for eligible studies published prior to November 2013. We extracted information regarding model structure, model input parameters, and study results. We compared the results across studies by projecting the health and economic impacts of vaccinating one million adults over their lifetimes.

RESULTS

We identified 15 cost-effectiveness studies performed in North America and Europe. Results ranged from approximately US$10,000 to more than US$100,000 per quality-adjusted life years (QALY) gained. Most studies in Europe concluded that zoster vaccination is likely to be cost-effective. Differences in results among studies are largely due to differing assumptions regarding duration of vaccine protection and a loss in quality of life associated with HZ and to a larger extent, PHN. Moreover, vaccine efficacy against PHN, age at vaccination, and vaccine cost strongly influenced the results in sensitivity analyses.

CONCLUSION

Most studies included in this review shows that vaccination against HZ is likely to be cost-effective. Future research addressing key model parameters and cost-effectiveness studies in other parts of the world are needed.

Mechanisms shaping the naïve T cell repertoire in the elderly - thymic involution or peripheral homeostatic proliferation?

The ability of the human immune system to repel infections is drastically diminished with age. Elderly individuals are more susceptible to new threats and are less able to control endogenous infections. The thymus, which is the sole source of new T cells, has been proposed as a target for regenerative efforts to improve immune competence, as thymic activity is dramatically reduced after puberty. In this review, we review the role of the thymus in the maintenance of T cell homeostasis throughout life and contrast the differences in mice and humans. We propose that in humans, lack of thymic T cell generation does not explain a decline in T cell receptor diversity nor would thymic rejuvenation restore diversity. Initial studies using next generation sequencing are beginning to establish lower boundaries of T cell receptor diversity. With increasing sequencing depth and the development of new statistical models, we are now in the position to test this model and to assess the impact of age on T cell diversity and clonality.

Ageing and myeloid-derived suppressor cells: possible involvement in immunosenescence and age-related disease

Infections, cancer and autoimmune diseases occur more frequently in the elderly, and although many factors contribute to this, the age-related remodelling of the immune system, termed immunosenescence, plays a major role. Over the last two decades, studies have evaluated the effect of ageing on both the adaptive and innate arms of the immune system and demonstrated compromised function in several cells including lymphocytes (naïve, effector and memory), regulatory T and B cells, monocytes, neutrophils and NK cells. In addition, a well-documented feature of ageing is the increase in systemic inflammatory status (inflammageing), with raised serum levels of IL6, TNFα and CRP as well as reduced IL10. Recently, myeloid-derived suppressor cells have been the focus of many reports as these cells show immunosuppressive properties and are present in higher frequency during infections, cancer and autoimmunity. Importantly, there have been publications showing increased numbers of myeloid-derived suppressor cells in aged mice and humans. In this review, we discuss the current literature on myeloid-derived suppressor cells, their possible role in altered immune function in the elderly, and whether it may be possible to manipulate these cells to alleviate age-related immune dysfunction.

Incidence of herpes zoster in patients with altered immune function

Purpose

To estimate the incidence of herpes zoster (HZ) and rates of post-zoster pain in both the total study population and separately in patients with selected conditions/treatments associated with altered immune function.

Methods

The health administrative claims databases for commercially insured, Medicare, and Medicaid populations, together accounting for approximately 51 million insured individuals, were analyzed between 2005 and 2009 in a retrospective cohort study. Incidence of HZ episodes per 1,000 person-years (PY) was estimated in all study populations as well as within nine potentially immune-altering conditions. Among patients with HZ, the 6-month rate of persistent post-zoster pain was estimated.

Results

Analysis of 90.2 million PY at risk revealed that the incidence of HZ in the total study population was 4.82/1,000 PY. The incidence of HZ was highest among patients with bone marrow or stem cell transplant (43.03 %) followed by solid organ transplant, human immunodeficiency virus infection, and systemic lupus erythematosus [95 % confidence interval (CI) 15.19–17.41 %]. HZ incidence rates were higher among persons on immunosuppressants/chemotherapy than among non-users. In the total study population, HZ incidence increased with age (18–49 years: 3.37/1,000 PY; 65+ years: 8.43/1,000 PY; P < 0.01) and female gender (incidence ratio vs. male 1.39, 95 % CI 1.38–1.40 %). The 6-month rate of persistent post-zoster pain was 4.29 % (95 % CI 4.22–4.36 %), which was higher in patients with the selected conditions.

Conclusions

Despite providing a relatively small fraction of overall HZ cases, persons with immune function-altering conditions make a large contribution to the societal healthcare burden because they have a higher risk of developing HZ and persistent post-zoster pain. These risk factors should be considered in HZ prevention efforts.

Zostavax : a subcutaneous vaccine for the prevention of herpes zoster

INTRODUCTION

Herpes zoster (HZ) occurs as a reactivation of dormant varicella zoster virus (VZV), and occurs more frequently in the aging population or the immunocompromised due to waning cell-mediated immunity. Up to 1 million cases of HZ are reported annually in the USA with an estimated 10 - 30% of the population being affected by shingles in their lifetime. HZ is a debilitating illness, and while mortality is low, morbidity remains a significant cause for concern with prevention efforts aimed at reducing VZV reactivation and its complications. The HZ vaccine was approved by the US Food and Drug Administration for individuals aged 50-years or older. However, the Center for Disease Control and Prevention's Advisory Committee for Immunization Practices recommends the vaccine in individuals aged 60-years or older.

AREAS COVERED

Recent literature investigating the efficacy and indications of live attenuated zoster vaccine.

EXPERT OPINION

Live attenuated zoster vaccine is safe and efficacious in preventing HZ and decreasing the morbidity associated with postherpetic neuralgia. The vaccine is FDA approved in individuals aged 50-years or older but further studies are warranted to investigate the vaccine's efficacy in immunosuppressed and immunocompromised patients.

Understanding immunosenescence to improve responses to vaccines

In the older adult, the benefits of vaccination to prevent infectious disease are limited, mainly because of the adaptive immune system's inability to generate protective immunity. The age-dependent decrease in immunological competence, often referred to as 'immunosenescence', results from the progressive deterioration of innate and adaptive immune responses. Most insights into mechanisms of immunological aging have been derived from studies of mouse models. In this Review, we explore how well such models are applicable to understanding the aging process throughout the 80-100 years of human life and discuss recent advances in identifying and characterizing the mechanisms that underlie age-associated defective adaptive immunity in humans.