Rocio D. Marchese

Varicella-Zoster Virus–Specific Immune Responses in Elderly Recipients of a Herpes Zoster Vaccine

BACKGROUND A double-blind, placebo-controlled trial that involved 38,546 subjects > or =60 years old demonstrated efficacy of a high-potency live-attenuated Oka/Merck varicella-zoster virus (VZV) vaccine. The trial included an immunology substudy to determine the relationship of VZV-specific immune responses to vaccination and clinical outcome. METHODS The immunology substudy enrolled 1395 subjects at 2 sites where blood samples obtained prior to vaccination, at 6 weeks after vaccination, and at 1, 2, and 3 years thereafter were tested for VZV-specific cell-mediated immunity (VZV-CMI) by gamma-interferon ELISPOT and responder cell frequency assays and for VZV antibody by glycoprotein ELISA. RESULTS VZV-CMI and VZV antibodies were significantly increased in vaccine recipients at 6 weeks after vaccination. The vaccine-induced increases in VZV-CMI persisted during the 3 years of follow-up, although their magnitude decreased over time. The magnitude of these VZV-specific immune responses was greater in subjects 60-69 years old than in subjects > or =70 years old. CONCLUSIONS The zoster vaccine induced a significant increase in VZV-CMI and VZV antibody. The magnitude and duration of the boost in VZV-CMI in vaccine recipients and the relationship of this boost to age paralleled the clinical effects of the vaccine observed during the efficacy trial. These findings support the hypothesis that boosting VZV-CMI protects older adults against herpes zoster and postherpetic neuralgia.

Memory T cells and vaccines

T lymphocytes play a central role in the generation of a protective immune response in many microbial infections. After immunization, dendritic cells take up microbial antigens and traffic to draining lymph nodes where they present processed antigens to naïve T cells. These naïve T cells are stimulated to proliferate and differentiate into effector and memory T cells. Activated, effector and memory T cells provide B cell help in the lymph nodes and traffic to sites of infection where they secrete anti-microbial cytokines and kill infected cells. At least two types of memory cells have been defined in humans based on their functional and migratory properties. T central-memory (T(CM)) cells are found predominantly in lymphoid organs and can not be immediately activated, whereas T effector-memory (T(EM)) cells are found predominantly in peripheral tissue and sites of inflammation and exhibit rapid effector function. Most currently licensed vaccines induce antibody responses capable of mediating long-term protection against lytic viruses such as influenza and small pox. In contrast, vaccines against chronic pathogens that require cell-mediated immune responses to control, such as malaria, Mycobacterium tuberculosis (TB), human immunodeficiency virus (HIV) and hepatitis C virus (HCV), are currently not available or are ineffective. Understanding the mechanisms by which long-lived cellular immune responses are generated following vaccination should facilitate the development of safe and effective vaccines against these emerging diseases. Here, we review the current literature with respect to memory T cells and their implications to vaccine development.

Safety and Antibody Response, Including Antibody Persistence for 5 Years, after Primary Vaccination or Revaccination with Pneumococcal Polysaccharide Vaccine in Middle-Aged and Older Adults

BACKGROUND This study assessed antibody levels for 5 years after primary vaccination or revaccination with 23-valent pneumococcal polysaccharide vaccine (PN23). METHODS Subjects were enrolled into 4 study groups by age (50-64 or > or = 65 years) and prior vaccination status (no prior vaccination or 1 vaccination 3-5 years previously). Blood was obtained on day 0 (before primary vaccination or revaccination), day 30, day 60, and annually during years 2-5. Levels of immunoglobulin G (IgG) to 8 vaccine serotypes were measured by enzyme-linked immunosorbent assay. RESULTS Of 1008 enrolled subjects, 551 completed year 5. For each serotype and age group, baseline geometric mean concentrations (GMCs) of IgG were higher in revaccination than primary vaccination subjects. Primary vaccination or revaccination with PN23 induced significant increases in levels of antibody to all serotypes tested. Although day 30 and 60 antibody levels tended to be modestly lower after revaccination, study groups had similar GMCs at later time points. For serotypes 4, 6B, 8, 9V, 12F, 14, and 23F, GMCs during years 2-5 after primary vaccination or revaccination remained higher than in vaccine-naive persons. Levels of antibody to serotype 3 returned to baseline by year 2. CONCLUSIONS Both primary vaccination and revaccination with PN23 induce antibody responses that persist during 5 years of observation.

Revaccination with a 23-Valent Pneumococcal Polysaccharide Vaccine Induces Elevated and Persistent Functional Antibody Responses in Adults Aged ⩾65 Years

BACKGROUND Older adults are at high risk of developing invasive pneumococcal disease, but the optimal timing and number of vaccine doses needed to prevent disease among this group are unknown. We compared revaccination with 23-valent pneumococcal polysaccharide vaccine (PN23) with primary vaccination for eliciting initial and persistent functional antibody responses. METHODS Subjects aged > or = 65 years were enrolled. Functional (opsonic) and total immunoglobulin (Ig) G antibody levels were measured following either PN23 primary vaccination (n = 60) or revaccination 3-5 years after receiving a first PN23 vaccination (n = 60). Antibody against vaccine serotypes 4, 14, and 23F was measured at prevaccination (day 0), 30 days after vaccination, and 5 years after vaccination. RESULTS By day 30, both primary vaccination and revaccination induced significant increases in opsonic and IgG antibody levels. Day 30 levels following revaccination were slightly lower but not significantly different than those after primary vaccination. Year 5 levels were similar in both groups and remained significantly higher than prevaccination levels for primary vaccination subjects. There was good agreement between postvaccination opsonic and IgG antibody levels. CONCLUSIONS Revaccination of older adults with PN23 was comparable to primary vaccination for inducing elevated and persistent functional and IgG antibody responses.

Antibody persistence ten years after first and second doses of 23-valent pneumococcal polysaccharide vaccine, and immunogenicity and safety of second and third doses in older adults.

In a study of older adults, first and second doses of 23-valent pneumococcal polysaccharide vaccine (PN23) induced IgG increases for all 8 vaccine serotypes tested. Participants (N=143, mean age 76 years) were re-enrolled to study antibody levels after ten years, and safety and immunogenicity of another PN23 dose. Ten years after first or second doses, mean IgG concentrations exceeded vaccine-naïve levels for 7 of 8 serotypes tested. Second and third doses administered at this time were generally well tolerated and were immunogenic, inducing similar postvaccination levels. Immunogenicity is preserved after multiple PN23 doses without evidence of a lower than expected immune response (i.e., without hyporesponsiveness).

Optimization and Validation of a Multiplex, Electrochemiluminescence-Based Detection Assay for the Quantitation of Immunoglobulin G Serotype-Specific Antipneumococcal Antibodies in Human Serum

ABSTRACT Pneumovax 23 consists of a mixture of highly purified capsular polysaccharides (Ps) from 23 of the most prevalent serotypes of Streptococcus pneumoniae. Testing of vaccine immunogenicity has been historically performed on the enzyme-linked immunosorbent assay (ELISA) platform, validated to measure immunoglobulin G (IgG) antibodies to all 23 serotypes included in Pneumovax 23. In order to significantly improve the throughput of this form of testing, we have developed and validated a direct binding electrochemiluminescence (ECL)-based multiplex assay that can measure the antibody response in human serum to eight serotypes within a single microtiter well. The pneumococcal (Pn) ECL assay is based on the Meso Scale Discovery (MSD) technology which utilizes a Sulfo-Tag-labeled anti-human IgG antibody that emits light upon electrochemical stimulation. The Pn ECL assay exhibits a wide dynamic range and provides the ability to read concentrations down to the minimum reported concentration in the Merck ELISA (0.1 μg/ml). Cross-reactivity assessment using type-specific monoclonal antibodies showed no cross talk between antigen spots within a well. By use of the WHO Pn sample reference panel, the results obtained with the Pn ECL assay were compared to the results obtained with the international Pn ELISA. The results for the Pn ECL assay satisfied the WHO-recommended acceptance criterion for concordance for all seven serotypes with published Pn ELISA values, and the overall correlation (r value) across the seven serotypes was 0.994. The MSD methodology has great potential to be extremely useful for simultaneously quantitating IgG responses to several Pn serotypes while conserving serum volumes and laboratory testing time.

Major depressive disorder and immunity to varicella-zoster virus in the elderly.

Major depressive disorder has been associated with activation of inflammatory processes as well as with reductions in innate, adaptive and non-specific immune responses. The objective of this study was to evaluate the association between major depression and a disease-relevant immunologic response, namely varicella-zoster virus (VZV)-specific immunity, in elderly adults. A cross-sectional cohort study was conducted in 104 elderly community dwelling adults ≥ 60years of age who were enrolled in the depression substudy of the shingles prevention study, a double blind, placebo-controlled vaccine efficacy trial. Fifty-two subjects had a current major depressive disorder, and 52 age- and sex-matched controls had no history of depression or any mental illness. VZV-specific cell-mediated immunity (VZV-CMI) was measured by VZV responder cell frequency (VZV-RCF) and interferon-γ enzyme-linked immunospot (ELISPOT) assays, and antibody to VZV was measured by an enzyme-linked immunosorbent assay against affinity-purified VZV glycoproteins (gpELISA). VZV-CMI, measured by VZV-RCF, was significantly lower in the depressed group than in the controls (p<0.001), and VZV-RCF was inversely correlated with the severity of depressive symptoms in the depressed patients. In addition, an age-related reduction in VZV-RCF was observed in the depressed patients, but not in the controls. Furthermore, there was a trend for depressive symptom severity to be associated with lower ELISPOT counts. Finally, VZV-RCF was higher in depressed patients treated with antidepressant medications as compared to untreated depressed patients. Since lower levels of VZV-RCF appear to explain the increased risk and severity of herpes zoster observed in older adults, these findings suggest that, in addition to increasing age, depression may increase the risk and severity of herpes zoster.

Varicella Zoster Virus–Specific Immune Responses to a Herpes Zoster Vaccine in Elderly Recipients With Major Depression and the Impact of Antidepressant Medications

BACKGROUND The Depression Substudy of the Shingles Prevention Study (SPS) was designed to evaluate the association between major depression and immune responses to a high-titer live attenuated varicella zoster virus (VZV) vaccine (zoster vaccine), which boosts cell-mediated immunity (CMI) to VZV and decreases the incidence and severity of herpes zoster (HZ). The Depression Substudy was a 2-year longitudinal cohort study in 92 community-dwelling adults≥60 years of age who were enrolled in the SPS, a large, double-blind, placebo-controlled Veterans Affairs Cooperative zoster vaccine efficacy study. METHODS Forty subjects with major depressive disorder, stratified by use of antidepressant medications, and 52 age- and sex-matched controls with no history of depression or other mental illness had their VZV-CMI measured prior to vaccination with zoster vaccine or placebo and at 6 weeks, 1 year, and 2 years postvaccination. RESULTS Depressed subjects who were not treated with antidepressant medications had lower levels of VZV-CMI following administration of zoster vaccine than nondepressed controls or depressed subjects receiving antidepressants even when antidepressant medications failed to alter depressive symptom severity (P<.005). Similar results were obtained taking into account the time-varying status of depression and use of antidepressant medications, as well as changes in depressive symptoms, during the postvaccination period. CONCLUSIONS Depressed patients have diminished VZV-CMI responses to zoster vaccine, and treatment with antidepressant medication is associated with normalization of these responses. Because higher levels of VZV-CMI correlate with lower risk and severity of HZ, untreated depression may increase the risk and severity of HZ and reduce the efficacy of zoster vaccine.

Enzyme-Linked Immunosorbent Assay for Measuring Antibodies to Pneumococcal Polysaccharides for the PNEUMOVAX 23 Vaccine: Assay Operating Characteristics and Correlation to the WHO International Assay

ABSTRACT The Merck pneumococcal (Pn) enzyme-linked immunosorbent assays (ELISAs) for measuring antibodies to 12 serotypes (serotypes 1, 3, 4, 6B, 7F, 8, 9V, 12F, 14, 18C, 19F, and 23F) were validated in 1999. Merck Laboratories developed the Pn assays using 10 μg/ml C polysaccharide, 100 μg/ml Pn polysaccharide (PnPs) 25, and 100 μg/ml PnPs 72 for preadsorption of samples, standards, and controls in order to improve the specificity to the Pn serotypes in the vaccine. The Pn assays utilize postimmunization sera obtained from subjects immunized with PNEUMOVAX 23 as standards for measuring immunoglobulin G concentrations in sera obtained from vaccine clinical trials with adults and infants. This material was calibrated to the Pn reference standard serum, 89SF, subjected to the Merck Pn ELISA adsorbants. Comparisons were made between the Merck Pn assay and the international Pn assay, showing moderate agreement between the two assay formats. This work describes the test procedures and operating characteristics of the Merck Pn assays and the results of experiments performed to compare the Merck Pn ELISAs to the international Pn ELISAs.

Safety, tolerability, and immunogenicity of 15-valent pneumococcal conjugate vaccine in healthy adults ☆ ☆☆

BACKGROUND Pneumococcal disease remains an important health priority despite successful implementation of pneumococcal conjugate vaccines (PCVs) in infant immunization programs, mainly due to the emergence of diseases caused by serotypes not included in licensed PCVs. A 15-valent pneumococcal conjugate vaccine (PCV-15) containing the 7 serotypes (4, 6B, 9V, 14, 18C, 19F, and 23F) included in licensed PCV-7 available at study initiation plus 8 additional serotypes (1, 3, 5, 6A, 7F, 19A, 22F, 33F) was developed and evaluated in healthy adults 18-45 years of age. METHODS Sixty subjects received one dose of PCV-15 or PCV-7. Injection-site and systemic adverse events (AEs) were collected for 14-days postvaccination and serious AEs were collected for 30-days postvaccination. Safety laboratory tests (hematology, chemistry, and urinalysis) were evaluated prior to vaccination and 14-days postvaccination. Serotype-specific IgG and opsonophagocytic killing activity (OPA) responses to 15 serotypes included in PCV-15 were measured immediately prior to vaccination and 30-days postvaccination. RESULTS AE incidences were comparable between vaccine groups although numerically higher frequencies of erythema (33.3% versus 13.3%), swelling (50.0% versus 23.3%), and myalgia (63.3% versus 36.7%) were reported among PCV-15 versus PCV-7 recipients. Majority of AEs, irrespective of vaccine received, were transient and of mild-to-moderate intensity. No clinically significant differences were observed when comparing AE duration and severity. No laboratory abnormalities, vaccine-related SAEs or discontinuations from the study due to AEs were reported. IgG concentrations for the shared serotypes substantially increased postvaccination at comparable levels between recipients of PCV-15 and PCV-7. Substantial increases in antibody (IgG and OPA) responses to 8 serotypes unique to PCV-15 were observed in PCV-15 recipients. Slight increases to 2 serotypes unique to PCV-15, serotypes 6A and 19A, were also noted in PCV-7 recipients. CONCLUSION PCV-15 displays an acceptable safety profile and induces IgG and OPA responses to all serotypes included in the vaccine.