Platelet response to influenza vaccination reflects effects of aging.

Platelets are uniquely positioned as mediators of not only hemostasis but also innate immunity. However, how age and geriatric conditions such as frailty influence platelet function during an immune response remains unclear. We assessed the platelet transcriptome at baseline and following influenza vaccination in Younger (age 21-35) and Older (age ≥65) adults (including community-dwelling individuals who were largely non-frail and skilled nursing facility (SNF)-resident adults who nearly all met criteria for frailty). Prior to vaccination, we observed an age-associated increase in the expression of platelet activation and mitochondrial RNAs and decrease in RNAs encoding proteins mediating translation. Age-associated differences were also identified in post-vaccination response trajectories over 28 days. Using tensor decomposition analysis, we found increasing RNA expression of genes in platelet activation pathways in young participants, but decreasing levels in (SNF)-resident adults. Translation RNA trajectories were inversely correlated with these activation pathways. Enhanced platelet activation was found in community-dwelling older adults at the protein level, compared to young individuals both prior to and post-vaccination; whereas SNF residents showed decreased platelet activation compared to community-dwelling older adults that could reflect the influence of decreased translation RNA expression. Our results reveal alterations in the platelet transcriptome and activation responses that may contribute to age-associated chronic inflammation and the increased incidence of thrombotic and pro-inflammatory diseases in older adults.

Neutralizing Antibody Kinetics and Immune Protection Against Herpes Simplex Virus 1 Genital Disease in Vaccinated Women.

BACKGROUND: Previously, our group conducted the Herpevac Trial for Women, a randomized efficacy field trial of type 2 glycoprotein D (gD2) herpes simplex virus (HSV) vaccine adjuvanted with ASO4 in 8323 women. Study participants were selected to be seronegative for HSV-1 and HSV-2. We found that the vaccine was 82% protective against culture-positive HSV-1 genital disease but offered no significant protection against HSV-2 genital disease. Efficacy against HSV-1 was associated with higher levels of antibody to gD2 at enzyme-linked immunosorbent assay (ELISA). METHODS: To better understand the results of the efficacy study, we measured postvaccination concentrations of neutralizing antibody (nAb) to either HSV-1 and HSV-2 from HSV-infected study participants and matched uninfected controls. Statistical modeling was used to determine whether these responses were correlated with protection against HSV. RESULTS: nAbs to either HSV-1 or HSV-2 were correlated with ELISA binding antibodies to gD2. HSV-1 or HSV-2 nAb findings support the observation of protection by higher levels of antibody against HSV-1 infection, but the lack of protection against HSV-2 remains unexplained. CONCLUSIONS: The protection against HSV-1 infection observed in the Herpevac Trial for Women was associated with nAbs directed against the virus, although the power to assess this was lower in the nAb study compared with the ELISA results owing to smaller sample size. CLINICAL TRIALS REGISTRATION: NCT00057330.

Failure of Herpes Simplex Virus Glycoprotein D Antibodies to Elicit Antibody-Dependent Cell-Mediated Cytotoxicity: Implications for Future Vaccines.

BACKGROUND: The glycoprotein D (gD)/AS04 vaccine failed to prevent herpes simplex virus (HSV) 2 in clinical trials. Failure was recapitulated in mice, in which the vaccine elicited neutralizing antibody but not antibody-dependent cell-mediated cytotoxicity (ADCC) responses. Preclinical findings suggest that ADCC is important for protection, but the clinical data are limited. We hypothesized that gD/AS04 and acute HSV-2 infection elicit primarily neutralizing antibodies, whereas ADCC emerges over time. METHODS: HSV-specific immunoglobulin G, subclass, function (neutralization, C1q binding and ADCC), and antigenic targets were compared (paired t test or Mann-Whitney U test) at enrollment and after gD/AS04 vaccination, before and after HSV-2 acquisition in vaccine controls, and in an independent cohort with chronic HSV-2 infection. RESULTS: Vaccination elicited only a neutralizing antibody response, whereas acute infection elicited neutralizing and C1q-binding antibodies but not a significant ADCC response. Antibodies to gD were exclusively immunoglobulin G1 and only neutralizing. In contrast, women with chronic HSV-2 infection had significantly greater ADCC responses and targeted a broader range of viral antigens compared with acutely infected or gD/AS04 vaccine recipients (P < .001). CONCLUSIONS: Results from gD/AS04 vaccinated or acutely infected women recapitulate murine findings of limited functional antibody responses, supporting the speculation that vaccines that generate polyfunctional and specifically ADCC responses may be required to prevent HSV-2 acquisition and limit recurrences.

Seasonal Variability and Shared Molecular Signatures of Inactivated Influenza Vaccination in Young and Older Adults.

The seasonal influenza vaccine is an important public health tool but is only effective in a subset of individuals. The identification of molecular signatures provides a mechanism to understand the drivers of vaccine-induced immunity. Most previously reported molecular signatures of human influenza vaccination were derived from a single age group or season, ignoring the effects of immunosenescence or vaccine composition. Thus, it remains unclear how immune signatures of vaccine response change with age across multiple seasons. In this study we profile the transcriptional landscape of young and older adults over five consecutive vaccination seasons to identify shared signatures of vaccine response as well as marked seasonal differences. Along with substantial variability in vaccine-induced signatures across seasons, we uncovered a common transcriptional signature 28 days postvaccination in both young and older adults. However, gene expression patterns associated with vaccine-induced Ab responses were distinct in young and older adults; for example, increased expression of killer cell lectin-like receptor B1 (KLRB1; CD161) 28 days postvaccination positively and negatively predicted vaccine-induced Ab responses in young and older adults, respectively. These findings contribute new insights for developing more effective influenza vaccines, particularly in older adults.

Correlation between herpes simplex virus neutralizing antibody titers determined by ELVIS cell and traditional plaque reduction assays.

Preventive viral vaccine efficacy trials require large-scale sample analysis to quantitate immune responses and their correlation with infection outcomes. Traditional plaque reduction assays measure a functionally important form of humoral immunity, neutralizing antibody titer. These assays, however, are time-consuming and laborious. We previously developed a higher throughput assay of neutralizing antibody to herpes simplex viruses 1 and 2 (Blevins et al., PLOS ONE, 10(12), e0144738) using the enzyme-linked virus inducible system (ELVIS) cell line; this cell line produces ß-galactosidase in response to HSV infection. Here, serum samples from recipients of an investigational vaccine in the Herpevac Trial for Women were used to compare the ELVIS cell assay with the lower throughput, traditional plaque reduction assay. We demonstrate that neutralizing antibody titers to HSV-1 or HSV-2 determined using ELVIS cells positively correlate with neutralizing antibody titers determined by traditional plaque reduction assay, thus validating a higher throughput alternative for large-scale sample analysis.

Comparisons of the Humoral and Cellular Immune Responses Induced by Live Attenuated Influenza Vaccine and Inactivated Influenza Vaccine in Adults.

Both live attenuated influenza vaccines (LAIV) and inactivated influenza vaccines (IIV) induce protective immunity against influenza. There is evidence that LAIV induces superior protection in children, whereas IIV may induce superior protection in adults. The immune mechanisms responsible for these differences have not been identified. We previously compared LAIV and IIV in young children of 6 to 36 months of age, and we demonstrated that while both induced similar hemagglutination inhibition (HAI) antibody responses, only LAIV induced significant increases in T cell responses. In the present study, 37 healthy adult subjects of 18 to 49 years of age were randomized to receive seasonal influenza vaccination with LAIV or IIV. Influenza virus-specific HAI, T cell, and secretory IgA (sIgA) responses were studied pre- and postvaccination. In contrast to the responses seen in young children, LAIV induced only minimal increases in serum HAI responses in adults, which were significantly lower than the responses induced by IIV. Both LAIV and IIV similarly induced only transient T cell responses to replication-competent whole virus in adults. In contrast, influenza virus-specific sIgA responses were induced more strongly by LAIV than by IIV. Our previous studies suggest that LAIV may be more protective than IIV in young children not previously exposed to influenza virus or influenza vaccines due to increased vaccine-induced T cell and/or sIgA responses. Our current work suggests that in adults with extensive and partially cross-reactive preexisting influenza immunity, LAIV boosting of sIgA responses to hemagglutinin (HA) and non-HA antigenic targets expressed by circulating influenza virus strains may be an important additional mechanism of vaccine-induced immunity.

Priming Vaccination With Influenza Virus H5 Hemagglutinin Antigen Significantly Increases the Duration of T cell Responses Induced by a Heterologous H5 Booster Vaccination.

BACKGROUND: Influenza A(H5N1) virus and other avian influenza virus strains represent major pandemic threats. Like all influenza A virus strains, A(H5N1) viruses evolve rapidly. Innovative immunization strategies are needed to induce cross-protective immunity. METHODS: Subjects primed with clade 1 H5 antigen, with or without adjuvant, and H5-naive individuals were boosted with clade 2 H5 antigen. The impact of priming on T cells capable of both proliferation and cytokine production after antigen restimulation was assessed. RESULTS: Subjects previously vaccinated with clade 1 H5 antigen developed significantly enhanced clade 2 H5 cross-reactive T cell responses detectable 6 months after vaccination with clade 2 H5 antigen. Priming dose (15 µg vs 45 or 90 µg) had no effect on magnitude of heterotypic H5 T cell responses. In contrast, age at priming negatively modulated both the magnitude and duration of heterotypic H5 T cell responses. Elderly subjects developed significantly less heterotypic H5 T cell boosting, predominantly for T cells capable of cytokine production. Adjuvant had a positive albeit weaker effect than age. The magnitude of CD4(+) interferon-γ producing T cells correlated with H5 antibody responses. CONCLUSIONS: H5 heterotypic priming prior to onset of an A(H5N1) pandemic may increase magnitude and duration of immunity against a newly drifted pandemic H5 virus.

Development of a high-throughput ß-Gal-based neutralization assay for quantitation of herpes simplex virus-neutralizing antibodies in human samples.

Measurement of neutralizing antibodies against herpes simplex virus (HSV) is important for evaluation of candidate vaccines. The established plaque-reduction neutralization assay is time consuming, labor intensive, and difficult to validate and transfer. Here, we describe the characterization of a HSV-neutralization assay based on the expression of a reporter gene, ß-galactosidase (ß-Gal). Using previously constructed HSV-ß-Gal recombinant viruses, HSV-2/Gal and HSV-1/tk12, we developed a colorimetric ß-Gal-based neutralization assay that is sensitive and highly reproducible, and performed in less than 48h. HSV-1 and HSV-2 neutralizing titers measured by the ß-Gal-based neutralization assay were equivalent to those obtained by a plaque reduction neutralization assay. Intra- and inter-assay precision studies demonstrated that the ß-Gal-based assay was repeatable and yielded low and acceptable variation. In addition, comparison of HSV-2 neutralizing antibody (NAb) titers measured in two independent laboratories by two unique ß-Gal-based assays showed a highly significant correlation (r=0.9499, p<0.0001) between the two assays. The new assay will serve as an important tool both for preclinical and clinical trials of new HSV vaccines.

Higher Throughput Quantification of Neutralizing Antibody to Herpes Simplex Viruses.

We report a rapid, higher throughput method for measuring neutralizing antibody to herpes simplex virus (HSV) in human sera. Clinical isolates and sera from the Herpevac Trial for Women were used in a colorimetric assay in which infection of tissue culture (lack of neutralization) was indicated by substrate metabolism by beta-galactosidase induced in the ELVIS cell line. The neutralization assay was optimized by addition of guinea pig complement, which particularly enhanced neutralizing antibody titers to HSV-2. Higher neutralizing antibody titers were also achieved using virus particles isolated from the supernatant of infected cells rather than lysate of infected cells as the source of virus. The effect of assay incubation time and incubation time with substrate were also optimized. We found that incubating with substrate until a standard optical density of 1.0 was reached permitted a better comparison among virus isolates, and achieved reliable measurement of neutralizing antibody activity. Interestingly, in contrast to results in the absence of complement, addition of complement allowed sera from HSV-2 gD-vaccinated subjects to neutralize HSV-1 and HSV-2 clinical and laboratory isolates with equal potency.

Aging-dependent alterations in gene expression and a mitochondrial signature of responsiveness to human influenza vaccination.

To elucidate gene expression pathways underlying age-associated impairment in influenza vaccine response, we screened young (age 21-30) and older (age≥65) adults receiving influenza vaccine in two consecutive seasons and identified those with strong or absent response to vaccine, including a subset of older adults meeting criteria for frailty. PBMCs obtained prior to vaccination (Day 0) and at day 2 or 4, day 7 and day 28 post-vaccine were subjected to gene expression microarray analysis. We defined a response signature and also detected induction of a type I interferon response at day 2 and a plasma cell signature at day 7 post-vaccine in young responders. The response signature was dysregulated in older adults, with the plasma cell signature induced at day 2, and was never induced in frail subjects (who were all non-responders). We also identified a mitochondrial signature in young vaccine responders containing genes mediating mitochondrial biogenesis and oxidative phosphorylation that was consistent in two different vaccine seasons and verified by analyses of mitochondrial content and protein expression. These results represent the first genome-wide transcriptional profiling analysis of age-associated dynamics following influenza vaccination, and implicate changes in mitochondrial biogenesis and function as a critical factor in human vaccine responsiveness.

Prolonged proinflammatory cytokine production in monocytes modulated by interleukin 10 after influenza vaccination in older adults.

We evaluated in vivo innate immune responses in monocyte populations from 67 young (aged 21-30 years) and older (aged ≥65 years) adults before and after influenza vaccination. CD14(+)CD16(+) inflammatory monocytes were induced after vaccination in both young and older adults. In classical CD14(+)CD16(-) and inflammatory monocytes, production of tumor necrosis factor α and interleukin 6, as measured by intracellular staining, was strongly induced after vaccination. Cytokine production was strongly associated with influenza vaccine antibody response; the highest levels were found as late as day 28 after vaccination in young subjects and were substantially diminished in older subjects. Notably, levels of the anti-inflammatory cytokine interleukin 10 (IL-10) were markedly elevated in monocytes from older subjects before and after vaccination. In purified monocytes, we found age-associated elevation in phosphorylated signal transducer and activator of transcription-3, and decreased serine 359 phosphorylation of the negative IL-10 regulator dual-specificity phosphatase 1. These findings for the first time implicate dysregulated IL-10 production in impaired vaccine responses in older adults.

A Phase I, dose-escalation trial in adults of three recombinant attenuated Salmonella Typhi vaccine vectors producing Streptococcus pneumoniae surface protein antigen PspA.

BACKGROUND: Live, attenuated, orally-administered Salmonella strains are excellent vectors for vaccine antigens and are attractive as vaccines based on previous use of S. Typhimurium in animals. A Phase I dose escalation trial was conducted to evaluate the safety and immunogenicity of three newly constructed recombinant attenuated Salmonella enterica serovar Typhi vaccine (RASV) vectors synthesizing Streptococcus pneumoniae surface protein A (PspA). METHODS: The 3 S. Typhi strains used as vectors to deliver PspA were S. Typhi ISP1820; S. Typhi Ty2 RpoS(-); and S. Typhi Ty2 RpoS(+). Sixty healthy adults (median age 25.2 years) were enrolled into 4 Arms (total 15 subjects per Arm); within each Arm, subjects were randomized 1:1:1 into 3 Groups of 5. All subjects in the same Group received the same vaccine vector, and all subjects in the same Arm received the same titer of vaccine (10(7), 10(8), 10(9) or 10(10)CFU). Adverse events, safety, shedding, and IgG and IgA titers against Salmonella outer membrane proteins (OMPs), lipopolysaccharide (LPS) and PspA were evaluated. RESULTS: In the highest dose group, no subject experienced severe reactions or serious adverse events. Most adverse events were mild; one subject had a positive blood culture. No subject shed vaccine in stool. No statistically significant differences for post vaccination ELISA or ELISPOT results between Groups were detected. However, a limited number of ≥ 4 fold increases from baseline for IgA anti-OMPs, IgA and IgG anti-LPS, and IgA anti-PspA occurred for a few individuals as measured by ELISA, and IgA anti-OMPs as measured by ELISPOT assay. CONCLUSIONS: All three S. Typhi vectored pneumococcal vaccines were safe and well-tolerated. Immunogenicity was limited possibly due to pre-existing high antibody titers prior to vaccination. Increases in IgA were most often observed.

Improved assay to detect neutralizing antibody following vaccination with diluted or undiluted vaccinia (Dryvax) vaccine.

The assessment of immunogenicity of a diluted vaccinia vaccine for possible widespread use of a diluted vaccine in the event of a bioterrorist attack prompted us to focus on the development of a sensitive and specific plaque reduction neutralization (PRN) assay to assess the antibody response of volunteers to a vaccinia (Dryvax) vaccine. Two incubation times, 1 h or overnight (approximately 15 h), were explored for the neutralization step of the assay. In addition, serum samples were evaluated using both sonicated and nonsonicated virus in PRN assays with 1 and 15 h of incubation. The use of the overnight incubation method resulted in the detection of antibody in two vaccinated individuals who exhibited a take, i.e., a major reaction indicative of successive vaccination as defined by the Centers for Disease Control and Prevention, but did not have a fourfold increase in antibody to vaccinia virus by the 1-h-incubation method and increased the sensitivity from 94 to 100%. In addition to the increased sensitivity of the assay, we noted a significant increase (approximately 40-fold) in the PRN titer of serum samples tested with the 15-h-incubation method. The use of sonicated virus increased the reproducibility of the virus titers and PRN titers. Forty-two percent of the samples tested using sonicated virus had a PRN titer that was fourfold higher or greater than that of nonsonicated virus in the assay. A PRN titer that was threefold higher or greater was observed in more than half (58%) of the samples using sonicated virus. Therefore, the more sensitive, specific, and reproducible plaque neutralization assay for the detection of antibody to vaccinia virus is the method using a 15-h-incubation time and freshly sonicated vaccinia virus.

Stability of undiluted and diluted vaccinia-virus vaccine, Dryvax.

The stability of Dryvax vaccine was examined to determine whether diluted vaccine could be used over an extended period, thereby increasing the number of available doses. Stability parameters that we evaluated include dilution (undiluted, diluted 1:5, and diluted 1:10), diluent (original Dryvax diluent, new Dryvax diluent, and phosphate-buffered saline), and temperature (refrigerator temperature and room temperature). Storage of reconstituted Dryvax vaccine at room temperature, regardless of dilution or diluent, resulted in a significantly greater decrease in titer than did storage at refrigerator temperature. At refrigerator temperature, the decrease in vaccinia-vaccine titer during the first year was not significantly different between the undiluted Dryvax vaccine and either of the 2 diluted forms of Dryvax vaccine, with any of the 3 diluents.