Vaccination With Detoxified Leukocidin AB Reduces Bacterial Load in a Staphylococcus aureus Minipig Deep Surgical Wound Infection Model.

Vaccines against Staphylococcus aureus have eluded researchers for >3 decades while the burden of staphylococcal diseases has increased. Early vaccine attempts mainly used rodents to characterize preclinical efficacy, and all subsequently failed in human clinical efficacy trials. More recently, leukocidin AB (LukAB) has gained interest as a vaccine antigen. We developed a minipig deep surgical wound infection model offering 3 independent efficacy readouts: bacterial load at the superficial and at the deep-seated surgical site, and dissemination of bacteria. Due to similarities with humans, minipigs are an attractive option to study novel vaccine candidates. With this model, we characterized the efficacy of a LukAB toxoid as vaccine candidate. Compared to control animals, a 3-log reduction of bacteria at the deep-seated surgical site was observed in LukAB-treated minipigs and dissemination of bacteria was dramatically reduced. Therefore, LukAB toxoids may be a useful addition to S. aureus vaccines and warrant further study.

A randomized phase 1/2a trial of ExPEC10V vaccine in adults with a history of UTI.

The safety, reactogenicity, and immunogenicity of 3 doses of ExPEC10V (VAC52416), a vaccine candidate to prevent invasive Escherichia coli disease, were assessed in a phase 1/2a study (NCT03819049). In Cohort 1, ExPEC10V was well tolerated; the high dose was selected as optimal and further characterized in Cohort 2. Cohort 2 comprised a maximum 28-day screening, vaccination (Day 1), double-blind 181-day follow-up, and open-label long-term follow-up until Year 1. Healthy participants (≥60 years) with a history of urinary tract infection (UTI) within 5 years were randomized to receive ExPEC10V or placebo. The primary endpoint evaluated the safety and reactogenicity of ExPEC10V (solicited local and systemic AEs [until Day 15]; unsolicited AEs [until Day 30], SAEs [until Day 181], and immunogenicity [Day 30]) via multiplex electrochemiluminescent (ECL) and multiplex opsonophagocytic assay (MOPA). 416 participants (ExPEC10V, n = 278; placebo, n = 138) were included (mean age [SD], 68.8 [6.52] years; female, 79.6%; White, 96.1%). The incidence of solicited AEs was higher with ExPEC10V (local, 50.0% [n = 139]; systemic, 50.0% [n = 139]) than placebo (15.9% [n = 22]; 38.4% [n = 53]); rates of unsolicited AEs were comparable (ExPEC10V, 28.4% [n = 79]; placebo, 26.1% [n = 36]). No vaccine-related SAEs or deaths were reported. ExPEC10V elicited a robust antibody-mediated immunogenic response across all serotypes with ECL (Day 30 geometric mean fold increase, 2.33-8.18) and demonstrated functional opsonophagocytic killing activity across all measured serotypes (Day 30 geometric mean fold increase, 1.81-9.68). ExPEC10V exhibited an acceptable safety profile and a robust vaccine-induced functional immunogenic response in participants with a history of UTI. Clinical trial registration details: https://clinicaltrials.gov/study/NCT03819049 .

Nonclinical vaccine safety evaluation: advantages of continuous temperature monitoring using abdominally implanted data loggers.

Fever has been reported as the most common adverse event after vaccination in infants and children. For this reason it is important that, prior to clinical testing of a new vaccine, change in body temperature following vaccination is tested carefully in nonclinical animal studies. Since both the timing and the height of the temperature peak after vaccination may differ from vaccine to vaccine, it is important that the time point for body temperature measurement should be chosen on a case-by-case basis with sufficient knowledge of the specific vaccine. In order to determine the best time point for rectal body temperature measurement after vaccination with a new vaccine candidate against N. meningitidis serogroup B, to be applied in a formal Good Laboratory Practice (GLP) toxicology study, miniature temperature data loggers were implanted into the peritoneal cavity of rabbits. The continuous body temperature monitoring appeared to give a complete picture of the entire body temperature kinetics after vaccination. The body temperature peaked at 4 h after vaccination, and this time point was subsequently applied in the toxicology study. Measured body temperature values at the selected time point of 4 h after vaccination were comparable in the continuous temperature setting and in the formal toxicology study, i.e. rectal temperature measurement at one time point. In the present study implanted temperature loggers were successfully used to define an adequate time point to be applied in determining rectal body temperature in a formal GLP toxicology study with a new vaccine candidate.

Safety, Reactogenicity, Immunogenicity, and Dose Selection of 10-Valent Extraintestinal Pathogenic Escherichia coli Bioconjugate Vaccine (VAC52416) in Adults Aged 60-85 Years in a Randomized, Multicenter, Interventional, First-in-Human, Phase 1/2a Study.

Background: ExPEC10V is a bioconjugate vaccine containing O-antigen polysaccharides of 10 extraintestinal pathogenic Escherichia coli (ExPEC) serotypes. This phase 1/2a study (NCT03819049) assessed the safety, reactogenicity, and immunogenicity of ExPEC10V (VAC52416) to prevent invasive E coli disease in elderly adults. Methods: The observer-blind, active-controlled design included a 28-day screening, vaccination, 181-day follow-up, and 1-year follow-up. Participants (60-85 years of age) were randomized to ExPEC10V low dose (antigen dose range, 4-8 µg), ExPEC10V medium dose (4-16 µg), or ExPEC10V high dose (8-16 µg); 4-valent ExPEC vaccine (ExPEC4V); or 13-valent pneumococcal conjugate vaccine (PCV13). The incidence of adverse events (AEs; solicited, day 15; unsolicited, day 30; serious AEs, day 181) and immunogenicity (electrochemiluminescent-based assay [ECL] and multiplex opsonophagocytic assay [MOPA]) were assessed. Optimal ExPEC10V dose was determined from safety data through day 30 and an immunogenicity dose selection algorithm based on day 15 ECL and MOPA results. Results: A total of 416 participants were included (median age, 64.0 years; 54.8% female). The incidences of solicited local and systemic AEs were, respectively, 44.2% and 39.4% for low-dose, 52.9% and 46.1% for medium-dose, 57.7% and 45.2% for high-dose ExPEC10V, and 74.1% and 48.1% for PCV13. Five serious AEs, not vaccine related, were reported. The ECL revealed a robust antibody response to ExPEC10V through year 1. Opsonophagocytic killing activity was detected against all but serotype O8; this lack of response against serotype O8 was linked to low assay sensitivity. Based on the totality of data, high-dose ExPEC10V was considered optimal. Conclusions: ExPEC10V was well tolerated and immunogenic in elderly adults against all but serotype O8.

Colonization with Escherichia coli ST131-H30R (H30R) Corresponds with Increased Serum Anti-O25 IgG Levels and Decreased TNFα and IL-10 Responsiveness to H30R.

An exceptional gut-colonizing ability may underlie the dramatic epidemiological success of the multidrug-resistant H30R subclone of Escherichia coli sequence type 131 (O25b:K+:H4). In order to inform the development of colonization-preventing measures, we studied systemic immune correlates of H30R intestinal colonization. Human volunteers' fecal samples were screened for H30R by selective culture and PCR. Subjects were assessed by enzyme immunoassay for serum levels of anti-O25 IgG (representing H30R) and anti-O6 IgG (representing non-H30 E. coli generally), initially and for up to 14 months. Whole blood was tested for the antigen-stimulated release of IFNγ, TNFα, IL-4, IL-10, and IL-17 after incubation with E. coli strains JJ1886 (H30R; O25b:K+:H4) or CFT073 (non-H30; O6:K2:H1). Three main findings were obtained. First, H30R-colonized subjects had significantly higher anti-O25 IgG levels than controls, but similar anti-O6 IgG levels, suggesting an IgG response to H30R colonization. Second, anti-O25 and anti-O6 IgG levels were stable over time. Third, H30R-colonized subjects exhibited a lower TNFα and IL-10 release than controls in response to strain JJ1886 (H30R) relative to strain CFT073 (non-H30R), consistent with TNFα hypo-responsiveness to H30R possibly predisposing to H30R colonization. Thus, H30R-colonized hosts exhibit a sustained serum anti-O25 IgG response and an underlying deficit in TNFα responsiveness to H30R that could potentially be addressed for colonization prevention.

Neutralizing antibodies elicited by a novel detoxified pneumolysin derivative, PlyD1, provide protection against both pneumococcal infection and lung injury.

Streptococcus pneumoniae pneumolysin (PLY) is a virulence factor that causes toxic effects contributing to pneumococcal pneumonia. To date, deriving a PLY candidate vaccine with the appropriate detoxification and immune profile has been challenging. A pneumolysin protein that is appropriately detoxified and that retains its immunogenicity is a desirable vaccine candidate. In this study, we assessed the protective efficacy of our novel PlyD1 detoxified PLY variant and investigated its underlying mechanism of protection. Results have shown that PlyD1 immunization protected mice against lethal intranasal (i.n.) challenge with pneumococci and lung injury mediated by PLY challenge. Protection was associated with PlyD1-specific IgG titers and in vitro neutralization titers. Pretreatment of PLY with PlyD1-specific rat polyclonal antiserum prior to i.n. delivery of toxin reduced PLY-mediated lung lesions, interleukin-6 (IL-6) production, and neutrophil infiltration into lungs, indicating that protection from lung lesions induced by PLY is antibody mediated. Preincubation of PLY with a neutralizing monoclonal PLY antibody also specifically reduced the cytotoxic effects of PLY after i.n. inoculation in comparison to nonneutralizing monoclonal antibodies. These results indicate that the induction of neutralizing antibodies against PLY can contribute to protection against bacterial pneumonia by preventing the development of PLY-induced lung lesions and inflammation. Our detoxified PlyD1 antigen elicits such PLY neutralizing antibodies, thus serving as a candidate vaccine antigen for the prevention of pneumococcal pneumonia.

Is a single dose of meningococcal serogroup C conjugate vaccine sufficient for protection? experience from the Netherlands.

BACKGROUND: The first meningococcal serogroup C (MenC) conjugate vaccine was licensed in 1999 and introduced in the United Kingdom. Countries that have implemented the MenC vaccine since then in their national immunisation programmes use different schedules. Nevertheless, all involved countries seem to experience substantial declines in the incidence of MenC disease. DISCUSSION: Since 2001, the MenC conjugate vaccine has been implemented in the Netherlands by offering a single dose to all children aged 14 months. Prior to the introduction of the vaccine into the national immunisation programme, a catch-up vaccination campaign was initiated in which a single dose of the MenC conjugate vaccine was offered to all children aged from 14 months up to and including 18 years. Since then, there has been no report of any case of MenC disease among immunocompetent vaccinees. Administration of a single dose of MenC conjugate vaccine after infancy could be beneficial considering the already complex immunisation schedules with large numbers of vaccinations in the first year of life. The present paper deals with the advantages and critical aspects of a single dose of the MenC conjugate vaccine. SUMMARY: A single dose of MenC conjugate vaccine at the age of 14 months in combination with a catch up vaccine campaign appeared to be a successful strategy to prevent MenC disease in the Netherlands, thereby confirming that a single dose of the vaccine could sufficiently protect against disease. Nevertheless, this approach can only be justified in countries with a relatively low incidence of serogroup C meningococcal disease in the first year of life. Furthermore, a good surveillance programme is recommended for timely detection of vaccine breakthroughs and outbreaks among non-vaccinees, since long-term protection after a single dose in the second year of life cannot currently be guaranteed.

Carriage of Streptococcus pneumoniae 3 years after start of vaccination program, the Netherlands.

To evaluate the effectiveness of the 7-valent pneumococcal conjugate vaccine (PCV7) program, we conducted a cross-sectional observational study on nasopharyngeal carriage of Streptococcus pneumoniae 3 years after implementation of the program in the Netherlands. We compared pneumococcal serotypes in 329 prebooster 11-month-old children, 330 fully vaccinated 24-month-old children, and 324 parents with age-matched pre-PCV7 (unvaccinated) controls (ages 12 and 24 months, n = 319 and n = 321, respectively) and 296 of their parents. PCV7 serotype prevalences before and after PCV7 implementation, respectively, were 38% and 8% among 11-month-old children, 36% and 4% among 24-month-old children, and 8% and 1% among parents. Non-PCV7 serotype prevalences were 29% and 39% among 11-month-old children, 30% and 45% among 24-month-old children, and 8% and 15% among parents, respectively; serotypes 11A and 19A were most frequently isolated. PCV7 serotypes were largely replaced by non-PCV7 serotypes. Disappearance of PCV7 serotypes in parents suggests strong transmission reduction through vaccination.

Lower immunoglobulin G antibody responses to pneumococcal conjugate vaccination at the age of 2 years after previous nasopharyngeal carriage of Streptococcus pneumoniae.

OBJECTIVE: To determine whether nasopharyngeal pneumococcal carriage with serotypes 6B, 19F, or 23F interferes with immunoglobulin G (IgG) antibody responses to vaccination with 7-valent pneumococcal conjugate vaccine (PCV7) at the age 24 months. STUDY DESIGN: Blood samples were collected before and after a PCV7 challenge vaccination at age 24 months from subsets of children participating in a randomized controlled trial. Children previously had received two doses of PCV7 at 2 and 4 months, two plus one doses of PCV7 at 2, 4, and 11 months, or no dosage until 24 months. Nasopharyngeal swabs were cultured at for Streptococcus pneumoniae at age 6 weeks and at 6, 12, 18, and 24 months. IgG responses were determined with enzyme immunoassay. RESULTS: Lower IgG responses against serotypes 6B, 19F, and 23F were observed on PCV7 challenge vaccination at 24 months in children who had received earlier PCV7 vaccinations and had been found positive for homologous carriage compared with non-carriers of these serotypes. Lower non-homologous IgG responses were observed after the PCV7 challenge at 24 months against serotype 6B after earlier 19F carriage and against serotype 19F after earlier 23F carriage compared with children who had not been positive for carriage of these serotypes. CONCLUSIONS: Pneumococcal colonization with serotypes 6B, 19F, and 23F is associated with diminished immune responses against these serotypes on PCV7 vaccination at 2 years of age. Underlying mechanisms deserve further investigation.

Next-generation outer membrane vesicle vaccines against Neisseria meningitidis based on nontoxic LPS mutants.

Outer membrane vesicles (OMVs) have been used extensively as experimental vaccines against Neisseria meningitidis. Classical meningococcal OMV vaccines contain wildtype lipopolysaccharide (LPS) with a hexa-acylated lipid A moiety, which is a very potent activator of the TLR4 receptor. While this may make the LPS an effective "internal" adjuvant, it also contributes to vaccine reactogenicity. Reduction of endotoxic activity has therefore been essential for the application of meningococcal OMV vaccines in humans. Classical OMV vaccines have a reduced LPS content as a result of detergent extraction, mostly with deoxycholate. An alternative method is the use of meningococcal strains with genetically detoxified LPS, in particular where mutation in the lpxL1 gene has resulted in penta-acylated lipid A with strongly attenuated endotoxic activity. This allows the use of native OMVs without any need for LPS removal by detergent extraction, making it a much easier to produce and more versatile vaccine platform. Several groups have now started the development of native OMV vaccines based on non-toxic LPS mutants, and this Commentary provides an overview of the various approaches and results thus far.

The structure of Neisseria meningitidis lipid A determines outcome in experimental meningococcal disease.

Lipopolysaccharide (LPS), a major component of the meningococcal outer membrane, is sensed by the host through activation of Toll-like receptor 4 (TLR4). Recently, we demonstrated that a surprisingly large fraction of Neisseria meningitidis disease isolates are lipid A mutants, due to inactivating mutations in the lpxL1 gene. The lpxL1 mutants activate human TLR4 much less efficiently than wild-type bacteria, which may be advantageous by allowing them to escape from the innate immune system. Here we investigated the influence of lipid A structure on virulence in a mouse model of meningococcal sepsis. One limitation, however, is that murine TLR4 recognizes lpxL1 mutant bacteria much better than human TLR4. We show that an lpxL2 mutant, another lipid A mutant lacking an acyl chain at a different position, activates murine TLR4 less efficiently than the lpxL1 mutant. Therefore, the lpxL2 mutant in mice might be a better model for infections with lpxL1 mutants in humans. Interestingly, we found that the lpxL2 mutant is more virulent in mice than the wild-type strain, whereas the lpxL1 mutant is actually much less virulent than the wild-type strain. These results demonstrate the crucial role of N. meningitidis lipid A structure in virulence.

Safety and immunogenicity of a vaccine for extra-intestinal pathogenic Escherichia coli (ESTELLA): a phase 2 randomised controlled trial.

BACKGROUND: ExPEC4V (JNJ-63871860) is a bioconjugate vaccine, containing O-antigens from Escherichia coli serotypes O1A, O2, O6A, and O25B, developed for the prevention of invasive extra-intestinal pathogenic E coli (ExPEC) disease. We aimed to assess safety, reactogenicity, and immunogenicity of ExPEC4V in healthy adults. METHODS: In this phase 2 randomised, double-blind placebo-controlled study, we recruited healthy adults (≥18 years with a body-mass index of 35 kg/m2 or less) between Nov 16, 2015, and Aug 8, 2017, and randomly assigned them to receive a single dose of ExPEC4V (antigen O1A:O2:O6A:O25B content 4:4:4:4 µg [group 1]; 4:4:4:8 µg [group 2], 8:8:8:8 µg [group 3], 8:8:8:16 µg [group 4], or 16:16:16:16 µg [group 5]) or placebo. The primary objectives were evaluation of the safety, tolerability, and immunogenicity of ExPEC4V and determination of its dose-dependent immunogenicity 15 days after vaccination by ELISA in individuals who had received at least one vaccination dose. Antibody titres and safety evaluation were used to select two ExPEC4V doses for assessment up to day 360. This trial is registered at ClinicalTrials.gov, number NCT02546960. FINDINGS: Of 848 enrolled participants, 843 (99%) received the ExPEC4V vaccine (757) or placebo (86) and were included in the safety analysis. Of 757 participants vaccinated with ExPEC4V, 222 (29%) had a solicited local adverse event and 325 (43%) had any solicited systemic adverse event, compared with 11 (13%) and 30 (35%) of 86 participants in the control group. Symptoms were mild-to-moderate. The most frequently reported solicited local adverse event was pain or tenderness (205 [27·1%] of 757 in combined ExPEC4V groups) and the most frequently reported solicited systemic adverse event was fatigue (208 [27·6%] of 757). Only 13 (2%) of 843 had a grade 3 event. At day 15, 80% or more of all participants achieved a two times or greater increase in serotype-specific IgG antibodies (except O25B at the lowest dose, 103 [72%] of 144). At day 360, 66% (95% CI 56·47-74·33) of participants in group 2 and 71% (62·13-78·95) of participants in group 4 selected for long-term follow-up maintained a two times or greater increase in serotype-specific antibody compared with baseline. INTERPRETATION: EXPEC4V seemed well tolerated and elicited robust and functional antibody responses across all serotypes, doses, and age groups. For the two dosages evaluated (4:4:4:8 µg and 8:8:8:16 µg), the immune response persisted for 1 year. FUNDING: Janssen Pharmaceuticals.

Increasing FIM2/3 antigen-content improves efficacy of Bordetella pertussis vaccines in mice in vivo without altering vaccine-induced human reactogenicity biomarkers in vitro.

Current acellular-pertussis (aP) vaccines appear inadequate for long-term pertussis control because of short-lived efficacy and the increasing prevalence of pertactin-negative isolates which may negatively impact vaccine efficacy. In this study, we added fimbriae (FIM)2 and FIM3 protein to licensed 2-, 3- or 5-component aP vaccines (Pentavac®, Boostrix®, Adacel®, respectively) to assess whether an aP vaccine with enhanced FIM content demonstrates enhanced efficacy. Vaccine-induced protection was assessed in an intranasal mouse challenge model. In addition, potential reactogenicity was measured by biomarkers in a human whole blood assay (WBA) in vitro and benchmarked the responses against licensed whole cell pertussis (wP) and aP vaccines including Easyfive®, Pentavac® and Pentacel®. The results show that commercial vaccines demonstrated reduced efficacy against pertactin-negative versus pertactin-positive strains. However, addition of higher amounts of FIM2/3 to aP vaccines reduced lung colonization and increased vaccine efficacy against a pertactin-negative strain in a dose-dependent manner. Improvements in efficacy were similar for FIM2 and FIM3-expressing strains. Increasing the amount of FIM2/3 proteins in aP formulations did not alter vaccine-induced biomarkers of potential reactogenicity including prostaglandin E2, cytokines and chemokines in human newborn cord and adult peripheral blood tested in vitro. These results suggest that increasing the quantity of FIM proteins in current pertussis vaccine formulations may further enhance vaccine efficacy against B. pertussis infection without increasing the reactogenicity of the vaccine.

Meningococcal B vaccine development and evaluation of efficacy.

In this commentary we stress that serum bactericidal activity is now internationally accepted as correlate of protection for evaluating new vaccines for epidemic and endemic meningococcal B control, and that the standardization of the assay and the choice of representative strains for each of the vaccine candidates are critical.

Safety, tolerability and immunogenicity of the ExPEC4V (JNJ-63871860) vaccine for prevention of invasive extraintestinal pathogenic Escherichia coli disease: A phase 1, randomized, double-blind, placebo-controlled study in healthy Japanese participants.

This Phase 1, randomized, double-blind, placebo-controlled study was conducted to evaluate the safety, tolerability and immunogenicity of different doses of ExPEC4V conjugate vaccine (4-16µg Polysaccharide [PS]/serotype) in healthy Japanese participants, stratified into younger (≥20 to <50 years) or older age groups (≥50 years). Within each age group, participants were randomized to a single vaccination with 1 of 3 dose levels of ExPEC4V (4, 8 and 16 µg PS/serotype) or placebo. Safety and tolerability were the primary objectives; immunogenicity was secondary. Of the 48 participants, 47 (98%) completed; one (2%) in the placebo group discontinued. A total of 48% participants had ≥1 AE (younger group: n = 13 [54%]; older group: n = 10 [41.7%]). Solicited and unsolicited AEs were reported in 44% and 8% participants, respectively in the combined ExPEC4V groups. Pain/tenderness (n = 11 [31%]) and redness (n = 9 [25%]) were the most frequently reported solicited local AEs, whereas fatigue (n = 4 [11%]), headache (n = 4 [11%]), muscle pain (n = 2 [6%]), and malaise (n = 5 [14%]) were the most common solicited systemic AEs in the combined ExPEC4V group. No serious AEs, deaths, or discontinuation due to AEs were reported. All doses were immunogenic with an increase in IgG (ELISA) geometric mean titers of at least 5-fold from baseline to Days 15 and 30 for all serotypes. Of participants vaccinated with ExPEC4V, 75% - 100% demonstrated an ELISA titer increase of ≥2-fold. Strong correlation observed between ELISA and OPK. ExPEC4V was well tolerated and elicited an immunogenic response at all dose levels (up to 16 µg PS/serotype) in healthy Japanese participants.

Immunodominance in T cell responses elicited against different domains of detoxified pneumolysin PlyD1.

Detoxified pneumolysin, PlyD1, is a protein vaccine candidate that induces protection against infections with Streptococcus pneumoniae in mouse models. Despite extensive knowledge on antibody responses against PlyD1, limited information is available about PlyD1 induced T cell recognition. Here we interrogated epitope breadth and functional characteristics of the T cell response to PlyD1 in two mouse strains. BALB/c (H-2d) and C57BL/6 (H-2b) mice were vaccinated with Al(OH)3-adjuvanted or non-adjuvanted PlyD1, or placebo, on day 0, 21 and 42 and were sacrificed at day 56 for collection of sera and spleens. Vaccination with adjuvanted and non-adjuvanted PlyD1 induced anti-pneumolysin IgG antibodies with neutralizing capacity in both mouse strains. Adjuvantation of PlyD1 enhanced the serological responses in both strains. In vitro restimulation of splenocytes with PlyD1 and 18-mer synthetic peptides derived from pneumolysin revealed specific proliferative and cytokine responses. For both mouse strains, one immunodominant and three subdominant natural epitopes were identified. Overlap between H-2d and H-2b restricted T cell epitopes was limited, yet similarities were found between epitopes processed in mice and predicted to be immunogenic in humans. H-2d restricted T cell epitopes were localized in pneumolysin domains 2 and 3, whereas H-2b epitopes were scattered over the protein. Cytokine responses show mostly a Th2 profile, with low levels of Th1 cytokines, in both mouse strains. In conclusion, PlyD1 evokes T cell responses in mice directed against multiple epitope regions, that is dependent on Major Histocompatibility Complex (MHC) background. These results are important to understand human PlyD1 T cell immunogenicity, to guide cell mediated immunity studies in the context of vaccine development.

Development and Qualification of an Opsonophagocytic Killing Assay To Assess Immunogenicity of a Bioconjugated Escherichia coli Vaccine.

The global burden of disease caused by extraintestinal pathogenic Escherichia coli (ExPEC) is increasing as the prevalence of multidrug-resistant strains rises. A multivalent ExPEC O-antigen bioconjugate vaccine could have a substantial impact in preventing bacteremia and urinary tract infections. Development of an ExPEC vaccine requires a readout to assess the functionality of antibodies. We developed an opsonophagocytic killing assay (OPA) for four ExPEC serotypes (serotypes O1A, O2, O6A, and O25B) based on methods established for pneumococcal conjugate vaccines. The performance of the assay was assessed with human serum by computing the precision, linearity, trueness, total error, working range, and specificity. Serotypes O1A and O6A met the acceptance criteria for precision (coefficient of variation for repeatability and intermediate precision, ≤50%), linearity (90% confidence interval of the slope of each strain, 0.80, 1.25), trueness (relative bias range, -30% to 30%), and total error (total error range, -65% to 183%) at five serum concentrations and serotypes O2 and O25B met the acceptance criteria at four concentrations (the lowest concentration for serotypes O2 and O25B did not meet the system suitability test of maximum killing of ≥85% of E. coli cells). All serotypes met the acceptance criteria for specificity (opsonization index value reductions of ≤20% for heterologous serum preadsorption and ≥70% for homologous serum preadsorption). The assay working range was defined on the basis of the lowest and highest concentrations at which the assay jointly fulfilled the target acceptance criteria for linearity, precision, and accuracy. An OPA suitable for multiple E. coli serotypes has been developed, qualified, and used to assess the immunogenicity of a 4-valent E. coli bioconjugate vaccine (ExPEC4V) administered to humans.

Safety, immunogenicity, and preliminary clinical efficacy of a vaccine against extraintestinal pathogenic Escherichia coli in women with a history of recurrent urinary tract infection: a randomised, single-blind, placebo-controlled phase 1b trial.

BACKGROUND: Escherichia coli infections are increasing worldwide in community and hospital settings. The E coli O-antigen is a promising vaccine target. We aimed to assess the safety and immunogenicity of a bioconjugate vaccine containing the O-antigens of four E coli serotypes (ExPEC4V). METHODS: In this multicentre phase 1b, first-in-human, single-blind, placebo-controlled trial, we randomly assigned (1:1) healthy adult women with a history of recurrent urinary tract infection (UTI) to receive a single injection of either intramuscular ExPEC4V or placebo. The primary outcome was the incidence of adverse events among vaccine and placebo recipients throughout the study. Secondary outcomes included immunogenicity and antibody functionality, and the incidence of UTIs caused by E coli vaccine serotypes in each group. This study is registered with ClinicalTrials.gov, number NCT02289794. FINDINGS: Between Jan 20, 2014, and Aug 27, 2014, 93 women received target-dose ExPEC4V and 95 received placebo. The vaccine was well tolerated: no vaccine-related serious adverse events occurred. Overall, 56 (60%) target-dose vaccines and 47 (49%) placebo recipients experienced at least one adverse event that was possibly, probably, or certainly related to injection. Vaccination induced significant IgG responses for all serotypes: at day 30 compared with baseline, O1A titres were 4·6 times higher, O2 titres were 9·4 times higher, O6A titres were 4·9 times higher, and O25B titres were 5·9 times higher (overall p<0·0001). Immune responses persisted at 270 days but were lower than those at 30 days. Opsonophagocytic killing activity showed antibody functionality. No reduction in the incidence of UTIs with 103 or more colony-forming units per mL of vaccine-serotype E coli was noted in the vaccine compared with the placebo group (0·149 mean episodes vs 0·146 mean episodes; p=0·522). In post-hoc exploratory analyses of UTIs with higher bacterial counts (≥105 colony-forming units per mL), the number of vaccine serotype UTIs did not differ significantly between groups (0·046 mean episodes in the vaccine group vs 0·110 mean episodes in the placebo group; p=0·074). However, significantly fewer UTIs caused by E coli of any serotype were noted in the vaccine group compared with the placebo group (0·207 mean episodes vs 0·463 mean episodes; p=0·002). INTERPRETATION: This tetravalent E coli bioconjugate vaccine candidate was well tolerated and elicited functional antibody responses against all vaccine serotypes. Phase 2 studies have been initiated to confirm these findings. FUNDING: GlycoVaxyn, Janssen Vaccines.

CC and CXC chemokine levels in children with meningococcal sepsis accurately predict mortality and disease severity.

INTRODUCTION: Chemokines are a superfamily of small peptides involved in leukocyte chemotaxis and in the induction of cytokines in a wide range of infectious diseases. Little is known about their role in meningococcal sepsis in children and their relationship with disease severity and outcome. METHODS: Monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP) 1alpha, growth-related gene product (GRO)-alpha and interleukin (IL)-8 were measured in 58 children with meningococcal sepsis or septic shock on admission and 24 hours thereafter. Nine patients died. Serum chemokine levels of survivors and nonsurvivors were compared, and the chemokine levels were correlated with prognostic disease severity scores and various laboratory parameters. RESULTS: Extremely high levels of all chemokines were measured in the children's acute-phase sera. These levels were significantly higher in nonsurvivors compared with survivors and in patients with septic shock compared with patients with sepsis (P < 0.0001). The cutoff values of 65,407 pg/ml, 85,427 pg/ml and 460 pg/ml for monocyte chemoattractant protein, for IL-8 and for macrophage inflammatory protein 1alpha, respectively, all had 100% sensitivity and 94-98% specificity for nonsurvival. Chemokine levels correlated better with disease outcome and severity than tumor necrosis factor (TNF)-alpha and correlated similarly to interleukin (IL)-6. In available samples 24 hours after admission, a dramatic decrease of chemokine levels was seen. CONCLUSION: Initial-phase serum levels of chemokines in patients with meningococcal sepsis can predict mortality and can correlate strongly with disease severity. Chemokines may play a key role in the pathophysiology of meningococcal disease and are potentially new targets for therapeutic approaches.

A Meningococcal Outer Membrane Vesicle Vaccine Incorporating Genetically Attenuated Endotoxin Dissociates Inflammation from Immunogenicity.

BACKGROUND: Group B Neisseria meningitidis, an endotoxin-producing Gram-negative bacterium, causes the highest incidence of group B meningococcus (MenB) disease in the first year of life. The Bexsero vaccine is indicated in Europe from 8 weeks of age. Endotoxin components of outer membrane vesicles (OMVs) or soluble lipopolysaccharide (LPS) represent a potential source of inflammation and residual reactogenicity. The purpose of this study was to compare novel candidate MenB vaccine formulations with licensed vaccines, including Bexsero, using age-specific human in vitro culture systems. METHODS: OMVs from wild type- and inactivated lpxL1 gene mutant-N. meningitidis strains were characterized in human neonatal and adult in vitro whole blood assays and dendritic cell (DC) arrays. OMVs were benchmarked against licensed vaccines, including Bexsero and whole cell pertussis formulations, with respect to Th-polarizing cytokine and prostaglandin E2 production, as well as cell surface activation markers (HLA-DR, CD86, and CCR7). OMV immunogenicity was assessed in mice. RESULTS: ΔlpxLI native OMVs (nOMVs) demonstrated significantly less cytokine induction in human blood and DCs than Bexsero and most of the other pediatric vaccines (e.g., PedvaxHib, EasyFive, and bacillus Calmette-Guérin) tested. Despite a much lower inflammatory profile in vitro than Bexsero, ΔlpxLI nOMVs still had moderate DC maturing ability and induced robust anti-N. meningitidis antibody responses after murine immunization. CONCLUSION: A meningococcal vaccine comprised of attenuated LPS-based OMVs with a limited inflammatory profile in vitro induces robust antigen-specific immunogenicity in vivo.