O-serotype distribution of Escherichia coli bloodstream infection isolates in critically ill patients in The Netherlands.

OBJECTIVES: Invasive infections by extra-intestinal pathogenic Escherichia coli (ExPEC) strains are increasing. We determined O-serogroups of E. coli isolates from ICU patients having bloodstream infections (BSI) and the potential coverage of a 10-valent O-polysaccharide conjugate vaccine currently in development for the prevention of invasive ExPEC disease. METHODS: We studied E. coli BSI among patients admitted to a tertiary ICU in the Netherlands between April 2011 and November 2016. O-serogroups were determined in vitro by agglutination and whole genome sequencing. RESULTS: Among 714 ICU patients having BSI, 70 (10%) had an E. coli BSI. Among 68 (97%) isolates serogrouped, the most common serogroups were O25 (n = 11; 16%), O8 (n = 5; 7%), O2 (n = 4; 6%), O6 (n = 4; 6%), and O15 (n = 4; 6%). The theoretical coverage of a 10-valent ExPEC vaccine was 54% (n = 37). CONCLUSIONS: A multi-valent ExPEC O-polysaccharide conjugate vaccine in development could potentially aid in the prevention of E. coli BSI in Dutch ICU patients.

Prediction of pneumococcal conjugate vaccine effectiveness against invasive pneumococcal disease using opsonophagocytic activity and antibody concentrations determined by enzyme-linked immunosorbent assay with 22F adsorption.

We compared the abilities of two serological readouts, antipolysaccharide IgG antibody concentrations and opsonophagocytic activity (OPA) titers, to predict the clinical effectiveness of the 7-valent pneumococcal conjugate vaccine (7vCRM) against invasive pneumococcal disease (IPD). We also assessed the accuracy of the previously established thresholds for GlaxoSmithKline's enzyme-linked immunosorbent assay with 22F adsorption (22F-ELISA) (≥0.2 µg/ml) and OPA assay (titer, ≥8) in predicting effectiveness. We showed that following a 3-dose 7vCRM primary vaccination, the serological response rates as determined using thresholds of ≥0.2 µg/ml IgG and an OPA titer of ≥8 corresponded well with overall effectiveness against IPD. In addition, the OPA assay seemed to better predict serotype-specific effectiveness than enzyme-linked immunoassay. Finally, when applied to post-dose-2 immune responses, both thresholds also corresponded well with the overall IPD effectiveness following a 2-dose 7vCRM primary vaccination. These results support the importance of the OPA assay in evaluating immune responses to pneumococcal conjugate vaccines.

Preventable hospital admissions related to medication (HARM): cost analysis of the HARM study.

OBJECTIVE: Adverse drug events (ADEs) can cause serious harm to patients and can lead to hospitalization or even death. ADEs are a burden not only to patients and their relatives, but also to society and have the potential to involve high costs. To provide more information on the economic burden of preventable adverse drug events of outpatients, we performed a cost study on the data collected in the Hospital Admissions Related to Medication (HARM) study. In this study we examined the frequency, preventability, and risk factors for hospital admissions related to medication. METHODS: The average costs for a preventable medication-related hospital admission were calculated by summing the direct medical costs and the production losses of all the preventable admissions, taking into account the different types of hospitals (academic and general) and the age of the admitted patients. RESULTS: The average medical costs for one preventable medication-related hospital admission were €5461. The average production loss costs for one admission were €1712 for a person younger than 65 years of age. Combining the medical costs and the costs of production losses resulted in average costs of €6009 for one, potentially preventable, medication-related hospital admission for all ages. CONCLUSIONS: The costs of potentially preventable hospital admissions related to medication are considerable. Therefore, patient safety interventions to prevent ADEs and hospital admissions may be cost-effective or even cost saving.

A dose-range study assessing immunogenicity and safety of one dose of a new candidate meningococcal serogroups A, C, W-135, Y tetanus toxoid conjugate (MenACWY-TT) vaccine administered in the second year of life and in young children.

Meningococcal disease incidence is highest in young children, yet a tetravalent conjugate vaccine is currently not available for this age group. This study evaluated a single dose of four different ACWY-TT conjugate vaccine formulations in 240 toddlers (12-14 months) and 268 children (3-5 years) compared to licensed age-appropriate control vaccines. In toddlers, rSBA-MenC GMTs for the selected formulation were statistically higher than after monovalent-MenC-conjugate vaccine. In children, rSBA-GMTs against each serogroup were statistically higher than after tetravalent polysaccharide vaccine. The safety profile was comparable to licensed controls. The new ACWY-TT conjugate vaccine promises high seroprotection levels against meningococcal disease from 1 year of age.

International Bordetella pertussis assay standardization and harmonization meeting report. Centers for Disease Control and Prevention, Atlanta, Georgia, United States, 19-20 July 2007.

An international meeting on Bordetella pertussis assay standardization and harmonization was held at the Centers for Disease Control and Prevention (CDC), Atlanta, GA, 19-20 July 2007. The goal of the meeting was to harmonize the immunoassays used for pertussis diagnostics and vaccine evaluation, as agreed upon by academic and government researchers, regulatory authorities, vaccine manufacturers, and the World Health Organization (WHO). The primary objectives were (1) to provide epidemiologic, laboratory, and statistical background for support of global harmonization; (2) to overview the current status of global epidemiology, pathogenesis and immunology of pertussis; (3) to develop a consensus opinion on existing gaps in understanding standardization of pertussis assays used for serodiagnosis and vaccine evaluation; and (4) to search for a multicenter process for addressing these priority gaps. Presentations and discussions by content experts addressed these objectives. A prioritized list of action items to improve standardization and harmonization of pertussis assays was identified during a group discussion at the end of the meeting. The major items included: (1) to identify a group that will organize, prepare, maintain, and distribute proficiency panels and key reagents such as reference and control sera; (2) to encourage the development and identification of one or more reference laboratories that can serve as an anchor and resource for other laboratories; (3) to define a performance-based assay method that can serve as a reference point for evaluating laboratory differences; (4) to develop guidance on quality of other reagents, e.g., pertussis toxin and other antigens, and methods to demonstrate their suitability; (5) to establish an international working group to harmonize the criteria to evaluate the results obtained on reference and proficiency panel sera; (6) to create an inventory to determine the amount of appropriate and well-characterized sera that are available globally to be used as bridging reagents for vaccine licensure; and (7) to seek specific guidance from regulatory authorities regarding the expectations and requirements for the licensure of new multicomponent pertussis vaccines.

The development of a new heptavalent diphtheria-tetanus-whole cell pertussis-hepatitis B-Haemophilus influenzae type b-Neisseria meningitidis serogroups A and C vaccine: a randomized dose-ranging trial of the conjugate vaccine components.

OBJECTIVE: To assess immunogenicity, antibody persistence, immune memory, and reactogenicity of a novel heptavalent DTPw-HBV/Hib-MenAC (diphtheria, tetanus, whole cell pertussis-hepatitis B virus/Haemophilus influenzae type b-Neisseria meningitidis serogroups A and C) vaccine. DESIGN: This was an open, randomized study in the Philippines, with DTPw-HBV/Hib-MenAC administered at 6, 10, and 14 weeks of age. Three different polysaccharide contents of the conjugate vaccine components were assessed with conjugated PRP (polyribosylribitol phosphate), MenA, and MenC polysaccharides at the following doses: 2.5 microg of each, 5 microg of each, or 2.5 microg of PRP and 5 microg each of MenA and MenC. Controls received licensed DTPw-HBV and Hib or DTPw-HBV/Hib and MenC conjugate vaccines separately. Immune memory was evaluated via plain polysaccharide challenge administered to half of the subjects at 10 months of age. RESULTS: After primary vaccination, at least 97.7% of DTPw-HBV/Hib-MenAC recipients had serum bactericidal antibody (SBA)-MenA and SBA-MenC titers > or =1:8, and at least 99% had anti-PRP antibody concentrations > or =0.15 microg/ml. Immune responses to DTPw-HBV components were not impaired by the lowest dose of Hib-MenAC vaccine. Plain polysaccharide challenge induced marked increases in Hib, MenA, and MenC antibodies in primed subjects, indicative of immune memory. All of the experimental vaccines were well tolerated. CONCLUSION: The lowest dose of DTPw-HBV/Hib-MenAC polysaccharide conjugate vaccine was well tolerated, immunogenic, had good persistence of antibodies, and demonstrated immune memory, and consequently was selected for further development.

Non-response to specific serotypes likely cause for failure to 23-valent pneumococcal polysaccharide vaccine in the elderly.

During a randomised controlled trial with the 23-valent pneumococcal vaccine in older persons, antibody concentrations and opsonophagocytic activity (OPA) were compared between eight patients who developed culture-verified pneumococcal pneumonia and 38 controls, matched for age, sex and vaccination status. Patients who developed pneumococcal pneumonia did not respond with a significant increase of antibody concentration (>1microg/ml) post-vaccination to the infecting serotype, but responded equally well as controls to most other serotypes. Neither was there any significant difference in the OPA post-vaccination between patients and controls. In conclusion, the 23-valent pneumococcal vaccine should be regarded as 23 different vaccines, rather than one. Older persons who fail to respond to one serotype may well be protected against infection by the other 22 serotypes.

Enhancement of vaccine-specific cellular immunity in infants by passively acquired maternal antibody.

The known protective effects of passively acquired maternal antibody on the resistance of newborns to infections have prompted widespread interest in maternal vaccination. However, a range of animal model and human studies indicate potential inhibitory effects of maternal antibody on vaccine-specific humoral responses in infants. In the present study we have examined the relationship between maternally acquired TT-specific IgG present before DTaP vaccination and subsequent TT-specific T-cell memory responses at 12 and 18 months, in a cohort of 118 infants. We demonstrate a strong positive association between TT-specific cellular immunity as evidenced by increased IL-4, IL-5 and IL-13 responses, and maternal TT-specific IgG.

Effects of adsorption of acellular pertussis antigens onto different aluminium salts on the protective activity in an intranasal murine model of Bordetella pertussis infection.

Adsorption of the pertussis antigens, pertussis toxoid (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) onto aluminium phosphate rather than aluminium hydroxide leads to a lower humoral response and poorer protection against intranasal pertussis challenge in mice. These effects could be reversed by inclusion of fimbriae (FIM) 2 and 3 in the formulation. These data emphasis the importance of correct formulation for such vaccines.

Protection against Streptococcus pneumoniae elicited by immunization with pneumolysin and CbpA.

The need for the development of cheap and effective vaccines against pneumococcal disease has necessitated the evaluation of common virulence-associated proteins of Streptococcus pneumoniae as potential vaccine antigens. In this study, we examined the capacity of active immunization with a genetic toxoid derivative of pneumolysin (PdB) and/or a fragment of choline binding protein A (CbpA; also known as PspC, Hic, and SpsA) to protect mice from intraperitoneal challenge with medium to very high doses of a highly virulent capsular type 2 pneumococcal strain, D39. The median survival times for mice immunized with the individual protein antigens in different adjuvant combinations were significantly longer than those for mice that received the respective adjuvants alone. Mice immunized with CbpA alone were significantly better protected than mice immunized with PdB alone. Correspondingly, the median survival times for mice that were immunized with a combination of PdB and CbpA were significantly longer than those for mice that received PdB alone but not significantly different from those that received CbpA alone. Mice immunized with the protein antigens in a mixture of monophospholipid A (MPL) and aluminium phosphate (AlPO4) adjuvants had higher antibody titers than mice that received the antigens in AlPO4 alone. Mice immunized with PdB in MPL plus AlPO4 were also significantly better protected than mice that received PdB in AlPO4 alone.

Heterogeneity in diphtheria-tetanus-acellular pertussis vaccine-specific cellular immunity during infancy: relationship to variations in the kinetics of postnatal maturation of systemic th1 function.

Cellular immunity to vaccines is highly variable during infancy. This study addressed the hypothesis that these responses are governed by the pace of maturational changes in adaptive immune competence, in particular, cellular functions that underlie the postnatal transition from Th2 to Th1 "bias." Tetanus-specific cytokine responses were tracked in peripheral blood mononuclear cells collected from infants at months 2, 4, 6, 12, and 18. These were compared with polyclonal responses. Results show that the Th2 component of the vaccine response develops rapidly and remains stable, unlike interferon (IFN)-gamma production, which also is initiated early but commonly declines after the final priming dose at 6 months. However, between 12 and 18 months, the IFN-gamma component of the vaccine-specific response has a spontaneous resurgence that coincides with a parallel increase in overall IFN-gamma production capacity. The Th2 component of vaccine-specific responses was more prominent in children with atopic family history.

Clinical relevance of lower Hib response in DTPa-based combination vaccines.

Combination vaccines are essential to enable administration of all the required antigens in routine infant immunisation schedules at any single visit. Some combinations of diphtheria-tetanus-acellular pertussis (DTPa) with Haemophilus influenzae type b (Hib) conjugate vaccines have been shown to result in lower Hib titres than when Hib is administered separately. While confirming that a primary series with a DTPa-HBV-IPV/Hib combination gives lower antibody levels than separate Hib conjugates, we show that the nature (isotype and IgG subclasses) and function (avidity and opsonic activity) of the antibodies are the same, and immunologic memory is induced. It is likely therefore that the DTPa-HBV-IPV/Hib combination will be efficacious against Hib disease.

Outer membrane protein vesicle vaccines for meningococcal disease.

Alternative strategies exist for prevention of group B Neisseria meningitidis (meningococcal) disease through vaccination (see Chapters 5 , 8 , 13 , 14 in this volume). However, the most promising approach to date has been the use of outer-membrane vesicle (OMV) vaccines for induction of bactericidal antibodies against cell-surface outer-membrane proteins (OMPs).

Animal models for meningococcal disease.

There are many in vitro systems for the study of meningococcal pathogenesis, but it is only in animal models of infection that the interactions of the bacteria with whole tissues and the humoral and cellular immune systems can be assessed. Animal-infection models are also of great importance for the assessment of the protective efficacy of existing and candidate vaccines. However, the relevance of these animal models to human disease and how well protection assessed in them corresponds to protection against human disease, must always be considered. Animal models for pathogenic Neisseria have been previously reviewed (1).

Antigen-specific responses to diphtheria-tetanus-acellular pertussis vaccine in human infants are initially Th2 polarized.

Immune responses to exogenous antigens in infant experimental animals display various degrees of Th2 polarization. Preliminary evidence from small human studies suggest a similar age-dependent response pattern to vaccines, but detailed investigations on vaccine immunity during infancy have not yet been undertaken. We report below the results of a comprehensive prospective study on responses to the tetanus component of the diphtheria, tetanus, acellular pertussis (DTaP) vaccine in a cohort of 55 healthy children, employing peripheral blood mononuclear cells (PBMC) collected at the 2-, 4-, and 6-month vaccinations and at 12 months. Antigen-specific production of interleukin-4 (IL-4), IL-5, IL-6, IL-9, IL-10, IL-13, and gamma interferon (IFN-gamma) was determined at each sample point, in parallel with polyclonal (phytohemagglutinin PHA-induced) cytokine responses. Our results indicate early and persistent Th2 responses to the vaccine, in contrast to a more delayed and transient pattern of IFN-gamma production. This initial disparity between the Th1 and Th2 components of the vaccine response was mirrored by patterns of polyclonally induced cytokine production, suggesting that the delayed maturation of the Th1 component of the vaccine response during infancy is secondary to developmental processes occurring within the overall Th cell system.

Immunogenicity studies with a genetically engineered hexavalent PorA and a wild-type meningococcal group B outer membrane vesicle vaccine in infant cynomolgus monkeys.

The immunogenicity of two meningococcal outer membrane vesicle (OMV) vaccines, namely the Norwegian wild-type OMV vaccine and the Dutch hexavalent PorA OMV vaccine, were examined in infant cynomolgus monkeys. For the first time, a wild-type- and a recombinant OMV vaccine were compared. Furthermore, the induction of memory and the persistence of circulating antibodies were measured. The Norwegian vaccine contained all four classes of major outer membrane proteins (OMP) and wild-type L3/L8 lipopolysaccharide (LPS). The Dutch vaccine consisted for 90% of class 1 OMPs, had low expression of class 4 and 5 OMP, and GalE LPS. Three infant monkeys were immunised with a human dose at the age of 1.5, 2.5 and 4.5 months. Two monkeys of each group received a fourth dose at the age of 11 months. In ELISA, both OMV vaccines were immunogenic and induced booster responses, particularly after the fourth immunisation. The Norwegian vaccine mostly induced sero-subtype P1.7,16 specific serum bactericidal antibodies (SBA), although some other SBA were induced as well. The antibody responses against P1.7,16, induced by the Norwegian vaccine, were generally higher than for the Dutch vaccine. However, the Dutch vaccine induced PorA specific SBA against all six sero-subtypes included in the vaccine showing differences in the magnitude of SBA responses to the various PorAs.

Developing a nontypeable Haemophilus influenzae (NTHi) vaccine.

There is a current high demand for nontypable Haemophilus influenzae (NTHi) vaccines. Various options for the composition of such vaccines are possible. Decisions about the vaccine composition have to take into account the antigenic variability of NTHi, so even complex immunogens such as whole bacteria would preferentially have a tailor-made antigenic composition. We will present a summary of NTHi vaccine development, describing research efforts from SmithKline Beecham and other laboratories. Currently, major (P1, P2, P4, P5) and minor (P6, D15, TbpA/B, ellipsis) outer membrane proteins, LPS, adhesins (HMW, Hia, pili, P5) are being studied. Preclinical results with LPD, P5 (LB1) and OMP26 from our laboratories will be described including the use of animal models of otitis and lung infection.

Cardiovascular aspects of experimental meningococcal sepsis in young and older awake piglets: age-related differences.

Severe meningococcal disease is characterized by: a high load of specific endotoxin, capillary leakage and coagulation disorders. We studied the possible age-related differences in global hemodynamic and regional blood flow responses to different dosages (1 and 10 microg/kg body weight) of rough meningococcal endotoxin in young (8 kg) and older piglets (40 kg). Animals were chronically instrumented and studied in the awake state. The response to plasma infusion (30 mL/kg in 30 min) was evaluated after placebo and endotoxin infusion. The clinical picture was similar in all groups. The mortality was 0/8, 3/8,1/8, 4/9 in young-low, young-high, old-low, and old-high dose respectively. Most important findings were that cardiac index (CI) decreased in the young animals after endotoxin infusion, while it was well preserved in the older animals; in the older animals the systemic vascular resistance dropped 20%, while in the younger ones there was no change in resistance. Conductance to the kidneys, intestines, and spleen decreased significantly more in the young animals, while the increase in conductance and flow to the liver was higher in the old animals; subsequent volume loading resulted only partly in a recovery of the hemodynamic parameters, but failed to improve oxygen delivery.