Serological versus molecular typing of surface-associated immune evading polysaccharide antigens-based phenotypes of Staphylococcus aureus

The aim of this study was to compare the performance of serological versus molecular typing methods to detect capsular polysaccharide (CP) and surface-associated polysaccharide antigen 336 phenotypes of Staphylococcus aureus isolates. Molecular typing of CP types 1, 5 and 8 was carried out using PCR, whereas serological typing of CP1, 2, 5, 8 and antigen 336 was carried out by slide agglutination using specific antisera. By genotyping, 14/31 strains were CP8 positive, 12/31 strains were CP5 and the remaining 6/31 isolates were non-typable (NT). One isolate was positive for both CP5 and CP8 by PCR, but was confirmed as CP8 type serologically. Detection of CP2 and type 336 by PCR was not possible because specific primers were either not available or non-specific. Using serotyping, 14/31 strains were CP8 positive, 11/31 CP5 positive and 2/31 positive for antigen 336. The remaining four S. aureus isolates were serologically NT. However, three of four NT and two 336-positive S. aureus isolates were encapsulated as determined by light microscopy after capsular staining. This discovery was surprising and warrants further investigations on the identification and characterization of additional capsular phenotypes prevalent among S. aureus clinical isolates. It was concluded that serological typing was a better method than molecular typing for use in epidemiological investigations based upon the distribution of surface-associated polysaccharide antigens-based phenotypes.

FluMum: a prospective cohort study of mother-infant pairs assessing the effectiveness of maternal influenza vaccination in prevention of influenza in early infancy

INTRODUCTION

Influenza vaccination in pregnancy is recommended for all women in Australia, particularly those who will be in their second or third trimester during the influenza season. However, there has been no systematic monitoring of influenza vaccine uptake among pregnant women in Australia. Evidence is emerging of benefit to the infant with respect to preventing influenza infection in the first 6 months of life. The FluMum study aims to systematically monitor influenza vaccine uptake during pregnancy in Australia and determine the effectiveness of maternal vaccination in preventing laboratory-confirmed influenza in their offspring up to 6 months of age.

METHODS AND ANALYSIS

A prospective cohort study of 10 106 mother-infant pairs recruited between 38 weeks gestation and 55 days postdelivery in six Australian capital cities. Detailed maternal and infant information is collected at enrolment, including influenza illness and vaccination history with a follow-up data collection time point at infant age 6 months. The primary outcome is laboratory-confirmed influenza in the infant. Case ascertainment occurs through searches of Australian notifiable diseases data sets once the infant turns 6 months of age (with parental consent). The primary analysis involves calculating vaccine effectiveness against laboratory-confirmed influenza by comparing the incidence of influenza in infants of vaccinated mothers to the incidence in infants of unvaccinated mothers. Secondary analyses include annual and pooled estimates of the proportion of mothers vaccinated during pregnancy, the effectiveness of maternal vaccination in preventing hospitalisation for acute respiratory illness and modelling to assess the determinants of vaccination.

ETHICS AND DISSEMINATION

The study was approved by all institutional Human Research Ethics Committees responsible for participating sites. Study findings will be published in peer review journals and presented at national and international conferences.

TRIAL REGISTRATION NUMBER

The study is registered with the Australia and New Zealand Clinical Trials Registry (ANZCTR) number: 12612000175875.

NOD1 and NOD2 expression and function in very preterm infant mononuclear cells

AIM

To evaluate mononuclear cell expression and function of the cytosolic nucleotide-binding oligomerization domain-containing receptors, NOD1 and NOD2, in very preterm and full-term infants.

METHODS

NOD1 and NOD2 gene and protein expression in very preterm infants, term infants and healthy adult, cord and peripheral blood mononuclear cells (C/PBMC) were quantified using qPCR and flow cytometry. Cytokine responses of purified infant and adult monocytes to NOD1- and NOD2-specific agonists were assessed using a multiplex immunoassay (Bioplex).

RESULTS

NOD1 and NOD2 were expressed by a range of infant and adult mononuclear cell types, including T- and B cells, with highest expression in classical (CD14(++) CD16(-) ) and intermediate (CD14(++) CD16(+) ) monocytes. NOD1 and NOD2 expression levels by monocytes from very preterm infant were similar to those in term infants or adults. Monocyte production of TNFα, IL-6 and IL-1β induced by activation of NOD1 and NOD2 was similar between very preterm infants, term infants and adults.

CONCLUSION

Monocyte expression and function of NOD1 and NOD2 in very preterm infants are intact and comparable/equivalent to term infants and adults. Functional deficiencies in monocyte NOD signalling pathways are unlikely to contribute to the increased susceptibility to bacterial sepsis in preterm infants.

Safety and immunogenicity of a vero cell culture-derived whole-virus influenza A(H5N1) vaccine in a pediatric population

BACKGROUND

Children are highly vulnerable to infection with novel influenza viruses. It is essential to develop candidate pandemic influenza vaccines that are safe and effective in the pediatric population.

METHODS

Infants and children aged 6-35 months and 3-8 years, respectively, were randomized to receive 2 immunizations with a 7.5-µg or 3.75-µg hemagglutinin (HA) dose of a nonadjuvanted whole-virus A/Vietnam(H5N1) vaccine; adolescents aged 9-17 years received a 7.5-µg dose only. A subset of participants received a booster immunization with an A/Indonesia(H5N1) vaccine approximately 1 year later. HA and neuraminidase antibody responses were assessed.

RESULTS

Vaccination was safe and well tolerated; adverse reactions were transient and predominantly mild. Two immunizations with the 7.5-µg dose of A/Vietnam vaccine induced virus microneutralization (MN) titers of ≥1:20 against the A/Vietnam strain in 68.8%-85.4% of participants in the different age groups. After the booster, 93.1%-100% of participants achieved MN titers of ≥1:20 against the A/Vietnam and A/Indonesia strains. Neuraminidase-inhibiting antibodies were induced in ≥90% of participants after 2 immunizations with the 7.5 µg A/Vietnam vaccine and in 100% of participants after the booster.

CONCLUSIONS

A whole-virus influenza A(H5N1) vaccine is suitable for prepandemic or pandemic immunization in a pediatric population.

CLINICAL TRIALS REGISTRATION

NCT01052402.

Does a 10-valent pneumococcal-Haemophilus influenzae protein D conjugate vaccine prevent respiratory exacerbations in children with recurrent protracted bacterial bronchitis, chronic suppurative lung disease and bronchiectasis: protocol for a randomised controlled trial

BACKGROUND

Recurrent protracted bacterial bronchitis (PBB), chronic suppurative lung disease (CSLD) and bronchiectasis are characterised by a chronic wet cough and are important causes of childhood respiratory morbidity globally. Haemophilus influenzae and Streptococcus pneumoniae are the most commonly associated pathogens. As respiratory exacerbations impair quality of life and may be associated with disease progression, we will determine if the novel 10-valent pneumococcal-Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) reduces exacerbations in these children.

METHODS

A multi-centre, parallel group, double-blind, randomised controlled trial in tertiary paediatric centres from three Australian cities is planned. Two hundred six children aged 18 months to 14 years with recurrent PBB, CSLD or bronchiectasis will be randomised to receive either two doses of PHiD-CV or control meningococcal (ACYW₁₃₅) conjugate vaccine 2 months apart and followed for 12 months after the second vaccine dose. Randomisation will be stratified by site, age (<6 years and ≥6 years) and aetiology (recurrent PBB or CSLD/bronchiectasis). Clinical histories, respiratory status (including spirometry in children aged ≥6 years), nasopharyngeal and saliva swabs, and serum will be collected at baseline and at 2, 3, 8 and 14 months post-enrolment. Local and systemic reactions will be recorded on daily diaries for 7 and 30 days, respectively, following each vaccine dose and serious adverse events monitored throughout the trial. Fortnightly, parental contact will help record respiratory exacerbations. The primary outcome is the incidence of respiratory exacerbations in the 12 months following the second vaccine dose. Secondary outcomes include: nasopharyngeal carriage of H. influenzae and S. pneumoniae vaccine and vaccine- related serotypes; systemic and mucosal immune responses to H. influenzae proteins and S. pneumoniae vaccine and vaccine-related serotypes; impact upon lung function in children aged ≥6 years; and vaccine safety.

DISCUSSION

As H. influenzae is the most common bacterial pathogen associated with these chronic respiratory diseases in children, a novel pneumococcal conjugate vaccine that also impacts upon H. influenzae and helps prevent respiratory exacerbations would assist clinical management with potential short- and long-term health benefits. Our study will be the first to assess vaccine efficacy targeting H. influenzae in children with recurrent PBB, CSLD and bronchiectasis.

TRIAL REGISTRATION

Australia and New Zealand Clinical Trials Registry (ANZCTR) number: ACTRN12612000034831.

Can linked emergency department data help assess the out-of-hospital burden of acute lower respiratory infections? A population-based cohort study

Background

There is a lack of data on the out-of-hospital burden of acute lower respiratory infections (ALRI) in developed countries. Administrative datasets from emergency departments (ED) may assist in addressing this.

Methods

We undertook a retrospective population-based study of ED presentations for respiratory-related reasons linked to birth data from 245,249 singleton live births in Western Australia. ED presentation rates <9 years of age were calculated for different diagnoses and predictors of ED presentation <5 years were assessed by multiple logistic regression.

Results

ED data from metropolitan WA, representing 178,810 births were available for analysis. From 35,136 presentations, 18,582 (52.9%) had an International Classification of Diseases (ICD) code for ALRI and 434 had a symptom code directly relating to an ALRI ICD code. A further 9600 presentations had a non-specific diagnosis. From the combined 19,016 ALRI presentations, the highest rates were in non-Aboriginal children aged 6–11 months (81.1/1000 child-years) and Aboriginal children aged 1–5 months (314.8/1000). Croup and bronchiolitis accounted for the majority of ALRI ED presentations. Of Aboriginal births, 14.2% presented at least once to ED before age 5 years compared to 6.5% of non-Aboriginal births. Male sex and maternal age <20 years for Aboriginal children and 20–29 years for non-Aboriginal children were the strongest predictors of presentation to ED with ALRI.

Conclusions

ED data can give an insight into the out-of-hospital burden of ALRI. Presentation rates to ED for ALRI were high, but are minimum estimates due to current limitations of the ED datasets. Recommendations for improvement of these data are provided. Despite these limitations, ALRI, in particular bronchiolitis and croup are important causes of presentation to paediatric EDs.

Polymorphisms in key innate immune genes and their effects on measles vaccine responses and vaccine failure in children from Mozambique

Despite an effective vaccine, measles remains a major health problem globally, particularly in developing countries. More than 30% of children show primary vaccine failure and therefore remain vulnerable to measles. Genetic variation in key innate pathogen recognition receptors, such as the measles cell entry receptors CD46 and SLAM, measles attachment receptor DC-SIGN, the antiviral toll-like receptors (TLR)3, TLR7 and TLR8, and the cytosolic antiviral receptor RIG-I, may significantly affect measles IgG antibody responses. Measles is still highly prevalent in developing countries such as those in Africa however there is no previous data on the effect of these innate immune genes in a resident African population. Polymorphisms (n=29) in the candidate genes were genotyped in a cohort of vaccinated children (n=238) aged 6 months-14 years from Mozambique, Africa who either had vaccine failure and contracted measles (cases; n=66) or controls (n=172). Contrasting previous associations with measles responses in Caucasians and/or strong evidence for candidacy, we found little indication that these key innate immune genes affect measles IgG responses in our cohort of Mozambican children. We did however identify that CD46 and TLR8 variants may be involved in the occurrence of measles vaccine failure. This study highlights the importance of genetic studies in resident, non-Caucasian populations, from areas where determining the factors that may affect measles control is of a high priority.

Immunogenicity and safety of measles-mumps-rubella and varicella vaccines coadministered with a fourth dose of Haemophilus influenzae type b and Neisseria meningitidis serogroups C and Y-tetanus toxoid conjugate vaccine in toddlers: a pooled analysis of randomized trials

A pooled analysis was conducted of 1257 toddlers who received a fourth dose of Haemophilus influenzae type b-Neisseria meningitidis serogroups C and Y-tetanus toxoid conjugate vaccine (HibMenCY-TT) or Hib conjugate vaccine (Hib polysaccharide conjugated to N. meningitidis outer membrane protein) coadministered with measles-mumps-rubella (MMR) and varicella (VAR) vaccines (NCT00134719/NCT00289783). Noninferiority of immunological responses to MMR and VAR was demonstrated between groups and incidences of MMR- and VAR-specific solicited symptoms were similar, indicating that HibMenCY-TT can be coadministered with MMR and VAR.

Responsiveness of human monocytes to the commensal bacterium Staphylococcus epidermidis develops late in gestation

INTRODUCTION

Staphylococcus epidermidis (SE) rarely causes infection in term infants but is a leading cause of late-onset sepsis in preterm infants. We hypothesized that the innate immune responses to SE in preterm infants are impaired in a gestational age (GA)-dependent manner.

METHODS

Cord and peripheral blood mononuclear cells (MNCs) were stimulated with SE bacteria, and a range of innate immune responses were assessed, including phagocytosis, intracellular killing, Toll-like receptor (TLR) pathway transcriptional activation, cytokine production, TLR2 and TLR4 expression, and cell signaling.

RESULTS

Phagocytosis and intracellular killing of SE bacteria were similar in neonatal and adult monocytes. Cytokine gene expression and protein synthesis increased in a GA-dependent manner, which was confirmed at the single-cell level. These GA-related effects were not associated with differences in expression of TLR2 or TLR4, nor with downstream activation of nuclear factor-κB or mitogen-activated protein kinase pathways.

DISCUSSION

The expression of TLRs, phagocytic capacity, and intracellular killing by monocytes develops early in fetal development, whereas the ability to mount a bacteria-induced cytokine response requires further maturation. The functional immaturity of monocyte activation pathways in the preterm infant may underpin their particular susceptibility to sepsis with commensal bacteria.

TLR3 and RIG-I gene variants: associations with functional effects on receptor expression and responses to measles virus and vaccine in vaccinated infants

Measles virus causes severe morbidity and mortality, despite the availability of measles vaccines. Successful defence against viral pathogens requires early recognition of virus-specific patterns by innate receptors like Toll-like receptor (TLR)3 and the RNA helicase, retinoic acid inducible gene-I (RIG-I). Genetic differences in these receptors may influence the primary immune responses to measles and the efficacy of measles vaccine. In 1-year-old Australian infants after their first measles vaccine dose, we investigated functional effects of TLR3 and RIG-I polymorphisms on intracellular protein expression using flow cytometry, cytokine responses to receptor ligands and measles lysate, and post-vaccination measles IgG levels. We found that TLR3 Leu412Phe was significantly associated with IFN-α/β response after stimulation with TLR3 ligand, poly(I:C) (P=0.024). Downregulation of TLR3 protein expression in NK cells after poly(I:C) was also associated with this variant (P=0.011). In contrast, measles-specific expression, cytokine responses and antibody responses were not associated with TLR3 polymorphisms. No associations were found with RIG-I variants. These results suggest that a TLR3 polymorphism has functional effects on receptor expression and cytokine response. However, this did not translate to an effect on specific responses to measles virus or vaccine. We found no evidence that RIG-I polymorphisms were involved in measles immune responses.

Use of data linkage to investigate the aetiology of acute lower respiratory infection hospitalisations in children

AIM

To document the aetiology of acute lower respiratory infection (ALRI) hospitalisations in Western Australian children by linking population-based laboratory data with hospital morbidity data.

METHODS

Data from all ALRI hospitalisations and laboratory records related to respiratory pathogens between 2000 and 2005 were extracted and linked through a population-based record linkage system. The proportion of specimens that were positive for each respiratory viral or bacterial pathogen was documented.

RESULTS

Eight thousand nine hundred and eighty (45.2%) ALRI hospitalisations were linked to a laboratory record. Admissions to a private hospital and admissions from non-metropolitan areas were less likely to have a linked laboratory record. In 57.9% of linked hospitalisations, a respiratory virus and/or a bacterial pathogen was identified. Frequently identified viral pathogens included respiratory syncytial virus (RSV; n= 3226; 39.5% of those tested), influenza viruses (n= 664; 8.5%), parainfluenza virus type 3 (n= 348; 4.6%), picornaviruses (n= 292; 22.3%) and adenoviruses (n= 211; 2.7%). RSV was identified in 63.7% of bronchiolitis admissions in those aged under 6 months and 33.1% of pneumonia admissions in those aged under 12 months. Influenza viruses were identified in 81.6% of influenza-coded admissions. When a test was requested, Bordetella pertussis was identified in 21.2% of ALRI hospitalisations (n= 354), including 86.8% of whooping cough-coded admissions.

CONCLUSIONS

This is the first report of population-based data linkage between statewide laboratory data and hospitalisation records and demonstrates proof of principle. RSV continues to be an important pathogen in ALRI. As pathogens were identified across all diagnoses, relying on hospital diagnosis coding alone may not accurately estimate the burden of different categories of ALRI.

A genomics-based approach to assessment of vaccine safety and immunogenicity in children

Immune responses to vaccines in infants and young children are typically Th2-biased, giving rise to concerns regarding potential atopy-like side effects, and antagonism of Th1-associated sterilising immunity. Conventional immunological methodology has limited capacity to effectively address these problems because of the inherent complexity of the immune responses involved. In the present study, we sought to develop an unbiased systems biology approach to elucidate superficially similar Th2-associated responses to paediatric vaccines and allergens, and to differentiate between them via gene coexpression network analysis. We demonstrate below that in immune responses to the diptheria/acellular pertussis/tetanus and pneumococcal polysaccharide conjugate vaccines, potentially antagonistic Th1-/IFN-associated and Th2-associated gene networks coexist in an apparent state of dynamic equilibrium, whereas in Th2-dominant allergen-specific responses of atopics the Th1 and IFN networks are respectively disrupted and downregulated. Capacity to detect and interpret these covert differences between responses to vaccines and allergens relies on the use of sophisticated algorithms that underpin coexpression network analysis, which identify genes that function co-ordinately in complex pathways. This methodology has significant potential to identify covert interactions between inflammatory pathways triggered by vaccination, and as such may be a useful tool in prediction of vaccine safety/efficacy.

Histologic chorioamnionitis is associated with reduced risk of late-onset sepsis in preterm infants

BACKGROUND

Histologic chorioamnionitis (HCA) is implicated in the onset of preterm labor and delivery. Chorioamnionitis is a known risk factor for early-onset sepsis and may modulate postnatal immunity. Preterm infants are at greatly increased risk of late-onset sepsis (LOS), particularly with coagulase-negative staphylococci (CoNS), but the impact of HCA on the risk of LOS is unknown.

METHODS

Eight hundred thirty-eight preterm infants born at <30 weeks gestational age at a single tertiary center were included. Histologic examination of placenta and extraplacental membranes was performed, and clinical data were extracted from hospital databases. The influence of HCA on the incidence of early-onset sepsis and LOS was examined using logistic regression analysis and Cox proportional hazards regression.

RESULTS

Mean gestational age was 26.9 ± 1.9 weeks, and mean birth weight was 936 ± 277 g. Two hundred and seventy-six (33%) of 838 infants developed LOS. The presence of fetal or maternal HCA, or maternal HCA and fetal HCA alone, was associated with a significantly decreased risk of LOS with any organism. Histologic chorioamnionitis correlated with a significantly decreased risk of CoNS LOS.

CONCLUSIONS

HCA is associated with a significantly reduced risk of acquiring LOS, both with CoNS and other bacteria. Perinatal inflammation may enhance the functional maturation of the preterm immune system and provide protection against LOS in high-risk preterm infants.

FBXO11, a regulator of the TGFβ pathway, is associated with severe otitis media in Western Australian children

Otitis media (OM) is a common childhood disease characterised by middle ear inflammation following infection. Susceptibility to recurrent acute OM (rAOM) and chronic OM with effusion (COME) is highly heritable. Two murine mutants, Junbo and Jeff, spontaneously develop severe OM with similar phenotypes to human disease. Fine-mapping of these mutants identified two genes (Evi1 and Fbxo11) that interact with the transforming growth factor β (TGFβ) signalling pathway. We investigated these genes, as well as four Sma- and Mad-related (SMAD) genes of the TGFβ pathway, as candidate rAOM/COME susceptibility genes in two predominantly Caucasian populations. Single-nucleotide polymorphisms (SNPs) within FBXO11 (family-based association testing Z-Score=2.61; P(best)=0.009) were associated with severe OM in family-based analysis of 434 families (561 affected individuals) from the Western Australian Family Study of OM. The FBXO11 association was replicated by directed analysis of Illumina 660W-Quad Beadchip data available for 253 cases and 866 controls (OR=1.55 (95% CI 1.28-1.89); P(best)=6.9 × 10(-6)) available within the Western Australian Pregnancy Cohort (Raine) Study. Combined primary and replication results show P(combined)=2.98 × 10(-6). Neither cohort showed an association with EVI1 variants. Family-based associations at SMAD2 (P=0.038) and SMAD4 (P=0.048) were not replicated. Together, these data provide strong evidence for FBXO11 as a susceptibility gene for severe OM.

A retrospective population-based cohort study identifying target areas for prevention of acute lower respiratory infections in children

BACKGROUND

Acute lower respiratory infections (ALRI) are a major cause of hospitalisation in young children. Many factors can lead to increased risk of ALRI in children and predispose a child to hospitalisation, but population attributable fractions for different risk factors and how these fractions differ between Indigenous and non-Indigenous children is unknown. This study investigates population attributable fractions of known infant and maternal risk factors for ALRI to inform prevention strategies that target high-risk groups or particular risk factors.

METHODS

A retrospective population-based data linkage study of 245,249 singleton births in Western Australia. Population attributable fractions of known maternal and infant risk factors for hospitalisation with ALRI between 1996 and 2005 were calculated using multiple logistic regression.

RESULTS

The overall ALRI hospitalisation rate was 16.1/1,000 person-years for non-Aboriginal children and 93.0/1,000 for Aboriginal children. Male gender, being born in autumn, gestational age <33 weeks, and multiple previous pregnancies were significant risk factors for ALRI in both Aboriginal and non-Aboriginal children. In non-Aboriginal children, maternal smoking during pregnancy accounted for 6.3% (95%CI: 5.0, 7.6) of the population attributable fraction for ALRI, being born in autumn accounted for 12.3% (10.8, 13.8), being born to a mother with three or more previous pregnancies accounted for 15.4% (14.1, 17.0) and delivery by elective caesarean accounted for 4.1% (2.8, 5.3). In Aboriginal children, being born to a mother with three or more previous pregnancies accounted for 16.5% (11.8, 20.9), but remote location at birth accounted for 11.7% (8.5, 14.8), maternal age <20 years accounted for 11.2% (7.8, 14.5), and being in the most disadvantaged socio-economic group accounted for 18.4% (-6.5, 37.4) of the population attributable fraction.

CONCLUSIONS

The population attributable fractions estimated in this study should help in guiding public health interventions to prevent ALRI. A key risk factor for all children is maternal smoking during pregnancy, and multiple previous pregnancies and autumnal births are important high-risk groups. Specific key target areas are reducing elective caesareans in non-Aboriginal women and reducing teenage pregnancies and improving access to services and living conditions for the Aboriginal population.

Emergency department presentation following falls: development of a routine falls surveillance system

INTRODUCTION

Falls are recognised as a major public health issue, particularly among older people, and have been targeted for attention by national service frameworks and National Institute for Health and Clinical Excellence guidelines in the UK. However, reliable epidemiological data are not easily available, and it remains difficult to monitor the effect of interventions that seek to reduce the public health impact of falls.

METHOD

In a 1-year study based in the emergency department (ED) of the University Hospital of Wales all Cardiff residents who described their presentation as following a fall were identified. From a catchment population of 305,353 people a total of 86,031 such ED presentations were recorded, 20,154 (23.4%) of which followed a fall.

RESULTS

This gives an overall falls incidence of 66/1000 population per year, meaning that in just a year one resident in 15 attended the ED following a fall. The impact of falls was greatest in the oldest age groups, and in women aged over 75 years the falls incidence of 139/1000 per year was significantly higher than the figure of 99/1000 per year observed in men of the same age.

CONCLUSIONS

This study describes a simple way for ED to establish routine falls surveillance. It offers the first estimate of the impact of falls on ED in the UK, suggesting that such services are dealing with 4 million falls-related attendances every year.

Method of bacterial killing differentially affects the human innate immune response to Staphylococcus epidermidis

BACKGROUND

In vitro investigations of human innate immune responses to extracellular bacteria commonly utilise killed preparations in preference to live organisms. The effects of the bacterial preparation method on the activation of innate signalling pathways by the common opportunistic pathogen Staphylococcus epidermidis (SE) are unknown.

MATERIALS AND METHODS

Mononuclear cell cytokine expression patterns induced by live (LSE), heat-killed (HKSE) and ethanol-killed SE (EKSE) were characterized at the transcriptional and translational level. Toll-like receptor (TLR)-activating capacity of the preparations was analysed using TLR-transfected human embryonic kidney cells.

RESULTS

Live SE activated NF-κB, STAT1, type I interferon, and inflammasome pathways. Killed preparations engaged the NF-κB pathway, but had significantly lower capacity to activate other innate immune pathways.

CONCLUSIONS

Killing of extracellular bacteria has significant qualitative and quantitative effects on key aspects of innate responses in vitro. Interpretation of in vitro data and extrapolation of findings should take into account the potential effects of bacterial preparation and should not assume that responses to killed bacteria are predictive of responses to live organisms.

Development of improved vaccines against whooping cough: current status

Prior to the introduction of killed whole cell pertussis vaccine [wP] in the 1940s, whooping cough was a major cause of infant death worldwide. Widespread vaccination of children with this vaccine caused a significant reduction in mortality. However in the 1990s and now more recently, there has been a resurgence of pertussis in several countries even in populations previously vaccinated with an acellular pertussis vaccine [aP]. In this review, we describe the epidemiology of whooping cough, the vast array of virulence factors produced by this pathogen potentially contributing to the resurgence of pertussis even in previously vaccinated populations of infants and children, history of whooping cough prophylaxis, possible mechanisms of immunity, lack of availability of a suitable non-toxic adjuvant capable of inducing both arms of the immune response, and the current status of development of improved vaccines with potential to induce longer-lasting protection, than is currently possible with the wP or aP vaccines, against whooping cough.

TLR2 mediates recognition of live Staphylococcus epidermidis and clearance of bacteremia

Background

Staphylococcus epidermidis (SE) is a nosocomial pathogen that causes catheter-associated bacteremia in the immunocompromised, including those at the extremes of age, motivating study of host clearance mechanisms. SE-derived soluble components engage TLR2; but additional signaling pathways have also been implicated, and TLR2 can play complex, at times detrimental, roles in host defense against other Staphylococcal spp. The role of TLR2 in responses of primary blood leukocytes to live SE and in clearance of SE bacteremia, the most common clinical manifestation of SE infection, is unknown.

Methodology/Principal Findings

We studied TLR2-mediated recognition of live clinical SE strain 1457 employing TLR2-transfected cells, neutralizing anti-TLR antibodies and TLR2-deficient mice. TLR2 mediated SE-induced cytokine production in human embryonic kidney cells, human whole blood and murine primary macrophages, in part via recognition of a soluble TLR2 agonist. After i.v. challenge with SE, early (1 h) cytokine/chemokine production and subsequent clearance of bacteremia (24–48 h) were markedly impaired in TLR2-deficient mice.

Conclusions/Significance

TLR2 mediates recognition of live SE and clearance of SE bacteremia in vivo.