Prospects for a vaccine against otitis media

Adherence of Nontypeable Haemophilus influenzae to Cells and Substrates of the Airway Is Differentially Regulated by Individual ModA Phasevarions

Adherence of nontypeable Haemophilus influenzae (NTHi) to the host airway is an essential initial step for asymptomatic colonization of the nasopharynx, as well as development of disease. NTHi relies on strict regulation of multiple adhesins for adherence to host substrates encountered in the airway. NTHi encode a phase-variable cytoplasmic DNA methyltransferase, ModA, that regulates expression of multiple genes; a phasevarion (phase-variable regulon). Multiple modA alleles are present in NTHi, in which different alleles methylate a different DNA target, and each controls a different set of genes. However, the role of ModA phasevarions in regulating adherence of NTHi to the host airway is not well understood. This study therefore sought to investigate the role of four of the most prevalent ModA phasevarions in the regulation of adherence of NTHi to multiple substrates of the airway. Four clinical isolates of NTHi with unique modA alleles were tested in this study. The adherence of NTHi to mucus, middle ear epithelial cells, and vitronectin was regulated in a substrate-specific manner that was dependent on the ModA allele encoded. The adhesins Protein E and P4 were found to contribute to the ModA-regulated adherence of NTHi to distinct substrates. A better understanding of substrate-specific regulation of NTHi adherence by ModA phasevarions will allow identification of NTHi populations present at the site of disease within the airway and facilitate more directed development of vaccines and therapeutics. IMPORTANCE Nontypeable Haemophilus influenzae (NTHi) is a predominant pathogen of the human airway that causes respiratory infections such as otitis media (OM) and exacerbations in the lungs of patients suffering from chronic obstructive pulmonary disease (COPD). Due to the lack of a licensed vaccine against NTHi and the emergence of antibiotic-resistant strains, it is extremely challenging to target NTHi for treatment. NTHi adhesins are considered potential candidates for vaccines or other therapeutic approaches. The ModA phasevarions of NTHi play a role in the rapid adaptation of the pathogen to different environmental stress conditions. This study addressed the role of ModA phasevarions in the regulation of adherence of NTHi to specific host substrates found within the respiratory tract. The findings of this study improve our understanding of regulation of adherence of NTHi to the airway, which may further be used to enhance the potential of adhesins as vaccine antigens and therapeutic targets against NTHi.

Preventing unnecessary tympanostomy tube placement in children

OBJECTIVE

In 2013 the American Academy of Otolaryngology published tympanostomy tube guidelines for children; Action Statement 6 recommends against tube placement without middle ear effusion (MEE) at time of assessment. To date, little research has directly evaluated this recommendation in reducing the need for ear tubes. We evaluated the effectiveness of this recommendation and potential risk factors that influence the success of watchful waiting.

METHODS

Retrospective chart review collecting demographics, daycare status, smoking exposure, and time of year of visit. Children aged 6 months to 12 years without MEE on presentation, but with 3 or more episodes of acute otitis media (AOM) in 6 months or 4 or more episodes in 12 months, were assigned to watchful waiting (WW) treatment. These patients were followed every 4 months or returned sooner with additional infections. Any continued AOM, or MEE on follow up leading to tube placement, defined WW failure.

RESULTS

123 patients met criteria, with 81 still in WW to date (66% success rate). 42 children failed WW and received tympanostomy tubes (34% failure rate). There were no statistically significant associations between age, race, gender, smoking exposure, daycare, or month of presentation between children who failed WW compared to children receiving tubes.

CONCLUSIONS

Tympanostomy tube guidelines mitigate unnecessary tube placement in a majority of children with recurrent AOM without MEE. To our knowledge, this is the first study supporting the 2013 recommendations, with a 66% success rate. Additionally, no significant associations between modifying risk factors in those who failed watchful waiting were identified.

Microbiology of otitis media in Indigenous Australian children: review

OBJECTIVES

To review research addressing the polymicrobial aetiology of otitis media in Indigenous Australian children in order to identify research gaps and inform best practice in effective prevention strategies and therapeutic interventions.

METHODS

Literature review.

RESULTS

Studies of aspirated middle-ear fluid represented a minor component of the literature reviewed. Most studies relied upon specimens from middle-ear discharge or the nasopharynx. Culture-based middle-ear discharge studies have found that non-typeable Haemophilus influenzae and Streptococcus pneumoniae predominate, with Moraxella catarrhalis, Staphylococcus aureus and Streptococcus pyogenes isolated in a lower proportion of samples. Alloiococcus otitidis was detected in a number of studies; however, its role in otitis media pathogenesis remains controversial. Nasopharyngeal colonisation is a risk factor for otitis media in Indigenous infants, and bacterial load of otopathogens in the nasopharynx can predict the ear state of Indigenous children.

CONCLUSION

Most studies have used culture-based methods and specimens from middle-ear discharge or the nasopharynx. Findings from these studies are consistent with international literature, but reliance on culture may incorrectly characterise the microbiology of this condition. Advances in genomic technologies are now providing microbiologists with the ability to analyse the entire mixed bacterial communities ('microbiomes') of samples obtained from Indigenous children with otitis media.

Otitis media

Otitis media (OM) or middle ear inflammation is a spectrum of diseases, including acute otitis media (AOM), otitis media with effusion (OME; 'glue ear') and chronic suppurative otitis media (CSOM). OM is among the most common diseases in young children worldwide. Although OM may resolve spontaneously without complications, it can be associated with hearing loss and life-long sequelae. In developing countries, CSOM is a leading cause of hearing loss. OM can be of bacterial or viral origin; during 'colds', viruses can ascend through the Eustachian tube to the middle ear and pave the way for bacterial otopathogens that reside in the nasopharynx. Diagnosis depends on typical signs and symptoms, such as acute ear pain and bulging of the tympanic membrane (eardrum) for AOM and hearing loss for OME; diagnostic modalities include (pneumatic) otoscopy, tympanometry and audiometry. Symptomatic management of ear pain and fever is the mainstay of AOM treatment, reserving antibiotics for children with severe, persistent or recurrent infections. Management of OME largely consists of watchful waiting, with ventilation (tympanostomy) tubes primarily for children with chronic effusions and hearing loss, developmental delays or learning difficulties. The role of hearing aids to alleviate symptoms of hearing loss in the management of OME needs further study. Insertion of ventilation tubes and adenoidectomy are common operations for recurrent AOM to prevent recurrences, but their effectiveness is still debated. Despite reports of a decline in the incidence of OM over the past decade, attributed to the implementation of clinical guidelines that promote accurate diagnosis and judicious use of antibiotics and to pneumococcal conjugate vaccination, OM continues to be a leading cause for medical consultation, antibiotic prescription and surgery in high-income countries.

Innate Immunity: Orchestrating Inflammation and Resolution of Otitis Media

Otitis media (OM) is a common disease in young children, accounting for more office visits and surgeries than any other pediatric condition. It is associated with an estimated cost of five billion dollars annually in the USA. Moreover, chronic and recurrent middle ear (ME) disease leads to hearing loss during critical periods of language acquisition and learning leading to delays in reaching developmental milestones and risking permanent damage to the ME and inner ear in severe cases. Therefore, research to understand the disease pathogenesis and identify new therapeutics is important. Although OM is a multifactorial disease, targeting the molecular mechanisms that drive inflammation and OM resolution is critical. In this review, we discuss the current evidence suggesting that innate immune receptors and effectors play key roles in OM by mediating both the ME inflammatory responses and recovery.

[Bacterial etiology of acute otitis media in Spain in the post-pneumococcal conjugate vaccine era]

INTRODUCTION

Acute otitis media (AOM) is common in children aged <3 years. A pneumococcal conjugate vaccine (PCV) (PCV7; Prevenar, Pfizer/Wyeth, USA) has been available in Spain since 2001, which has a coverage rate of 50-60% in children aged <5 years.

MATERIALS AND METHODS

Children aged ≥3 to 36 months with AOM confirmed by an ear-nose-throat specialist were enrolled at seven centers in Spain (February 2009-May 2012) (GSK study identifier: 111425). Middle-ear-fluid samples were collected by tympanocentesis or spontaneous otorrhea and cultured for bacterial identification. Culture-negative samples were further analyzed using polymerase chain reaction (PCR).

RESULTS

Of 125 confirmed AOM episodes in 124 children, 117 were analyzed (median age: 17 months (range: 3-35); eight AOM episodes were excluded from analyses. Overall, 69% (81/117) episodes were combined culture- and PCR-positive for ≥1 bacterial pathogen; 44% (52/117) and 39% (46/117) were positive for Haemophilus influenzae (Hi) and Streptococcus pneumoniae (Spn), respectively. 77 of 117 episodes were cultured for ≥1 bacteria, of which 63 were culture-positive; most commonly Spn (24/77; 31%) and Hi (32/77; 42%). PCR on culture-negative episodes identified 48% Hi- and 55% Spn-positive episodes. The most common Spn serotype was 19F (4/24; 17%) followed by 19A (3/24; 13%); all Hi-positive episodes were non-typeable (NTHi). 81/117 AOM episodes (69%) occurred in children who had received ≥1 pneumococcal vaccine dose.

CONCLUSIONS

NTHi and Spn were the main etiological agents for AOM in Spain. Impact of pneumococcal vaccination on AOM requires further evaluation in Spain, after higher vaccination coverage rate is reached.

Predominant Bacteria Detected from the Middle Ear Fluid of Children Experiencing Otitis Media: A Systematic Review

BACKGROUND

Otitis media (OM) is amongst the most common childhood diseases and is associated with multiple microbial pathogens within the middle ear. Global and temporal monitoring of predominant bacterial pathogens is important to inform new treatment strategies, vaccine development and to monitor the impact of vaccine implementation to improve progress toward global OM prevention.

METHODS

A systematic review of published reports of microbiology of acute otitis media (AOM) and otitis media with effusion (OME) from January, 1970 to August 2014, was performed using PubMed databases.

RESULTS

This review confirmed that Streptococcus pneumoniae and Haemophilus influenzae, remain the predominant bacterial pathogens, with S. pneumoniae the predominant bacterium in the majority reports from AOM patients. In contrast, H. influenzae was the predominant bacterium for patients experiencing chronic OME, recurrent AOM and AOM with treatment failure. This result was consistent, even where improved detection sensitivity from the use of polymerase chain reaction (PCR) rather than bacterial culture was conducted. On average, PCR analyses increased the frequency of detection of S. pneumoniae and H. influenzae 3.2 fold compared to culture, whilst Moraxella catarrhalis was 4.5 times more frequently identified by PCR. Molecular methods can also improve monitoring of regional changes in the serotypes and identification frequency of S. pneumoniae and H. influenzae over time or after vaccine implementation, such as after introduction of the 7-valent pneumococcal conjugate vaccine.

CONCLUSIONS

Globally, S. pneumoniae and H. influenzae remain the predominant otopathogens associated with OM as identified through bacterial culture; however, molecular methods continue to improve the frequency and accuracy of detection of individual serotypes. Ongoing monitoring with appropriate detection methods for OM pathogens can support development of improved vaccines to provide protection from the complex combination of otopathogens within the middle ear, ultimately aiming to reduce the risk of chronic and recurrent OM in vulnerable populations.

Middle Ear and Eustachian Tube Mucosal Immunology

Mucosal immune responses within the middle ear and eustachian tube generally provide an effective and efficient response to the presence of microbial pathogens, with approximately 80% of clinically recognizable middle ear infections resolved within 7 days. Particularly for young children aged less than 3 years of age, the proximity and direct connection of the middle ear, via the eustachian tube, to the nasopharynx provide increased risk of commensal bacteria and upper respiratory tract viruses infecting the middle ear. Mucosal immunological defense in the middle ear and eustachian tube utilizes a number of mechanisms, including physicochemical barriers of mucus and the mucosal epithelial cells and innate immune responses such as inflammation, cellular infiltration, effusion, and antimicrobial protein secretions, in addition to adaptive host immune responses. Recent advances in otopathogen recognition via microbial pattern recognition receptors and elucidation of complex signaling cascades have improved understanding of the coordination and regulation of the middle ear mucosal response. These advances support vaccine development aiming to reduce the risk of otitis media in children.

Non-typeable Haemophilus influenzae, an under-recognised pathogen

Non-typeable Haemophilus influenzae (NTHi) is a major cause of mucosal infections such as otitis media, sinusitis, conjunctivitis, and exacerbations of chronic obstructive pulmonary disease. In some regions, a strong causal relation links this pathogen with infections of the lower respiratory tract. In the past 20 years, a steady but constant increase has occurred in invasive NTHi worldwide, with perinatal infants, young children, and elderly people most at risk. Individuals with underlying comorbidities are most susceptible and infection is associated with high mortality. β-lactamase production is the predominant mechanism of resistance. However, the emergence and spread of β-lactamase-negative ampicillin-resistant strains in many regions of the world is of substantial concern, potentially necessitating changes to antibiotic treatment guidelines for community-acquired infections of the upper and lower respiratory tract and potentially increasing morbidity associated with invasive NTHi infections. Standardised surveillance protocols and typing methodologies to monitor this emerging pathogen should be implemented. International scientific organisations need to raise the profile of NTHi and to document the pathobiology of this microbe.

Cellular immune response in young children accounts for recurrent acute otitis media

Acute otitis media (AOM) is a common disease in young children. Streptococcus pneumoniae (Spn) and Haemophilus influenzae (NTHi) are the two most common pathogens that cause AOM. Over the past 5 years, our group has been studying the immunologic profile of children that experience repeated AOM infections despite tympanocentesis drainage of middle ear fluid and individualized antibiotic treatment; we call these children stringently-defined otitis prone(sOP). Although protection against AOM is primarily mediated by ototpathogen-specific antibody, our recent studies suggest that suboptimal memory B and T cell responses and an immaturity in antigen-presenting cells may play a significant role in the propensity to recurrent AOM infections. This review focuses on the studies performed to define immunologic dysfunction in sOP children.

Comprehensive antigen screening identifies Moraxella catarrhalis proteins that induce protection in a mouse pulmonary clearance model

Moraxella catarrhalis is one of the three most common causative bacterial pathogens of otitis media, however no effective vaccine against M. catarrhalis has been developed so far. To identify M. catarrhalis vaccine candidate antigens, we used carefully selected sera from children with otitis media and healthy individuals to screen small-fragment genomic libraries that are expressed to display frame-selected peptides on a bacterial cell surface. This ANTIGENome technology led to the identification of 214 antigens, 23 of which were selected by in vitro or in vivo studies for additional characterization. Eight of the 23 candidates were tested in a Moraxella mouse pulmonary clearance model, and 3 of these antigens induced significantly faster bacterial clearance compared to adjuvant or to the previously characterized antigen OmpCD. The most significant protection data were obtained with the antigen MCR_1416 (Msp22), which was further investigated for its biological function by in vitro studies suggesting that Msp22 is a heme binding protein. This study comprises one of the most exhaustive studies to identify potential vaccine candidate antigens against the bacterial pathogen M. catarrhalis.

Moraxella catarrhalis: from interactions with the host immune system to vaccine development

Moraxella catarrhalis is a human-restricted commensal that over the last two decades has developed into an emerging respiratory tract pathogen. The bacterial species is equipped with various adhesins to facilitate its colonization. Successful evasion of the human immune system is a prerequisite for Moraxella infection. This strategy involves induction of an excessive proinflammatory response, intervention of granulocyte recruitment to the infection site, activation of selected pattern recognition receptors and cellular adhesion molecules to counteract the host bacteriolytic attack, as well as, finally, reprogramming of antigen presenting cells. Host immunomodulator molecules are also exploited by Moraxella to aid in resistance against complement killing and host bactericidal molecules. Thus, breaking the basis of Moraxella immune evasion mechanisms is fundamental for future invention of effective therapy in controlling Moraxella infection.

Streptococcus pneumoniae--a review of carriage, infection, serotype replacement and vaccination

Invasive pneumococcal infection remains a leading global cause of morbidity and mortality in young children. In developed nations, a substantial decrease in the incidence of IPD has been achieved with inclusion of the 7 valent protein conjugated pneumococcal vaccines (7vPCV) into paediatric vaccine schedules. In contrast, the incidence of IPD has changed little in developing nations. This is likely due to poor access to medical care and pneumococcal vaccination, the accompanying HIV and malnutrition burden, and the fact that 7vPCV does not contain the most common serotypes (1,5, 6A) responsible for IPD in many developing nations. The battle against IPD in developed nations is not over, with the rise of non-7vPCV serotypes since routine 7vPCV vaccination. This has necessitated the development and distribution of pneumococcal vaccines containing 3 or 6 additional serotypes. This article provides an overview on pneumococcal carriage and risk factors for IPD, the rise of non-7vCPV serotypes in the era of 7vPCV vaccination, and the current and newly available broader valent pneumococcal vaccines.

Future challenges in the elimination of bacterial meningitis

Despite the widespread implementation of several effective vaccines over the past few decades, bacterial meningitis caused by Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis and Group B Streptococcus (GBS) still results in unacceptably high levels of human mortality and morbidity. A residual disease burden due to bacterial meningitis is also apparent due to a number of persistent or emerging pathogens, including Mycobacterium tuberculosis, Escherichia coli, Staphylococcus aureus, Salmonella spp. and Streptococcus suis. Here, we review the current status of bacterial meningitis caused by these pathogens, highlighting how past and present vaccination programs have attempted to counter these pathogens. We discuss how improved pathogen surveillance, implementation of current vaccines, and development of novel vaccines may be expected to further reduce bacterial meningitis and related diseases in the future.

Bactericidal antibody response against P6, protein D, and OMP26 of nontypeable Haemophilus influenzae after acute otitis media in otitis-prone children

The bactericidal antibody response to three nontypeable Haemophilus influenzae (NTHi) outer membrane proteins (D, P6, and OMP26) was studied in 24 otitis-prone children (aged 7-28 months) after an acute otitis media (AOM) caused by NTHi. The study was carried out to understand the contribution of antigen-specific bactericidal antibody responses in the class of children who are most vulnerable to recurrent otitis media infections. Levels of protein D (P = 0.005) and P6 (P = 0.026) but not OMP26 antibodies were higher in bactericidal sera compared with nonbactericidal sera. For five (24%) and 16 (76%) of 21 bactericidal sera tested, removal of anti-protein D and P6 antibody, respectively, resulted in a two- to fourfold drop in bactericidal antibody. Antibodies to OMP26 did not make any contribution to the overall bactericidal activity in any serum samples. Eleven of 21 sera (52%) had bactericidal activity against a heterologous NTHi (86-028 NP) strain but the titers were significantly lower (P < 0.05) as compared to the homologous strains. Future studies of protein D, P6, OMP26, and other potential NTHi vaccine antigens should include studies of bactericidal antibody in children who are otitis prone as a possible correlate of protection.

Impact of pneumococcal conjugate vaccination on otitis media: a systematic review

Reduced rates of consultations for otitis media after introduction of pneumococcal conjugate vaccines (PCVs) have been overinterpreted. This systematic review suggests that PCV is only somewhat modestly effective against all-cause otitis media.

Acute otitis media (AOM) is a leading cause of visits to physicians and of antibiotic prescriptions for young children. We systematically reviewed studies on all-cause AOM episodes and physician visits in which impact was attributed to pneumococcal conjugate vaccines, either as efficacy or effectiveness. Of 18 relevant publications found, most used the 7-valent pneumococcal conjugate vaccine (7vCRM). The efficacy of 7vCRM against all-cause AOM episodes or visits was 0%–9% in randomized trials and 17%–23% in nonrandomized trials. In observational database studies, physician visits for AOM were already declining in the 3–5 years before 7vCRM introduction (mean change, −15%; range, +14% to −24%) and continued to decline afterward (mean, −19%; range, +7% to −48%). This vaccine provides some protection against OM, but other factors have also contributed to the recent decline in OM incidence. Future effectiveness studies should thus use better-controlled methods to estimate the true impact of vaccination on AOM.

Polymicrobial interactions: impact on pathogenesis and human disease

Microorganisms coexist in a complex milieu of bacteria, fungi, archaea, and viruses on or within the human body, often as multifaceted polymicrobial biofilm communities at mucosal sites and on abiotic surfaces. Only recently have we begun to appreciate the complicated biofilm phenotype during infection; moreover, even less is known about the interactions that occur between microorganisms during polymicrobial growth and their implications in human disease. Therefore, this review focuses on polymicrobial biofilm-mediated infections and examines the contribution of bacterial-bacterial, bacterial-fungal, and bacterial-viral interactions during human infection and potential strategies for protection against such diseases.

Haemophilus influenzae uses the surface protein E to acquire human plasminogen and to evade innate immunity

Pathogenic microbes acquire the human plasma protein plasminogen to their surface. In this article, we characterize binding of this important coagulation regulator to the respiratory pathogen nontypeable Haemophilus influenzae and identify the Haemophilus surface protein E (PE) as a new plasminogen-binding protein. Plasminogen binds dose dependently to intact bacteria and to purified PE. The plasminogen-PE interaction is mediated by lysine residues and is also affected by ionic strength. The H. influenzae PE knockout strain (nontypeable H. influenzae 3655Δpe) bound plasminogen with ∼65% lower intensity as compared with the wild-type, PE-expressing strain. In addition, PE expressed ectopically on the surface of Escherichia coli also bound plasminogen. Plasminogen, either attached to intact H. influenzae or bound to PE, was accessible for urokinase plasminogen activator. The converted active plasmin cleaved the synthetic substrate S-2251, and the natural substrates fibrinogen and C3b. Using synthetic peptides that cover the complete sequence of the PE protein, the major plasminogen-binding region was localized to a linear 28-aa-long N-terminal peptide, which represents aa 41-68. PE binds plasminogen and also vitronectin, and the two human plasma proteins compete for PE binding. Thus, PE is a major plasminogen-binding protein of the Gram-negative bacterium H. influenzae, and when converted to plasmin, PE-bound plasmin aids in immune evasion and contributes to bacterial virulence.

Viral-bacterial interactions and risk of acute otitis media complicating upper respiratory tract infection

Acute otitis media (AOM) is a common complication of upper respiratory tract infection whose pathogenesis involves both viruses and bacteria. We examined risks of acute otitis media associated with specific combinations of respiratory viruses and acute otitis media bacterial pathogens. Data were from a prospective study of children ages 6 to 36 months and included viral and bacterial culture and quantitative PCR for respiratory syncytial virus (RSV), human bocavirus, and human metapneumovirus. Repeated-measure logistic regression was used to assess the relationship between specific viruses, bacteria, and the risk of acute otitis media complicating upper respiratory tract infection. In unadjusted analyses of data from 194 children, adenovirus, bocavirus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis were significantly associated with AOM (P < 0.05 by χ(2) test). Children with high respiratory syncytial virus loads (≥3.16 × 10(7) copies/ml) experienced increased acute otitis media risk. Higher viral loads of bocavirus and metapneumovirus were not significantly associated with acute otitis media. In adjusted models controlling for the presence of key viruses, bacteria, and acute otitis media risk factors, acute otitis media risk was independently associated with high RSV viral load with Streptococcus pneumoniae (odds ratio [OR], 4.40; 95% confidence interval [CI], 1.90 and 10.19) and Haemophilus influenzae (OR, 2.04; 95% CI, 1.38 and 3.02). The risk was higher for the presence of bocavirus and H. influenzae together (OR, 3.61; 95% CI, 1.90 and 6.86). Acute otitis media risk differs by the specific viruses and bacteria involved. Acute otitis media prevention efforts should consider methods for reducing infections caused by respiratory syncytial virus, bocavirus, and adenovirus in addition to acute otitis media bacterial pathogens.

Hyporesponsiveness and its clinical implications after vaccination with polysaccharide or glycoconjugate vaccines

Hyporesponsiveness (immune tolerance) follows vaccination with meningococcal polysaccharide and many pneumococcal polysaccharide serotypes. Hyporesponsiveness after Haemophilus influenzae type b polysaccharide vaccination has not been directly observed, but may follow exposure during disease in some individuals. Use of currently licensed conjugate vaccines has not been associated with hyporesponsiveness to date, with the possible exception of pneumococcal serotype 3. Introduction of polysaccharide vaccines anywhere into a conjugate vaccination schedule may result in reduced immune responses on subsequent exposure. This review of vaccine-induced hyporesponsiveness and its potential clinical implications considers recent evidence suggesting that hyporesponsiveness may occur for specific components of combined conjugate vaccines, such as pneumococcal serotype 3. These data have implications for the development of new multivalent vaccines.

Viral-bacterial co-infection in Australian Indigenous children with acute otitis media

Background

Acute otitis media with perforation (AOMwiP) affects 40% of remote Indigenous children during the first 18 months of life. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis are the primary bacterial pathogens of otitis media and their loads predict clinical ear state. Our hypothesis is that antecedent respiratory viral infection increases bacterial density and progression to perforation.

Methods

A total of 366 nasopharyngeal swabs from 114 Indigenous children were retrospectively examined. A panel of 17 respiratory viruses was screened by PCR, and densities of S. pneumoniae, H. influenzae and M. catarrhalis were estimated by quantitative real time PCR. Data are reported by clinical ear state.

Results

M. catarrhalis (96%), H. influenzae (91%), S. pneumoniae (89%) and respiratory viruses (59%) were common; including rhinovirus (HRV) (38%), polyomavirus (HPyV) (14%), adenovirus (HAdV) (13%), bocavirus (HBoV) (8%) and coronavirus (HCoV) (4%). Geometric mean bacterial loads were significantly higher in children with acute otitis media (AOM) compared to children without evidence of otitis media. Children infected with HAdV were 3 times more likely (p < 0.001) to have AOM with or without perforation.

Conclusion

This study confirms a positive association between nasopharyngeal bacterial load and clinical ear state, exacerbated by respiratory viruses, in Indigenous children. HAdV was independently associated with acute ear states.

Antibody response to Haemophilus influenzae outer membrane protein D, P6, and OMP26 after nasopharyngeal colonization and acute otitis media in children

Development of natural antibodies to 3 nontypeable Haemophilus influenzae (NTHi) outer membrane proteins (D, P6 and OMP26) was prospectively studied in 130 children 6-30 months of age during NP colonization and acute otitis media (AOM). IgG antibody to protein D, P6 and OMP26 increased with age (p<0.001). Serum IgG responses to NP colonization were different for the 3 proteins: protein D responses occurred at a later age than P6, and OMP26 responses were minimal. For all 3 proteins serum antibody levels in the convalescent phase of AOM infection were not as high as after NP colonization. Antibodies to protein D and P6 but not OMP26 were bactericidal.

Otitis media: viruses, bacteria, biofilms and vaccines

Otitis media typically presents as either acute otitis media (AOM), with symptoms including fever, otalgia, otorrhoea or irritability and short duration; or as otitis media with effusion (OME), which is often asymptomatic and characterised by accumulation of fluid in the middle ear.

Diagnostic certainty of otitis media is challenging, given the young age of patients and variability of symptoms.

Otitis media predominantly occurs as coincident to viral upper respiratory tract infections and/or bacterial infections.

Common viruses that cause upper respiratory tract infection are frequently associated with AOM and new‐onset OME. These include respiratory syncytial virus, rhinovirus, adenovirus, parainfluenza and coronavirus.

Predominant bacteria that cause otitis media are Streptococcus pneumoniae, Moraxella catarrhalis, and non‐typeable Haemophilus influenzae.

Antibiotic therapy does not significantly benefit most patients with AOM, but long‐term prophylactic antibiotic therapy can reduce the risk of otitis media recurrence among children at high risk.

In Australia, 84% of AOM is treated with antibiotic therapy, which contributes to development of antibiotic resistance.

Vaccine development is a key future direction for reducing the world burden of otitis media, but requires polymicrobial formulation and ongoing monitoring and modification to ensure sustained reduction in disease burden.

10-valent pneumococcal nontypeable Haemophilus influenzae PD conjugate vaccine: Synflorix

The global burden of disease due to Streptococcus pneumoniae remains high. The licensed 7-valent pneumococcal conjugate vaccine (7vCRM, Prevenar/Prevnar) has successfully reduced invasive disease in the USA, but serotype coverage is incomplete and some evidence suggests that serotype replacement has occurred. Recently, a new 10-valent pneumococcal nontypeable Haemophilus influenzae (NTHi) protein D (PD) conjugate vaccine (PHiD-CV, Synflorix) has been licensed in more than 40 countries, including Europe, for the prevention of invasive disease and acute otitis media (AOM) due to pneumococcus in infants and children. PHiD-CV is immunogenic in infants when administered as a three-dose primary vaccination in a range of schedules and has a safety profile comparable to that of 7vCRM. Additional serotypes in PHiD-CV (1, 5 and 7F) increase overall serotype coverage and improve coverage in specific age groups and against specific disease syndromes. The use of the PD carrier, which provided protection against AOM caused by NTHi in a large efficacy trial testing a prototype of the final vaccine formulation, suggests that PHiD-CV will also provide some protection against AOM due to NTHi.

Efficacy of injectable trivalent virosomal-adjuvanted inactivated influenza vaccine in preventing acute otitis media in children with recurrent complicated or noncomplicated acute otitis media

BACKGROUND

Most cases of acute otitis media (AOM) follow an upper respiratory infection due to viruses, including influenza viruses. As effective and safe influenza vaccines are available, their use has been considered among the possible measures of AOM prophylaxis.

OBJECTIVES

To evaluate the efficacy of an inactivated virosomal-adjuvanted influenza vaccine in preventing AOM in children with a history of noncomplicated recurrent AOM (rAOM) or rAOM complicated by spontaneous perforation.

METHODS

In this prospective, randomized, single-blinded, placebo-controlled study, 180 children aged 1 to 5 years with a history of rAOM and previously unvaccinated against influenza were randomized to receive the inactivated virosomal-adjuvanted subunit influenza vaccine (n = 90) or no treatment (n = 90), and AOM-related morbidity was monitored every 4 to 6 weeks for 6 months.

RESULTS

The number of children experiencing at least 1 AOM episode was significantly smaller in the vaccinated group (P < 0.001), as was the mean number of AOM episodes (P = 0.03), the mean number of AOM episodes without perforation (P < 0.001), and the mean number of antibiotic courses (P < 0.001); the mean duration of bilateral OME was significantly shorter (P = 0.03). The only factor that seemed to be associated with the significantly greater efficacy of influenza vaccine in preventing AOM was the absence of a history of recurrent perforation (crude odds ratio, P = 0.01; adjusted odds ratio, P = 0.006).

CONCLUSIONS

The intramuscular administration of injectable trivalent inactivated virosomal-adjuvanted influenza vaccine in children with a history of rAOM significantly reduces AOM-related morbidity. However, the efficacy of this preventive measure seems to be reduced in children with rAOM associated with repeated tympanic membrane perforation.

Protection against nontypeable Haemophilus influenzae challenges by mucosal vaccination with a detoxified lipooligosaccharide conjugate in two chinchilla models

Otitis media (OM) can occur following outset of upper respiratory tract infections. Inhibition of bacterial colonization in nasopharynx (NP) by mucosal vaccination may prevent OM by reducing bacterial invasion of the middle ears (MEs). In this study, 80 chinchillas were intranasally (i.n.) immunized with a detoxified lipooligosaccharide (dLOS)-tetanus toxoid conjugate vaccine of nontypeable Haemophilus influenzae (NTHi) mixed with cholera toxin (CT) or CT alone. All vaccinated animals responded with elevated levels of mucosal and serum anti-LOS antibodies. Two weeks after the last immunization, 40 chinchillas were challenged i.n. with NTHi to evaluate NP colonization and ME infection while the rest of the animals were challenged transbullarly (T.B.) to examine the development of OM. Compared to the control group, the vaccination inhibited not only bacterial colonization in NP and transmission to MEs in the i.n. challenge group but also bacterial colonization in NP and transmission to unchallenged ears in the T.B. challenge group. Though no difference was found in the challenged ears of either group right after the T.B. challenge, an early clearance of NTHi from NP and unchallenged ears as well as less severity of OM in the unchallenged ears were observed in vaccinated animals. Current results along with our previous data indicate that mucosal vaccination is capable of inhibiting NTHi NP colonization and preventing OM occurrence in chinchillas; the i.n. challenge model is preferable for testing the mucosal vaccines while the T.B. challenge model is superior for testing the systemic vaccines.

Nontypeable Haemophilus influenzae protein E binds vitronectin and is important for serum resistance

Nontypeable Haemophilus influenzae (NTHi) commonly causes local disease in the upper and lower respiratory tract and has recently been shown to interfere with both the classical and alternative pathways of complement activation. The terminal pathway of the complement system is regulated by vitronectin that is a component of both plasma and the extracellular matrix. In this study, we identify protein E (PE; 16 kDa), which is a recently characterized ubiquitous outer membrane protein, as a vitronectin-binding protein of NTHi. A PE-deficient NTHi mutant had a markedly reduced survival in serum compared with the PE-expressing isogenic NTHi wild type. Moreover, the PE-deficient mutant showed a significantly decreased binding to both soluble and immobilized vitronectin. In parallel, PE-expressing Escherichia coli bound soluble vitronectin and adhered to immobilized vitronectin compared with controls. Surface plasmon resonance technology revealed a K(D) of 0.4 microM for the interaction between recombinant PE and immobilized vitronectin. Moreover, the PE-dependent vitronectin-binding site was located at the heparin-binding domains of vitronectin and the major vitronectin-binding domain was found in the central core of PE (aa 84-108). Importantly, vitronectin bound to the surface of NTHi 3655 reduced membrane attack complex-induced hemolysis. In contrast to incubation with normal human serum, NTHi 3655 showed a reduced survival in vitronectin-depleted human serum, thus demonstrating that vitronectin mediates a protective role at the bacterial surface. Our findings show that PE, by binding vitronectin, may play an important role in NTHi pathogenesis.

Pneumococcal conjugate vaccination and otitis media: differences among high-risk and low-risk populations

The impact of the heptavalent pneumococcal conjugate vaccine (PCV7) on the natural history of otitis media (OM) has been studied recently. In a high-risk population, PCV7 significantly reduced the risk of recurrent, bilateral or multiple tympanic membrane perforation, as well as the risk of chronic suppurative OM at 9 months of age. PCV7 did not reduce the time to the development of OM nor the burden of OM. Major challenges are the polymicrobial etiology of OM (Streptococcus pneumoniae and Haemophilus influenzae) in high-risk populations and the serotype replacement among pneumococcal strains. A vaccine including nontypable H. influenzae and 11 pneumococcal serotypes has been identified as a more efficacious option for preventing OM. In the near future, the development and evaluation of a vaccine containing pneumococcal protein, such as pneumococcal surface protein A, which is a structurally variable and serologically cross-reactive surface protein important to the pneumococcal virulence, will be a potential tool against OM.

Common variable immunodeficiency disorders in children: delayed diagnosis despite typical clinical presentation

OBJECTIVE

To characterize common variable immunodeficiency disorder (CVID) in childhood.

STUDY DESIGN

We retrospectively investigated clinical findings in 32 children with primary CVID by questionnaire and file review.

RESULTS

Clinical presentation included recurrent or chronic respiratory tract infections (88%), sinusitis (78%), otitis media (78%), and intestinal tract infections (34%), mainly with encapsulated bacteria. Meningitis was found in 25%, sepsis in 16%, and pyelonephritis in 16% of patients. Poliomyelitis after vaccination occurred in 2 patients and opportunistic infections occasionally. Allergic disorders were present in 38%, and autoimmune disease in 31% of patients. Eighty percent of the patients underwent surgical procedures because of recurrent infections. Growth retardation was seen in 28% of patients, and 16% showed retarded mental development. Bronchiectasis developed in 34%, and lymphoid proliferative disease in 13%. Incidence of allergic and autoimmune diseases was increased in first-degree relatives with normal immunologic findings. Mean time between symptoms and induction of immunoglobulin substitution therapy was 5.8 years (0.2-14.3).

CONCLUSIONS

CVID in children presents with comparable symptoms and disorders as in adults. We found a significant influence on growth and development. The marked delay of diagnosis may be due to overlap with common pediatric disorders, while also reflecting insufficient awareness of these disorders.

Nontypeable Haemophilus influenzae adhesin protein E: characterization and biological activity

The adhesin protein E (PE) of the human respiratory pathogen nontypeable Haemophilus influenzae (NTHi) exists in all clinical isolates. In the present study, NTHi adherence to epithelial cells of various origins was further analyzed. The number of intraepithelial PE-deficient NTHi was decreased compared with PE-expressing NTHi. Interestingly, PE-expressing NTHi or Escherichia coli transformants, in addition to soluble recombinant PE22-160 without a lipid moiety, induced a proinflammatory cell response. The adhesive PE domain was defined within PE84-108, and preincubation of epithelial cells with this peptide blocked adhesion of several clinical NTHi isolates. Mice immunized with PE84-108 cleared NTHi up to 8-fold more efficiently on pulmonary challenge than did mice immunized with a control peptide. Finally, anti-PE mouse antibodies from vaccinated mice prevented NTHi adhesion. Our data suggest that the ubiquitous adhesin PE plays an important role in the pathogenesis of NTHi infection.

Formation of biofilm by Haemophilus influenzae isolated from pediatric intractable otitis media

OBJECTIVES

The aims of this study are to evaluate biofilm formation by nontypeable Haemophilus influenzae (NTHi) isolated from children with acute otitis media (AOM) and its relation with clinical outcome of the disease.

METHODS

Biofilm formations by NTHi clinical isolates from pediatric AOM patients were evaluated by a crystal violet microtiter plate and a 98 well pin-replicator assay with a confocal laser scanning microscopy (CLSM). Optical density values of clinical isolates were compared with a positive control and the ratio of clinical isolates to a positive control was defined as biofilm formation index (BFI).

RESULTS

84.3% clinical isolates of NTHi were biofilm forming strains (BFI> or =0.4). The BFI represented the levels of biofilm formation and adherence on the surface. The identical strains isolated from both middle ear fluids (MEFs) and nasopharynx showed biofilm formation at the same level. The prevalence of biofilm forming isolates was significantly higher among the susceptible strains than resistant strains. The level of biofilm formation of NTHi isolated from AOM cases who was not improved by amoxicillin (AMPC) was significantly higher than that of NTHi isolated from AOM cases who was improved by AMPC.

CONCLUSION

We clearly showed the biofilm formation of clinical NTHi isolates from AOM children. In addition, the biofilm formed by NTHi would play an important role in persistent or intractable clinical course of AOM as a result of lowered treatment efficacy of antibiotics.

Association of IS1016 with the hia adhesin gene and biotypes V and I in invasive nontypeable Haemophilus influenzae

A subset of invasive nontypeable Haemophilus influenzae (NTHI) strains has evidence of IS1016, an insertion element associated with division I H. influenzae capsule serotypes. We examined IS1016-positive invasive NTHI isolates collected as part of Active Bacterial Core Surveillance within the Georgia Emerging Infections Program for the presence or absence of hmw1 and hmw2 (two related adhesin genes that are common in NTHI but absent in encapsulated H. influenzae) and hia (homologue of hsf, an encapsulated H. influenzae adhesin gene). Isolates were serotyped using slide agglutination, confirmed as NTHI strains using PCR capsule typing, and biotyped. Two hundred twenty-nine invasive NTHI isolates collected between August 1998 and December 2006 were screened for IS1016; 22/229 (9.6%) were positive. Nineteen of 201 previously identified IS1016-positive invasive NTHI isolates collected between January 1989 and July 1998 were also examined. Forty-one IS1016-positive and 56 randomly selected IS1016-negative invasive NTHI strains were examined. The hia adhesin was present in 39 of 41 (95%) IS1016-positive NTHI strains and 1 of 56 (1.8%) IS1016-negative NTHI strains tested; hmw (hmw1, hmw2, or both) was present in 50 of 56 (89%) IS1016-negative NTHI isolates but in only 5 of 41 (12%; all hmw2) IS1016-positive NTHI isolates. IS1016-positive NTHI strains were more often biotype V (P < 0.001) or biotype I (P = 0.04) than IS1016-negative NTHI strains, which were most often biotype II. Pulsed-field gel electrophoresis revealed the expected genetic diversity of NTHI with some clustering based on IS1016, hmw or hia, and biotypes. A significant association of IS1016 with biotypes V and I and the presence of hia adhesins was found among invasive NTHI. IS1016-positive NTHI strains may represent a unique subset of NTHI strains, with characteristics more closely resembling those of encapsulated H. influenzae.

Galactose residues on the lipooligosaccharide of Moraxella catarrhalis 26404 form the epitope recognized by the bactericidal antiserum from conjugate vaccination

Lipooligosaccharide (LOS) from Moraxella catarrhalis has the potential to elicit bactericidal antibodies against the pathogen. We generated LOS-based conjugate vaccines that elicited bactericidal antibodies in animal models. However, epitopes on the LOS recognized by the functional anti-LOS antibodies remain unidentified. In this study, a mutant strain, D4, which lost the recognition by a bactericidal anti-LOS rabbit serum in Western blotting was generated from a serotype C strain 26404 by random transposon mutagenesis. Sequence analysis revealed there was an insertion of a kanamycin resistance gene in the lgt2 gene of D4, which encodes beta(1-4)-galactosyltransferase. An isogenic lgt2 mutant, 26404lgt2, was constructed. Structural analysis indicated that the mutant strain produced a truncated LOS lacking terminal galactoses from 4- and 6-linked oligosaccharide chains of strain 26404. Further studies showed that the antiserum lost the recognition of both mutant cells and LOSs in Western blotting, an enzyme-linked immunosorbent assay (ELISA), or a flow cytometry assay. The antiserum also lost the ability to kill the mutant strain in a bactericidal assay, whereas it showed a bactericidal titer of 1:80 to strain 26404. In an inhibition ELISA, d-(+)-galactose or 26404lgt2 LOS showed no inhibition. However, the 26404 LOS and a serotype A O35E LOS with terminal galactoses on its 6-linked oligosaccharide chain showed >90% inhibition, while a serotype B 26397 LOS showed >60% inhibition. These studies suggest that the terminal alpha-Gal-(1-->4)-beta-Gal on the 6-linked oligosaccharide chain of 26404 LOS plays a critical role in forming the epitope recognized by the bactericidal antiserum induced by immunization with our conjugate vaccine.

Analysis of genetic relatedness of Haemophilus influenzae isolates by multilocus sequence typing

The gram-negative bacterium Haemophilus influenzae is a human-restricted commensal of the nasopharynx that can also be associated with disease. The majority of H. influenzae respiratory isolates lack the genes for capsule production and are nontypeable (NTHI). Whereas encapsulated strains are known to belong to serotype-specific phylogenetic groups, the structure of the NTHI population has not been previously described. A total of 656 H. influenzae strains, including 322 NTHI strains, have been typed by multilocus sequence typing and found to have 359 sequence types (ST). We performed maximum-parsimony analysis of the 359 sequences and calculated the majority-rule consensus of 4,545 resulting equally most parsimonious trees. Eleven clades were identified, consisting of six or more ST on a branch that was present in 100% of trees. Two additional clades were defined by branches present in 91% and 82% of trees, respectively. Of these 13 clades, 8 consisted predominantly of NTHI strains, three were serotype specific, and 2 contained distinct NTHI-specific and serotype-specific clusters of strains. Sixty percent of NTHI strains have ST within one of the 13 clades, and eBURST analysis identified an additional phylogenetic group that contained 20% of NTHI strains. There was concordant clustering of certain metabolic reactions and putative virulence loci but not of disease source or geographic origin. We conclude that well-defined phylogenetic groups of NTHI strains exist and that these groups differ in genetic content. These observations will provide a framework for further study of the effect of genetic diversity on the interaction of NTHI with the host.

Differential uptake and processing of a Haemophilus influenzae P5-derived immunogen by chinchilla dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells involved in the initiation and modulation of immune responses after immunization via their ability to process and present antigen to naive T cells. We wanted to examine the role of DCs in the development of protective immunity against nontypeable Haemophilus influenzae (NTHI)-induced experimental otitis media (OM) after intranasal immunization of chinchillas with an NTHI P5-derived synthetic peptide immunogen called LB1. As chinchilla DCs have not been described, we adapted well-established protocols to induce the differentiation of chinchilla bone marrow precursor cells into DCs, which resulted in cells that were morphologically and phenotypically similar to DCs of other species. In vitro, chinchilla DCs readily internalized LB1, upregulated expression of the maturation markers CD80 and major histocompatibility complex class II, and presented processed LB1 to primed CD3+ T cells, which resulted in antigen-specific T-cell proliferation. In vivo, LB1-activated DCs trafficked from the chinchilla nasal cavity primarily to the nasal-associated lymphoid tissues and were detected in close proximity to CD3+ T cells within this lymphoid aggregate. These data are the first to characterize chinchilla DCs and their functional properties. Furthermore, they suggest an important role for chinchilla DCs in the development of protective immunity against experimental NTHI-induced OM after intranasal immunization.

Identification of a novel Haemophilus influenzae protein important for adhesion to epithelial cells

Non-typable Haemophilus influenzae (NTHi) is an important human-specific respiratory pathogen colonizing the mucosa of the upper respiratory tract. The bacterium is a common cause of acute otitis media in children and exacerbations in patients with chronic obstructive pulmonary disease (COPD). An immunoglobulin (Ig) D-lambda myeloma protein was found to detect a 16 kDa surface protein that we designated protein E (PE). The pe gene was cloned using an NTHi genomic DNA library, and a truncated PE-derived protein lacking the endogenous signal peptide (PE22-160) was synthesized and produced in large amounts in Escherichia coli. Interestingly, PE was expressed at the bacterial surface of NTHi as revealed by flow cytometry using the IgD-lambda myeloma protein or PE-specific polyclonal antibodies. A PE-deficient NTHi mutant was produced and lost 50% of its adhesive capacity as compared to the wild-type counterpart when analysed for adhesion to type II lung alveolar epithelial cells. In parallel, E. coli expressing full-length PE1-160 adhered significantly more efficiently to epithelial cells as compared to wild-type E. coli. Recombinant IgD that recognized the chemical dansyl-chloride did not interact with PE indicating that the IgD-lambda myeloma protein most likely was an antibody directed against the H. influenzae surface epitope. In conclusion, we have discovered a novel NTHi outer membrane protein with adhesive properties using an IgD-myeloma protein.

Investigation of the potential of a 48kDa protein as a vaccine candidate for infection against nontypable Haemophilus influenzae

This study determined the conservation and protective efficacy of a 48 kDa nontypable Haemophilus influenzae (NTHi) protein (P48). This protein was highly conserved across the strains of NTHi examined and mucosal immunization with recombinant P48 (rP48) significantly reduced the numbers of viable NTHi recovered from the lung following challenge. rP48 induced predominantly an IgG2a antibody response that correlated with the reduction in the number of viable NTHi in the lung. These antibodies were not bactericidal against NTHi. The results suggest that P48 warrants further investigation as a vaccine component for NTHi disease.

Biological and immunological characteristics of lipooligosaccharide-based conjugate vaccines for serotype C Moraxella catarrhalis

Moraxella catarrhalis is an important bacterial cause of otitis media in children and respiratory tract infections in the elderly. Lipooligosaccharide (LOS), a major surface antigen of this bacterium, is a potential vaccine component against the organism. There are three major LOS serotypes (serotypes A, B, and C) in clinical isolates of M. catarrhalis. Our previous studies demonstrated that serotype A and B LOS-based conjugates were immunogenic in animals and elicited bactericidal antibodies. In this study, LOS from serotype C strain 26404 was isolated, detoxified, and conjugated to tetanus toxoid (TT) or the cross-reactive mutant (CRM) of diphtheria toxin to form detoxified LOS (dLOS)-TT, dLOS-CRM-1, and dLOS-CRM-2 vaccine candidates. The molar ratios (dLOS/protein) of the resulting conjugates were 47:1, 19:1, and 32:1, respectively, while the weight ratios were 0.94, 0.84 and 1.44, respectively. All conjugates were highly immunogenic in both mouse and rabbit models. Three subcutaneous injections of each conjugate formulated with the Ribi adjuvant elicited >700-fold increases in serum anti-LOS immunoglobulin G levels in mice (5 microg of dLOS) and >2,000-fold increases in rabbits (50 microg of dLOS). The resulting mouse and rabbit antisera showed complement-mediated bactericidal activity against the homologous strain. In addition, a representative rabbit antiserum showed bactericidal activity against 14 of 18 testable strains, and this bactericidal activity could be 100% inhibited by the serotype C or A LOS but only 30% inhibited by the serotype B LOS. These results indicate that the serotype C LOS-based conjugates can be used as vaccine components for further investigation in humans.