Antibody responses to the outer membrane protein P6 of non-typeable Haemophilus influenzae and pneumococcal capsular polysaccharides in otitis-prone children

The Peptidoglycan-associated lipoprotein Pal contributes to the virulence of Burkholderia mallei and provides protection against lethal aerosol challenge

Burkholderia mallei

is a highly pathogenic bacterium that causes the fatal zoonosis glanders. The organism specifies multiple membrane proteins, which represent prime targets for the development of countermeasures given their location at the host-pathogen interface. We investigated one of these proteins, Pal, and discovered that it is involved in the ability of B. mallei to resist complement-mediated killing and replicate inside host cells in vitro, is expressed in vivo and induces antibodies during the course of infection, and contributes to virulence in a mouse model of aerosol infection. A mutant in the pal gene of the B. mallei wild-type strain ATCC 23344 was found to be especially attenuated, as BALB/c mice challenged with the equivalent of 5,350 LD₅₀ completely cleared infection. Based on these findings, we tested the hypothesis that a vaccine containing the Pal protein elicits protective immunity against aerosol challenge. To achieve this, the pal gene was cloned in the vaccine vector Parainfluenza Virus 5 (PIV5) and mice immunized with the virus were infected with a lethal dose of B. mallei. These experiments revealed that a single dose of PIV5 expressing Pal provided 80% survival over a period of 40 days post-challenge. In contrast, only 10% of mice vaccinated with a PIV5 control virus construct survived infection. Taken together, our data establish that the Peptidoglycan-associated lipoprotein Pal is a critical virulence determinant of B. mallei and effective target for developing a glanders vaccine.

Clinical practice guidelines for the diagnosis and management of acute otitis media in children-2018 update

OBJECTIVE

"Clinical Practice Guidelines for the Diagnosis and Management of Acute Otitis Media in Children-2018 update (2018 Guidelines)" aim to provide appropriate recommendations about the diagnosis and management of children with acute otitis media (AOM), including recurrent acute otitis media (recurrent AOM), in children under 15 years of age. These evidence-based recommendations were created with the consensus of the subcommittee members, taking into consideration unique characteristics of bacteriology and antimicrobial susceptibilities of AOM pathogens in Japan, as well as global advances in vaccines.

METHODS

The subcommittee re-evaluated key clinical issues based on SCOPE (a master plan of the guidelines) and created clinical questions (CQ) about the diagnosis and management of AOM patients. A literature search of the publications from 2013 to 2016 were added to the Guidelines 2013, not only to assess the evidence on the effectiveness of vaccines, but also to provide up to date information of the bacteriology and antimicrobial susceptibilities of AOM causative pathogens in Japan.

RESULTS

We have proposed guidelines for disease severity-based management of AOM patients, after classifying AOM severity into mild, moderate, and severe, based on age, clinical manifestations, and otoscopic findings.

CONCLUSIONS

Precise otoscopic findings are essential for judging AOM severity, which can lead to appropriate management of AOM patients.

Peripheral blood immunological parameters of children with adenoid hypertrophy with otitis media with effusion: propensity score matching

PURPOSE

To evaluate peripheral blood immunological parameters and the possible correlation with age, gender and adenoid size in children with adenoid hypertrophy with OME.

METHODS

A total of 664 children with adenoid hypertrophy were initially enrolled in our study, of which 83 had concomitant OME. To minimize selection bias, we performed one to two propensity score matching (PSM) between children with and without OME. After PSM, 80 children with OME (OME group) and 157 children without OME (adenoid hypertrophy [AH] group) were selected. The patients' peripheral blood samples were prepared prior to surgery and their immunological parameters were compared between groups.

RESULTS

Compared to the AH group, the serum level of C3 was significantly higher in the OME group (0.88 ± 0.01 g/L vs. 0.94 ± 0.02 g/L; p = 0.014), which was the only independent risk factor for OME (odds ratio 13.58, 95% confidence interval 1.25-147.99; p = 0.032). However, no such difference was seen for serum immunoglobulin (IgG, IgA, IgM, IgE), T cell subsets (CD3+, CD4+ and CD8+ T cells), or lymphocytes and monocytes. Further subgroup analyses showed that in children ≤ 5 years old, the C3 level was significantly higher in OME patients (p = 0.023). A subgroup analysis based on sex indicated that there was a significantly higher level of serum C3 (p = 0.009) and lower CD3+ and CD4+ T cells (p = 0.010 and p = 0.021, respectively) in girls with OME compared to those without OME. No association between immunological parameters and adenoid size was found.

CONCLUSIONS

There were no significant differences in cellular immunology and humoral immune indicators in children with adenoid hypertrophy with or without OME. In children ≤ 5 years old, significantly higher serum C3 levels in patients with OME demonstrate excessively activated C3 in comparison to patients without OME. For girls, a higher serum level of C3 with a lower amount of CD3+ and CD4+ T cells may be associated with OME.

No evidence for impaired humoral immunity to pneumococcal proteins in Australian Aboriginal children with otitis media

BACKGROUND

The Australian Aboriginal population experiences disproportionately high rates of otitis media (OM). Streptococcus pneumoniae is one of the main pathogens responsible for OM and currently no vaccine offering cross strain protection exists. Vaccines consisting of conserved antigens to S. pneumoniae may reduce the burden of OM in high-risk populations; however no data exists examining naturally acquired antibody in Aboriginal children with OM.

METHODS

Serum and salivary IgA and IgG were measured against the S. pneumoniae antigens PspA1 and 2, CbpA and Ply in a cross sectional study of 183 children, including 36 non-Aboriginal healthy control children and 70 Aboriginal children and 77 non-Aboriginal children undergoing surgery for OM using a multiplex bead assay.

RESULTS

Significant differences were observed between the 3 groups for serum anti-PspA1 IgA, anti-CbpA and anti-Ply IgG and for all salivary antibodies assessed. Aboriginal children with a history of OM had significantly higher antibody titres than non-Aboriginal healthy children with no history of OM and non-Aboriginal children with a history of OM for several proteins in serum and saliva. Non-Aboriginal children with a history of OM had significantly higher salivary anti-PspA1 IgG than healthy children, while all other titres were comparable between the groups.

CONCLUSIONS

Conserved vaccine candidate proteins from S. pneumoniae induce serum and salivary antibody responses in Aboriginal and non-Aboriginal children with a history of OM. Aboriginal children do not have an impaired antibody response to the antigens measured from S. pneumoniae and they may represent vaccine candidates in Indigenous populations.

Randomized controlled trial of juzen-taiho-to in children with recurrent acute otitis media

OBJECTIVE

Recurrent acute otitis media (AOM) in young children is rapidly increasing worldwide. Repeated antibiotic use leads to antibiotic-resistant pathogen development. Complementary and alternative medicine approaches have been suggested as a supplemental treatment option to conventional antimicrobial medicine. This randomized, parallel-group, open-label, non-herbal medicine controlled trial assessed the efficacy of a traditional Japanese herbal medicine, juzen-taiho-to (JTT) for AOM prevention in otitis-prone children.

METHODS

Children prone to recurrent AOM aged 6-48 months were recruited from 26 otolaryngology clinics in Japan and received conventional AOM treatment based on Japanese guidelines with or without 2 daily oral doses of JTT (0.10-0.25g/kg/day). The mean number of AOM episodes, coryza episodes, and duration of total antibiotic administration per month were compared during 3-month intervention.

RESULTS

At least one episode of AOM was diagnosed in 71% of JTT-group and 92% of control participants during follow-up. JTT administration reduced the frequency of AOM episodes by 57% compared with children who received conventional treatment alone (0.61±0.54 vs. 1.07±0.72 AOM instances/month; P=0.005) and also significantly decreased number of coryza episodes (P=0.015) and total antibiotic administration (P=0.024).

CONCLUSIONS

This is the first report of recurrent AOM prevention by herbal medication. JTT appears to effectively prevent recurrent AOM in children. Subsequent double-blind studies are needed to confirm the beneficial effects of JTT on recurrent AOM and upper respiratory tract infections.

Developing a vaccine to prevent otitis media caused by nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is a predominant organism of the upper respiratory nasopharyngeal microbiota. Its disease spectrum includes otitis media, sinusitis, non-bacteremic pneumonia and invasive infections. Protein-based vaccines to prevent NTHi infections are needed to alleviate these infections in children and vulnerable populations such as the elderly and those with chronic obstructive pulmonary disease (COPD). One NTHi protein is included in a pneumococcal conjugate vaccine and has been shown to provide efficacy. Our lab has been interested in understanding the immunogenicity of NTHi vaccine candidates P6, protein D and OMP26 for preventing acute otitis media in young children. We expect that continued investigation and progress in the development of an efficacious protein based vaccine against NTHi infections is achievable in the near future.

Epitope-specific immune recognition of the nontypeable Haemophilus influenzae outer membrane protein 26

Previous studies using rodent respiratory infection models of nontypeable Haemophilus influenzae (NTHi) infection have established the 26-kDa outer membrane protein of the bacterium, OMP26, as a potential vaccine antigen for NTHi. This study undertook a comprehensive immunological identification of OMP26 T- and B-cell epitopes. A series of OMP26 peptides were constructed and regions of the OMP26 antigen involved in recognition by lymphocyte receptors and induction of acquired immune responses were identified. The dominant T-cell epitopes for OMP26 were located toward the C-terminus between amino acid residues 95 and 197 (T3+T4 region) as mapped using antigen-specific lymphocyte proliferation assays. The newly identified T-cell epitopes exhibited strong capacity for efficient T-cell activation, suggesting that, compared with other OMP26 regions; epitopes within the T3+T4 region have the highest affinity for binding to major histocompatibility complex molecules. In contrast, the predominant B-cell epitopes of OMP26 were located more centrally within the molecule between amino acid residues 45 and 145 (T2+T3 region) as determined using enzyme-linked immunosorbent assay and surface plasmon resonance assays. The T2+T3 region was immunodominant in several species including chinchilla, mice and rats when assessed using both mucosal and parenteral immunization regimes. In addition, the antibodies directed against the T2+T3 region bound to intact NTHi cell surface, according to flow cytometry. Collectively, these results specifically locate the amino acid sequences containing the OMP26 T- and B-cell epitopes, which, as newly mapped antigenic epitopes for lymphocyte recognition, will be useful to improve existing NTHi vaccine strategies. Comprehensive definition of the minimum epitope length required for optimal B- and T-cell responses requires further study.

IgG responses to Pneumococcal and Haemophilus influenzae protein antigens are not impaired in children with a history of recurrent acute otitis media

Background

Vaccines including conserved antigens from Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) have the potential to reduce the burden of acute otitis media. Little is known about the antibody response to such antigens in young children with recurrent acute otitis media, however, it has been suggested antibody production may be impaired in these children.

Methods

We measured serum IgG levels against 4 pneumococcal (PspA1, PspA 2, CbpA and Ply) and 3 NTHi (P4, P6 and PD) proteins in a cross-sectional study of 172 children under 3 years of age with a history of recurrent acute otitis media (median 7 episodes, requiring ventilation tube insertion) and 63 healthy age-matched controls, using a newly developed multiplex bead assay.

Results

Children with a history of recurrent acute otitis media had significantly higher geometric mean serum IgG levels against NTHi proteins P4, P6 and PD compared with healthy controls, whereas there was no difference in antibody levels against pneumococcal protein antigens. In both children with and without a history of acute otitis media, antibody levels increased with age and were significantly higher in children colonised with S. pneumoniae or NTHi compared with children that were not colonised.

Conclusions

Proteins from S. pneumoniae and NTHi induce serum IgG in children with a history of acute otitis media. The mechanisms in which proteins induce immunity and potential protection requires further investigation but the dogma of impaired antibody responses in children with recurrent acute otitis media should be reconsidered.

Maternal immunization with pneumococcal surface protein A protects against pneumococcal infections among derived offspring

Pathogen-specific antibody plays an important role in protection against pneumococcal carriage and infections. However, neonates and infants exhibit impaired innate and adaptive immune responses, which result in their high susceptibility to pneumococci. To protect neonates and infants against pneumococcal infection it is important to elicit specific protective immune responses at very young ages. In this study, we investigated the protective immunity against pneumococcal carriage, pneumonia, and sepsis induced by maternal immunization with pneumococcal surface protein A (PspA). Mother mice were intranasally immunized with recombinant PspA (rPspA) and cholera toxin B subunit (CTB) prior to being mated. Anti-PspA specific IgG, predominantly IgG1, was present at a high level in the serum and milk of immunized mothers and in the sera of their pups. The pneumococcal densities in washed nasal tissues and in lung homogenate were significantly reduced in pups delivered from and/or breast-fed by PspA-immunized mothers. Survival after fatal systemic infections with various types of pneumococci was significantly extended in the pups, which had received anti-PspA antibody via the placenta or through their milk. The current findings strongly suggest that maternal immunization with PspA is an attractive strategy against pneumococcal infections during early childhood. (191 words)

Serum antibody response to five Streptococcus pneumoniae proteins during acute otitis media in otitis-prone and non-otitis-prone children

BACKGROUND

Streptococcus pneumoniae (Spn) is one of the common bacteria responsible for episodic acute otitis media (AOM; non-otitis-prone), recurrent AOM (otitis-prone), and AOM treatment failure (AOMTF) in children.

OBJECTIVE

From a population of 268 children, we sought to compare the serum IgG antibody titers of 5 different Spn proteins (PhtD, LytB, PcpA, PhtE, and Ply) that are vaccine candidates in children with episodic AOM (n = 34), who were otitis prone (n = 35) and who had AOMTF (n = 25) caused by Spn.

METHODS

Antibody was quantitated by enzyme-linked immunosorbent assay.

RESULTS

At their AOM visit, anti-PhtD, -LytB, -PhtE, and -Ply IgG antibody titers in otitis-prone children were significantly lower compared with non-otitis-prone children (P < 0.05) and children with AOMTF (P < 0.05). On comparing acute to convalescent geometric mean IgG antibody titers after AOM against the 5 proteins we found that otitis-prone, AOMTF, and non-otitis-prone children had no significant change in titers (except for PhtE in children with AOMTF), but detailed analysis showed that about one-third of the children in each cohort had a 2-fold rise in antibody to the studied antigens. Although non-otitis-prone children had significant increases (P < 0.001) between 6 and 24 months of age in anti-PhtD, PcpA, PhtE, and Ply IgG antibody titers as a consequence of nasopharyngeal colonization and AOM, otitis-prone children either failed to show rises or the rises were significantly less than the non-otitis-prone children.

CONCLUSION

Otitis-prone and AOMTF children mount less of an IgG serum antibody response as compared with non-otitis-prone children to Spn proteins after AOM and nasopharyngeal colonization.

Haemophilus influenzae vaccine candidate outer membrane protein P6 is not conserved in all strains

An outer membrane protein of nontypeable Haemophilus influenzae (NTHi), P6, is a vaccine candidate because it has been characterized as conserved among all H. influenzae strains. Among 151 isolates from children, age 6 to 30 months, evaluating NTHi nasopharyngeal (NP) and oropharyngeal (OP) colonization and tympanocentesis confirmed acute otitis media we identified 14 strains (9.3%) that had variant protein sequences of P6. One atypical omp P6 isolate had sequence mutations in the binding site of a proposed major antigenic epitope of omp P6 identified by monoclonal antibody 7F3. Eight strains (5.3%) had non-homologous variations in amino acids that could result in significant changes to the protein structure of P6, and 5 other strains had amino acid substitutions at four previously described key residue sites. These results show that NTHi omp P6 is not invariant in its structure among respiratory isolates from children.

Serum antibody response to three non-typeable Haemophilus influenzae outer membrane proteins during acute otitis media and nasopharyngeal colonization in otitis prone and non-otitis prone children

Non-typeable Haemophilus influenzae (NTHi) is the most common bacteria responsible for episodic acute otitis media (AOM; non-otitis prone), recurrent AOM (rAOM; otitis prone) and AOM treatment failure (AOMTF) in children. In this 3.5 years of prospective study, we measured the serum antibody response to outer membrane proteins D, P6 and OMP26 of NTHi in children with AOM (n=26), rAOM (n=32), AOMTF (n=27). The geometric mean titers (GMTs) of IgG at their acute AOM visit against Protein D in otitis prone children were significantly lower compared to AOMTF (p value<0.01) and non-otitis prone (p value<0.03) children; otitis prone children had significantly lower IgG levels to P6 compared to AOMTF children (p value<0.02); otitis prone children had significantly lower IgG levels to OMP26 compared to AOMTF children (p value<0.04). Comparing acute to convalescent titers after AOM, otitis prone and AOMTF children had no significant change in total IgG against all the three proteins, while non-otitis prone children had significant increases to Protein D. Anti-protein D, P6 and OMP26 antibody levels measured longitudinally during NP colonization between age 6 and 24 months in 10 otitis prone children and 150 non-otitis prone children showed <2-fold increases over time in otitis prone children compared to >4 fold increases in the non-otitis prone children (p value<0.001). We conclude that otitis prone children mount less of an IgG serum antibody response toward Protein D, P6 and OMP26 after AOM which may account for recurrent infections. The data on acute sera of otitis prone vs non-otitis prone children and the acute-to-convalescence response in non-otitis prone children point to a possible link of anti-PD to protection. Moreover, the data suggest that otitis prone children should be evaluated for their responses to Protein D, P6 and OMP26 vaccine antigens of NTHi.

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.

Effects of Japanese herbal medicine, Juzen-taiho-to, in otitis-prone children--a preliminary study

CONCLUSION

Juzen-taiho-to (JTT, TJ-48), a Japanese herbal medicine that improves immune function, was found to be effective in otitis-prone in children.

OBJECTIVE

To evaluate the efficacy of JTT against intractable and recurrent infections in immature immune systems, we administered JTT to otitis-prone infants and investigated clinical changes before and during JTT administration.

SUBJECTS AND METHODS

Twenty-four otitis-prone infants were administered JTT at 0.10-0.14 g/kg/day twice a day for 3 months. We compared clinical course, such as frequency of acute otitis media (AOM), duration of fever and antibiotics administration, and hospital visits for the periods before and during JTT administration.

RESULTS

Medication compliance rate was 87.5%, and administration of JTT led to remission in 95.2% patients. No apparent side effects were observed. The frequency of AOM decreased significantly (Wilcoxon signed rank test, p=0.000) with JTT. The duration of fever (p=0.000) and administration of antibiotics (p=0.001), as well as the number of hospital visits (p=0.001) and emergent hospital visits (p=0.000) showed significant decreases after JTT administration. After the end of the JTT period, 14 of 21 (66.7%) patients started to take it again, as they experienced purulent otitis media and/or other infections after discontinuation. The frequency of AOM increased significantly after stopping JTT (p=0.004) and decreased again with JTT resumption (p=0.005).

Factors associated with the presence of drug-resistant bacteria and recurrent acute otitis media in children--a study in a private clinic

CONCLUSIONS

The proportion of drug-resistant bacteria was lower than previous reports. In children with acute otitis media (AOM), lower age, presence of multiple bacteria, and otitis media with effusion (OME) represented significant factors for recurrent AOM and the presence of drug-resistant bacteria.

OBJECTIVE

Recently, the proportion of drug-resistant bacteria has been increasing in children with AOM. We studied the proportion of drug-resistant bacteria and background factors for detection of drug-resistant bacteria and recurrent AOM in a private clinic.

SUBJECTS AND METHODS

Subjects comprised 170 patients <12 years old with AOM. Middle ear fluid was collected and pathogenic bacteria were identified. The following factors were considered: age, sex, use of antibiotics in the past 1 month, past history of recurrent AOM, presence of OME, and multiple bacteria of the three main strains (Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis).

RESULTS

A total of 169 strains were detected in 77% of children with AOM. Drug-resistant bacteria comprised 44 of the 169 strains (26%). Lower age (p=0.001) and presence of multiple bacteria (p<0.001) represented significant factors for the presence of drug-resistant bacteria. OME was a significant factor for recurrent AOM (p<0.001).

Study of nasopharyngeal bacterial flora. Variations in nasopharyngeal bacterial flora in schoolchildren and adults when administered antimicrobial agents

Changes in nasopharyngeal bacterial flora in adults with acute upper respiratory tract infection on administration of antimicrobial agents were investigated, and how these changes contrasted with those in children. Many patients with acute sinusitis due to allergies, and patients with malignancy and diabetes mellitus were included in the investigation. The detection rates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, the major bacteria of acute otitis media (AOM), were 22%, 10%, and 7% respectively, which were significantly lower than those for children. Gram stain examination of nasopharyngeal swab samples showed a significant relation between leukocyte infiltration and the detection amount of S. pneumoniae (P = 0.0086). A significant relation (P = 0.0134) was also observed when H. influenzae was simultaneously detected. No significant change in the three major AOM bacteria present in nasopharyngeal bacterial flora after administration of antimicrobial agents was observed. However, all S. pneumoniae and H. influenzae detected after antimicrobial agent administration had the beta-lactam-resistance gene. It was observed that a significant improvement in leukocyte infiltration occurred 6 to 10 days after antimicrobial agent administration. In contrast, a significant improvement in children was observed at 2 to 5 days. In the adult subjects, this improvement was probably due to spontaneous remission rather than the effect of the antimicrobial agents. Although investigation of the long-term administration of antimicrobial agents was also conducted, its benefits for the patients were not elucidated.

Reliability and validity of functional health status and health-related quality of life questionnaires in children with recurrent acute otitis media

In this study the reliability and validity of generic and disease-specific questionnaires has been assessed focusing on responsiveness. This is part of a study on the effects of recurrent acute otitis media (rAOM) on functional health status (FHS) and health-related quality of life (HRQoL) in 383 children with rAOM participating in a randomized clinical trial. The following generic questionnaires were studied: 1. RAND general health rating index, 2. Functional Status Questionnaire (FSQ Generic and FSQ Specific), 3. TNO-AZL Infant Quality of Life (TAIQOL), and the following disease-specific questionnaires: 1. Otitis Media-6 (OM-6), 2. Numerical rating scales (NRS) for child and caregiver (NRS Child and NRS Caregiver), and 3. a new Family Functioning Questionnaire (FFQ). Reliability was good to excellent (Cronbach’s α range 0.80–0.90, intraclass correlation coefficient range 0.76–0.93). Moderate to strong correlations were found between the questionnaires as well as between questionnaires and relevant clinical indicators (r = 0.29–0.49), demonstrating construct validity. Discriminant validity for children with few versus frequent episodes of acute otitis media per year was good for most questionnaires (P < 0.004) but poor for the otitis media-related subscales of the TAIQOL (P = 0.10–0.97) and both NRS (P = 0.22 and 0.48). Except for the TAIQOL subscales, change scores were significant (P < 0.003) for generic and disease-specific questionnaires. Effect sizes were somewhat higher for disease-specific compared to generic questionnaires (0.55–0.95 versus 0.32–0.60) except for the TAIQOL subscales, which showed very poor sensitivity to change. Anchor-based methods resulted in a somewhat larger range of estimates of MCID than distribution-based methods. Combining distribution-based and anchor-based methods resulted in similar ranges for the minimally clinical important differences for generic and disease-specific questionnaires: 2–15 points on a 0–100 scale. Apart from the generic TAIQOL subscales, both generic and disease-specific questionnaires used in this study showed good psychometric qualities and responsiveness for use in clinical studies on children with rAOM.

Construction of a mutant and characterization of the role of the vaccine antigen P6 in outer membrane integrity of nontypeable Haemophilus influenzae

Outer membrane protein P6 is the subject of investigation as a vaccine antigen to prevent infections caused by nontypeable Haemophilus influenzae, which causes otitis media in children and respiratory tract infections in adults with chronic lung disease. P6 induces protective immune responses in animal models and is the target of potentially protective immune responses in humans. P6 is a 16-kDa lipoprotein that shares homology with the peptidoglycan-associated lipoproteins of gram-negative bacteria and is highly conserved among strains of H. influenzae. To characterize the function of P6, an isogenic mutant was constructed by replacing the P6 gene with a chloramphenicol resistance cassette. The P6 mutant showed altered colony morphology and slower growth in vitro than that of the parent strain. By electron microscopy, the P6 mutant cells demonstrated increased size, variability in size, vesicle formation, and fragility compared to the parent cells. The P6 mutant showed hypersensitivity to selected antibiotics with different mechanisms of action, indicating increased accessibility of the agents to their targets. The P6 mutant was more sensitive to complement-mediated killing by normal human serum. Complementation of the mutation in trans completely or partially restored the phenotypes. We concluded that P6 plays a structural role in maintaining the integrity of the outer membrane by anchoring the outer membrane to the cell wall. The observation that the absence of expression of P6 is detrimental to the cell is a highly desirable feature for a vaccine antigen, supporting further investigation of P6 as a vaccine candidate for H. influenzae.

Antibody levels after regular childhood vaccinations in the immunological screening of children with recurrent otitis media

Recurrent otitis media may be related to defects in specific antibody production, as suggested previously. This might be reflected in lower antibody responses to vaccinations administered in the context of the national childhood vaccination program in children suffering from recurrent otitis media. In a cross-sectional study we determined the levels of antidiphtheria, antitetanus, anti- Haemophilus influenzae type b (anti-Hib) and antimeasles antibodies in sera of 163 children with two or more episodes of acute otitis media per year and in 143 children with repeated periods of persistent otitis media with effusion each lasting at least 3 months. The control group consisted of 521 age-matched healthy children, who were free of recurrent respiratory tract infections. Children with recurrent acute otitis media, including highly otitis-prone children, showed higher antidiphtheria and antitetanus antibody titers compared to controls. No differences were observed in anti-Hib and antimeasles antibody levels between children with recurrent acute otitis media and controls, nor did any of the antibody levels in children with persistent otitis media with effusion differ from those in controls. Therefore, the results of our study do not point toward a generalized immunological hyporesponsiveness in children with recurrent acute otitis media and persistent otitis media with effusion. Determination of antibody responses to regular vaccines is not indicative for otitis-proneness.

Immunoglobulins in otitis-prone children

Defective or immature antibody responses to pathogens in children may explain the increased susceptibility to acute otitis media (AOM) in otitis-prone children. In literature, data on immunology have been based on studies of small groups of severely otitis-prone children and have not been consistent. Humoral immune status was assessed in 365 children, 1-7 years old, with two or more documented episodes of AOM in the previous year. Children with 4 or more episodes in the preceding year were defined as otitis-prone. Serum immunoglobulin levels were determined by radial immunodiffusion. Immunoglobulin levels of otitis-prone children were compared with those of children who had experienced 2-3 AOM episodes per year. Children with recurrent episodes of AOM were found to have normal or increased serum IgA, IgM, IgG, and IgG1 levels compared with normal values for age, whereas the serum IgG2 levels were mostly in the lower normal range. Twenty-two percent of all children showed IgG2 levels lower than 2 SD below the age-specific mean. Interestingly, the otitis-prone group of children showed significantly lower median and mean levels for all immunoglobulins compared with those children with only 2-3 previous AOM episodes. Lower immunoglobulin levels in otitis-prone children suggest a generalized decreased antibody response in otitis-prone children.

Intranasal immunization with recombinant outer membrane protein P6 induces specific immune responses against nontypeable Haemophilus influenzae

OBJECTIVE

Nontypeable Haemophilus influenzae (NTHi) is one of the leading causative pathogens for otitis media. The outer membrane protein P6 of NTHi is highly conserved among the strains and is an attractive candidate for a preventive vaccine. However, for the production of a relatively small amount P6 containing lipopolysaccharides, the development of a recombinant version of this protein is required. This study was designed to investigate the specific mucosal immunity induced by intranasal immunization of recombinant P6 (rP6) with cholera toxin (CT).

METHODS

BALB/c mice were immunized with of rP6 (30 microg) and CT (2 microg) intranasally every 2 days for 2 weeks. Anti-rP6 specific IgG, IgA and IgM antibodies and the subclass of anti-rP6 specific IgG antibody were determined by enzyme linked immunosorbent assay (ELISA). Anti-rP6 specific IgA in nasopharyngeal washings were also determined by ELISA. Nasopharyngeal clearance of inoculated NTHi after the intranasal immunization were assessed. All statistical differences between the two groups were assessed by ANOVA parametric test.

RESULTS

Intranasal immunization with rP6 and CT evoked rP6-specific mucosal IgA immune response as well as the systemic IgG immune response against rP6 and enhanced nasopharyngeal clearance of inoculated live NTHi.

CONCLUSION

These results indicate the good immunogenicities of rP6 to induce specific immune responses against NTHi. Intranasal immunization with rP6 will be an effective approach to protect infections of NTHi.

Lymphocyte proliferative response to P6 of Haemophilus influenzae is associated with relative protection from exacerbations of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by periodic exacerbations, some of which are caused by nontypeable Haemophilus influenzae (NTHI). P6 is an outer membrane lipoprotein that is highly conserved among strains of NTHI. We hypothesized that lymphocytes from patients with COPD who have exacerbations due to NTHI have a decreased ability to recognize P6. The in vitro lymphocyte proliferative response to P6 in 36 patients with COPD and 12 healthy control subjects was studied. Ten patients who had exacerbations due to NTHI in the previous 12 months showed statistically significant lower proliferation to P6 (stimulation index, log transformed mean +/- standard error 0.82 +/- 0.17) compared with 26 patients who had no exacerbations due to NTHI in the previous 12 months (1.42 +/- 0.13) and to 12 healthy control subjects (1.61 +/- 0.16). These three groups had no significant difference in the lymphocyte proliferative response to tetanus toxoid. There was no difference in serum antibody levels to P6 in the two groups with COPD. These results indicate that decreased proliferation of T cells to P6 is associated with exacerbations of COPD and suggest that the ability of T cells to recognize P6 is associated with relative protection from exacerbations due to NTHI.