Breast-feeding is associated with a reduced frequency of acute otitis media and high serum antibody levels against NTHi and outer membrane protein vaccine antigen candidate P6

Nontypeable Haemophilus influenzae (NTHi) causes acute otitis media (AOM) in infants. Breast-feeding protects against AOM and/or nasopharyngeal (NP) colonization; however, the mechanism of protection is incompletely understood. Children with AOM and healthy children were studied according to feeding status: breastfed,breast/formula fed, or formula fed. Cumulative episodes of AOM, ELISA titers of serum IgG antibodies to whole-cell NTHi and vaccine candidate outer membrane protein P6, bactericidal titers of serum and NP colonization by NTHi were assessed. A lower incidence of AOM was found in breast- versus formula-fed children. Levels of specific serum IgG antibody to NTHi and P6 were highest in breast-fed, intermediate in breast/formula fed, and lowest in formula-fed infants. Serum IgG antibody to P6 correlated with bactericidal activity against NTHi. Among children with AOM, the prevalence of NTHi in the NP was lower in breast- versus nonbreast-fed infants. We conclude that breast-feeding shows an association with higher levels of antibodies to NTHi and P6, suggesting that breast-feeding modulates the serum immune response to NTHi and P6. Higher serum IgG might facilitate protection against AOM and NP colonization in breast-fed children.

Intranasal immunization enhances clearance of nontypeable Haemophilus influenzae and reduces stimulation of tumor necrosis factor alpha production in the murine model of otitis media

Nontypeable Haemophilus influenzae (NTHi) is a major pathogen causing otitis media (OM). One of the outer membrane proteins of NTHi, P6, is a common antigen to all strains and is considered a candidate for mucosal vaccine. We have previously reported that intranasal immunization with P6 and cholera toxin (CT) could induce P6-specific immunoglobulin A (IgA) antibodies in the middle ear. In the present study, we assessed the effect of intranasal immunization for the protection against NTHi-induced OM. Mice were immunized intranasally with P6 and CT as an adjuvant on days 0, 7, and 14. Control mice were given phosphate-buffered saline (PBS) without antigen. One week after the final immunization, a suspension of live NTHi (10(7) CFU) was injected into the tympanic cavity to induce experimental OM. On days 3 and 7 after bacterial challenge, mice were killed and middle ear effusions (MEEs) were collected. All immunized mice showed elevated titers of P6-specific antibodies in MEEs. The rank order of specific antibody included, from highest to lowest levels, IgG, IgA, and IgM. In addition, immunized mice showed enhanced clearance of NTHi from the middle ear and the number of NTHi in MEEs of immunized mice was reduced by 97% on day 3 and by 92% on day 7 after bacterial challenge relative the number in the MEEs of control mice. The protective effect of intranasal immunization on the incidence of NTHi-induced experimental OM was evident on day 7 after challenge. By day 7, the number of MEEs in immunized mice was 64% less than that in control mice and the incidence of NTHi culture-positive MEEs in immunized mice was 56% less than that in control mice. Less stimulation of tumor necrosis factor alpha (TNF-alpha) production in the middle ear was evident on day 3 after challenge. Immunized mice showed lower concentrations of TNF-alpha in MEEs. These results indicate that intranasal immunization affords protection against experimental OM as evidenced by enhanced clearance of NTHi and less stimulation of TNF-alpha production in the middle ear. These findings suggest that a nasal vaccine might be useful for preventing OM.

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.

Intranasal vaccination of infant mice induces protective immunity in the absence of nasal-associated lymphoid tissue

Intranasal (i.n.) immunization is an effective regimen for the prophylaxis of respiratory diseases in early life. The aim of this study was to assess the need for nasal-associated lymphoid tissue (NALT) and cervical lymph nodes (CLN) in induction of protective immunity following mucosal vaccination of infant mice. We developed surgical techniques to eliminate NALT and CLN in young (8 days old) mice. i.n. vaccination of NALT- or CLN-deficient mice with pneumococcal polysaccharide conjugate vaccine plus interleukin-12 as a mucosal adjuvant (days 10 and 17) was followed by i.n. pneumococcal challenge (days 24-28). Mice were sacrificed on day 31 and nasal mucosal and systemic immune responses as well as pneumococcal colonization in the middle ear and nasopharynx were assessed. Elimination of NALT did not impair the ability of infant (3 weeks old) mice to produce nasal or serum antibody responses following i.n. immunization. In contrast, surgical removal of CLN significantly impaired the ability to express IgA antibody in nasopharyngeal washes and total antibody in serum. Similarly, protection against pneumococcal colonization in the nasopharynx and middle ears of immunized mice was decreased in the absence of CLN but not in the absence of NALT. These findings suggest that surgical removal of NALT tissue, at least in a mouse model, does not affect the ability to respond to subsequent i.n. vaccination. In addition, in the young mice CLN play a more important role than NALT for induction of protective mucosal and systemic antibody responses following i.n. immunization.

Intranasal vaccination of neonatal mice with polysaccharide conjugate vaccine for protection against pneumococcal otitis media

Streptococcus pneumoniae is the leading bacterial cause of acute otitis media (OM) in young children, and can often produce invasive disease. Typical intramuscular routes of vaccination are poorly protective against development of OM. In the present study, we intranasally (i.n.) inoculated neonatal 1-week-old mice with pneumococcal polysaccharide conjugate vaccine using IL-12 as a mucosal adjuvant. The protective efficacy of this treatment was tested by challenging immunized infant (3-week-old) mice with bacteria to induce OM and invasive disease. i.n. vaccination was found to enhance levels of specific antibodies in middle ear (ME) washes and sera from wild-type (but not IFN-gamma(-/-)) mice. Immunization in the presence of IL-12 resulted in enhanced clearance of S. pneumoniae from the ME. Opsonization of bacteria with ME wash fluids or sera from immunized mice caused increased bacterial clearance from the ME of naïve mice. In addition, immunized mice demonstrated 89% survival after OM-induced invasive pneumococcal infection, compared to 22% survival in unvaccinated mice. These results indicate that i.n. vaccination of neonatal mice in the presence of IL-12 is able to enhance IFN-gamma dependent ME mucosal and systemic immune responses to pneumococci and efficiently protect against both OM and invasive infection.

Mouse models for the study of mucosal vaccination against otitis media

Otitis media (OM) is one of the most common infectious diseases in humans. The pathogenesis of OM involves nasopharyngeal (NP) colonization and retrograde ascension of the pathogen up the Eustachian tube into the middle ear (ME). Due to increasing rates of antibiotic resistance, there is an urgent need for vaccines to prevent infections caused by the most common causes of bacterial OM, including nontypeable Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis. Current vaccine strategies aim to diminish bacterial NP carriage, thereby reducing the likelihood of developing acute OM. To be effective, vaccination should induce local mucosal immunity both in the ME and in the NP. Studies in animal models have demonstrated that the intranasal route of vaccination is particularly effective at inducing immune responses in the nasal passage and ME for protection against OM. The mouse is increasingly used in these models, because of the availability of murine reagents and the existence of technology to manipulate murine models of disease immunologically and genetically. Previous studies confirmed the suitability of the mouse as a model for inflammatory processes in acute OM. Here, we discuss various murine models of OM and review the applicability of these models to assess the efficacy of mucosal vaccination and the mechanisms responsible for protection. In addition, we discuss various mucosal vaccine antigens, mucosal adjuvants and mucosal delivery systems.

Intranasal immunization with outer membrane protein P6 and cholera toxin induces specific sinus mucosal immunity and enhances sinus clearance of nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) is one of the leading pathogens in sinusitis. One of the outer membrane proteins of NTHi, P6, is a common antigen to all strains and is an attractive candidate for a subunit bacterial vaccine. In this study, we characterized normal sinus mucosa (SM) and investigated the potential of intranasal immunization with P6 and cholera toxin (CT) for induction of mucosal protective immunity against NTHi in the maxillary sinuses of rats. Intranasal immunization induced P6-specific sinus mucosal and systemic immunological responses, mainly of the IgA and IgG isotype. The protective effect of intranasal immunization was demonstrated by enhancement of sinus clearance of NTHi. The present study showed that unilateral intranasal immunization has a capacity to induce protective immunity against NTHi in the bilateral maxillary sinuses. Systemic administration of the vaccine did not affect sinus clearance of NTHi. These findings suggest that a nasal vaccine might be useful for preventing sinusitis.

Learning abnormal physical examination signs: an introductory course

CONTEXT

The acquisition of clinical skills is an essential part of the osteopathic medical school curriculum. Preclinical medical students, especially at osteopathic medical schools, have limited exposure to abnormal physical examination (PE) findings that are not typically seen in a student's peers or in a standardized patient (SP). The early exposure of first-year medical students (MS1s) to normal and abnormal findings in the simulation settings better equips them to identify abnormalities when they encounter them in a clinical setting.

OBJECTIVES

The aim of this project was to develop and implement the introductory course on learning abnormal PE signs and pathophysiology of abnormal clinical findings to address the educational needs of MS1s.

METHODS

The didactic part of the course consisted of PowerPoint presentations and lecture on the topics related to the simulation. The practical skill session was 60 min, during which time students first practiced PE signs and then were assessed on their ability to accurately identify abnormal PE signs on a high-fidelity (HF) mannequin. Faculty instructors guided students through clinical cases and challenged them with probing questions in clinically relevant content. Before- and after-simulation evaluations were created to assess students' skills and confidence. Student satisfaction levels after the training course were also assessed.

RESULTS

This study demonstrated significant improvements in five PE skills (p<0.0001) after the introductory course of abnormal PE clinical signs. The average score for five clinical skills increased from 63.1 to 88.74% (before to after simulation). The confidence of students in performing clinical skills and their understanding of the pathophysiology of abnormal clinical findings also increased significantly (p<0.0001) after simulation activity and educational instruction. The average confidence score increased from 3.3 to 4.5% (before to after simulation) on a 5-point Likert scale. Survey results demonstrated high satisfaction with the course among learners with mean satisfaction score 4.7 ± 0.4 on 5-point Likert scale. The introductory course was well received by MS1s and they left positive feedback.

CONCLUSIONS

This introductory course offered MS1s with novice PE skills the ability to learn a variety of abnormal PE signs, including heart murmurs and rhythms, lung sounds, measurement of blood pressure (BP), and palpation of the femoral pulse. This course also allowed abnormal PE findings to be taught in a time-efficient and faculty-resource-efficient manner.