Mucosal immunity of the middle ear: analysis at the single cell level

Impact of IL-17-producing γδ T cells on chronic otitis media induced by nontypeable Haemophilus influenzae in a mouse model

Nontypeable Haemophilus influenzae (NTHi) is considered a major pathogen underlying middle ear infection. This study aimed to investigate the impact of IL-17 on chronic otitis media (COM) induced by NTHi in mice. NTHi was inoculated into the tympanic bulla with eustachian tubal obstruction. Middle ear effusions (MEEs) and tissues were collected on days 3, 14, and at 1, 2, and 6 months after injection. The expression of interleukin-17A (IL-17A) in MEEs was significantly elevated compared to that in the control group at the translational and transcriptional levels during the experiments. The quantities of IL-17-producing γδ T cells were significantly increased compared to that in the control group during COM, but that of Th17 cells did not. Depletion of γδ T cells by anti-γδ T-cell receptor (TCR) monoclonal antibody (mAb) administration significantly decreased the bacteria counts and the concentrations of IL-1β, IL-6, IL-17A, TNF-α, and IL-10 in MEEs. Our results suggest that IL-17 may play an important role in prolonging the inflammation in the middle ear in COM and that IL-17-producing γδ T cells may contribute to the exacerbated inflammatory response in the middle ear. In this study, anti-γδ TCR mAb administration was found to improve chronic middle ear inflammatory conditions.

Temporomandibular disorder: A previously unreported complication of chronic suppurative otitis media

OBJECTIVE

The aim of the current clinical study was to test the hypothesis that chronic suppurative otitis media (CSOM) might be significantly associated with signs of temporomandibular joint (TMJ) internal derangement.

METHODS

The study involved 79 patients with CSOM and 79 control subjects. The TMJ was clinically examined in both groups.

RESULTS

Signs of internal derangement of the TMJ(s) were found in 67.1% of CSOM patients versus 26.6% of control subjects (p = .001).

CONCLUSION

CSOM may be associated with the extension of the inflammatory process into the TMJ, thereby predisposing to internal derangement of the joint.

Probing Immune-Mediated Clearance of Acute Middle Ear Infection in Mice

Acute otitis media (AOM) is commonly caused by bacterial pathobionts of the nasopharynx that ascend the Eustachian tube to cause disease in the middle ears. To model and study the various complexities of AOM, common human otopathogens are injected directly into the middle ear bullae of rodents or are delivered with viral co-infections which contribute to the access to the middle ears in complex and partially understood ways. Here, we present the novel observation that Bordetella bronchiseptica, a well-characterized respiratory commensal/pathogen of mice, also efficiently ascends their Eustachian tubes to colonize their middle ears, providing a flexible mouse model to study naturally occurring AOM. Mice lacking T and/or B cells failed to resolve infections, highlighting the cooperative role of both in clearing middle ear infection. Adoptively transferred antibodies provided complete protection to the lungs but only partially protected the middle ears, highlighting the differences between respiratory and otoimmunology. We present this as a novel experimental system that can capitalize on the strengths of the mouse model to dissect the molecular mechanisms involved in the generation and function of immunity within the middle ear.

Innate Immunity in the Middle Ear Mucosa

Otitis media (OM) encompasses a spectrum of clinical presentations ranging from the readily identifiable Acute OM (AOM), which is characterised by otalgia and fever, to chronic otitis media with effusion (COME) where impaired hearing due to middle ear effusion may be the only clinical symptom. Chronic suppurative OM (CSOM) presents as a more severe form of OM, involving perforation of the tympanic membrane. The pathogenesis of OM in these varied clinical presentations is unclear but activation of the innate inflammatory responses to viral and/or bacterial infection of the upper respiratory tract performs an integral role. This localised inflammatory response can persist even after pathogens are cleared from the middle ear, eustachian tubes and, in the case of respiratory viruses, even the nasal compartment. Children prone to OM may experience an over exuberant inflammatory response that underlies the development of chronic forms of OM and their sequelae, including hearing impairment. Treatments for chronic effusive forms of OM are limited, with current therapeutic guidelines recommending a "watch and wait" strategy rather than active treatment with antibiotics, corticosteroids or other anti-inflammatory drugs. Overall, there is a clear need for more targeted and effective treatments that either prevent or reduce the hyper-inflammatory response associated with chronic forms of OM. Improved treatment options rely upon an in-depth understanding of OM pathogenesis, particularly the role of the host innate immune response during acute OM. In this paper, we review the current literature regarding the innate immune response within the middle ear to bacterial and viral otopathogens alone, and as co-infections. This is an important consideration, as the role of respiratory viruses as primary pathogens in OM is not yet fully understood. Furthermore, increased reporting from PCR-based diagnostics, indicates that viral/bacterial co-infections in the middle ear are more common than bacterial infections alone. Increasingly, the mechanisms by which viral/bacterial co-infections may drive or maintain complex innate immune responses and inflammation during OM as a chronic response require investigation. Improved understanding of the pathogenesis of chronic OM, including host innate immune response within the middle ear is vital for development of improved diagnostic and treatment options for our children.

The effects of adenoidectomy of serum insulin-like growth factor-1 (IGF-1) and ghrelin in hypertrophied adenoids in children with otitis media with effusion

<b>Aim:</b> The aim of the current study was to assess the serum levels of insulin-like growth factor-1 (IGF-1) and ghrelin in hypertrophied adenoids in children suffering with or without otitis media with effusion before and after adenoidectomy. <br><b>Material and methods:</b> Serum IGF-1 and ghrelin concentrations were measured with specific enzyme-linked immunoassay (ELISA) methods. The study was carried out in 20 children with otitis media with effusion. The reference group comprised 24 children with hypertrophied adenoid, while control group included 19 children. <br><b>Results:</b> This mean values of IGF-1 in children with otitis media with effusion and children with hypertrophied adenoid before adenoidectomy were significantly lower than those found in healthy children. Serum levels of IGF-1 were higher after adenoidectomy. There was a significant difference of serum ghrelin levels between both examined groups and the control group. <br><b>Conclusion:</b> Our results suggest that adenoidectomy in children with hypertrophied adenoids and in children with otitis media with effusion significantly increases the level of IGF-1 in serum compared to before surgery through the effect of the GH-IGF-1 axis, which could contribute to children's growth.

Immunoglobulins and Transcription Factors in Otitis Media

The causes of otitis media (OM) involve bacterial and viral infection, anatomo-physiological abnormalities of the Eustachian canal and nasopharynx, allergic rhinitis, group childcare centers, second-hand smoking, obesity, immaturity and defects of the immune system, formula feeding, sex, race, and age. OM is accompanied by complex and diverse interactions among bacteria, viruses, inflammatory cells, immune cells, and epithelial cells. The present study summarizes the antibodies that contribute to immune reactions in all types of otitis media, including acute otitis media, otitis media with effusion, and chronic otitis media with or without cholesteatoma, as well as the transcription factors that induce the production of these antibodies. The types and distribution of B cells; the functions of B cells, especially in otorhinolaryngology; antibody formation in patients with otitis media; and antibodies and related transcription factors are described. B cells have important functions in host defenses, including antigen recognition, antigen presentation, antibody production, and immunomodulation. The phenotypes of B cells in the ear, nose, and throat, especially in patients with otitis media, were shown to be CD5^low, CD23^high, CD43^low, B220^high, sIgM^low, sIgD^high, Mac-1^low, CD80(B7.1)^low, CD86(B7.2)^low, and Syndecam-1^low. Of the five major classes of immunoglobulins produced by B cells, three (IgG, IgA, and IgM) are mainly involved in otitis media. Serum concentrations of IgG, IgA, and IgM are lower in patients with OM with effusion (OME) than in subjects without otitis media. Moreover, IgG, IgA, and IgM concentrations in the middle ear cavity are increased during immune responses in patients with otitis media. B cell leukemia/lymphoma-6 (Bcl-6) and paired box gene 5 (Pax-5) suppress antibody production, whereas B lymphocyte inducer of maturation program 1 (Blimp-1) and X-box binding protein 1 (XBP-1) promote antibody production during immune responses in patients with otitis media.

[The modern approaches to the evaluation of the importance of chronic inflammation in the mucous membrane of the middle ear]

Despite the ever growing progress in antibiotic therapy and the advent of the new methods for this purpose, the number of patients suffering from chronic focal infection of the ENT organs has not decreased during the last decades which turns the problem of chronization of inflammation into a serious challenge for the physicians as exemplified by chronic inflammation in the mucous membrane of the middle ear. Pathological changes in the middle ear make up a large fraction of ENT diseases of importance not only for otorhinolaryngologists but also for the specialists in the related medical disciplines. The present article is an overview of etiological, pathogenetic, and pathomorphological aspects of chronization of the inflammation process that are known to occur in the mucous membrane of the middle ear. In the overwhelming majority of the cases, the main cause of the conversion of acute inflammation in the middle ear into the chronic condition is the inadequate (incorrect), inopportune or incomplete treatment of the acute inflammatory process in the middle ear.

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.

Prospects for a vaccine against otitis media

Otitis media is a major cause of morbidity in 80% of all children less than 3 years of age and often goes undiagnosed in the general population. There is evidence to suggest that the incidence of otitis media is increasing. The major cause of otitis media is infection of the middle ear with microbes from the nasopharynx. The anatomical orientation of the eustachian tube, in association with a number of risk factors, predisposes infants and young children to the infection. Bacteria are responsible for approximately 70% of cases of acute otitis media, with Streptococcus pneumoniae, nontypeable Haemophilus influenzae and Moraxella catarrhalis predominating as the causative agents. The respiratory viruses, respiratory syncytial virus, rhinovirus, parainfluenza and influenza, account for 30% of acute otitis media cases. Over the past decade, there has been a profound increase in the reported resistance to antibiotics, which, with increased disease burden, has focussed attention on vaccine development for otitis media. A polymicrobial formulation containing antigens from all major pathogens would have the greatest potential to deliver a sustained reduction in the disease burden globally. The disappointing outcomes for otitis media seen with the polysaccharide pneumococcal conjugate vaccine have raised major challenges for the vaccination strategy. Clearly, more knowledge is required concerning immune mechanisms in the middle ear, as well as vaccine formulations containing antigens that are more representative of the polymicrobial nature of the disease. Antigens that have been extensively tested in animal models are now available for testing in human subjects.

Antibody in middle ear fluid of children originates predominantly from sera and nasopharyngeal secretions

The human middle ear is devoid of any immunocompetent cells in normal mucosa. We sought to determine the source of antibody present in the middle ear of children. Total IgG, IgA, and secretory IgA antibodies were determined by enzyme-linked immunosorbent assay from the nasopharyngeal, middle ear, and serum samples of children with acute otitis media. The two-dimensional gel electrophoresis pattern of the entire array of IgA antibodies in the nasal wash (NW) and middle ear fluid (MEF) was compared from the MEF and NW samples using isoelectric focusing and Western blotting. The total IgG and IgA antibodies in the MEF and NW samples of 137 children were compared. The ratio of IgG to IgA in the MEF was significantly different (P < 0.008) compared to NW because IgA levels were higher and IgG levels lower in NW. The IgG/IgA ratio of MEF resembled serum consistent with transudation to the MEF. Small amounts of secretory IgA were detected in MEF but the electrophoresis patterns of the entire array of IgA antibodies in the MEF and NW were virtually identical in each child evaluated; thus, IgA in MEF derived predominantly from serum and the nasopharynx by reflux via the Eustachian tube. The IgG/IgA antibody levels in the MEF and the same composition of IgA antibody in the MEF and NW identifies the predominant source of antibody in the MEF as a transudate of serum combined with nasal secretions refluxed from the nasopharynx in children.

Efficacy of a topical suspension of bacterial antigens for the management of chronic suppurative otitis media

The aim of this study was to compare the efficacy and safety of a topical suspension of bacterial antigens for the management of chronic suppurative otitis media (CSOM). Two-hundred ten patients with CSOM were enrolled in this study. The patients were divided into two numerically equal groups and randomized to receive a topical suspension of bacterial antigens, Lantigen B (group A), or placebo (group B), according to the following protocol: 5 drops thrice a day for 12 consecutive weeks in the external acoustic duct. The topical suspension of bacterial antigens and placebo were administered by identical, anonymous dispensers in order to maintain double-blind conditions. Before, at the end and 3 months, and after the end of the treatment, all patients who entered in the study underwent pure tone audiometry, microscopic examination of ears, microbiological examination of the ear swab, aural suctioning and subjective assessment of symptoms by visual analog scale. In group A, we saw a statistically significant improvement in the different items measured. A topical suspension of bacterial antigens was significantly more effective than placebo in the treatment of CSOM.

Reduced iNOS expression in adenoids from children with otitis media with effusion

Nitric oxide (NO) is a key mediator in the local immune response of human airways. Inducible NO-synthases (iNOS), and endothelial NO-synthases (eNOS) are two enzymes known to regulate its production. The role of NO in middle ear disease is not fully known. Previous studies suggest that NO might have a dual role, both promoting and suppressing middle ear inflammation. The aim of the present study was to compare the eNOS and iNOS expression in adenoids obtained from children with otitis media with effusion (OME) with the expression seen in adenoids derived from children without middle ear disease. In addition, the expression of IL-1β and TNF-α were analyzed, because of their role in the iNOS-induction pathway. The iNOS and eNOS expression were analyzed with real-time PCR in 8 OME and 11 control adenoids. The corresponding proteins were demonstrated by immunohistochemical staining of adenoid tissue. A Luminex(®) assay was performed to analyze IL-1β and TNF-α in nasopharyngeal secretion in 10 OME and 8 controls, and immunohistochemistry was performed on adenoid tissue and imprints from the adenoid surface. Children with OME exhibited lower levels of iNOS than controls without middle ear disease. No such difference was seen for eNOS. The corresponding proteins were found mainly in conjunction with surface epithelium. No significant changes were seen among the cytokines tested. The present results indicate that local induction of iNOS in adenoids might be of importance for preventing development of OME.

Construction and immunogenicity of recombinant adenovirus vaccines expressing the HMW1, HMW2, or Hia adhesion protein of nontypeable Haemophilus influenzae

The objective of the present study was to construct and assess the immunogenicity of recombinant adenovirus vectors expressing the HMW1, HMW2, or Hia protein of nontypeable Haemophilus influenzae (NTHi). These proteins are critical adhesins and potential protective antigens expressed by NTHi. Segments of the hmw1A and hmw2A structural genes that encode the distal one-half of mature HMW1 or HMW2 were cloned into the T7 expression vector pGEMEX-2. These constructs encoded stable HMW1 or HMW2 recombinant fusion protein that expresses B-cell epitopes common to most NTHi strains. A segment of the hia gene that encodes the surface-exposed portion of mature Hia was also cloned into pGEMEX-2. The resulting T7 gene 10 translational fusions were excised from the parent plasmids and cloned into the shuttle plasmid pDC316. Cotransfection of HEK 293 cells with the pDC316 derivatives and pBHGloxΔE1,3Cre resulted in the production of viral plaques from which recombinant adenoviruses expressing fusion proteins were recovered. Chinchillas immunized intraperitoneally with a single 10(8)-PFU dose of either the HMW2 or Hia adenoviral construct developed high anti-HMW2 or anti-Hia serum antibody titers within 4 weeks of immunization. Chinchillas immunized intranasally with a single 10(7)- to 10(9)-PFU dose of the Hia adenoviral construct also developed high anti-Hia serum antibody titers within 8 weeks of immunization. Recombinant adenoviruses represent a promising system to induce mucosal and systemic immunity and protection against mucosal diseases such as otitis media. Recombinant adenoviruses expressing recombinant HMW1, HMW2, or Hia protein will be important new tools in NTHi vaccine development efforts.

B cells in murine cervical lymph nodes are conventional B-2 cells

We investigated the characteristic features of cervical lymph node B cells to determine whether their behavior differs from that of B cells located elsewhere, because cervical lymph nodes may be exposed to continual antigenic stimulation from the naso- and/or oropharynx. B cells were isolated from cervical lymph nodes, spleen and peritoneal fluid of mice, cultured in medium, and exposed to various stimuli. The expression of various surface molecules characteristic of lymphoid B cells was assayed by flow cytometry, and immunoglobulin secreted into the culture supernatants was evaluated by enzyme-linked immunosorbent assay. B220+ cells were cultured in medium alone or with lipopolysaccharide, and their entrance into S phase in response to stimuli was measured by proliferative assays. Phenotypic characteristics of cervical lymph node B cells included CD5 low, CD23high, CD43low, B7.1low, B7.2low, and Syndecan-1low. Unstimulated lymphoid B cells did not secrete immunoglobulin, but, upon stimulation, secretion of IgM was increased more than secretion of IgA and IgG. B cells actively entered S phase after 48 hr stimulation. These results show that B cells in cervical lymph nodes are conventional B2 cells, like splenic B cells.

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.

Characteristic features of B cells in murine cervical lymph nodes

CONCLUSION

B cells in cervical lymph nodes correspond to typical conventional B cells (B-2).

OBJECTIVE

The special status of cervical lymph nodes in relation to the oropharynx, and the need to maintain the integrity of the oropharnygeal mucosal barrier, suggest the possibility that cervical lymph node B cells located in the oropharynx may behave differently from B cells located elsewhere. In this study we examined the symmetry or lack thereof between cervical lymph node B cells and other B-cell subsets.

MATERIAL AND METHODS

We isolated B cells from murine cervical lymph node tissue and evaluated them in vitro according to several criteria.

RESULTS

We found that cervical lymph node B cells expressed typical B-cell phenotypic markers and proliferated normally in response to mitogenic stimulation. They did not spontaneously secrete immunoglobulin and, in keeping with this, did not express elevated levels of either CD138 (Syndecan-1), a marker for plasma cells, or BLIMP-1, a putative master regulator of B-cell differentiation.

Eustachian tube possesses immunological characteristics as a mucosal effector site and responds to P6 outer membrane protein of nontypeable Haemophilus influenzae

The eustachian tube (ET) plays an important role in the pathogenesis of otitis media (OM). To better understand its biology and to develop a nasal vaccine for preventing OM, mucosal lymphocytes in the ET were analyzed, and the ET's immunological function was investigated. Mononuclear cells were isolated from murine ET, and lymphocyte subsets were analyzed by flow cytometry. Antibody-producing cells were determined by enzyme-linked immunospot assay. The expression of cytokine mRNA in ET CD4(+) T cells was determined by RT-PCR. Results in naive mice showed that the ET contained many immunocompetent cells, including a relative large number of IgA-producing cells and Th2 cytokine-expressing T cells. Next, we investigated antigen-specific immune responses in the ET. Mice were immunized intranasally with the P6 outer membrane of nontypeable Haemophilus influenzae (NTHi) and cholera toxin (CT), and P6-specific immune responses in the ET were examined. P6-specific IgA producing cells markedly increased in the ET. Moreover, in vitro stimulation with P6 of purified CD4(+) T cells from immunized mice resulted in the proliferation of CD4(+) T cells that expressed Th2 cytokine mRNA. These results indicate that the ET might be characterized as a mucosal effector site and that antigen-specific IgA and Th2 immune responses could be induced in the ET by intranasal immunization. These findings suggest that the ET might be a key immunological organ in the pathogenesis of OM, and in the development of a nasal vaccine.

Lymphocyte subpopulations in middle ear effusions: flow cytometry analysis

OBJECTIVE

The aim of this study was to identify lymphocyte subpopulations in middle ear effusions, peripheral blood, and adenoids in children suffering from otitis media with effusion.

SETTING

Tertiary referral center.

PATIENTS

Thirty-three children (55 ears) undergoing myringotomy for otitis media with effusion.

METHODS

CD3, CD4, CD8, CD19, and natural killer cell populations were investigated in middle ear effusion, peripheral blood, and adenoids using a three-color monoclonal antibody and flow cytometry method for quantitative estimation.

RESULTS

T cells (CD3) are dominating lymphocytes in middle ear effusion. Among T lymphocytes, the majority are those of the helper type (CD4). The dominating isoform among CD4 lymphocytes are memory cells (CD4CD45RO); among CD8 lymphocytes, naive cells (CD8CD45RA). The percentage of CD4 cells, CD8 cells, and the CD4/CD8 ratio was significantly higher in middle ear effusions than in blood. The percentage of memory CD4 lymphocytes and naive CD8 lymphocytes was significantly lower in the middle ear effusion. Lymphocyte subsets were compared between 22 pairs of effusions from each patient. The percentage of each type of cell did not differ significantly.

CONCLUSION

The results of this study indicate local regulation of the lymphocyte profile in middle ear effusions and the same phase of immune response in two ears of the same patient.