Acute otitis media in children aged less than 2 years: drug treatment issues

[The role of innate immunity in otitis media]

Otitis media (OM) belongs to the most common pediatric diseases and causes more medical contacts, surgical interventions, and drug prescriptions than any other infectious disease. Recent findings have identified a critical role of innate immunity in recovery from OM. The middle ear mucosa identifies invading pathogens by sensing pathogen-associated molecule patterns (PAMPs) via pattern recognition receptors such as the Toll-like receptors (TLRs). They generate immediate antimicrobial responses and cytokine release, leading to an inflammatory reaction as seen in acute or chronic OM. Cross-talk between TLRs can enhance or suppress the healing process in the middle ear. In order to prevent over-activation on the one hand and insufficient immune response on the other, the signaling network between different TLRs must be integrated and controlled by positive and negative feedback loops. This guarantees a proper immune response in the middle ear after infection. In this review, we focus on the involvement of the innate immune system and TLRs in OM, as well on their relevance for new vaccination strategies and immunotherapies.

Age-dependent changes in pattern recognition receptor and cytokine mRNA expression in children with otitis media with effusion

OBJECTIVE

To investigate age-dependent changes in expression of pattern recognition receptors (PRRs) and cytokines in pediatric OME.

MATERIALS AND METHODS

Ninety five pediatric patients with OME were divided into 4 age groups: 0-2, 2-4, 4-7, and over 7 years. The presence of bacteria, and the levels of expression of mRNAs encoding Toll-like receptor (TLRs), NOD like receptors (NLRs) and cytokines in middle ear fluid were assessed, as were their correlations with age, gender, presence of bacteria and accompanying disease.

RESULTS

Bacteria were detected in 32.6% of patients. The levels of expression of PRR and cytokine mRNAs tended to be lower in children aged 2-4 and 4-7 years. The levels of expression of TLR-2, TLR-9, NOD-1, NOD-2, IL-1, IL-6, and TNF-α mRNAs in effusion fluid were significantly lower in these two groups than in children aged 0-2 and over 7 years (p<0.05 each). The levels of expression of TLR-4, TLR-5, TLR-9, and NOD-1 mRNAs were significantly lower in culture positive than in culture negative patients (p<0.05 each). However, the expression levels of PRR and cytokine mRNAs were unrelated to gender and accompanying disease (p>0.05 each).

CONCLUSIONS

The levels of expression of PRR and cytokine mRNAs differed by age in children with OME.

Acute otitis media in neonatal life: a review

Acute otitis media is frequently encountered by general practitioners and pediatricians. In the neonatal period acute otitis media may present as an isolated local infection or as part of septicemia. Diagnosis of the condition by otoscopy is difficult. Considering the wide spectrum of middle ear disorders (acute otitis media, otitis media with effusion, chronic suppurative otitis media) one can appreciate why opinions on the management of the condition are diverse. This is a review of the literature on clinical presentation, etiology, risk factors, treatment and prevention of acute otitis media in neonatal life.

Innate signaling in otitis media: pathogenesis and recovery

Otitis media (OM) is the most prevalent childhood disease in developed countries. Involvement of innate immunity mediated by Toll-like receptors (TLRs) in OM has been implicated primarily in cell lines and by association studies of innate immune gene polymorphisms with OM prevalence. However, the precise role of innate immunity in OM is incompletely understood. We review recent research that has advanced our understanding of how innate immunity in the middle ear is mediated by the interaction of pathogen molecules with receptors such as the TLRs, leading to the activation of adaptor molecules and production of proinflammatory cytokines. TLR genes and signaling molecules are upregulated in OM in a murine model. Deletion of several key innate immune genes results in persistent OM in mice, coupled with an inability to clear bacterial infection from the middle ear. It is concluded that an intact innate immune signaling system is critical to recovery from bacterial OM.

The role of DNA sensing and innate immune receptor TLR9 in otitis media

Otitis media (OM), a common infectious disease in children, is associated with bacterial middle ear (ME) infection. Toll-like receptors (TLRs) are important mediators of innate immune responses, and TLR9 specifically recognizes the unmethylated cytidine-phosphate-guanosine (CpG) motifs in bacterial DNA. Additional sensors of foreign DNA have recently been identified. The role of DNA sensing and TLR9 was investigated in a murine model of OM induced by non-typeable Haemophilus influenzae (NTHi). Expression of genes related to DNA-sensing pathways involved in innate immunity was assessed via DNA microarray, qPCR and immunohistochemistry. Middle ear responses to NTHi were examined in wild-type and TLR9(-/-) mice by histopathology and bacterial culture. Expression of TLR9 signaling genes was modestly up-regulated during OM, as was TLR9 protein in both ME mucosal cells and infiltrating leukocytes. However, genes known to be regulated by CpG DNA were dramatically up-regulated, as were genes involved in DNA sensing by DIA, Pol-III and AIM2. Toll-like receptor 9 deletion significantly prolonged the inflammatory response induced by NTHi in the ME and delayed bacterial clearance. The results suggest that DNA sensing via TLR9 plays a role in OM pathogenesis and recovery. Alternative forms of DNA sensing may also contribute to OM.

Challenges in reducing the burden of otitis media disease: an ENT perspective on improving management and prospects for prevention

Acute otitis media (AOM) is a major public health concern. This frequent disease of childhood is a leading cause of physician visits, a major component of paediatric healthcare burden, and a key contributor to antibiotic resistance. An international expert group comprising mainly ear, nose, and throat physicians met in June 2008 to discuss the optimal management of AOM, particularly with regards to unmet needs in diagnosis and management. Current guidelines do not help identify which patients are most at risk for severe or complicated AOM. Diagnosis of AOM is also complicated by a lack of correlation between clinical signs and symptoms and responsible pathogens. Consequently, treatment of AOM is not always appropriate, and the long-term overuse of antibiotics in AOM reduces the effectiveness of treatment and places children at risk for drug-resistant infections. There is a need for educational and research initiatives to improve diagnostic accuracy and management of AOM. Because there is currently no ideal treatment, vaccination is an attractive additional approach for managing AOM and reducing its burden.

The toll-Like receptor adaptor TRIF contributes to otitis media pathogenesis and recovery

Background

Toll-like receptor (TLR) signalling is crucial for innate immune responses to infection. The involvement of TLRs in otitis media (OM), the most prevalent childhood disease in developed countries, has been implicated by studies in middle ear cell lines, by association studies of TLR-related gene polymorphisms, and by altered OM in mice bearing mutations in TLR genes. Activated TLRs signal via two alternative intracellular signaling molecules with differing effects; MyD88 (Myeloid differentiation primary response gene 88) inducing primarily interleukin expression and TRIF (Tir-domain-containing adaptor inducing interferon β) mediating type I interferon (IFN) expression. We tested the hypothesis that TRIF and type I IFN signaling play a role in OM, using a murine model of OM induced by non-typeable Haemophilus influenzae (NTHi). The ME inflammatory response to NTHi was examined in wild-type (WT) and TRIF-/- mice by qPCR, gene microarray, histopathology and bacterial culture.

Results

Expression of TRIF mRNA was only modesty enhanced during OM, but both type I IFN signalling genes and type I IFN-inducible genes were significantly up-regulated in WT mice. TRIF-deficient mice showed reduced but more persistent mucosal hyperplasia and less leukocyte infiltration into the ME in response to NTHi infection than did WT animals. Viable bacteria could be cultured from MEs of TRIF-/- mice for much longer in the course of disease than was the case for middle ears of WT mice.

Conclusion

Our results demonstrate that activation of TRIF/type I IFN responses is important in both the pathogenesis and resolution of NTHi-induced OM.

TLR4-mediated induction of TLR2 signaling is critical in the pathogenesis and resolution of otitis media

Otitis media is the most prevalent childhood disease in developed countries. The involvement of Toll-like receptors (TLRs) in otitis media pathophysiology has been implicated by studies in cell lines and association studies of TLR gene polymorphisms. However, precise functions of TLRs in the etiology of otitis media in vivo have not been examined. We investigated the inflammatory response to nontypeable Haemophilus influenzae using a model of otitis media in wild-type, TLR2(- /-) and TLR4(-/ -) mice by gene microarray, qPCR, immunohistochemistry, Western blot analysis and histopathology. Toll-like receptor-2(- /-) and TLR4(- /-) mice exhibited a more profound, persistent inflammation with impaired bacterial clearance compared to controls. While wild-type mice induced tumor necrosis factor-a (TNF) after non-typeable H. influenzae challenge, TLR2(-/-) and TLR4(-/-) mice lack TNF induction in the early phase of otitis media. Moreover, lack of TLR2 resulted in a late increase in IL-10 expression and prolonged failure to clear bacteria. Toll-like receptor-4(-/- ) mice showed impaired early bacterial clearance and loss of TLR2 induction in early otitis media. Our results demonstrate that both TLR2 and TLR4 signalling are critical to the regulation of infection in non-typeable H. influenzae-induced otitis media. Toll-like receptor-4 signalling appears to induce TLR2 expression, and TLR2 activation is critical for bacterial clearance and timely resolution of otitis media.