SP-A and SP-D expression has been localized to the microvillar epithelial cells in the pig eustachian tube (Paananen et?al., 2001) BRD7-IN-1 free base and may contribute to the prevention of bacterial ascension to the middle ear. responses. Recent improvements in otopathogen acknowledgement via microbial pattern acknowledgement receptors and elucidation of complex signaling cascades have improved understanding of the coordination and regulation of the middle ear mucosal response. These improvements support vaccine development aiming to reduce the risk of otitis media in children. (NTHi), and are normal commensal flora and the most common bacterial microbes detected in MEF from children with AOM (Ruohola et?al., 2006). Group A is also reported as an otopathogen (Segal et?al., 2005) and is reported as a significant otopathogen in some population groups (Ashhurst-Smith et?al., 2012). Mucosal immune responses within the middle ear and eustachian tube may be overwhelmed by the extent of early bacterial colonization and result in unresolved inflammation within the middle ear. For example, the nasopharyngeal carriage rate for NTHi is usually higher in children with OME compared to healthy children. Children who experience dense bacterial colonization of the nasopharynx early in life are at significantly increased risk of early OM development and more severe disease, including tympanic membrane perforation, and are at very high risk of suppurative BRD7-IN-1 free base complications of OM (Leach et?al., 1994, Smith-Vaughan et?al., 2006). Effective mucosal immune responses within the middle ear may reduce the impact of bacterial weight and/or virulence of the otopathogen. For example, single gene deletion of (streptococcal lipoprotein rotamase A) or in combination with gene (putative proteinase maturation protein A) significantly reduced bacterial weight CD3G and virulence in the nasopharynx and middle ear in a murine experimental AOM model (Stol et?al., 2009). The additive effects of deletion of these genes on bacterial colonization and virulence provides further challenge for vaccine development. The effectiveness of the endogenous mucosal immune responses to AOM, for the children of developed countries at low risk of severe BRD7-IN-1 free base OM (i.e., low rates of suppurative complications of OM) is usually indicated by the high rate of self-resolving OM episodes (80%) (Glasziou et?al., 2004), in turn implying the success of the host mucosal immune responses. For healthy children, middle ear effusion normally resolves within 7?days in 40% of cases, and in 75C90% of cases resolution occurs within 4?weeks (Mandel et?al., 2008). Failure of the middle ear contamination to self-resolve can result in ongoing persistence of bacterial OM, as either COME or recurrent AOM. Persistent bacterial infection of the adenoids has been the focus of recent microbial studies that demonstrated that can invade and survive within adenoidal cells (Forsgren et?al., 1994). Furthermore, intracellular localization of bacteria within the middle ear mucosal cells has now been confirmed and the bacterial species subsequently recognized (Coates et?al., 2008, Thornton et?al., 2011). Multi-species bacterial biofilms made up of these species have been visualized on the middle ear mucosa and characterized using confocal microscopy. The presence of multiple bacterial species, within the same middle ear mucosal samples, could provide additional protection to each microbe, protecting them from host innate and acquired immune defenses (Armbruster et?al., 2010). Biofilm formation is known to significantly increase bacterial protection from antibiotic treatment (Slinger et?al., 2006) and the host immune system responses. Biofilm formation has also been observed in both the nasopharynx and middle ear in the chinchilla model after initial intranasal inoculation with influenza A followed by a week later (Hoa et?al., 2009). Inoculation with a variety of bacterial species, in combination with prior viral contamination, increases the incidence and severity of OM (in a murine model) (Krishnamurthy et?al., 2009). Biofilm formation occurs rapidly and the presence of bacteria, not successfully cleared by local or systemic immune responses or antibiotic therapy, poses a challenge for vaccine efficacy. The presence of multiple otopathogens within biofilms also increases the rate of horizontal gene transfer between microbes (Madsen et?al., 2012), which may further increase the challenge for the host mucosal immune response and targeting of successful vaccine development for OM. Importantly, bacterial OM, including biofilm formation, is usually most frequently the result of contamination by commensal bacteria. Commensal microbes are well adapted to minimize recognition by the hosts immune system through molecular mimicry or modulation of host cell innate immune regulation. Recent evidence shows that existing biofilms can be eradicated, in?vitro, using an antibody directed against PilA, suggesting that it is possible to develop vaccine strategies that may both prevent and treat OM (Novotny et?al., 2012) through activation of the host immune system. Immunoregulation in the Middle Ear Mucosal responses to bacterial and viral colonization within the eustachian tube and middle ear include a quick inflammatory response that effectively seals the eustachian.