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Moraxella catarrhalis is a gram negative bacterium and a leading causative agent of otitis media (OM) in children. Recent reports have provided strong evidence for the presence of high levels of matrix metalloproteinase (MMPs) in effusion fluids from children suffering with OM, however, the precise mechanisms by which MMPs are generated are currently unknown. We hypothesized that MMPs are secreted from macrophages in the presence of M. catarrhalis lipooligosaccharide (LOS). In this report, we demonstrate that in vitro stimulation of murine macrophage RAW 264.7 cells with LOS leads to secretion of MMP-9 as determined by ELISA and zymogram assays. We have also shown that inhibition of ERK1/2 and p38 kinase completely blocked LOS induced MMP-9 production. In contrast, inhibition of JNK1/2 by the specific inhibitor SP600125 actually increased the level of expression and production of MMP-9 at both mRNA and protein levels, respectively by almost five fold. This latter result was confirmed by knocking down JNK1/2 using siRNA. Similar results have been observed in murine bone marrow derived macrophages in vitro. In contrast to and in parallel with the LOS-induced increased levels of MMP-9 in the presence of SP600125, we found a corresponding dose-dependent inhibition of TIMP-1 (tissue inhibitor of matrix metalloproteinase-1) secretion. Results of subsequent in vitro studies provided evidence that when JNK1/2 was inhibited prior to stimulation with LOS, it significantly increased both the extent of macrophage cell migration and invasion compared to control cells or cells treated with LOS alone. The results of these studies contribute to an increased understanding of the underlying pathophysiology of OM with effusion in children.

Moraxella catarrhalis is a gram negative bacterium and a leading causative agent of otitis media (OM) in children. Several recent reports have provided strong evidence for an association between toll like receptors and OM. It has been found that both Streptococcus pneumoniae and nontypeable Haemophilus influenzae activate host protective immune responses through toll like receptors (TLRs), however, the precise mechanism by which Moraxella catarrhalis initiates the host immune response is currently unknown. In this report, using murine macrophages generated from a series of knock-out mice, we have demonstrated that M. catarrhalis lipooligosaccharide (LOS) and either heat killed or live bacteria are recognized by one or more TLRs. LOS activates the host immune response through a membrane bound CD14-TLR4 complex, while both heat killed and live M.cat require recognition by multiple toll like receptors such as TLR2, TLR4 and TLR9 without the requirement of CD14. We have also shown that M.cat stimuli are capable of triggering the host innate immune response by both MyD88- and TRIF- dependent signaling pathways. We further showed that M.cat induced activation of mitogen activated protein kinase (MAPK) is essential in order to achieve optimal secretion of pro-inflammatory cytokine TNF-α. We finally showed that TLR4 mutant C3H/HeJ mice produce significantly lower levels of pro-inflammatory cytokines TNF-α and IL-6 in vivo, An increased bacterial loads at 12 and 24 hours (P

There are no licensed vaccines available against Moraxella catarrhalis, a significant human respiratory pathogen. Lipooligosaccharide (LOS) based conjugate vaccines derived from individual serotype M. catarrhalis only showed partial protection coverage. A vaccine combining LOS conjugates of two or three serotypes might provide a broader protection.Mice were immunized intranasally with the combined conjugates consisting of LOS from serotype A and B or serotype A, B, and C followed by challenge with different M. catarrhalis strains of three serotypes. Mouse lungs, nasal washes, and sera were collected after each challenge for bacterial counts, histological evaluation, cytokine profiles, antibody level and binding activity determinations.Intranasal administration of the combined LOS conjugates not only enhanced pulmonary bacterial clearance of all three serotypes of M. catarrhalis strains in vaccinated mice, but also elevated serotype-specific anti-LOS immunoglobulin (Ig)A and IgG titers in nasal wash and serum respectively. Mice vaccinated with the combined LOS conjugates also showed increased interferon (IFN)-γ, interleukin (IL)-12, and IL-4 in the lungs after challenges. Compared to the control group, mice immunized with the combined LOS conjugates also showed reduced lung inflammation after M. catarrhalis infections. The hyperimmune sera induced by the combined conjugates exhibited a broad cross-reactivity toward all three serotypes of M. catarrhalis under transmission electron microscopy.The combined vaccine of serotype A and B LOS conjugates provides protection against most M. catarrhalis strains by eliciting humoral and cellular immune responses.