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PubMed1998

Antibodies specific to outer membrane antigens of Moraxella catarrhalis in sera and middle ear effusions from children with otitis media with effusion.

OBJECTIVE: Recent studies have shown that bacterial DNA is present in a significant percentage of middle ear effusions, suggesting that persistent bacterial infection may be more important in pathogenesis and recurrence of otitis media with effusion (OME) than previously considered. Although Moraxella (M.) catarrhalis is one of the most common pathogens of otitis media, relatively little is known about immune response to the organism. The objective of the present study is to investigate how systemic and local immune activities against M. catarrhalis may be associated with severity of OME. METHODS: The antibody levels specific to outer membrane antigens of M. catarrhalis in sera and middle ear effusions (MEEs) from 59 children with OME were measured by enzyme-linked immunosorbent assay. Their ages ranged from 1 to 12 years with a median 5.0 years. The children were followed 1 year prospectively and classified into two groups with or without recurrent/persistent OME according to severity of OME during the follow-up 1 year. RESULTS: Serum IgG, IgM, and IgA antibodies specific to outer membrane antigens of M. catarrhalis were detected in all samples and the median levels were 35, 0.93, and 1.2 microg/ml respectively. The MEE IgG, IgM, IgA, and secretory IgA antibodies were detected in over 95% samples tested and the median levels were 371, 158, 20, and 50 ng/mg total protein respectively. A comparison between acute and subacute/chronic phases revealed that the median levels of MEE IgG and IgM antibodies were higher at the acute phase (692 vs. 340, P = 0.06; 35 vs. 10, P = 0.02, respectively); while the MEE secretory IgA antibody level was increased at the subacute/chronic phase (74 vs. 35, P = 0.02). Either serum or MEE IgG antibody level was significantly lower in recurrent/persistent OME group than that in nonrecurrent/non-persistent OME group (13 vs. 43 ,microg/ml, P = 0.009; 238 vs. 577 ng/mg protein, P = 0.006, respectively). CONCLUSIONS: These data provide additional information on the immunologic aspects of children with OME. Decreased serum and MEE IgG antibody levels specific to outer membrane antigens of M. catarrhalis may lead to failure to eliminate this organism, resulting in persistent and/or recurrent appearance of MEE.

Antibodies, Bacterial↗
PubMed2000

Simultaneous detection of gfp-marked Moraxella sp. G21r and lux-marked Ralstonia eutrophas H850Lr using most-probable-number method.

The green fluorescent protein encoded by gfp gene and the luminescent protein encoded by luxAB genes were used as markers to detect p-nitrophenol (PNP)-degrading Moraxella sp. G21r and polychlorinated biphenyl (PCB)-degrading Ralstonia eutrophas H850Lr cells, respectively, in mixed liquid cultures and in soil samples using a most-probable-number (MPN) assay. Population estimates for both gfp-marked G21r and lux-marked H850Lr by using MPN assays were similar to viable colony counts. The MPN assay with microtiter plates permitted the simultaneous detection of fluorescent and luminescent bacteria in soil samples faster than conventional plate counting.

Bacteriological Techniques↗
PubMed1998

Formation of amino acid (L-leucine, L-phenylalanine) derived volatile flavour compounds by Moraxella phenylpyruvica and Staphylococcus xylosus in cured meat model systems.

A bacterial strain isolated from Danish immersion curing brine, Moraxella phenylpyruvica 0100, and a commercial meat starter culture, Staphylococcus xylosus DD34, were tested for their ability to form characteristic volatile compounds in minimal medium with the added amino acid L-leucine or L-phenylalanine under different environmental conditions (pH 5.5 and 6.0; 0 and 210 ppm nitrate; pre-incubation with and without agitation) and compared with respect to their ability to form volatile compounds in cured meat extracts and vacuum-packed cured meat cuts. The characteristic cured meat aroma precursors/compounds 3-methylbutanal and 3-methylbutanol were found to be formed in cured meat extracts and vacuum-packed cured meat cuts inoculated with M. phenylpyruvica. These volatiles are most probably formed by metabolic conversion of the amino acid L-leucine by M. phenylpyruvica, as they were also produced in minimal media with added L-leucine inoculated with this organism. The characteristic L-phenylalanine derived compound, benzaldehyde, formed by M. phenylpyruvica in minimal medium in the presence of nitrate (210 ppm), was not produced in any noticeable amount in cured meat extracts or vacuum-packed cured meat inoculated with M. phenylpyruvica. In contrast, benzacetaldehyde, which has been described as a possible metabolic product of the microbial conversion of L-phenylalanine, was found to be a characteristic volatile compound formed in cured meat extracts and vacuum-packed cured meat inoculated with M. phenylpyruvica, indicating an alternative metabolic pathway for L-phenylalanine by this organism in a cured meat environment. Even though S. xylosus was able to form volatile compounds characteristic of cured meats (3-methylbutanal, 3-methylbutanol) in minimal media with added L-leucine, this bacterial strain seemed not to be able to produce these characteristic volatiles in the studied cured meat systems. The present data imply that M. phenylpyruvica, in particular, is a potential meat starter for ensuring superior flavour development in cured meat.

Aldehydes↗
PubMed1997

Middle ear mucin glycoprotein: purification and interaction with nontypable Haemophilus influenzae and Moraxella catarrhalis.

Nontypable Haemophilus influenzae and Moraxella catarrhalis are important pathogens in children and adults. The mechanisms of their adherence to the epithelial cell surface and colonization are not clear. For the pathogen to adhere to the epithelial cell, it must first attach to and penetrate the mucus barrier. Mucin glycoproteins of the mucus layer generally are thought to be involved in bacterial attachment. To understand the precise mechanisms of middle ear mucin-bacterial interactions, we used an overlay binding assay with a highly purified middle ear mucin and outer membrane proteins of both nontypable H. influenzae and M. catarrhalis. Outer membrane proteins P2 and P5 were identified as the major components that medicate the binding between nontypable H. influenzae and human middle ear mucin. Moreover, the 57 kDa protein, CD, of the outer membrane protein of M. catarrhalis was found to be the only protein binding human middle ear mucin. Finally, it appears that a protein-oligosaccharide interaction is responsible for binding because asialo-mucin does not bind to either of the bacteria. Knowledge of the specific bacterial-mucin interaction may provide an understanding of the bacterial-epithelial cell colonization. Conversely, comprehension of this interaction between bacteria and purified mucin may be a strategy to prevent colonization of potential pathogens that cause otitis media and sinusitis in children.

Amino Acids↗
PubMed2000

Vaccines for Moraxella catarrhalis.

Vaccine development for Moraxella catarrhalis is in the antigen identification stage. M. catarrhalis does not appear to synthesize secreted antigens such as exotoxins, nor does it appear to possess a carbohydrate capsule. Modified forms of these antigens are usually good vaccine components. There is some interest in whole bacterial cells and membrane fractions, but the search has largely focused on purified outer surface antigens. All of the present antigens have been selected based on the response seen in animals, although the antibody response seen in people exposed to the bacterium provides some guidance. The antibody response provides information related to the cross-strain preservation of epitopes and whether they are surface exposed. Antigens that elicit antibodies that have complement dependent bactericidal capacity, opsonophagocytic activity or interfere with one of the antigen's known functions such as adhesion or nutrient acquisition are particularly valued. In addition to examining the antibody response, some antigens have been evaluated in a murine pulmonary clearance model. Using these assays and model, several vaccine candidates have been identified. The antigens may be roughly classified by the function they serve the bacterium. One set appears to promote adhesion to host tissues and includes the hemagglutinins, ubiquitous surface protein A1 (UspA1), and possibly the CD protein. A second set is involved in nutrient acquisition. This set includes the lactoferrin binding protein A (LbpA) and lactoferrin binding protein B (LbpB), the transferrin binding protein A (TbpA) and transferrin binding protein B (TbpB), the CD and E porins, and the Catarrhalis outer membrane protein B (CopB). A third set is comprised of antigens involved in virulence and it includes lipooligosaccharide (LOS) and the ubiquitous surface protein A2 (UspA2). Antigens of unknown function, such as the 200K protein, may also be vaccine candidates. The antigens that are most suitable will be determined in clinical studies that are only beginning now.

Adhesins, Bacterial↗
PubMed2002

The outer membrane proteins UspA1 and UspA2 of Moraxella catarrhalis are highly conserved in nasopharyngeal isolates from young children.

UspA1 and UspA2 of Moraxella catarrhalis are vaccine candidates. The aims of this study were to determine: (1) the frequencies of occurrence and (2) the degrees of conservation of two surface-exposed epitopes of the uspA1 and uspA2 genes and their respective gene products in 108 nasopharyngeal isolates from young children. The uspA1 and uspA2 genes were detected in 107 (99%) and 108 (100%) isolates, respectively. Twenty-three of 108 uspA2 genes (21%) were identified as the variant gene uspA2H. One-hundred and five isolates (97%) expressed the mAb17C7-reactive epitope shared by UspA1 and UspA2, and 103 isolates (95%) reacted with the UspA1-specific mAb24B5. The only isolate which lacked a uspA1 gene demonstrated reduced adherence to HEp-2 cells and complement sensitivity. The data indicate that both uspA genes and the expression of at least two surface-exposed epitopes are virtually ubiquitous in isolates from a population at risk for otitis media. A vaccine capable of inducing a bactericidal immune response against the mAb17C7- and/or mAb24B5-reactive epitopes appears promising.

Antibodies, Monoclonal↗
PubMed2002

A new intra-NALT route elicits mucosal and systemic immunity against Moraxella catarrhalis in a mouse challenge model.

Mucosally administered antigens are often poorly immunogenic due to the difficulty of transporting antigens through the mucosal epithelium. We investigated a new route of intranasal-associated lymphoid tissue (intra-NALT) administration of antigens to circumvent the antigen transportation barrier. A comparative study was carried out on mice administered with killed whole cells of Moraxella catarrhalis strain 25238 plus cholera toxin (CT) by intra-NALT injection and nasal inoculation. Both routes induced significant elevations of several isotype antibodies against strain 25238 in saliva, lung lavage, and serum as measured by an enzyme-linked immunosorbent assay (ELISA). Most of these antibodies were paralleled by the numbers of their corresponding antibody forming cells in mucosal or systemic lymphoid tissues. However, intra-NALT injection elicited higher levels of immunoglobulin (Ig) A and IgG in saliva, IgA and IgG in lung lavage, and IgG and IgM in sera than nasal inoculation (P<or=0.05). In addition, both routes generated significant reductions of bacteria in lungs following an aerosol challenge with strain 25238 in a mouse model of pulmonary clearance. Once again, intra-NALT route showed better bacterial clearance in mouse lungs than nasal inoculation (P<0.01). These results demonstrate that intra-NALT administration of antigens is a convenient and effective route for mucosal immunization that elicits improved mucosal and systemic immunity. This new route can be used as a model to study mucosal antigens or vaccine candidates for antigen activation and interaction with the NALT that is one of major inductive sites for common mucosal immune system.

Administration, Intranasal↗
PubMed2003

Total genome polymorphism and low frequency of intra-genomic variation in the uspA1 and uspA2 genes of Moraxella catarrhalis in otitis prone and non-prone children up to 2 years of age. Consequences for vaccine design?

Intra-genomic variation in the uspA1 and uspA2 genes of Moraxella catarrhalis was studied using pulsed field gel electrophoresis (PFGE) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. From a set of 91 M. catarrhalis isolates, 19 pairs of PFGE identical isolates were found. Five pairs originated from otitis non-prone children, 11 pairs from otitis prone children and for 3 pairs, one of the pair originated from an otitis prone and the other from an otitis non-prone child. No particular M. catarrhalis isolate was associated with either the otitis prone or non-prone children. One of these 19 pairs of isolates was found to exhibit both uspA1 and uspA2 intra-genomic variation, whilst another pair exhibited uspA2 intra-genomic variation only. Sequence data obtained from these variants showed that PCR-RFLP pattern differences reflected actual changes in predicted amino acid composition and that minor amino acid changes in a 23 base pair "NINNIY" repeat region (a conserved UspA1 and UspA2 binding site for the neutralising antibody mAb17C7) occurred. Variation in the uspA2 5' non-coding "AGAT" repeat region was also observed. These results may have implications for future M. catarrhalis vaccines comprising UspA1 or UspA2 components.

Amino Acid Sequence↗
PubMed1999

Evaluation of a 74-kDa transferrin-binding protein from Moraxella (Branhamella) catarrhalis as a vaccine candidate.

An outer membrane protein from Moraxella catarrhalis with a mass of 74-kDa was isolated and evaluated as a vaccine candidate. The 74-kDa protein binds transferrin, and appears to be related to the other proteins from the organism that are reported to bind transferrin. The 74-kDa protein possessed conserved epitopes exposed on the bacterial surface. This is based on the reactivity with whole bacterial cells as well as complement dependent bactericidal activity of sera from mice immunized with the isolated proteins from the O35E and TTA24 isolates. However, there was divergence in the degree of antibody cross-reactivity with the protein from one strain to another. This serotypic divergence was reflected in both the complement-dependent bactericidal activities of the antibodies elicited in mice and the capacity of immune mice to clear the bacteria in a murine pulmonary model. Antibodies affinity purified from human plasma lacked bactericidal activity even though they were reactive with all the tested isolates. The 74-kDa protein appears to be a good vaccine candidate, but more studies are needed to understand its antigenic variability and whether antibodies toward it are protective.

Amino Acid Sequence↗
PubMed1999

Investigation of mucosal immunisation in pulmonary clearance of Moraxella (Branhamella) catarrhalis.

Moraxella (Branhamella) catarrhalis is a common cause of otitis media in children and respiratory infection in adults with chronic obstructive pulmonary disease. To identify immune responses that may facilitate the development of a mucosal vaccine, a mouse model to study pulmonary responses was established. Regimes involving intra-Peyer's patch, intratracheal and intranasal routes of immunisation with killed M. catarrhalis were investigated. A mucosal immunisation regime of a primary intra-Peyer's patch immunisation with an intratracheal boost resulted in significantly enhanced pulmonary clearance of bacteria compared to controls following an intratracheal challenge with live bacteria. Additional intratracheal boosts did not induce further enhancement of clearance. Intra-Peyer's patch immunisation alone, intratracheal and intranasal immunisations did not induce enhanced clearance. The levels of specific IgG and IgA in serum and bronchoalveolar lavage fluid correlated with pulmonary clearance. The present study showed that mucosal immunisation induced enhanced pulmonary clearance of M. catarrhalis following live bacterial challenge. This mucosal immunisation model has demonstrated that a mucosal vaccine, particularly an oral vaccine, would be feasible.

Animals↗
PubMed1999

An aerosol challenge mouse model for Moraxella catarrhalis.

A simple, reproducible, and non-invasive mouse pulmonary clearance model for Moraxella catarrhalis via aerosol challenge was established. All of eight tested strains could be inoculated into mice at more than 10(5) colony-forming units (CFU)/lung with a challenge concentration of 1x10(9)-6x10(9) CFU/ml in a nebulizer. The number of bacteria retained at 6 h postchallenge was more than 10(4) CFU/lung while at 24 h postchallenge, approximate 10(3) CFU/ml or less remained in the lungs. A maximum of 100 mice could be challenged per aerosol exposure. The number of bacteria inoculated in the lungs could be adjusted by the bacterial challenge concentration, the exposure time, and the negative pressure. Lung tissue sections revealed that bacteria were evenly distributed in the lungs. Passive immunization significantly enhanced pulmonary clearance of the homologous strain in this model. These data indicate that this model will be useful for evaluating M. catarrhalis vaccine candidates and studying roles of immunity against M. catarrhalis.

Aerosols↗
PubMed2001

Immunoblot analysis of cyanogen bromide-cleaved Moraxella bovis pilin reveals presence of shared antigenic determinants on pili from heterologous strains.

Moraxella bovis pilus proteins, collected and purified from four strains of M. bovis, were cleaved with cyanogen bromide. Two major fragments were produced. Antisera were produced in rabbits to the pilin protein fragments and to whole uncleaved pili from these strains. Immunoblots of whole and cyanogen bromide-cleaved pilin were reacted with the homologous and heterologous antisera to whole pili and cleaved pilin. Antisera to whole pili reacted strongly with homologous pilin. Weaker and inconsistent reactions were detected with heterologous pilin. Antisera produced to cyanogen bromide-cleaved pilin proteins reacted strongly with homologous and heterologous pilin fragments and uncleaved pilin proteins. These findings demonstrate the presence of conserved antigenic determinants on pili from heterologous strains that are non-immunogenic in the intact pilus but are immunogenic after treatment with cyanogen bromide. Cyanogen bromide-treated pilus preparation might have potential as a vaccine because antibodies are induced against heterologous strains of M. bovis, whether these cross-reactive antibodies are protective remains to be determined.

Animals↗
PubMed2003

Whole-bacterial cell enzyme-linked immunosorbent assay for cell-bound Moraxella bovis pili.

Infectious bovine keratoconjunctivitis (IBK), caused by Moraxella bovis, is a disease of major importance in cattle industry. M. bovis has several virulence factors among which pili are crucial antigen for the protective capacity of vaccines against this disease. The production of vaccines against IBK therefore requires a reliable technique for cellular piliation level assessment on cells to be included as vaccine components. In this study we describe a specific whole-bacterial cell enzyme-linked immunosorbent assay (bact-ELISA) capable of detecting pili antigen on M. bovis cell surface. A sequential competitive bact-ELISA was developed using highly piliated M. bovis cells as antigen. Samples to be analyzed were allowed to react with anti-pilus serum prior to incubation in wells coated with piliated cells of M. bovis. This assay proved useful for the rapid, sensitive and reproducible evaluation of piliation on M. bovis cells, and represents an important tool for cellular piliation monitoring daburing M. bovis cells production in stirred bioreactors.

Animals↗
PubMed2003

An RTX operon in hemolytic Moraxella bovis is absent from nonhemolytic strains.

Pathogenic isolates of Moraxella bovis express a calcium-dependent transmembrane pore forming cytotoxin that is an RTX toxin encoded by mbxA. The DNA flanking mbxA was cloned and sequenced to determine if M. bovis contained a classical RTX operon. Open reading frames (ORFs) with deduced amino acid sequence homology to putative activation (RTX C) and transport (RTX B and D) proteins were identified and have been designated MbxC, MbxB, and MbxD, respectively. Thus, hemolytic M. bovis contains a typical RTX operon comprised of four genes arranged (5'-3') mbxCABD. In addition, the deduced amino acid sequences of DNA flanking mbxCABD revealed ORFs with amino acid sequence similarity to transposases (5'). At the 3' end of the mbx gene cluster, an ORF with homology to bacterial tolC genes was identified. Thus, as with the cya RTX operon of Bordetella pertussis, M. bovis appears to have a secretion accessory protein linked to RTX genes. Analysis of genomic DNA isolated from 5 nonhemolytic M. bovis strains by PCR and Southern blotting revealed the absence of mbxCABD. These strains did, however, amplify with primers specific for the 5' region flanking mbxC. M. bovis harbors a classical RTX operon that is absent in nonhemolytic strains.

Amino Acid Sequence↗
PubMed1998

Antimicrobial susceptibility of Moraxella bovis.

The antimicrobial susceptibility of 55 isolates of Moraxella bovis to seven antibiotics was evaluated by broth microdilution procedures. The isolates had an MIC90 of < or = 1 mg/l to erythromycin, ceftiofur, and ampicillin; 4 mg/l to tilmicosin; 16 mg/l to tylosin and gentamicin; and had MIC90s of > or = 32 mg/l for oxytetracycline. The modal MIC values for these antibiotics were as follows: ampicillin, < 0.25 mg/l; ceftiofur, < or = 0.125 mg/l; tilmicosin, 2 mg/l; tylosin, 8 mg/l; erythromycin 1 mg/l; oxytetracycline, < or = 0.5 mg/l; and gentamicin, < or = 0.5 mg/l. This in vitro data showed most antibiotics have low MICs that are suggestive of clinical efficacy.

Ampicillin↗
PubMed1999

Analyses of lipopolysaccharides, outer membrane proteins and DNA fingerprints reveal intraspecies diversity in Moraxella bovis isolated in Argentina.

Intra-specific diversity within Moraxella bovis was investigated analysing DNA fingerprints, outer membrane proteins (OMP) and lipopolysaccharides (LPS) profiles. Three collection strains and 57 isolates of M. bovis, collected during 3 years from cattle with infectious bovine keratoconjunctivitis (IBK) symptoms, from diverse geographical locations of Argentina, were examined. The LPS and OMP profiles were studied through SDS-PAGE analysis and genotype was determined by PCR-DNA fingerprinting. Genotyping identified five DNA types while analysis of LPS and OMP profiles identified three rough LPS types and three OMP types among the 60 isolates of M. bovis including the three collection strains. None of the three methods employed to assess diversity was discriminating when used alone because the degree of heterogeneity in each group of surface structures was limited, but when data of each typing method were combined, 15 distinct subgroups were determined. This subgrouping was clearly able to differentiate isolates of the same genotype. These typing methods appear to be useful to assess different aspects of the disease such as the diversity within a population of M. bovis associated to epidemic conditions, track the causal agent in an outbreak of the disease, monitoring vaccination programs and studies on virulence.

Animals↗
PubMed2001

Method for reducing endotoxin in Moraxella catarrhalis UspA2 protein preparations.

The UspA2 protein from the bacterium Moraxella catarrhalis is a potential vaccine candidate for preventing human diseases caused by this organism. Before a vaccine can be administered parentally, the level of endotoxin must be reduced as much as possible. However, in this case the endotoxin was very tightly complexed with the UspA2 protein and could not be dissociated with Triton X-100. It was found that it dissociated from the protein with the zwitterionic detergents Zwittergent 3-12 and Zwittergent 3-14. The endotoxin could then be separated from the protein by either ion-exchange or gel filtration chromatography. Using the limulus amoebocyte lysate assay for quantitation, the endotoxin was reduced approximately 20,000-fold. The removal of residual endotoxin from UspA2 preparations had no detrimental effect on the immunological properties of the protein. Mouse antisera raised against UspA2 prior to, and following endotoxin reduction exhibited comparable antibody and bactericidal titers against the tested strains. Further, mice immunized with both preparations, followed by pulmonary challenge with either a homologous or a heterologous isolate, exhibited comparable levels of clearance.

Animals↗
PubMed1997

Experimental otitis media induced by nonviable Moraxella catarrhalis in the guinea pig model.

Moraxella catarrhalis is a normal resident of the human nasopharyngeal flora, but it is also isolated from middle ear fluid of acute otitis media and otitis media with effusion patients. To determine whether M. catarrhalis has direct pathogenicity in the middle ear, heat-killed M. catarrhalis was inoculated into the middle ear bullae of guinea pigs, and the inflammatory response was investigated. Middle ear mucosal histopathology observed in M. catarrhalis-inoculated ears included subepithelial edema, capillary dilatation, thickening of lamina propria mucosa, inflammatory cell and erythrocyte infiltration into the lamina propria mucosa. Inflammatory cell numbers, lysozyme and myeloperoxidase concentrations in the middle ear washing suspensions of M. catarrhalis-inoculated ears were significantly higher than control ears throughout the experiment. Therefore, nonviable M. catarrhalis induced middle ear inflammation and mucoperiosteal histopathology, which might be caused by direct injury of the nonviable bacteria (e.g. lipooligosaccharide or outer membrane proteins) and metabolic products of inflammatory cells.

Animals↗