Antigenic Structure of Outer Membrane Protein E of
            <i>Moraxella catarrhalis</i>
            and Construction and Characterization of Mutants

Murphy, Timothy F.; Brauer, Aimee L.; Yuskiw, Norine; Hiltke, Thomas J.

doi:10.1128/iai.68.11.6250-6256.2000

Cited by 33 publications

(24 citation statements)

References 33 publications

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“…The identity of the gene product(s) responsible for this phenotype has been the subject of much research interest over the past decade, and it was first suggested by Verduin et al (54) that a proteinaceous substance on the surface of M. catarrhalis was responsible for complement resistance. Initial studies attempting to identify either the proposed resistance factor or the mechanism of resistance utilized serum-resistant and serum-sensitive clinical isolates (8,54,55), and only in the past few years have isogenic parent-mutant pairs been tested (3,14,22,36,60). These studies indicated that there were several mutations affecting The results of the present study showed that UspA2 is directly involved in the expression of serum resistance by some strains of M. catarrhalis.…”

Section: Discussionmentioning

confidence: 81%

The UspA2 Protein of Moraxella catarrhalis Is Directly Involved in the Expression of Serum Resistance

et al. 2005

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Many strains of Moraxella catarrhalis are resistant to the bactericidal activity of normal human serum. Previous studies have shown that mutations involving the insertion of an antibiotic resistance cartridge into the M. catarrhalis uspA2 gene resulted in the conversion of a serum-resistant strain to a serum-sensitive phenotype. In the present study, the deletion of the entire uspA2 gene from the serum-resistant M. catarrhalis strain O35E resulted in a serum-sensitive phenotype and did not affect either the rate of growth or the lipooligosaccharide expression profile of this mutant. Inactivation of the classical complement pathway in normal human serum with Mg 2؉ and EGTA resulted in the survival of this uspA2 mutant. In contrast, blocking of the alternative complement pathway did not protect this uspA2 mutant from complement-mediated killing. To determine whether the UspA2 protein is directly involved in serum resistance, transformation and allelic exchange were used to replace the uspA2 gene in the serum-resistant strain O35E with the uspA2 gene from the serum-sensitive M. catarrhalis strain MC317. The resultant O35E transformant exhibited a serum-sensitive phenotype. Similarly, when the uspA2 gene from the serum-resistant strain O35E was used to replace the uspA2 gene in the serum-sensitive strain MC317, the MC317 transformant acquired serum resistance. The use of hybrid O35E-MC317 uspA2 genes showed that the N-terminal half of the O35E protein contained a 102-aminoacid region that was involved in the expression of serum resistance. In addition, when the uspA2 genes from strains O35E and MC317 were cloned and expressed in Haemophilus influenzae DB117, only the O35E UspA2 protein caused a significant increase in the serum resistance of the H. influenzae recombinant strain. These results prove that the UspA2 protein is directly involved in the expression of serum resistance by certain M. catarrhalis strains.Moraxella catarrhalis has gone from being regarded as a relatively harmless commensal organism found in the human nasopharynx to a pathogen which can cause a significant amount of disease (27,35,47,53). In the upper respiratory tract, M. catarrhalis is an important cause of otitis media in infants and young children (27). This unencapsulated, gramnegative bacterium can also cause infectious exacerbations of chronic obstructive pulmonary disease (46,47) and is an infrequent cause of other diseases, including pneumonia and sinusitis (reviewed in reference 35).Virtually nothing is known about the virulence mechanisms used by M. catarrhalis to produce disease. The lack of a relevant animal model for otitis media caused by this organism (27) has precluded direct investigation of this process at the experimental level. Numerous M. catarrhalis gene products that could be involved in the colonization of the human nasopharynx by this organism or in its ability to spread into other anatomic niches in the human body have been identified (reviewed in references 27 and 53), and recent studies have highlighted additional ...

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Section: Discussionmentioning

confidence: 81%

The UspA2 Protein of Moraxella catarrhalis Is Directly Involved in the Expression of Serum Resistance

et al. 2005

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“…The CD outer membrane protein (33) has been shown to bind middle ear mucin in vitro (51), a function that could be involved in the colonization process or in the development of otitis media. The UspA1 protein has been shown to be an adhesin, at least in vitro (38), whereas both the UspA2 protein (38) and outer membrane protein E (50) have been implicated in serum resistance. Both UspA1 and UspA2, consistent with their functional activities, have been localized to the surface of M. catarrhalis, where they are accessible to antibodies (2,45).…”

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confidence: 99%

AhagMutant ofMoraxella catarrhalisStrain O35E Is Deficient in Hemagglutination, Autoagglutination, and Immunoglobulin D-Binding Activities

et al. 2002

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Moraxella (Branhamella) catarrhalis is an important cause of disease in both the upper and lower respiratory tracts (35,48). This unencapsulated gram-negative coccobacillus has been shown to express a number of different outer membrane proteins on its cell surface, some of which are antigenically conserved (47, 49). At present, information about the M. catarrhalis gene products that are involved in the ability of this organism to colonize the mucosa of the nasopharynx and survive in this hostile environment is limited at best. Much effort has been expended recently on documenting the human immune response to selected M. catarrhalis surface-exposed proteins (6,12,25,53,65), providing evidence that these particular gene products are expressed in vivo during otitis media or infections of the bronchial tree. A few of these outer membrane proteins now have a function ascribed to them, mainly with respect to iron acquisition (7,9,10,15,42,43).In contrast, there is relatively little known about other surface proteins of M. catarrhalis that might be involved in the ability of this organism to colonize and survive in the nasopharynx (35). The CD outer membrane protein (33) has been shown to bind middle ear mucin in vitro (51), a function that could be involved in the colonization process or in the development of otitis media. The UspA1 protein has been shown to be an adhesin, at least in vitro (38), whereas both the UspA2 protein (38) and outer membrane protein E (50) have been implicated in serum resistance. Both UspA1 and UspA2, consistent with their functional activities, have been localized to the surface of M. catarrhalis, where they are accessible to antibodies (2, 45).Scott and colleagues (16, 17) correlated both hemagglutination activity and the expression of a 200-kDa protein by some M. catarrhalis isolates with the presence of a fibrillar surface array. In addition, Sasaki and colleagues reported that the 200-kDa protein expressed by M. catarrhalis was subject to phase variation in vitro (K. Sasaki, L. Myers, S. M. Loosmore, and M. H. Klein, Abstr. 99th Gen. Meet. Am. Soc. Microbiol., abstr. B/D-306, 1999) and determined the nucleotide sequence of the gene encoding this protein (54). In the present study, we used analysis of mutants to show that this protein, designated Hag (hemagglutinin), is involved not only in hemagglutination but also in autoagglutination and the binding of human immunoglobulin D (IgD) by M. catarrhalis strain O35E. In addition, we determined that the Hag protein, together with the UspA1 and UspA2 proteins (3), all form fibrillar projections on the M. catarrhalis cell surface.

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“…Seven MAbs which recognize epitopes on OMP E have been described previously (4,17). MAb 2E11 was developed from a fusion in which mice were immunized subcutaneously with 50 g of purified recombinant OMP E from M. catarrhalis strain ATCC 25240 (4) with incomplete Freund's adjuvant on days 0 and 14.…”

Section: Methodsmentioning

confidence: 99%

“…The protein is expressed in all strains of M. catarrhalis studied thus far (2,4,16). Three independent lines of experiments indicate that OMP E contains epitopes on the bacterial surface; these include adsorption studies with polyclonal antisera raised to whole bacterial cells (16), immunofluorescence microscopy with polyclonal antisera raised to purified OMP E (4), and flow cytometry with monoclonal antibodies (MAbs) (4,17).…”

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Conservation of Outer Membrane Protein E among Strains of Moraxella catarrhalis

et al. 2001

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Outer membrane protein E (OMP E) is a 50-kDa protein of Moraxella catarrhalis which has several features that suggest that the protein may be an effective vaccine antigen. To assess the conservation of OMP E among strains of M. catarrhalis, 22 isolates were studied with eight monoclonal antibodies which recognize epitopes on different regions of the protein. Eighteen of 22 strains were reactive with all eight antibodies. The sequences of ompE from 16 strains of M. catarrhalis were determined, including the 4 strains which were nonreactive with selected monoclonal antibodies. Analysis of sequences indicate a high degree of conservation among strains, with sequence differences clustered in limited regions of the gene. To assess the stability of ompE during colonization of the human respiratory tract, the sequences of ompE of isolates collected from patients colonized with the same strain for 3 to 9 months were determined. The sequences remained unchanged. These results indicate that OMP E is highly conserved among strains of M. catarrhalis, and preliminary studies indicate that the gene which encodes OMP E remains stable during colonization of the human respiratory tract.Moraxella catarrhalis is a common and important human respiratory tract pathogen. It is the third most common cause of otitis media in children, accounting for approximately 3.5 million episodes of otitis media annually in the United States (6,11,15,20,25). Adults with chronic obstructive pulmonary disease (COPD) experience recurrent lower respiratory tract infections, often called exacerbations. M. catarrhalis is a common cause of these infections (15,18,23,27,30). Exacerbations of COPD lead to substantial morbidity and mortality and increased health care costs worldwide (14,19,22). In view of the impact of M. catarrhalis infections, there is considerable interest in developing a vaccine to prevent infections caused by M. catarrhalis. Infants would be immunized to prevent otitis media, with particular emphasis on preventing otitis media in otitis-prone children who experience recurrent episodes of otitis media. The second population which would benefit from such a vaccine would be adults with COPD.Outer membrane protein E (OMP E) is a 50-kDa heatmodifiable OMP which has characteristics indicating that it may be an effective vaccine antigen (3, 4). The protein is expressed in all strains of M. catarrhalis studied thus far (2, 4, 16). Three independent lines of experiments indicate that OMP E contains epitopes on the bacterial surface; these include adsorption studies with polyclonal antisera raised to whole bacterial cells (16), immunofluorescence microscopy with polyclonal antisera raised to purified OMP E (4), and flow cytometry with monoclonal antibodies (MAbs) (4, 17).An important consideration in evaluating an OMP as a potential vaccine is the extent to which the protein is conserved among strains of the species. An ideal vaccine candidate would be highly conserved among strains so that immunization with the protein from one strain would gene...

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Antigenic Structure of Outer Membrane Protein E of Moraxella catarrhalis and Construction and Characterization of Mutants

Cited by 33 publications

References 33 publications

The UspA2 Protein of Moraxella catarrhalis Is Directly Involved in the Expression of Serum Resistance

The UspA2 Protein of Moraxella catarrhalis Is Directly Involved in the Expression of Serum Resistance

AhagMutant ofMoraxella catarrhalisStrain O35E Is Deficient in Hemagglutination, Autoagglutination, and Immunoglobulin D-Binding Activities

Conservation of Outer Membrane Protein E among Strains of Moraxella catarrhalis

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