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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several chromosomal loci are involved in lipopolysaccharide (LPS) biosynthesis by Haemophilus influenzae. Two of these, lic1 and lic2, contain multiple open-reading frames (ORFs) and include tandem repeats of the tetramer CAAT within and at the 5' end of the coding region of the first ORF in each locus. Variation in the number of repeats of CAAT is involved in the variable expression of LPS epitopes, and genes within these loci are involved in the biosynthesis of these epitopes. lic3 also contains multiple ORFs and the CAAT repeats in the same arrangement as in the other two lic loci. However, in lic3 metabolic functions are encoded by the downstream genes. ORF2 is galE, encoding uridine 5'-diphosphogalactose 4-epimerase, and ORF4 is adk, encoding adenylate kinase. A mutant H. influenzae with a deleted galE gene had an altered LPS when grown on media lacking galactose and was of reduced virulence in infant rats.
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PMID:Molecular biology of phase-variable lipopolysaccharide biosynthesis by Haemophilus influenzae. 158 88

The composition of lipooligosaccharide (LOS) can modify the virulence of Haemophilus influenzae type b (Hib). A genomic library of Hib strain A2 was constructed in the lambda bacteriophage EMBL3. Twenty-six phage clones expressed a Hib LOS oligosaccharide epitope in Escherichia coli that was detected by the monoclonal antibody (MAb) 6E4. None of the clones bound a polyclonal sera specific for Hib A2 LOS or an anti-H. influenzae lipid A MAb. One clone, designated EMBLOS-1, assembled an oligosaccharide with an apparent molecular weight of 1,400 (the 1.4K oligosaccharide) on a 4.1K lipopolysaccharide (LPS) species in E. coli LE392 and produced a novel 5.5K LPS that bound 6E4. Binding of 6E4 to the 5.5K EMBLOS-1 LPS band was abolished by treatment with sodium metaperiodate but was not affected by digestion with proteinase K, confirming the carbohydrate nature of the epitope. The EMBLOS-1 Haemophilus insert hybridized to similar restriction fragments in type b and nontypeable strains regardless of whether they expressed the 6E4 epitope. The 6E4 epitope did not undergo phase variation in Hib strain A2 at a frequency of greater than 10(-3). The oligosaccharide of the Salmonella minnesota Re mutant and 2-keto-3-deoxyoctulosonic acid (KDO) inhibited binding of 6E4 to Hib A2 LOS. We conclude that a gene(s) encoding an enzyme(s) that assembles a stable Hib LOS epitope containing KDO is conserved in H. influenzae and that the cloned Hib LOS synthesis gene products assemble a Hib LOS epitope on an E. coli K-12 LPS core.
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PMID:Cloning and expression in Escherichia coli of a Haemophilus influenzae type b lipooligosaccharide synthesis gene(s) that encodes a 2-keto-3-deoxyoctulosonic acid epitope. 169 6

Phase variation of lipopolysaccharide epitopes of an Haemophilus influenzae serotype b strain (strain RM.7004) occurs through a mechanism which depends on multiple tandem repeats of the DNA sequence 5'-CAAT-3' situated within the chromosomal locus lic1. We report here that the same tetranucleotide repeats are also found in two other genomic loci (lic2 and lic3) of RM.7004. Similar to lic1, there are multiple tandem repeats of 5'-CAAT-3' present at the 5' ends of long open reading frames in lic2 and lic3. Variation in the number of repeats of CAAT, by shifting the upstream initiation codons in or out of phase with the remainder of the open reading frame, could switch on or off the translation of downstream genes. Similar to previously reported findings for lic1, site-directed mutations in the open reading frame downstream (3') from the repeats of CAAT in lic2 abolished phase variation and identified DNA sequences required for the expression of additional oligosaccharide epitopes. When we used an oligonucleotide comprising five repeats of CAAT or DNA sequences specific for lic1, lic2, and lic3 as probes, a survey of other encapsulated H. influenzae strains (serotypes a through f) and nontypable H. influenzae strains (including biotype aegyptius) showed that the chromosome of H. influenzae can have from two to five regions which contain multiple tandem repeats of CAAT in addition to other sequences which hybridize to lic1 and lic2.
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PMID:Characterization of repetitive sequences controlling phase variation of Haemophilus influenzae lipopolysaccharide. 169 45

Monoclonal antibodies raised against Haemophilus influenzae and Neisseria gonorrhoeae were used to investigate similarities or differences in the lipopolysaccharide antigens of pathogenic and commensal strains of several Gram-negative bacteria indigenous to mucosal surfaces of humans. In immunoblotting experiments, 20 of 36 monoclonal antibodies showed cross-reactions between species of Neisseria and Haemophilus. The common epitopes were present on N. gonorrhoeae, N. meningitidis, N. lactamica, H. influenzae including biogroup aegyptius, and occasionally H. parainfluenzae. No other commensal Neisseria or Gram-negative organisms tested reacted with the monoclonal antibodies with one exception; a single strain of pathogenic Escherichia coli was recognised by a N. gonorrhoeae-specific monoclonal antibody. One monoclonal antibody, raised against N. gonorrhoeae lipopolysaccharide, reacted with N. gonorrhoeae (32 of 59 strains), N. meningitidis (9 of 26 strains), H. influenzae (6 of 16 strains). An epitope expressed by H. influenzae and implicated in its virulence was also present on 14 of 59 strains of N. gonorrhoeae and was shown to comprise a digalactoside structure, alpha-galactosyl-1,4-beta-galactose (Gal alpha 1,4Gal beta), also found on human cells.
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PMID:Antigenic similarities in lipopolysaccharides of Haemophilus and Neisseria and expression of a digalactoside structure also present on human cells. 171 Nov 42

The mouse and rabbit intradermal injection models have been used to define factors that may be important in Haemophilus ducreyi pathogenesis. We used H. ducreyi strains with diverse geographic origins and phenotypic characteristics to evaluate the experimental models. Injection of live and heat-killed bacteria caused skin abscesses in both models. Semiquantitative cultures of skin injected with live bacteria showed that H. ducreyi failed to replicate in animal tissue. These data suggested that the experimental lesions were caused by a heat-stable substance such as lipooligosaccharide (LOS). In mice, injection of H. ducreyi and Haemophilus influenzae LOS and Escherichia coli lipopolysaccharide caused mild to moderate inflammation. In rabbits, injection of H. ducreyi LOS caused intradermal abscesses that were histologically similar to those caused by live and heat-killed bacteria. H. ducreyi and Neisseria gonorrhoeae LOS caused significantly larger lesions than equivalent amounts of H. influenzae LOS and E. coli lipopolysaccharide in the rabbit model. We conclude that the intradermal injection models are not valid models to study the growth of H. ducreyi in vivo. However, these data indicate that H. ducreyi LOS may play an important role in the pathogenesis of chancroid and that the rabbit model should be useful in studying H. ducreyi LOS toxicity at the cellular level.
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PMID:Role of lipooligosaccharides in experimental dermal lesions caused by Haemophilus ducreyi. 185 79

The incidence, case fatality rate (CFR), age distribution, serotype distribution and transmission of Haemophilus influenzae meningitis worldwide are reviewed. This organism is a commensal in the throat, but serotype b can become invasive and causes the majority of meningitis disease in infants in most countries. The incidence is estimated at 47/100,000 in the US, and 20-30/100,000 in Europe for children 5 years. In non-industrialized settings, data are available for Alaska and The Gambia, where incidence is 60/100,000 children 5. In Africa the peak age is 6 months of age, compared to 8-9 months is the West, where 60% of cases occur in adults as well. The CFR ranges from 1.95-5% in the West, a function of hospital facilities, but is reported to be 26% in Nigeria and 57% in Egypt. H. influenzae serotype b predominates in most countries. Only 3 common outer membrane protein antigens are common, but the lipopolysaccharide types vary widely. In West Africa serotype a is more prevalent, and in The Gambia an entirely different clone was isolated. The carriage rate appears to be low, around 2-4% in most communities, but in some closed communities, such as day care centers, up to 56% carriage has been found. It is theorized that introduction of new strains is the reason for infection of very young children in developing areas.
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PMID:World-wide epidemiology of Haemophilus influenzae meningitis; industrialized versus non-industrialized countries. 189 57

Twenty-four Haemophilus influenzae type b strains from 836 children and young adults in an open population were subtyped by outer-membrane-protein (OMP) analysis on sodium dodecyl sulphate-polyacrylamide gels, lipopolysaccharide serotyping and biotyping. The results were compared with those obtained with H. influenzae type b strains from 97 patients with meningitis in the same city (Amsterdam). OMP subtype 1 was significantly more common among the CSF isolates than in carrier strains (82% vs 50%; p less than 0.002). The other OMP subtypes found among carriers were rarely isolated from patients. The lipopolysaccharide serotype and biotype distribution did not differ between the two groups. The combination of OMP subtype 1, lipopolysaccharide 1, biotype I was much more common in isolates from patients than in those from carriers (71% vs 42%; p less than 0.01). The data suggest that various H. influenzae type b subtypes are less virulent than those commonly isolated from invasive infections.
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PMID:Differences in subtype distribution of Haemophilus influenzae type b from carriers in the general population and patients with meningitis. 205 15

Incubation of Haemophilus influenzae type b at less than or equal to 10(7) CFU/ml with serum ultrafiltrate induces a phenotypic conversion in which complement-mediated bactericidal activity by somatic antibodies decreases while killing by capsular antibody is unchanged. Conversion had been shown to occur in a capsule-deficient (b-) mutant of strain Eag (thus appearing independent of capsulation), to include an increase in lipopolysaccharide content, and to be inhibited by chloramphenicol or puromycin. In the present study, in several strains not previously examined, conversion was not inhibited by the drugs and the corresponding b- mutants did not convert. Incubation in ultrafiltrate was also found to increase capsulation, as detected by radioassay, only 1.6-fold in Eag but 4.5-fold in DL26, the strain with the largest increase in resistance; moreover, complement-mediated opsonization by capsular antibody was greatly decreased. Thus, multiple mechanisms, capsule dependent as well as independent, appear to contribute to the serum factor-induced resistance of H. influenzae type b to antibody.
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PMID:Multiple mechanisms in serum factor-induced resistance of Haemophilus influenzae type b to antibody. 231 34

Monoclonal antibodies (Mabs) were produced against outer-membrane proteins (OMPs) of Haemophilus influenzae type b. The clones were screened by ELISA with outer-membrane preparations of H. influenzae type b and untypable strains as coating antigens. Antibodies directed against the proteins of mol. wt (10(3)) 43, 37 and 13 were identified by immunoblotting of SDS-PAGE patterns of OMPs. Proteolytic enzyme treatments of the OMPs resulted in reduction of Mab reactivity as measured by ELISA. Furthermore, the absence of reactivity of Mab Hb-2 with a preparation of lipopolysaccharide confirmed the protein nature of its corresponding epitope. Binding assays with live bacteria showed that Hb-2 reacted with a cell surface-exposed antigenic determinant. Mab Hb-2 was bactericidal in vitro in the presence of complement. The characterisation of Hb-2 (IgG2a) by Western immunoblotting analysis revealed that it was directed against the 37 X 10(3)-mol. wt OMP. In a dot-enzyme immunoassay, Hb-2 reacted specifically with 326 strains of H. influenzae type b. It did not cross-react with the other serotypes or untypable strains of H. influenzae or with other bacterial species. This is the first report of a monoclonal antibody identifying a serotype-specific surface-exposed OMP of H. influenzae type b.
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PMID:A monoclonal antibody directed against a serotype-specific, outer-membrane protein of Haemophilus influenzae type b. 243 7

The cross-reactivity of exposed surface epitopes of outer membrane proteins from a spectrum of Haemophilus influenzae type b isolates that varied in their evolutionary distance from each other and in their outer membrane protein composition was analyzed by using an immunoblot assay. The results for outer membrane proteins a, n, and b/c were as follows. (i) A total of 13 of 14 strains possessing a protein a with similar mobilities on gels (i.e., the same apparent molecular weight) as protein a of strain Eag absorbed antibodies to protein a of strain Eag. These strains represented a broad spectrum on a scale of evolutionary distance. (ii) In contrast, only one of seven strains possessing a protein a with different mobilities absorbed these antibodies. (iii) Of five isolates close to strain Eag on the evolutionary scale, the four with a protein n with the same mobility as protein n of strain Eag absorbed antibodies to protein n of strain Eag. (iv) In contrast, of five isolates distant from strain Eag on the evolutionary scale, none absorbed antibodies to protein n, including one strain that had a protein n of the same mobility as that of strain Eag. (v) All strains that absorbed antibodies to protein b/c also absorbed antibodies to lipopolysaccharide, and the reverse of this was also true. Evolutionary distance and mobility of protein b/c on gels were not factors. Control experiments indicated that this result was an artifact due to the strong association of lipopolysaccharide with protein b/c on the gel and subsequent blot. The important conclusions from these experiments, especially pertinent for consideration of these proteins in either whole or peptide vaccines, are that proteins with apparently identical molecular weights can possess different surface-exposed epitopes, that proteins with different molecular weights can possess cross-reactive surface-exposed epitopes, and that some surface-exposed epitopes have been conserved even though the bacterium has undergone evolutionary divergence. In addition, experiments were also performed to determine whether H. influenzae type b strains maintained their integrity during the absorption step, i.e., incubation in antiserum. Strain Eag, which was used as a prototype type b strain, released a small proportion of its membrane (0.13%), but this did not result in exposure of epitopes that were usually buried. In contrast, strain S2, an unencapsulated mutant of strain Eag, was quite unstable, releasing three times as much membrane and a large proportion of its periplasmic proteins.
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PMID:Cross-reactivity of surface-exposed epitopes of outer membrane antigens of Haemophilus influenzae type b. 244 84


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