From genome to proteome: protein map of Haemophilus influenzae

High-resolution two-dimensional (2-D) polyacrylamide gel electrophoresis allows the separation of complex biological mixtures (i.e., several hundred proteins from a bacterial cell lysate) in a single experiment. In this report proteins from Haemophilus influenzae were separated by 2-D gels and analyzed by peptide mass fingerprinting and/or amino acid analysis. By comparing the peptide mass profiles and the amino acid composition with the Haemophilus influenzae database, 119 protein spots were identified. The combination of amino acid analysis and peptide mass fingerprinting is a powerful tool for a rapid and economical identification of a large number of proteins resolved by 2-D gels. Studies on gene regulation and changes of protein expression upon drug treatment require quick and serial analysis techniques to efficiently identify potential new drug targets.     

Binding of heme-hemopexin complexes by soluble HxuA protein allows utilization of this complexed heme by Haemophilus influenzae

Utilization of heme-hemopexin as a source of heme by Haemophilus influenzae type b is dependent on expression by this bacterium of the 100-kDa HxuA protein, which is both present on the bacterial cell surface and released into the culture supernatant (L. D. Cope, R. Yogev, U. Muller-Eberhard, and E. J. Hansen, J. Bacteriol. 177:2644-2653, 1995). Radioimmunoprecipitation analysis showed that the soluble HxuA protein present in H. influenzae type b culture supernatant bound heme-hemopexin complexes in solution. An isogenic H. influenzae type b hxuA mutant was unable to utilize soluble heme-hemopexin complexes for growth in vitro unless soluble HxuA protein was provided exogenously. Soluble HxuA protein secreted by a nontypeable H. influenzae strain also allowed growth of this H. influenzae type b hxuA mutant. These results indicated that the heme present in heme-hemopexin complexes is rendered accessible to H. influenzae when these complexes are bound by the soluble HxuA protein.     

Protein D of Haemophilus influenzae is not a universal immunoglobulin D-binding protein

Haemophilus influenzae type b and nontypeable H. influenzae have been reported to bind human immunoglobulin D (IgD). IgD myeloma sera from five patients were tested for the ability of IgD to bind to H. influenzae. Serotype b strains bound human IgD in four of the five sera tested. IgD in the fifth serum bound strongly to type b strain MinnA but poorly to other type b strains. Additionally, IgD binding was not observed when nontypeable strains were tested. The gene for protein D, the putative IgD-binding protein, was cloned from the IgD-binding H. influenzae type b strain MinnA and expressed in Escherichia coli. IgD binding to E. coli expressing protein D was not demonstrable. Recombinant protein D was purified, and antisera were generated in rabbits. Using these rabbit sera, we detected protein D in nontypeable as well as serotype b strains by Western blotting (immunoblotting). In contrast, IgD myeloma protein 4490, which was previously reported to bind to protein D by Ruan and coworkers (M. Ruan, M. Akkoyunlu, A. Grubb, and A. Forsgren, J. Immunol. 145:3379-3384), bound strongly to both type b and nontypeable H. influenzae as well as to E. coli expressing protein D. Thus, IgD binding is a general property of H. influenzae type b strains but not a general property of nontypeable strains, although both type b and nontypeable strains produce protein D. With the exception of IgD myeloma protein 4490 binding, we have no evidence for a role of protein D in IgD binding to H. influenzae.     

Antibody response to outer membrane protein of nontypeable Haemophilus influenzae in otitis-prone children

One of the major outer membrane proteins of nontypeable Haemophilus influenzae, P6, is highly conserved among strains, serves as a target for bactericidal antibody, and has been proposed as a possible vaccine candidate. The serum antibody response to P6 was studied in otitis-prone and normal children by an enzyme-linked immunosorbent assay. Of 20 otitis-prone children, 12 (60%) had a serum IgG antibody response to P6 after otitis media; however, the mean acute antibody level for the group, 4.6 micrograms/ml, was not significantly different from the convalescent level, 5.4 micrograms/ml. Anti-P6 antibody levels were also measured longitudinally for 10 to 25 months in 30 otitis-prone and 13 healthy children. Antibody levels increased sevenfold in the normal group compared with less than three-fold for the otitis-prone group and were significantly higher in the normal children after the age of 18 months (p < 0.05). Finally, otitis-prone children who had two or more episodes of otitis media with nontypeable H. influenzae did not have an anamnestic antibody response to P6. The failure to recognize P6 as a specific immunogen may account for recurrent infections. Moreover, the data suggest that otitis-prone children may not respond adequately to a vaccine containing P6.     

Mathematical models of Haemophilus influenzae type b

Electron microscopic anterograde autoradiography has been used to analyze the morphology and postsynaptic relationships of area 17 cortical terminals in the lateral division of the lateral posterior nucleus (LPl) of the cat and medial division of the inferior pulvinar nucleus (IPm) of the owl monkey. Such terminals are thought to arise exclusively from layer 5 in the cat and primate (Lund et al. [1975] J. Comp. Neurol. 164:287-304; Abramson and Chalupa [1985] Neuroscience 15:81-95). All labeled terminals in both nuclei exhibited the morphology of ascending "lemniscal" afferents. That is, they contained round vesicles, were large, made asymmetrical synaptic and filamentous nonsynaptic contacts, and were classified as RLs. These cortical RLs also exhibited the postsynaptic relationships of lemniscal afferents. Thus, they were presynaptic to large dendrites within glial encapsulated glomeruli, where a majority was involved in complex synaptic arrangements called triads. They also were found adjacent to terminal profiles with pleomorphic vesicles but never adjacent to small terminals containing round vesicles. Our results suggest that the layer 5 projection from area 17 provides a functional "drive" for some LPl and IPm neurons. Information carried over this "re-entrant" pathway (Guillery [1995] J. Anat. 187:583-592) could be modified within the LPl and IPm by both cortical and subcortical pathways and subsequently conveyed to higher visual cortical areas, where it could be integrated with messages carried through the well-documented corticocortical pathways (Casagrande and Kaas [1994] Cerebral cortex New York: Plenum Press).     

Nosocomial transmission of disease caused by nontypeable strains of Haemophilus influenzae

PURPOSE: The authors evaluated a geographic and temporal cluster of lower respiratory tract infections due to unencapsulated (serologically nontypeable) Haemophilus influenzae to determine whether this event represented the transmission of a single clone. METHODS AND MATERIALS: H influenzae was recovered from eight patients at a nursing home and from three patients in an adjacent acute care hospital. Serotypes, biotypes, outer membrane protein profiles, and multilocus enzyme genotypes were determined to characterize bacterial isolates. Patient records were retrospectively examined to determine clinical and epidemiologic characteristics. RESULTS: During a 10-day period in September 1991, lower respiratory tract infections caused by H influenzae were diagnosed in four patients residing in a single nursing home unit. Oropharyngeal cultures from four of seven asymptomatic roommates of these patients also grew H influenzae. During the month before and after the nursing home cluster of cases, four other individuals in acute care areas of the hospital had positive sputum cultures for H influenzae. Three of these latter specimens were also available for analysis. All H influenzae isolates were unencapsulated and beta-lactamase-negative. Eight of the nine isolates from the nursing home patients (two morphologically distinct colony types of H influenzae were isolated from one case) had a single outer membrane protein profile arbitrarily designated as X and a single multilocus enzyme genotype arbitrarily designated as A. In contrast, none of the isolates from the acute care cases had this profile (P < or = 0.02; two-tailed Fisher's exact test). The isolates obtained from two of the patients in acute care areas had an outer membrane protein profile arbitrarily designated as Y and a single multilocus enzyme genotype designated as B. These two patients were contemporaneously hospitalized in adjacent intensive care unit cubicles. The remaining isolates displayed an outer membrane protein profile arbitrarily designated as W. All roommates of the four patients in the nursing home were administered oral rifampin 600 mg daily for 4 days. H influenzae was not recovered from follow-up oropharyngeal cultures obtained 1 week after the completion of therapy. No beta-lactamase-negative H influenzae were identified in this unit during the subsequent 9 months. CONCLUSION: This study furnishes strong evidence for the nosocomial transmission of a clone of unencapsulated H influenzae in a nursing home unit. Epidemiologic data showed temporal and geographic clustering of respiratory tract infections and colonization by H influenzae. Outer membrane protein profiles and multilocus enzyme genotype analysis indicated that seven of eight patients at the nursing home carried a single clone of unencapsulated H influenzae. Laboratory and epidemiologic data also demonstrated the presence, and possible nosocomial transmission, of a second clone of unencapsulated H influenzae in a physically separate area of the hospital. Finally, although a causal relationship is not proven, the outbreak ended following the administration of rifampin prophylaxis of asymptomatic carriers.     

hgpB, a gene encoding a second Haemophilus influenzae hemoglobin- and hemoglobin-haptoglobin-binding protein

Haemophilus influenzae requires heme for growth and can utilize both hemoglobin and hemoglobin-haptoglobin as heme sources. We previously identified a hemoglobin- and hemoglobin-haptoglobin-binding protein, HgpA, in H. influenzae HI689. Mutation of hgpA did not affect binding or utilization of either heme source. The hgpA mutant exhibited loss of a 120-kDa protein and increased expression of a 115-kDa protein. These data suggested that at least one other gene product is involved in binding of these heme sources by H. influenzae. A 3.2-kbp PCR product derived from HI689 was cloned. The nucleotide sequence indicated a separate, distinct gene with high homology to hgpA, which would encode a 115-kDa protein. Primers were designed for directional cloning of the structural gene in the correct reading frame. Sonicates of induced Escherichia coli harboring the cloned open reading frame bound both hemoglobin and hemoglobin-haptoglobin. An insertion/deletion mutant of H. influenzae at the newly identified locus, designated hgpB, was constructed. The 115-kDa protein was not detected in the mutant after affinity purification using biotinylated hemoglobin. An hgpA hgpB double-mutant strain exhibited a reduced ability to utilize hemoglobin-haptoglobin, although it was unaltered in the ability to utilize hemoglobin. Affinity isolation of hemoglobin-binding proteins from the double mutant resulted in isolation of an approximately 120-kDa protein. Internal peptide sequencing revealed this protein to be a third distinct protein, highly homologous to HgpA and HgpB. In summary a second hemoglobin- and hemoglobin-haptoglobin-binding protein of H. influenzae has been identified and characterized, and the presence of an additional protein of similar function has been revealed.     

A routine high-performance size-exclusion chromatography to determine molecular size distribution of Haemophilus influenzae type b conjugate vaccines

High-performance size exclusion chromatography has been used to determine the molecular size distribution of Haemophilus influenzae type b (Hib) conjugate vaccines. Both high molecular weight preparations of native Hib capsular polysaccharide coupled to tetanus toxoid and low molecular weight vaccines with Hib oligosaccharides linked to the CRM197 nontoxic mutant diphtheria protein were analysed. Columns with different fractionation ranges were used for the two kinds of vaccines. This method showed to be rapid, accurate and reproducible for different lots of Hib vaccine of different composition produced by various manufacturers. It could replace more time-consuming chromatographic methods enabling control authorities to employ a single methodological approach for different Hib vaccines.     

Clonality of multidrug-resistant nontypeable strains of Haemophilus influenzae

The genetic structure of a population of multidrug-resistant nontypeable (unencapsulated) Haemophilus influenzae strains isolated at a hospital in Barcelona, Spain, was investigated by using multilocus enzyme electrophoresis to determine the allelic variation in 15 structural loci. In our study we have also included some antimicrobial agent-susceptible strains isolated at the same hospital. All enzymes were polymorphic for two to eight electromorphs, and the analysis revealed 43 distinct electrophoretic types among the 44 isolates. The mean genetic diversity of the entire population was 0.55. Multilocus linkage disequilibrium analysis of the isolates revealed a strong association between alleles, suggesting little possibility of recombination. Furthermore, the dendrogram and the allele mismatch distribution are typical of a population with no extensive genetic mixing.     

Large-scale identification of proteins of Haemophilus influenzae by amino acid composition analysis

Two-dimensional protein maps of microorganisms are useful tools for elucidation and detection of target proteins, a process essential in the development of new pharmaceutical products. We applied amino acid composition analysis, following separation by two-dimensional gel electrophoresis, for large-scale identification of proteins of Haemophilus influenzae. H. influenzae is a bacterium of pharmaceutical interest of which the entire genome, comprising approximately 1700 open reading frames, has been sequenced. For amino acid analysis, we used both precolumn derivatization of amino acids followed by reversed-phase chromatography of the derivatized residues and post-column derivatization of the residues previously separated on an ion exchanger. The composition analyses derived from both methods allowed the identification of 110 protein spots. The proteins were identified using the AACompldent software on the ExPASy server accessible via the World Wide Web with a success rate of 52%. In some cases, introduction of the analysis data of 12 residues was sufficient for a correct identification. Proteins which contained an unusually high percentage of one residue could be unambiguously identified. Amino acid composition analysis proved to be an error-robust, efficient method for protein identification. The method can be practically established in every biochemical laboratory and, complementary to mass spectrometry, represents an important analytical tool for the mapping of the proteomes of organisms of interest.     

Polymerase chain reaction-based strain characterization of noncapsulate Haemophilus influenzae

A polymerase chain reaction-based typing method for noncapsulate Haemophilus influenzae was developed. Randomly amplified polymorphic DNA fingerprints were generated from boiled supernatants prepared directly from bacterial colonies without the need for DNA extraction. The technique was applied to isolates obtained during putative outbreaks of chest infection and validated by comparison with sodium dodecyl sulfatepolyacrylamide gel electrophoresis analysis of outer membrane protein-enriched preparations and rRNA gene restriction analysis. There was complete concordance between the three techniques. The results show that randomly amplified polymorphic DNA analysis provides a highly discriminatory method of characterizing strains of noncapsulate H. influenzae which is eminently suitable as an epidemiological tool for the rapid investigation of outbreaks of infection.     

Functional characterization of the Haemophilus influenzae 4.5S RNA

General registration of congenital malformations was established in Denmark in the early 1960s as a consequence of the thalidomide tragedy. The aims of the present paper are to describe the registration of congenital malformations in Denmark since the thalidomide tragedy, to discuss the limitations of these data and to point towards possibilities for improving the registration of congenital malformations in the future. Important components in a surveillance system are compulsory detailed reporting of malformations shortly after the diagnoses have been made and continuous expert evaluation of all reports. However, since 1995 the registration of congenital malformations in Denmark is based mainly on routine discharge diagnoses from hospitals. A high quality registration of congenital malformations in Denmark would be particularly valuable, because such a register together with existing health related registers and an ongoing large scale cohort study of pregnant women would provide a unique resource for etiological research in congenital malformations. Considering the consequences of congenital malformations for the affected children, their families and society, the establishment of a high quality registration of congenital malformations seems justifiable--and the Swedish experience shows that it is feasible.     

Two-dimensional elution map of GalNAc-containing N-linked oligosaccharides

We have previously published a two-dimensional (2-D) mapping technique for N-linked oligosaccharides using pyridylaminated derivatives (PA-oligosaccharides) (N. Tomiya et al. Anal. Biochem. 171, 73-90, 1988). We now report an extension of this method to GalNAc-containing N-linked oligosaccharides. The new 2-D map was prepared from the elution data of 40 different GalNAc-containing oligosaccharides, 16 of which were obtained directly from human urinary kallidinogenase by digestion with glycopeptidase A. The other 24 oligosaccharides were derived by subsequent digestion of the 16 original oligosaccharides with beta-galactosidase or alpha-fucosidase. Each of the 40 oligosaccharide derivatives was separated by high-performance liquid chromatography using ODS-silica and amide-silica columns. The 2-D map constructed by plotting elution position of each oligosaccharide (expressed in terms of glucose units) can be useful as such in delineating the structure of an unknown oligosaccharide by direct placement of its elution positions in the 2-D map. Multiple regression analysis of the data as performed previously yielded parameters related to the contribution of each component monosaccharide unit to the elution profile. The best results were obtained when the GalNAc-containing PA-oligosaccharides were classified into an F-series (those containing Fuc alpha 6GlcNAc-PA) and a Z-series (all others), based on our previous classification method. These calculated values are useful in predicting oligosaccharide structure from known elution values as well as to predict elution volumn from a known structure. The structure of a minor GalNAc-containing oligosaccharide in human urinary kallidinogenase was elucidated using these newly calculated values.     

Comparison of multiple immunization schedules for Haemophilus influenzae type b-conjugate and tetanus toxoid vaccines following bone marrow transplantation

Antibody concentrations to vaccine-preventable diseases decline following BMT and an optimal schedule for vaccination after transplant has not been established. We examined antibody responses to tetanus toxoid (TT) and Haemophilus influenzae type b-conjugate (HIB) vaccines of BMT patients immunized at 6, 12 and 24 months (6 month group, n = 21) and compared them to those previously reported for patients immunized at 3, 6, 12 and 24 months (3 month group, n = 74) or at 12 and 24 months (12 month group, n = 17) following transplantation. Geometric mean total anti-HIB and IgG anti-TT concentrations were significantly higher after the 12 month dose in the 3 and 6 month immunization groups compared to the group who received their first dose at 12 months. Although HIB antibody concentrations were higher in the 3 month and 6 month groups 12 to 24 months after BMT, the proportion of patients with protective levels was not significantly different from the proportion protected in the 12 month group. Following the 24 month immunizations, geometric mean antibody concentrations to HIB and TT were similar for all three immunization groups. The proportion of patients in each group with protective levels of HIB antibody after the 24 month dose was > or = 80%. A two dose schedule of HIB and TT vaccines at 12 and 24 months after BMT should afford protection.     

Evolution of the major pilus gene cluster of Haemophilus influenzae

Haemophilus influenzae is a ubiquitous colonizer of the human respiratory tract and causes diseases ranging from otitis media to meningitis. Many H. influenzae isolates express pili (fimbriae), which mediate adherence to epithelial cells and facilitate colonization. The pilus gene (hif) cluster of H. influenzae type b maps between purE and pepN and resembles a pathogenicity island: it is present in invasive strains, absent from the nonpathogenic Rd strain, and flanked by direct repeats of sequence at the insertion site. To investigate the evolution and role in pathogenesis of the hif cluster, we compared the purE-pepN regions of various H. influenzae laboratory strains and clinical isolates. Unlike Rd, most strains had an insert at this site, which usually was the only chromosomal locus of hif DNA. The inserts are diverse in length and organization: among 20 strains, nine different arrangements were found. Several nontypeable isolates lack hif genes but have two conserved open reading frames (hicA and hicB) upstream of purE; their inferred products are small proteins with no data bank homologs. Other isolates have hif genes but lack hic DNA or have combinations of hif and hic genes. By comparing these arrangements, we have reconstructed a hypothetical ancestral genotype, the extended hif cluster. The hif region of INT1, an invasive nontypeable isolate, resembles the hypothetical ancestor. We propose that a progenitor strain acquired the extended cluster by horizontal transfer and that other variants arose as deletions. The structure of the hif cluster may correlate with colonization site or pathogenicity.     

Conjugate vaccines and the carriage of Haemophilus influenzae type b

Pharyngeal carriage of Haemophilus influenzae type b (Hib) is important in the transmission of Hib organisms, the pathogenesis of Hib disease, and the development of immunity to the bacterium. The remarkable success of current vaccination programs against Hib has been due in part to the effect of conjugate Hib vaccines in decreasing carriage of Hib. This review explores evidence for this effect, and discusses the possible mechanisms of the mucosal influence of Hib conjugate vaccines.