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Phillips ZN, Jennison AV, Whitby PW, Stull TL, Staples M, Atack JM. Examination of phase-variable haemoglobin-haptoglobin binding proteins in Non-typeable Haemophilus influenzae reveals a diverse distribution of multiple variants. FEMS Microbiol Lett 2022; 369:6648706. [PMID: 35867873 PMCID: PMC9341677 DOI: 10.1093/femsle/fnac064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 06/14/2022] [Accepted: 07/20/2022] [Indexed: 11/25/2022] Open
Abstract
Non-typeable Haemophilus influenzae (NTHi) is a major human pathogen for which there is no globally licensed vaccine. NTHi has a strict growth requirement for iron and encodes several systems to scavenge elemental iron and heme from the host. An effective NTHi vaccine would target conserved, essential surface factors, such as those involved in iron acquisition. Haemoglobin–haptoglobin binding proteins (Hgps) are iron-uptake proteins localized on the outer-membrane of NTHi. If the Hgps are to be included as components of a rationally designed subunit vaccine against NTHi, it is important to understand their prevalence and diversity. Following analysis of all available Hgp sequences, we propose a standardized grouping method for Hgps, and demonstrate increased diversity of these proteins than previously determined. This analysis demonstrated that genes encoding variants HgpB and HgpC are present in all strains examined, and almost 40% of strains had a duplicate, nonidentical hgpB gene. Hgps are also phase-variably expressed; the encoding genes contain a CCAA(n) simple DNA sequence repeat tract, resulting in biphasic ON–OFF switching of expression. Examination of the ON–OFF state of hgpB and hgpC genes in a collection of invasive NTHi isolates demonstrated that 58% of isolates had at least one of hgpB or hgpC expressed (ON). Varying expression of a diverse repertoire of hgp genes would provide strains a method of evading an immune response while maintaining the ability to acquire iron via heme. Structural analysis of Hgps also revealed high sequence variability at the sites predicted to be surface exposed, demonstrating a further mechanism to evade the immune system—through varying the surface, immune-exposed regions of the membrane anchored protein. This information will direct and inform the choice of candidates to include in a vaccine against NTHi.
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Affiliation(s)
- Zachary N Phillips
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia
| | - Amy V Jennison
- Queensland Department of Health, Public Health Microbiology, Forensic and Scientific Services, Brisbane, Queensland, Australia
| | | | | | - Megan Staples
- Queensland Department of Health, Public Health Microbiology, Forensic and Scientific Services, Brisbane, Queensland, Australia
| | - John M Atack
- Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia.,School of Environment and Science, Griffith University, Gold Coast, Queensland, Australia
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Sullivan MV, Dennison SR, Archontis G, Reddy SM, Hayes JM. Toward Rational Design of Selective Molecularly Imprinted Polymers (MIPs) for Proteins: Computational and Experimental Studies of Acrylamide Based Polymers for Myoglobin. J Phys Chem B 2019; 123:5432-5443. [DOI: 10.1021/acs.jpcb.9b03091] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mark V. Sullivan
- School of Physical Sciences & Computing, Division of Chemistry, University of Central Lancashire, Preston PR1 2HE, United Kingdom
| | - Sarah R. Dennison
- School of Pharmacy & Biomedical Sciences, University of Central Lancashire, Preston PR1 2HE, United Kingdom
| | | | - Subrayal M. Reddy
- School of Physical Sciences & Computing, Division of Chemistry, University of Central Lancashire, Preston PR1 2HE, United Kingdom
| | - Joseph M. Hayes
- School of Pharmacy & Biomedical Sciences, University of Central Lancashire, Preston PR1 2HE, United Kingdom
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Nontypeable Haemophilus influenzae Has Evolved Preferential Use of N-Acetylneuraminic Acid as a Host Adaptation. mBio 2019; 10:mBio.00422-19. [PMID: 31064827 PMCID: PMC6509186 DOI: 10.1128/mbio.00422-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Host-adapted bacterial pathogens such as NTHi cannot survive out of their host environment and have evolved host-specific mechanisms to obtain nutrients and evade the immune response. Relatively few of these host adaptations have been characterized at the molecular level. NTHi utilizes sialic acid as a nutrient and also incorporates this sugar into LOS, which is important in biofilm formation and immune evasion. In the present study, we showed that NTHi has evolved to preferentially utilize the Neu5Ac form of sialic acid. This adaptation is due to the substrate preference of the enzyme CMP-Neu5Ac synthetase, which synthesizes the activated form of Neu5Ac for macromolecule biosynthesis. This adaptation allows NTHi to evade killing by a human antibody response against the nonhuman sialic acid Neu5Gc. Nontypeable Haemophilus influenzae (NTHi) is a Gram-negative bacterial pathogen that is adapted exclusively to human hosts. NTHi utilizes sialic acid from the host as a carbon source and as a terminal sugar on the outer membrane glycolipid lipooligosaccharide (LOS). Sialic acid expressed on LOS is critical in NTHi biofilm formation and immune evasion. There are two major forms of sialic acids in most mammals, N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc), the latter of which is derived from Neu5Ac. Humans lack the enzyme to convert Neu5Ac to Neu5Gc and do not express Neu5Gc in normal tissues; instead, Neu5Gc is recognized as a foreign antigen. A recent study showed that dietary Neu5Gc can be acquired by NTHi colonizing humans and then presented on LOS, which acts as an antigen for the initial induction of anti-Neu5Gc antibodies. Here we examined Neu5Gc uptake and presentation on NTHi LOS. We show that, although Neu5Gc and Neu5Ac are utilized equally well as sole carbon sources, Neu5Gc is not incorporated efficiently into LOS. When equal amounts of Neu5Gc and Neu5Ac are provided in culture media, there is ∼4-fold more Neu5Ac incorporated into LOS, suggesting a bias in a step of the LOS biosynthetic pathway. CMP-Neu5Ac synthetase (SiaB) was shown to have ∼4,000-fold-higher catalytic efficiency for Neu5Ac than for Neu5Gc. These data suggest that NTHi has adapted preferential utilization of Neu5Ac, thus avoiding presentation of the nonhuman Neu5Gc in the bacterial cell surface. The selective pressure for this adaptation may represent the human antibody response to the Neu5Gc xenoantigen.
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Choby JE, Skaar EP. Heme Synthesis and Acquisition in Bacterial Pathogens. J Mol Biol 2016; 428:3408-28. [PMID: 27019298 PMCID: PMC5125930 DOI: 10.1016/j.jmb.2016.03.018] [Citation(s) in RCA: 193] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/16/2016] [Accepted: 03/17/2016] [Indexed: 02/06/2023]
Abstract
Bacterial pathogens require the iron-containing cofactor heme to cause disease. Heme is essential to the function of hemoproteins, which are involved in energy generation by the electron transport chain, detoxification of host immune effectors, and other processes. During infection, bacterial pathogens must synthesize heme or acquire heme from the host; however, host heme is sequestered in high-affinity hemoproteins. Pathogens have evolved elaborate strategies to acquire heme from host sources, particularly hemoglobin, and both heme acquisition and synthesis are important for pathogenesis. Paradoxically, excess heme is toxic to bacteria and pathogens must rely on heme detoxification strategies. Heme is a key nutrient in the struggle for survival between host and pathogen, and its study has offered significant insight into the molecular mechanisms of bacterial pathogenesis.
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Affiliation(s)
- Jacob E Choby
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA; Tennessee Valley Healthcare System, U.S. Department of Veterans Affairs, Nashville, TN, USA.
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Whitby PW, VanWagoner TM, Seale TW, Morton DJ, Stull TL. Comparison of transcription of the Haemophilus influenzae iron/heme modulon genes in vitro and in vivo in the chinchilla middle ear. BMC Genomics 2013; 14:925. [PMID: 24373462 PMCID: PMC3879429 DOI: 10.1186/1471-2164-14-925] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 12/17/2013] [Indexed: 08/30/2023] Open
Abstract
Background Haemophilus influenzae is a significant cause of childhood otitis media, and also has an absolute growth requirement for heme. Recent microarray studies using three H. influenzae isolates were used to propose a putative core of genes responsive to iron and heme levels. Included in the core modulon were thirty seven genes that are preferentially expressed under iron/heme limitation, most of which are directly involved with iron and or heme acquisition. In this report, the core iron/heme modulon was further refined following microarray analysis of two additional nontypeable H. influenzae isolates from patients with otitis media. The transcriptional status of the genes comprising the refined iron/heme core modulon was then assessed in vivo, in a chinchilla model of otitis media. These in vivo experiments were performed to address the hypothesis that iron and heme regulated genes are both highly expressed in vivo and important, during clinical infection. Results Microarray analysis of two additional H. influenzae strains resulted in the definition of a core of iron/heme responsive genes. This core consisted of 35 genes maximally expressed under heme restriction and a further 20 genes maximally expressed in heme replete conditions. In vivo studies were performed with two nontypeable H. influenzae strains, 86-028NP and HI1722. The majority of operons identified as members of the core modulon by microarray were also actively upregulated in the chinchilla ear during otitis media. In 86-028NP, 70% of the operons were significantly upregulated while in HI1722 100% of the operons were upregulated in samples recovered from the chinchilla middle ear. Conclusion This study elucidates a conserved core of H. influenzae genes the transcription of which is altered by the availability of iron and heme in the growth environment, and further assesses transcription of these genes in vivo. Elucidation of this modulon allows for identification of genes with unrecognized roles in iron/heme acquisition or homeostasis and/or potential roles in virulence. Defining these core genes is also of potential importance in identifying targets for therapeutic and vaccine designs since products of these genes are likely to be preferentially expressed during growth in iron/heme restricted sites of the human body.
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Affiliation(s)
- Paul W Whitby
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City 73104, OK, USA.
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Abstract
The proliferative capability of many invasive pathogens is limited by the bioavailability of iron. Pathogens have thus developed strategies to obtain iron from their host organisms. In turn, host defense strategies have evolved to sequester iron from invasive pathogens. This review explores the mechanisms employed by bacterial pathogens to gain access to host iron sources, the role of iron in bacterial virulence, and iron-related genes required for the establishment or maintenance of infection. Host defenses to limit iron availability for bacterial growth during the acute-phase response and the consequences of iron overload conditions on susceptibility to bacterial infection are also examined. The evidence summarized herein demonstrates the importance of iron bioavailability in influencing the risk of infection and the ability of the host to clear the pathogen.
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Plasma protein changes in horse after prolonged physical exercise: A proteomic study. J Proteomics 2012; 75:4494-504. [DOI: 10.1016/j.jprot.2012.04.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 03/26/2012] [Accepted: 04/10/2012] [Indexed: 11/19/2022]
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Morton DJ, Turman EJ, Hensley PD, VanWagoner TM, Seale TW, Whitby PW, Stull TL. Identification of a siderophore utilization locus in nontypeable Haemophilus influenzae. BMC Microbiol 2010; 10:113. [PMID: 20398325 PMCID: PMC2859871 DOI: 10.1186/1471-2180-10-113] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 04/15/2010] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Haemophilus influenzae has an absolute aerobic growth requirement for either heme, or iron in the presence of protoporphyrin IX. Both iron and heme in the mammalian host are strictly limited in their availability to invading microorganisms. Many bacterial species overcome iron limitation in their environment by the synthesis and secretion of small iron binding molecules termed siderophores, which bind iron and deliver it into the bacterial cell via specific siderophore receptor proteins on the bacterial cell surface. There are currently no reports of siderophore production or utilization by H. influenzae. RESULTS Comparative genomics revealed a putative four gene operon in the recently sequenced nontypeable H. influenzae strain R2846 that encodes predicted proteins exhibiting significant identity at the amino acid level to proteins involved in the utilization of the siderophore ferrichrome in other bacterial species. No siderophore biosynthesis genes were identified in the R2846 genome. Both comparative genomics and a PCR based analysis identified several additional H. influenzae strains possessing this operon. In growth curve assays strains containing the genes were able to utilize ferrichrome as an iron source. H. influenzae strains lacking the operon were unable to obtain iron from ferrichrome. An insertional mutation in one gene of the operon abrogated the ability of strains to utilize ferrichrome. In addition transcription of genes in the identified operon were repressible by high iron/heme levels in the growth media. CONCLUSIONS We have identified an iron/heme-repressible siderophore utilization locus present in several nontypeable H. influenzae strains. The same strains do not possess genes encoding proteins associated with siderophore synthesis. The siderophore utilization locus may enable the utilization of siderophores produced by other microorganisms in the polymicrobial environmental niche of the human nasopharynx colonized by H. influenzae. This is the first report of siderophore utilization by H. influenzae.
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Affiliation(s)
- Daniel J Morton
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Elizabeth J Turman
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Patrick D Hensley
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Timothy M VanWagoner
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Department of Biology, Oklahoma Christian University, Oklahoma City, OK 73136, USA
| | - Thomas W Seale
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Paul W Whitby
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Terrence L Stull
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
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Whitby PW, Seale TW, Morton DJ, VanWagoner TM, Stull TL. Characterization of the Haemophilus influenzae tehB gene and its role in virulence. MICROBIOLOGY-SGM 2010; 156:1188-1200. [PMID: 20075041 DOI: 10.1099/mic.0.036400-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The Haemophilus influenzae ORF designated HI1275 in the Rd KW20 genomic sequence encodes a putative S-adenosyl methyltransferase with significant similarity to tellurite-resistance determinants (tehB) in other species. While the H. influenzae tehB can complement an Escherichia coli tehB mutation, thus restoring tellurite resistance, its role in H. influenzae is unknown. In a previous study defining the iron and haem modulon of H. influenzae, we showed that transcription of this gene in H. influenzae Rd KW20 increases during growth in iron- and haem-restricted media. Since iron and haem uptake genes, and other known virulence factors, constitute the majority of the iron- and haem-regulated gene set, we postulated that tehB may play a role in nutrient acquisition and/or the virulence of H. influenzae. A tehB mutant was constructed in the H. influenzae type b strain 10810 and was evaluated for growth defects in various supplemented media, as well as for its ability to cause infection in rat models of infection. Deletion of tehB leads to an increase in sensitivity both to tellurite and to the oxidizing agents cumene hydroperoxide, tert-butyl hydroperoxide and hydrogen peroxide. The tehB mutant additionally showed a significantly reduced ability to utilize free haem as well as several haem-containing moieties including haem-human serum albumin, haemoglobin and haemoglobin-haptoglobin. Examination of the regulation kinetics indicated that transcription of tehB was independent of both tellurite exposure and oxidative stress. Paired comparisons of the tehB mutant and the wild-type H. influenzae strain 10810 showed that tehB is required for wild-type levels of infection in rat models of H. influenzae invasive disease. To our knowledge this is the first report of a role for tehB in virulence in any bacterial species. These data demonstrate that H. influenzae tehB plays a role in both resistance to oxidative damage and haem uptake/utilization, protects H. influenzae from tellurite exposure, and is important for virulence of this organism in an animal model of invasive disease.
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Affiliation(s)
- Paul W Whitby
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Thomas W Seale
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Daniel J Morton
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Timothy M VanWagoner
- Department of Biology, Oklahoma Christian University, Oklahoma City, OK 73136, USA
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Terrence L Stull
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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Morton DJ, Seale TW, Bakaletz LO, Jurcisek JA, Smith A, VanWagoner TM, Whitby PW, Stull TL. The heme-binding protein (HbpA) of Haemophilus influenzae as a virulence determinant. Int J Med Microbiol 2009; 299:479-88. [PMID: 19451029 PMCID: PMC2749905 DOI: 10.1016/j.ijmm.2009.03.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 03/09/2009] [Accepted: 03/27/2009] [Indexed: 01/29/2023] Open
Abstract
Haemophilus influenzae has an absolute growth requirement for heme and the heme-binding lipoprotein (HbpA) and has been implicated in the utilization of this essential nutrient. We constructed an insertional mutation of hbpA in a type b and a nontypeable H. influenzae strain. In the type b strain, the hbpA mutant was impaired in utilization of heme complexed to either hemopexin or to albumin and in the utilization of low levels of heme but not in the utilization of heme at high levels or of hemoglobin or hemoglobin-haptoglobin complexes. In contrast, the hbpA mutant derivative of the nontypeable strain was impaired in utilization of all tested heme sources. We further examined the impact of the hbpA mutation in animal models of H. influenzae disease. The hbpA mutant of the nontypeable strain was indistinguishable from the wild-type strain in the chinchilla model of otitis media. The hbpA mutant derivative of the type b strain caused bacteremia as well as the wild-type strain in 5-day old infant rats. However, in 30-day old rats the hbpA caused significantly lower rates of bacteremia than the wild-type strain indicating a role for hbpA and heme acquisition in virulence in this model of H. influenzae disease. In conclusion, HbpA is important for heme utilization by multiple H. influenzae strains and is a virulence determinant in a model of H. influenzae invasive disease.
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Affiliation(s)
- Daniel J Morton
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
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Whitby PW, Seale TW, VanWagoner TM, Morton DJ, Stull TL. The iron/heme regulated genes of Haemophilus influenzae: comparative transcriptional profiling as a tool to define the species core modulon. BMC Genomics 2009; 10:6. [PMID: 19128474 PMCID: PMC2627913 DOI: 10.1186/1471-2164-10-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 01/07/2009] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Haemophilus influenzae requires heme for aerobic growth and possesses multiple mechanisms to obtain this essential nutrient. Although an understanding of the heme acquisition mechanisms of H. influenzae is emerging, significant gaps in our knowledge remain. Unresolved issues include the identities of all genes exhibiting altered transcription in response to iron and heme availability, the fraction of such genes functioning in iron/heme acquisition, and the heterogeneity of this gene set among clinical isolates. Previously we utilized H. influenzae strain Rd KW20 to demonstrate the utility of transcriptional profiling in defining the genes exhibiting altered transcription in response to environmental iron and heme levels. The current study expands upon those observations by determining the iron/heme modulons of two clinical isolates, the type b isolate 10810 and the nontypeable isolate R2866. These data are used to begin to define the core iron/heme modulon of the species. RESULTS Microarray studies were performed to compare gene expression on transition from iron/heme-restricted to iron/heme-replete conditions for each isolate. Of 1820 ORFs on the array corresponding to R2866 genes, 363 were significantly differentially expressed: 233 were maximally transcribed under iron/heme-replete conditions and 130 under iron/heme-restricted conditions. Of the 1883 ORFs representing genes of strain 10810, 353 were significantly differentially transcribed: 150 were preferentially transcribed under iron/heme-replete conditions and 203 under iron/heme-restricted conditions. Comparison of the data sets indicated that 163 genes exhibited similar regulation in both isolates and that 74 of these exhibited similar patterns of regulation in Rd KW20. These comprise the putative core iron/heme modulon. CONCLUSION This study provides evidence for a conserved core of H. influenzae genes the transcription of which is altered by the availability of iron and/or heme in the growth environment. Elucidation of this modulon provides a means to identify genes with unrecognized roles in iron/heme acquisition or homeostasis, unanticipated responsiveness to environmental levels of the micronutrients or potential roles in virulence. Defining these core genes is also of potential importance in identifying targets for therapeutic and vaccine designs since products of these genes are likely to be preferentially expressed during growth in iron/heme restricted sites of the human body.
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Affiliation(s)
- Paul W Whitby
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Thomas W Seale
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Timothy M VanWagoner
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Department of Biology, Oklahoma Christian University, Oklahoma City, OK 73136, USA
| | - Daniel J Morton
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | - Terrence L Stull
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
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Morton DJ, Seale TW, Madore LL, VanWagoner TM, Whitby PW, Stull TL. The haem–haemopexin utilization gene cluster (hxuCBA) as a virulence factor of Haemophilus influenzae. Microbiology (Reading) 2007; 153:215-224. [PMID: 17185550 DOI: 10.1099/mic.0.2006/000190-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Haemophilus influenzae has an absolute growth requirement for a porphyrin source, which can be supplied in vitro by haem, haemoglobin, or the haemoglobin-haptoglobin, haem-haemopexin and haem-albumin complexes. Utilization of the haem-haemopexin complex is known to be mediated by the products of the hxuCBA gene cluster. It was demonstrated that hxuC, but not hxuA or hxuB, is also essential for the utilization of haem from haem-albumin complexes. Mutants of the type b strain E1a lacking genes in the hxuCBA gene cluster were examined for their ability to cause bacteraemia in rat models of invasive disease. In 5-day-old rats, mutants in the hxuCBA genes yielded a significantly reduced bacteraemic titre compared to the wild-type strain. In addition, 5-day-old rats infected with the hxuCBA mutant strains exhibited significantly improved survival rates compared to those infected with the wild-type strain. Mutations in the haemoglobin/haemoglobin-haptoglobin-binding protein genes (hgps), either alone or in combination with the hxuCBA mutations, had no impact on virulence in 5-day-old rats. In 30-day-old rats infected with either the hxuCBA mutants or the wild-type strains, there was no significant difference in the ability to establish bacteraemia although bacterial titres were lower in rats infected with the hxuCBA mutants than in those infected with the wild-type strain. These age-related differences in the impact of mutations in the hxuCBA gene cluster may be related to changes in levels of host haem-binding proteins during development of the rat.
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Affiliation(s)
- Daniel J Morton
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Thomas W Seale
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Larissa L Madore
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Timothy M VanWagoner
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Paul W Whitby
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Terrence L Stull
- Department of Microbiology/Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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Seale TW, Morton DJ, Whitby PW, Wolf R, Kosanke SD, VanWagoner TM, Stull TL. Complex role of hemoglobin and hemoglobin-haptoglobin binding proteins in Haemophilus influenzae virulence in the infant rat model of invasive infection. Infect Immun 2006; 74:6213-25. [PMID: 16966415 PMCID: PMC1695506 DOI: 10.1128/iai.00744-06] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Haemophilus influenzae requires an exogenous heme source for aerobic growth in vitro. Hemoglobin or hemoglobin-haptoglobin satisfies this requirement. Heme acquisition from hemoglobin-haptoglobin is mediated by proteins encoded by hgp genes. Both Hgps and additional proteins, including those encoded by the hxu operon, provide independent pathways for hemoglobin utilization. Recently we showed that deletion of the set of three hgp genes from a nontypeable strain (86-028NP) of H. influenzae attenuated virulence in the chinchilla otitis media model of noninvasive disease. The present study was undertaken to investigate the role of the hgp genes in virulence of the wild-type serotype b clinical isolate HI689 in the infant rat model of hematogenous meningitis, an established model of invasive disease requiring aerobic growth. Bacteremia of high titer and long duration (>14 days) and histopathologically confirmed meningitis occurred in >95% of infant rats challenged at 5 days of age with strain HI689. While mutations disrupting either the Hgp- or Hxu-mediated pathway of heme acquisition had no effect on virulence in infant rats, an isogenic mutant deficient for both pathways was unable to sustain bacteremia or produce meningitis. In contrast, mutations disrupting either pathway decreased the limited ability of H. influenzae to initiate and sustain bacteremia in weanling rats. Biochemical and growth studies also indicated that infant rat plasma contains multiple heme sources that change with age. Taken together, these data indicate that both the hgp genes and the hxuC gene are virulence determinants in the rat model of human invasive disease.
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Affiliation(s)
- Thomas W Seale
- Department of Pediatrics, CHO 2308, University of Oklahoma Health Sciences Center, 940 NE 13th Street, Oklahoma City, OK 73104, USA
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Whitby PW, Vanwagoner TM, Seale TW, Morton DJ, Stull TL. Transcriptional profile of Haemophilus influenzae: effects of iron and heme. J Bacteriol 2006; 188:5640-5. [PMID: 16855256 PMCID: PMC1540045 DOI: 10.1128/jb.00417-06] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Haemophilus influenzae requires either heme or a porphyrin and iron source for growth. Microarray studies of H. influenzae strain Rd KW20 identified 162 iron/heme-regulated genes, representing approximately 10% of the genome, with > or =1.5-fold changes in transcription in response to iron/heme availability in vitro. Eighty genes were preferentially expressed under iron/heme restriction; 82 genes were preferentially expressed under iron/heme-replete conditions.
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Affiliation(s)
- Paul W Whitby
- Department of Pediatrics, CHO 2308, 940 NE 13th St., Oklahoma City, OK 73104, USA
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