H. influenzae: Role of Sialic Acid in Virulence

Summary

Principal Investigator: Michael A Apicella
Abstract: DESCRIPTION (provided by applicant): Nontypeable Haemophilus influenzae (NTHi) commonly colonize the mucosal surfaces of the human upper respiratory tract. For the most part, this species resides in that environment in a benign (symbiotic?) relationship with the human host. With pathophysiologic changes (obstruction of outflow ducts, loss of the mucociliary elevator, viral infection, etc.) in the airway anatomy and mucosal surface, NTHi can cause human upper and lower tract respiratory infections. The serum resistant phenotype appears to be a prerequisite for NTHi to initiate systemic infection (acute bronchitis, otitis media, etc). Studies from our laboratory and others have shown that sialic acid is important in the biology of many NTHi strains. Sialylation of LOS increases resistance to the bactericidal effect of normal human serum and is an important constituent of the NTHi biofilm. NTHi cannot synthesize sialic acid and must acquire it from its environment. Free sialic acid is quite limited in the human respiratory tract while sialoglycoproteins, such as mucin, are abundant. In our progress report, we have demonstrated that NTHi can remove sialic acid from mucin and incorporate this sugar into its LOS. The mechanism by which this is accomplished is unknown. Analysis of the 13 annotated NTHi genomes indicate that there are no genes homologous to any known eukaryotic or prokaryotic neuraminidase. We have also found that about 40% of NTHi strains do not incorporate sialic acid into their LOS. The factors determining NTHi LOS-based serum resistance and sensitivity are poorly defined. Better definition may lead to novel vaccines approaches. We have recently performed an NTHi human colonization experiment with NTHi 2019strR. The NTHi 2019strR strains recovered from 4 patients six days after infection demonstrated genomic changes after 454 pyrosequencing of these strains and NTHI 2019strR. The hypotheses underlying the studies in this proposal are: A) NTHi can scavenge sialic acid from human mucin by a unique glycosidase system, B) the LOS is a major determinant of serum resistance in NTHi including strains which do not sialylate their LOS, C) NTHi residence in the human nasopharynx selects for specific LOS phase variants and D) the transformability of NTHi allows introduction of foreign DNA into the NTHi genome. The following specific aims are proposed to resolve these hypotheses: 1) Identification of the mechanism by which sialic acid is removed from human mucin, 2) Comparative analysis of the LOS of selected serum resistant NTHi and serum sensitive NTHi strains which cannot sialylate their LOS to determine if specific LOS glycoforms are the basis of serum sensitivity and 3) Analysis of the phase-variation state of genes involved in LPS biosynthesis and the uptake and expression of foreign DNA in NTHi strain 2019strR recovered from patients during human colonization experiments. PUBLIC HEALTH RELEVANCE: This proposal describes studies which will elucidate the mechanism(s) by which nontypeable Haemophilus influenzae (NTHi) scavenges sialic acid from airway glycoproteins. Studies are also proposed which will elucidate the role of the non-sialylated lipooligosaccaride in resistance to serum bactericidal activity. Finally, studies of isolates from human subjects colonized with NTHi 2019strR will examine the role of phase variation on LOS structure and determine if foreign DNA is acquired by NTHi during colonization.
Funding Period: 1988-03-01 - 2015-02-28
more information: NIH RePORT

Top Publications

  1. pmc Utilizing the O-antigen lipopolysaccharide biosynthesis pathway in Escherichia coli to interrogate the substrate specificities of exogenous glycosyltransferase genes in a combinatorial approach
    Eric B Johansen
    Department of Pharmaceutical Chemistry and Pharmaceutical Sciences, University of California, San Francisco, CA 94143, USA
    Glycobiology 20:763-74. 2010
  2. pmc Sialic acid transport and catabolism are cooperatively regulated by SiaR and CRP in nontypeable Haemophilus influenzae
    Jason W Johnston
    Department of Microbiology, Immunology, and Molecular Genetics, The University of Kentucky, Lexington, KY, USA
    BMC Microbiol 10:240. 2010
  3. pmc The lipid A from Vibrio fischeri lipopolysaccharide: a unique structure bearing a phosphoglycerol moiety
    Nancy J Phillips
    Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, USA
    J Biol Chem 286:21203-19. 2011
  4. pmc Identification, structure, and characterization of an exopolysaccharide produced by Histophilus somni during biofilm formation
    Indra Sandal
    Center for Molecular Medicine and Infectious Diseases, Virginia Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, USA
    BMC Microbiol 11:186. 2011
  5. pmc O-antigen and core carbohydrate of Vibrio fischeri lipopolysaccharide: composition and analysis of their role in Euprymna scolopes light organ colonization
    Deborah M B Post
    Buck Institute for Research on Aging, Novato, California 94945, USA
    J Biol Chem 287:8515-30. 2012
  6. pmc Nontypeable Haemophilus influenzae: the role of N-acetyl-5-neuraminic acid in biology
    Michael A Apicella
    Departments of Microbiology and Internal Medicine, The Carver College of Medicine, The University of Iowa, Iowa City IA, USA
    Front Cell Infect Microbiol 2:19. 2012
  7. pmc Analysis of nontypeable haemophilus influenzae phase-variable genes during experimental human nasopharyngeal colonization
    Jessica Poole
    Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
    J Infect Dis 208:720-7. 2013

Detail Information

Publications7

  1. pmc Utilizing the O-antigen lipopolysaccharide biosynthesis pathway in Escherichia coli to interrogate the substrate specificities of exogenous glycosyltransferase genes in a combinatorial approach
    Eric B Johansen
    Department of Pharmaceutical Chemistry and Pharmaceutical Sciences, University of California, San Francisco, CA 94143, USA
    Glycobiology 20:763-74. 2010
    ..This method can be generalized and readily adapted to study the substrate specificity of other putative or uncharacterized glycosyltransferases...
  2. pmc Sialic acid transport and catabolism are cooperatively regulated by SiaR and CRP in nontypeable Haemophilus influenzae
    Jason W Johnston
    Department of Microbiology, Immunology, and Molecular Genetics, The University of Kentucky, Lexington, KY, USA
    BMC Microbiol 10:240. 2010
    ..The transport and catabolism of sialic acid, a critical virulence factor for nontypeable Haemophilus influenzae, is regulated by two transcription factors, SiaR and CRP...
  3. pmc The lipid A from Vibrio fischeri lipopolysaccharide: a unique structure bearing a phosphoglycerol moiety
    Nancy J Phillips
    Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, USA
    J Biol Chem 286:21203-19. 2011
    ..Given their unusual nature, it is possible that these features of the V. fischeri lipid A may underlie the ability of E. scolopes to recognize its symbiotic partner...
  4. pmc Identification, structure, and characterization of an exopolysaccharide produced by Histophilus somni during biofilm formation
    Indra Sandal
    Center for Molecular Medicine and Infectious Diseases, Virginia Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, Virginia, USA
    BMC Microbiol 11:186. 2011
    ..somni. However, H. somni does form a biofilm in vitro and in vivo, and the biofilm matrix of most bacteria consists of a polysaccharide...
  5. pmc O-antigen and core carbohydrate of Vibrio fischeri lipopolysaccharide: composition and analysis of their role in Euprymna scolopes light organ colonization
    Deborah M B Post
    Buck Institute for Research on Aging, Novato, California 94945, USA
    J Biol Chem 287:8515-30. 2012
    ..These studies indicate that the unusual V. fischeri O-antigen sugars play a role in the early phases of bacterial colonization of the squid...
  6. pmc Nontypeable Haemophilus influenzae: the role of N-acetyl-5-neuraminic acid in biology
    Michael A Apicella
    Departments of Microbiology and Internal Medicine, The Carver College of Medicine, The University of Iowa, Iowa City IA, USA
    Front Cell Infect Microbiol 2:19. 2012
    ..In very rare instances, evolution of antibodies to sialylated lipooligosaccharide (LOS) mimics of human antigens can result in autoimmune disease...
  7. pmc Analysis of nontypeable haemophilus influenzae phase-variable genes during experimental human nasopharyngeal colonization
    Jessica Poole
    Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA
    J Infect Dis 208:720-7. 2013
    ..The purpose of this study was to determine the genes that underwent phase variation during a 6-day period of experimental human nasopharyngeal colonization...