Pathogenesis of Indoor Fungal Disease

1
Pathogenesis of Indoor Fungal Disease

• Michael R. McGinnis, Ph.D.
• Department of Pathology
• University of Texas Medical Branch
• Galveston, Texas

2
Health Problem
Establishing the cause-effect relationship
between indoor amplification of fungi and the
health problem of the building resident.
3
Indoor Bioaerosols

• Pollen
• Algae
• Bacteria
• Viruses
• Protozoa

• Mites
• Insects and feces
• Pet dander
• Dried pet saliva
• Yeasts
• Moulds

4

Aw lt 0.80
Aw lt 0.80-0.90
Aw gt0.90
water
H2O
Aw Minimum water activity level at 25C Aw
gt0.90, ERH gt90
5

Aspergillus versicolor Aw 0.74-0.79
Ulocladium chartarum Aw 0.89
Stachybotrys chartarum Aw 0.94
Aw Minimum water activity level at 25C Aw
gt0.90, ERH gt90
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Aw Levels for Colonization

• Low (aw lt0.85), primary colonizer
• a. Aspergillus versicolor (25C)
• b. Eurotium spp.
• c. Penicillium aurantiogriseum
• d. P. brevicompactum
• e. P. chrysogenum
• f. Wallemia sebi

Flannigan et al. Microorganisms in Home and
Indoor Work Environments.Taylor Francis,
London, 2001.
7
2. Intermediate (aw 0.85-0.90),
secondary colonizer a. Aspergillus
flavus b. A. nidulans c. A.
sydowii d. A. versicolor (12C)
e. Cladosporium cladosporioides f.
C. sphaerospermum
Flannigan et al. Microorganisms in Home and
Indoor Work Environments.Taylor Francis,
London, 2001.
8
3. High (aw gt0.90), tertiary colonizer
a. Alternaria alternata
b. Aspergillus fumigatus c.
Chaetomium spp. d. Exophiala spp.
e. Fusarium spp. f.
Memnoniella echinata g.
Phialophora spp. h. Rhodotorula
spp. i. Stachybotrys chartarum
j. Trichoderma spp.
Flannigan et al. Microorganisms in Home and
Indoor Work Environments.Taylor Francis,
London, 2001.
9
Stachybotrys chartarum
http//www.apsnet.org./online/feature/Stachybotrys
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Idiopathic Pulmonary Hemorrhage Hemosiderosis
Proposed Fungal Pathogenesis

• Inhalation of Stachybotrys chartarum
• conidia containing mycotoxins and other
  secondary metabolites.
• 2. Disruption of lung capillary blood vessel
  walls.

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Proposed Fungal Pathogenesis (continued)

• 3. Lysis of red blood cells by hemolysin.
• 4. Lung tissue damage by proteinase.
• 5. Satratoxin immunomodulation, protein
• synthesis inhibition, skin irritation, and
• induced host cell apoptosis.

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Exposure and Disease

• 1. exposure
• a. inhalation of conidia, spores, hyphae,
  cell
• wall components, mycotoxins, MVOCs.
•     b. contact by conidia, spores, hyphae, cell
• wall components, mycotoxins, MVOCs.
•     c. ingestion of conidia, spores, hyphae,
• mycotoxins.

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Exposure and Disease (continued)

• 2. disease
• a. allergic
• alveolitis, anaphylaxis, asthma,
• conjunctivitis, dermatitis,
  hypersensitivity
• pneumonitis, rhinitis, rhinosinusitis,
  sinusitis
• b. irritant

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Exposure and Disease (continued)

• c. mycotoxicosis
• 1). fungal volatile organic compounds
• mycotoxin biosynthetic pathway
• 2). mycotoxins and other secondary
• metabolites
• inhalation, ingestion, skin contact

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Exposure and Disease (continued)

• d. invasive
• 1). exceptionally rare
• 2). immunocompromised patients
• 3). aspergillosis
• 4). invasive sinusitis

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Ga Protein-cAMP-Protein Kinase Transduction
Pathway

• Link external stimuli to coordinated response.
• Coordinate events at late growth stage
• a. conidiation
• b. mycotoxin biosynthesis (gene
  clusters)
• c. melanin biosynthesis (gene cluster)
• d. sclerotium development

Calvo AM et al. Microbiol. Mol. Biol. Rev.
66447-459, 2002. Langfelder K et al. Fungal Gen.
Biol. 38143-158, 2003
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Deoxynivalenol (DON)
Diacetoxyscirpenol (DAS) Nivalenol (NIV),
Roridin, Satratoxin, T-2, Verrucarin
Trichodiene synthase
FPP
DHN-melanin
Aflatoxin B1 B2 G1 G2 Alternariol,
Citrinin, Penicillic acid, Ochratoxin,
Sterigmatocystin zearalenone
PKSs
Acetyl-coenzyme A Malonyl-coenzyme A
FPP Farnesyl pyrophosphate DHN-melanin
1,8-dihydroxynaphthalene melanin PKSs polyketide
synthases
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Mycotoxins Detected in Crude Building Materials

• Acetyl-T-2 toxin
  Satratoxin G
• Citrinine
  Sterigmatocystin
• Diacetoxyscirpenol T-2
  toxin
• Deoxynivalenol T-2
  tetraol
• HT-2 toxin
  T-2 triol
• Nivalenol
  Verrucarine A
• Ochratoxin A
  Verrucarol
• Tuomi et al. Appl. Environ. Microbiol.
  661899-1904, 2000.

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Mycotoxicosis Severity

• Type of mycotoxin.
• Exposure duration and dose.
• Age.
• Nutritional status and health of individual.
• Synergistic effect with other chemicals or
  mycotoxins.
• Primary target organs.
• liver, lungs, kidney, and nervous,
• endocrine, immune systems

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Trichothecene Groups
Group A. Not belonging to groups B-D.
Highly toxic. Group B. Possesses C8-keto
group. Fusarium spp. only. Group
C. Ring from R2-R3 alcohol group.
Macrocyclic Trichothecenes. Group D. C-7,8 or
C-9,10 epoxy group. Rare.
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Mycotoxin Pulmonary Disease

• Exposure dose.
• Site of deposition.
• a. tracheobronchial tree
• b. alveoli
• 3. Time in pulmonary zone.
• 4. Sensitivity of individual.

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Mycotoxin Symptoms in Humans

• 1. fatigue
• 2. nausea
• 3. headaches
• 4. respiratory irritation
• 5. eye irritation
• 6. discomfort
• 7. inability to concentrate
• 8. dermatitis

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Asthma Symptoms

• 1. difficult to breathe
• 2. wheezing
• 3. shortness of breath
• 4. coughing
• 5. constriction of air passages
• 6. Inflammation of air passages

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Hydrophobins

• 1. Plant toxins
• 2. Fungal attachment
• 3. Coat air-exposed fungal surfaces
• 4. Influence conidial wall structure
• 5. Escape aqueous environments
• 6. Proteins with 8 cysteine residues

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Hydrophobins (continued)

• 7. Highly insoluble complexes on outermost cell
• wall.
• 8. Occur as regularly shaped rodlets (class 1).
• 9. One or two different hydrophobins on
• conidium cell wall depending upon species.
• a. Class 1, RodAp (16-kDa) and DewAp (14-
• kDa).
• b. Aspergillus fumigatus, A. nidulans and
• A. niger.

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Hydrophobins (continued)

• 10. Hydrophobins on conidial cell wall different
• than those on hyphal cell wall.
• 11. Conidial cell wall hydrophobins protective
• against mouse alveolar macrophages.
• 12. Variable protein folding at 8 conserved
• cysteine (disulfide bridges) residues
• 13. Class 1 and Class 2 hydrophobins
• a. class 1 highly insoluble
• b. class 2 less insoluble

Paris S et al. Appl. Environ. Microbiol.
691581-1588, 2003.
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Hydrophobins (continued)

• Wosten de Vocht. Biochim Biophys. Acta BAR
  146979-86, 2000.

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Squid Melanin
Jacobson. Clin. Microbiol. Rev. 13708-717, 2000.
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Dihydroxynaphthalene Melanin Biosynthetic Pathway
Wang Breuil. Mol. Genet. Genomics 267557-563,
2002
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Melanized Cells
Cryptococcus neoformans
Cryptococcus neoformans
Aspergillus niger
Rosas et al. J. Immunol. Meth. 24469-80, 2000.
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Indoor Events

• 1.  Intrusion and condensation of water.
• 2.  Impact of conidium or spore from air.
• 3.  Germination of conidium or spore.
• 4.  Penetration of substrate.
• 5.  Development of vegetative hyphae.
• 6. Translocation of nutrients.
• 7. Self-assembly of hydrophobins and
• development of aerial hyphae and.
•  

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Indoor Events (continued)

• 8. Ga protein-cAMP- protein kinase transduction
• pathway, conidiogenesis or ascocarp
• formation, melanin biosynthesis, mycotoxin
• production, conidial cell wall
  hydrophobins.
• 9. Release of MVOCs
• a. bio-signal compounds
• b. mycotoxin biosynthetic pathway molecules

34
Indoor Events (continued)

• 10. Liberation and air dispersal of conidia,
  spores,
• hyphal fragments, cell wall pieces, melanin
• particles.
• 11. Inhalation, skin contact