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Presented by
Lionel Williamson
Aspergillus species
 Kingdom: Fungi
Phylum: Ascomycota
Order: Eurotiales
Family: Trichocomaceae
Genus gi: Aspergillus
 Aspergillus is a filamentous, ubiquitous fungus
found in nature. It is commonly isolated from soil,
plant debris, and indoor air environments.
Types of Aspergillus
 The genus Aspergillus includes over 185
species. Around 20 species have so far been
reported as causative agents of opportunistic
infections in man
 A. flavus produces aflotoxins
 A. nidulans produces cutaneous
aspergillosis
 A. oryzae used to make soy sauce, and sake
A. fumigatus
 Is the second most common opportunistic
fungal infection (Candida)
 This species is the most common agent of
aspergillosis in both man and animals. It is a
thermophilic species (growth at 40°C and
beyond) that may be extremely
angioinvasive, particularly in the
compromised patient
Key words
 T helper 1- TH1 Cytokine response that deals with pro
inflammatory response
 T helper 2- TH2 Cytokine response that deals with antiinflammatory response
 PBMC are macrophages and are involved with the
innate immune response
 Innate immunity refers to antigen-nonspecific defense
mechanisms that a host uses immediately or within
several hours after exposure to almost any antigen.
This is the immunity one is born with and is the initial
response by the body to eliminate microbes and prevent
infection.
Cytokines
 Proteins produced by white blood cells that
act as chemical messengers between cells.
They can stimulate or inhibit the growth and
activity of various immune cells
 Pro-inflammatory response ( TNF, IL-1)
 Anti-inflammatory response (IL-10)
Structure of Aspergillus
 Conidia are asexual spores that grown on elaborate
structures called conidiophores. These are usually
stalked, lifting the conidia off the substrate for better
dispersal and to avoid microscopic grazing animals.
They often produce hundreds or thousands of conidia
at a time
 Hyphae A hypha (plural hyphae) is a long, branching
filament that, with other hyphae, forms the feeding
thallus of a fungus called the mycelium. A typical
hypha consists of a tubular wall, usually made of chitin,
which surrounds, supports, and protects the cells that
compose a hypha. For most fungi, a cell within a hyphal
filament is separated from other cells by internal crosswalls called septa
Hyphae vs. conidia
The University of Adelaide
Life cycle of Aspergillus
 A fungus begins its existence as an
independent biont as some sort of
propagule, most often a spore. From the
spore, the fungus grows in a thread-like,
branching formation known as a hypha.
 The hypha grow and intertwine and form
mycelia which become the body of the
fungus.
Germinating conidia
Requirement of spermidine for developmental transitions in Aspergillus nidulans Yuan Jin 1 , Jin Woo Bok
2 , Doralinda Guzman-de-Peña 3 and Nancy P. Keller
Toll like receptors
 Are pattern-recognition receptors believed
to play a role in innate immunity
 The receptor was first isolated from
Drosophila as a gene required for
ontogenesis and antifungal resistance
 There have been several TLR’s isolated
from humans
Types of TLR’s
 TLR 2 recognizes peptidoglycan that are
associated with gram positive bacteria
 TLR 4 recognizes LPS associated with
gram negative bacteria
 TLR5 recognizes flagella
 TLR9 recognizes bacterial DNA
Experiment 1
 Challenged mouse macrophages with
conidia or hyphae from A. fumigatus
 They found that maximal cytokine release
induced by stimulation with 10^7 cfu
 Assessed TLR4’s role by using a TLR4deficient mutant compared to a control
 Assessed TLR2’s role by using a TLR2deficient mutant compared to a control
Exp 1 cont
Experiment 2
 To prove that TLR4 was involved in conidia and
not hyphae recognition
 Using a NF-kB reporter plasmid that drives CD 25
expression
 Used a cell line (3E10) that expressed TLR4 but
not TLR2
 Stimulated the cells with LPS (TLR4 antagonist)
Pam3cys (TLR2 antagonist)
 Then they transfected cDNA for TLR2
Exp 2
Experiment 3
 They wanted to see what roles TLR4 and
TLR2 played on the Pro-inflammatory
response
 Used PBMC’s with antibodies blocking the
TLR4 then stimulating with 10^7 cfu
 The same experiment was repeated with
TLR2
Exp 3 cont.
Experiment 4
 Which TLR stimulated IL-10
 Recent data suggests that TLR2 stimulates TH-2
response and TLR4 stimulates a TH-1 response
 Role of IL-10 in invasive aspergillosis:
increased resistance of IL-10 gene knockout
mice to lethal systemic aspergillosis
K. V. Clemons, G. Grunig* , R. A. Sobel , L. F. Mirels, D. M. Rennick*
& D. A. Stevens
Exp 4 cont.
My conclusion
 I think that what happens is that Aspergillus conidia gets
into the body and meets the macrophages that expresses
TLR4. This causes an increase of expression of IL-1 and
TNF, this kills the most of the fungus.
 The fungus counteracts this by germinating from the
conidia to the hyphae forms. TLR4 does not recognize the
new form and the hyphae grows. In a normal immune
system TLR2 which has 2 functions (pro-inflammatory and
anti-inflammatory) with the help of the cell mediated
response the body is able to fight off the fungal infection
Immunocompromised
 The same things occur but there is a diminished
cell mediated response due to the disease process
 TLR2 is releasing both pro-inflammatory and an
Anti-inflammatory response
 This decreases the destruction of the hyphae and
they continue to grow.
 Where they form mycelia and cause Aspergillosis.
Aspergillosis
 - Pulmonary aspergillosis 1
- CNS aspergillosis
- Sinonasal aspergillosis
- Osteomyelitis
- Endophthalmitis
- Endocarditis
- Renal abscesses
- Cutaneous
 Why do you think pulmonary aspergillosis is the
number one form?
This is the air sacs of a hen
during an outbreak of
aspergillosis
The University of Adelaide
Fungal balls made up of
hyphae isolated from the lungs
The University of Adelaide
Aspergillus fumigatus in lung tissue, note
conidial heads forming in an alveolus
The University of Adelaide
Aspergilloma found at post-mortem in the lung of a
child with leukemia. Note fungus ball occupying cavity
The University of Adelaide
I’m so glad we had this time
together