Secreted effectors of Aspergillus fumigatus influence platelet activity of the human host

Ref ID: 19414

Author:

A. Schedler,1 K. Czakai,2 B. Nieswandt,3 S. Krappmann4 and J.
Loffler2

Author address:

1University Hospital W€urzburg, Germany; 2University Hospital
W€urzburg, Medical Clinic and Policlinic II, Germany; 3University
W€urzburg, Rudolf Virchow Center, Germany and 4University
Hospital Erlangen, Microbiological Institute, Germany

Full conference title:

6th Trends in Medical Mycology 2013

Date: 11 October 2014

Abstract:

Objectives Aspergillus fumigatus is a ubiquitous fungus colonizing soil
and decomposing organic matter. It produces small conidia that are
distributed by the air and reach the alveoli of the human lung when
inhaled. In immunocompromised patients this opportunistic pathogen
can cause several forms of diseases, the most severe form being Inva-
sive Aspergillosis (IA). IA and also bronchopulmonary forms of asper-
gillosis can be accompanied by local tissue damage as well as local
bleedings and thrombus formations at the site of infection. This could
be the result of potentially exaggerated and uncontrolled cells of the
specific immune system, mechanical destruction of lung tissue caused
by steadily growth of the fungus during invasion, or alteration of the
local haemostasis by Aspergillus at the site of infection.
Methods To elucidate the influence of A. fumigatus on haemostasis,
platelets from healthy donors were isolated by centrifugation and
collagen- or ADP- induced aggregation was analysed. Platelets were
coincubated with conidia, swollen conidia, germtubes and hyphae of
the wild type isolate ATCC46645 as well as with native and concen-
trated culture filtrates from germtubes and hyphae. In addition, pro-
tease-containing culture filtrates of ATCC46645, of the prtT-
knockout strain AfS61 as well as the reconstituted strain AfS62 were
used. Platelets were also treated with decreasing concentrations of
the mycotoxin gliotoxin. Results were confirmed by flow cytometry
(platelet-activation markers CD62P and CD63). Here also a time-
kinetic experiment was performed by coincubation of platelets with
gliotoxin (5, 15, 30 min). In addition, activated thromboplastine
time (PTT), prothrombin time (TPZ) and the levels of fibrinogen and
of D-dimers of platelet-poor plasma was analysed after coincubation
with the above mentioned effectors.
Results The analysis of coagulation parameters revealed no influ-
ence of morphologies, culture filtrates or gliotoxin on coagulation.
Aggregation assays of human platelets coincubated with different A.
fumigatus morphologies showed an increased aggregation of platelets
conincubated with hyphae or its concentrated culture supernatant.
In addition, the coincubation of protease-containing culture filtrates
of ATCC46645 and AfS62 appeared to activate resting platelets
whereas the AfS61 culture filtrate had no significant effect. Heat
inactivation as well as protease-inhibitors could not reverse the acti-
vating effect to full extent, which was validated by flow cytometry.
Furthermore, purified gliotoxin was used and a concentration-depen-
dent inhibition on collagen- or ADP-induced platelet aggregation
could be shown. This inhibition was confirmed by flow cytometry.
Time-kinetic experiment of platelets coincubated with gliotoxin
revealed a decrease in CD62P-expression on resting and ADP-acti-
vated platelets over time.
Conclusion Taken together, these data imply an effect of A. fumiga-
tus secreted effectors and secondary metabolites on host haemostasis.
The discovery of the targets and the mode of action for these effectors
and metabolites may lead to new insights into the mechanisms of A.
fumigatus pathogenicity to support antifungal therapy.

Abstract Number: p174

Conference Year: 2013

Link to conference website: NULL

New link: NULL

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