Parasitic nematodes are of major socio-economic impact worldwide, as they
represent significant pathogens of humans and animals and impose a substantial economic
and public health burden. Widespread and increasing anthelmintic resistance has
fundamental research, since a better understanding of pivotal developmental processes is
imperative for designing alternative intervention and control strategies against these
parasites. Biological pathways in nematodes might provide new anthelmintic targets. Ecdysis
(moulting of the cuticle) constitutes a critical developmental process which is absent from the
host and might provide a new target.
Using an integrative approach, by combining
assays with transcriptomic,
proteomic and bioinformatic analyses, the present thesis aimed at elucidating the
moulting process of the porcine nodule worm
Oesophagostomum dentatum, a model
organism for parasitic nematodes of socio-economic importance.
Molecules involved in the
vitro moult from third-stage larvae (L3s) to fourth-stage larvae of
by comparing the proteomic profile of a moulting-inhibited larval phenotype with
that of control larvae by two-dimensional (2D) gel electrophoresis. Additionally, the
by employing a newly established filter-based technique and
L3s before, during and after exsheathment
by 2D difference gel
electrophoresis. Exsheathment represents the final and completing step of the moulting
process and also marks the transition from the free-living to the parasitic life
style in strongylid nematodes.
proteins differentially expressed in moulting-inhibited L3s
compared to control larvae and/or over-expressed in L3s during exsheathment, but not
before or after this transition, were detected. Subsequent mass spectrometric and
bioinformatic analysis revealed an involvement of these proteins
in energy metabolism,
stress response and host-pathogen interactions, structure and motility, signalling and
interaction and/or development and growth.
study of the moulting process in
showed the involvement
of proteins in moulting
in related nematode species (e.g. peptidyl-prolyl cis-transisomerase, cuticlin-1, intermediate filament protein B
and tropomyosin), affirmed previous findings of
proteins with predicted functions during nematode moult (e.g.
fructose-bisphosphate aldolase, propionyl-CoA carboxylase and phosphoenolpyruvate carboxykinase [GTP]) and
suggested new molecules to be crucial for moulting/exsheathment in
aspartyl protease inhibitor and transthyretin-like protein 5).
proteins were down-regulated in the
L3s in comparison to their controls and also over-expressed in L3s
during exsheathment, and nine protein homologues could be
linked to dauer formation in the free-living nematode
these molecules are likely to act on all four moults in
and might be part of a
conserved pathway or mechanism of moulting in
This first proteomic analysis of the moulting process of
understanding of the molecular and biochemical mechanisms and regulating pathways
underlying this fundamental developmental process. This study
might have implications for
a foundation for tackling a range of basic and applied aspects
of developmental parasitology and exploring new intervention targets.