TABLE CONTENTS

SESSION THIRTY – ROLE AND EXPRESSION OF NEMATODE
PARASITISM GENES
CONVENORS: ERIC DAVIS & ANN BURNELL
Hookworm Genes and the Infectious Process
Datu, B. (1), R. Gasser (2), A. Hofmann (3), J. Mulvenna (1) & A. Loukas (1)
(1) Queensland Institute of Medical Research, Brisbane, Australia; (2) University of Melbourne, Melbourne,
Australia; (3) Griffith University, Brisbane, Australia
Third-stage larvae (L3) of the canine hookworm, Ancylostoma caninum, undergo arrested
development preceding transmission to a host. Many of the mRNAs up-regulated at this stage
are likely to encode proteins that facilitate the transition from a free-living to a parasitic larva.
The initial phase of mammalian host invasion by A. caninum L3 (herein termed ‘activation’)
can be mimicked in vitro by culturing L3 in serum-containing medium. The mRNAs
differentially transcribed between activated and non-activated L3 were identified by
suppression subtractive hybridisation (SSH). The analysis of these mRNAs on a custom
oligonucleotide microarray printed with the SSH expressed sequence tags (ESTs) and
publicly available A. caninum ESTs (non-subtracted) yielded 602 differentially expressed
mRNAs, of which the most highly represented sequences encoded members of the
pathogenesis-related protein (PRP) superfamily and proteases. Comparison of these A.
caninum mRNAs with those of Caenorhabditis elegans larvae exiting from developmental
(dauer) arrest demonstrated unexpectedly large differences in gene ontology profiles. C.
elegans dauer exiting L3 up-regulated expression of mostly intracellular molecules involved
in growth and development. Such mRNAs are virtually absent from activated hookworm
larvae, and instead are over-represented by mRNAs encoding extracellular proteins with
putative roles in host-parasite interactions. One family of proteins inparticular, the
Ancylostoma Secreted Proteins (ASPs), has undergone enormous expansion in the hookworm
genome and seventeen of the thirty most highly upregulated genes encoded for ASPs. The
functions of ASPs are mostly unknown, but structural and modelling studies show a large
peptide-binding groove which likely accommodates host-derived ligands. Although the data
presented here should not invalidate C. elegans dauer exit as a model for hookworm
activation, it highlights the limitations of this free-living nematode as a model organism for
the transition of nematode larvae from a free-living to a parasitic state.
5 th International Congress of Nematology, 2008 108