Abstract
BackgroundThird-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.Methodology/Principal FindingsThe 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.Conclusions/SignificanceAlthough this 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.
Highlights
Parasitic nematodes are of considerable medical, veterinary and agricultural importance
Using a suppression subtractive hybridisation (SSH)-based expressed sequence tags (ESTs) approach, we explored transcription in the L3 stage of A. caninum during the transition from a free-living to a parasitic larva, by simulating the earliest stage of parasitism by hookworms in the mammalian host via serum stimulation
Having identified a suite of mRNAs associated with serum stimulation, future efforts should be focused on gaining an understanding of the biological function/s of selected members of these parasitism-associated genes
Summary
Parasitic nematodes are of considerable medical, veterinary and agricultural importance. It is estimated that the morbidity attributable to hookworms, Trichuris and Ascaris, the three most prevalent parasitic nematodes in humans globally, could be as high as 39 disability adjusted life years (DALY) [1]. This assessment takes into account the long-term impact of infection on cognitive and physical development and the overall health of the host. 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 ( termed ‘‘activation’’) can be mimicked in vitro by culturing L3 in serum-containing medium
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