Research Article: Microarray-Based Analysis of Differential Gene Expression between Infective and Noninfective Larvae of Strongyloides stercoralis

Date Published: May 3, 2011

Publisher: Public Library of Science

Author(s): Roshan Ramanathan, Sudhir Varma, José M. C. Ribeiro, Timothy G. Myers, Thomas J. Nolan, David Abraham, James B. Lok, Thomas B. Nutman, Elodie Ghedin.

Abstract: BackgroundDifferences between noninfective first-stage (L1) and infective third-stage (L3i)
larvae of parasitic nematode Strongyloides stercoralis at the
molecular level are relatively uncharacterized. DNA microarrays were developed and
utilized for this purpose.Methods and FindingsOligonucleotide hybridization probes for the array were designed to bind 3,571
putative mRNA transcripts predicted by analysis of 11,335 expressed sequence tags
(ESTs) obtained as part of the Nematode EST project. RNA obtained from S.
stercoralis L3i and L1 was co-hybridized to each array after labeling
the individual samples with different fluorescent tags. Bioinformatic predictions
of gene function were developed using a novel cDNA Annotation System software. We
identified 935 differentially expressed genes (469 L3i-biased; 466 L1-biased)
having two-fold expression differences or greater and microarray signals with a p
value<0.01. Based on a functional analysis, L1 larvae have a larger number of genes putatively involved in transcription (p = 0.004), and L3i larvae have biased expression of putative heat shock proteins (such as hsp-90). Genes with products known to be immunoreactive in S. stercoralis-infected humans (such as SsIR and NIE) had L3i biased expression. Abundantly expressed L3i contigs of interest included S. stercoralis orthologs of cytochrome oxidase ucr 2.1 and hsp-90, which may be potential chemotherapeutic targets. The S. stercoralis ortholog of fatty acid and retinol binding protein-1, successfully used in a vaccine against Ancylostoma ceylanicum, was identified among the 25 most highly expressed L3i genes. The sperm-containing glycoprotein domain, utilized in a vaccine against the nematode Cooperia punctata, was exclusively found in L3i biased genes and may be a valuable S. stercoralis target of interest.ConclusionsA new DNA microarray tool for the examination of S. stercoralis biology has been developed and provides new and valuable insights regarding differences between infective and noninfective S. stercoralis larvae. Potential therapeutic and vaccine targets were identified for further study.

Partial Text: Strongyloides stercoralis is a parasitic nematode endemic to the
tropics and subtropics that infects an estimated 30–100 million people worldwide.
Chronically infected individuals have the potential to develop hyperinfection syndrome
or disseminated disease, clinical entities that carry a very high (87–100%)
mortality if unrecognized [1].

In this microarray based analysis of differential gene expression between infective and
noninfective S. stercoralis larvae, we uncovered differences in the
expression of genes putatively encoding transcription factors, heat shock proteins and
antigens known to be immunoreactive in sera from infected humans. A comparative
microarray analysis of our data revealed several differences between S.
stercoralis L3i and C. elegans dauer stage larvae, such as
in the expression of genes putatively encoding collagen and myosin. Potential
therapeutic and vaccine targets were identified for further study.