Echinococcus P29 antigen: molecular characterization and implication on post-surgery follow-up of CE patients infected with different species of the Echinococcus granulosus complex

Ghalia Boubaker; Bruno Gottstein; Andrew Hemphill; Hamouda Babba; Markus Spiliotis

doi:10.1371/journal.pone.0098357

Echinococcus P29 antigen: molecular characterization and implication on post-surgery follow-up of CE patients infected with different species of the Echinococcus granulosus complex

PLoS One. 2014 May 22;9(5):e98357. doi: 10.1371/journal.pone.0098357. eCollection 2014.

Authors

Ghalia Boubaker¹, Bruno Gottstein², Andrew Hemphill², Hamouda Babba³, Markus Spiliotis²

Affiliations

¹ Institute of Parasitology, University of Berne, Berne, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Berne, Berne, Switzerland; Department of Clinical Biology B, Laboratory of Parasitology and Mycology, University of Monastir, Monastir, Tunisia.
² Institute of Parasitology, University of Berne, Berne, Switzerland.
³ Department of Clinical Biology B, Laboratory of Parasitology and Mycology, University of Monastir, Monastir, Tunisia.

Abstract

The protein P29 is a potential serological marker for post-treatment monitoring of cystic echinococcosis (CE) especially in young patients. We now have demonstrated that P29 is encoded in the Echinococcus genus by a single gene consisting of 7 exons spanning 1.2 kb of DNA. Variability of the p29 gene at inter- and intra-species level was assessed with 50 cDNA and 280 genomic DNA clones isolated from different E. granulosus s.l. isolates (E. granulosus sensu stricto (G1), E. equinus (G4), E. ortleppi (G5), E. canadensis (G6), E. canadensis (G7) and E. canadensis (G10)) as well as four E. multilocularis isolates. Scarce interspecies polymorphism at the p29 locus was observed and affected predominantly E. granulosus s.s. (G1), where we identified two alleles (A1 and A2) coding for identical P29 proteins and yielding in three genotypes (A1/A1, A2/A2 and A1/A2). Genotypic frequencies expected under Hardy-Weinberg equilibrium revealed a high rate of heterozygosity (47%) that strongly supports the hypothesis that E. granulosus s.s. (G1) is predominantly outbreeding. Comparative sequence analyses of the complete p29 gene showed that phylogenetic relationships within the genus Echinococcus were in agreement with those of previous nuclear gene studies. At the protein level, the deduced P29 amino acid (AA) sequences exhibited a high level of conservation, ranging from 97.9% AA sequence identity among the whole E. granulosus s.l. group to 99.58% identity among E. multilocularis isolates. We showed that P29 proteins of these two species differ by three AA substitutions without implication for antigenicity. In Western-blot analyses, serum antibodies from a human CE patient infected with E. canadensis (G6) strongly reacted with recombinant P29 from E. granulosus s.s. (G1) (recEg(G1)P29). In the same line, human anti-Eg(G1)P29 antibodies bound to recEcnd(G6)P29. Thus, minor AA sequence variations appear not to impair the prognostic serological use of P29.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Antigens, Helminth / blood
Antigens, Helminth / chemistry*
Base Sequence
Blotting, Western
DNA Primers
Echinococcosis / immunology
Echinococcosis / parasitology
Echinococcosis / surgery*
Echinococcus granulosus / immunology
Echinococcus granulosus / isolation & purification*
Follow-Up Studies
Humans
Postoperative Period

Substances

Antigens, Helminth
DNA Primers
P-29 antigen

Grants and funding

This work was supported by the Swiss National Science Foundation (grant no. 31003A_141039/1) and the UNESCO-L'OREAL international “For women in science” Fellowships (http://www.unesco.org/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.