Echinococcus P29 Antigen: Molecular Characterization and Implication on Post-Surgery Follow-Up of CE Patients Infected with Different Species of the Echinococcus granulosus Complex

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.

Spatiotemporal Expression Patterns and Antibody Reactivity of Taeniidae Endophilin B1

“…Echinococcus granulosus P29 antigen has proved useful for diagnosis and posttreatment monitoring of CE patients (15)(16)(17)29). This study provides evidence that TsMEndoB1 may be applicable for serodiagnosis of NC and other Taeniidae infections, such as CE and AE.…”

“…In the course of our experiments, we cloned and expressed E. granulosus endophilin B1 and observed that the protein exhibited comparable diagnostic sensitivity and specificity, compared with rTsMEndoB1, in diagnosing NC, CE, and AE (data not shown). Several different strains of E. granulosus complex and E. multilocularis that were examined harbored endophilin B1 orthologs that shared 97.9 to 99.6% sequence identity (29). We surmise that these endophilin B1 proteins may also be useful as biomarkers for the detection of specific antibodies in patients with NC, CE, and AE.…”

“…1). Echinococcus granulosus P29 (15,29) and antigen S (30), both of which were shown to be effective serodiagnostic antigens for CE, were found to be a protein identical to and a partial fragment (amino acids 70 to 221) of these molecules, respectively. The sequence identity values of the Taeniidae proteins were markedly decreased, compared to homologs isolated from other Cestoda (Hymenolepidae) and Trematoda species, i.e., 22.6 to 56.7%, but all of those proteins harbored amino acid residues responsible for dimerization (Fig.…”

Follow‐up of surgically treated patients with cystic echinococcosis: can novel recombinant antigens compete with imaging? Analysis of a patient cohort

“…Serum samples were examined by ELISA to measure specific IgG and IgG4 antibodies against both the 2B2t and the EgP29 antigens. Serological testing was performed at the Instituto de Recursos Naturales y Agrobiología de Salamanca (IRNASA‐CSIC), Salamanca, Spain.…”

“…We tested two recombinant antigens, EgP29 and the novel 2B2t , in a clinically well‐defined patient cohort to address the following question: Does serology reproduce surgical cure as defined by imaging?…”