Identification of a differentially expressed Echinococcus multilocularis protein Em6 potentially related to antigen 5 of Echinococcus granulosus

Abstract

By a strategy of differential immunological screening of an expression library constructed from adult Echinococcus multilocularis parasites, a partial cDNA sequence encoding a protein termed Em6 was isolated. This molecule displayed high sequence homology to the recombinant antigen 'Eg6' which was previously described as an immunogenic epitope of antigen 5 of E. granulosus. Further Em6 sequences and the corresponding sequences from a cattle isolate of E. granulosus were obtained by a PCR approach. By immunoblot analyses using affinity purified antibodies, expression of Em6 in fertile cysts producing protoscoleces of the E. multilocularis metacestode stage was observed. However, Em6 was absent in non-fertile metacestodes. The demonstration of a protein in E. multilocularis displaying identities to 'antigen 6' of E. granulosus could potentially contribute to the future elucidation of the relationship between antigen 5 and 'antigen 6' in the genus Echinococcus, and shed some lights on the performance of serodiagnostic assays for hydatid disease based on the respective antigens.

Isolation and molecular characterization of recombinant Echinococcus granulosus P29 protein (recP29) and its assessment for the post-surgical serological follow-up of human cystic echinococcosis in young patients

“…31 Therefore, we can assume that sera from E. multilocularis patients may exhibit a cross-reactive potential with recP29, and we will address this point in future investigations.…”

“…Homology searches in the SwissProt database using the quick Blast P engine showed that P29 has a full identity to the Antigen 'S' epitope (Fragment) of Echinococcus granulosus 30 and 97% identity to antigen 6 (Fragment) [Adama6] of Echinococcus multilocularis. 31 Alignments of P29 with these homologous proteins are shown in Figure 1. …”

An Easy and Efficient Method for Native and Immunoreactive Echinococcus granulosus Antigen 5 Enrichment from Hydatid Cyst Fluid

“…However, as reported several years ago [45], and as confirmed by western blotting in this work, a proportion of CE patients with active cysts do not develop a detectable humoral response against AgB (Figure 2, sera 2–3). On the other hand, the use of Ag5, either partially or highly purified, has declined because of the numerous references to potential cross-reactivity issues [13], [16], as well as to low sensitivity-specificity [1]. Many scientists deduced their conclusions stating that part of this cross-reactivity was associated with the presence of phosphorylcholine bound to the 38 kDa subunit.…”

“…This liquid is a mixture containing a wide range of proteins of both parasite and host origin, the complexity and heterogeneity of which has already been highlighted by the proteomic characterization of HCF collected from sheep, cattle and humans [12]. The most abundant and immunogenic HCF proteins, despite the countless controversial publications about their specificity [1], [2], [13], [14], [15], [16], are Antigen 5 (Ag5) and Antigen B (AgB) [17]–[18]. Ag5 is an oligomeric thermolabile glycoprotein which migrates as 57 kDa and 67 kDa bands in sodium-dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) under non-reducing conditions, and as 38 kDa and 22 kDa bands under reducing conditions [19].…”

Echinococcus granulosus antigen 5 is closely related to proteases of the trypsin family

“…Apart from the N-terminal amino acid sequences reported for the 38 kDa subunit [12], there have been no significant advances in the molecular characterization of the antigen. Different groups, using antibodies reactive against the 38 kDa subunit, isolated partial cDNA sequences from E. granulosus libraries [13] and its homologous sequence from E. multilocularis [14]. These cDNAs, however, were shown recently [15] to code for P-29, a molecule immunologically related to, but distinct from, Ag5.…”