The biological function of the EG95/45W proteins is largely unknown. However,
they all share a common domain structure of a signal peptide, followed by one single fibronectin III (Fn3) domain and a hydrophobic transmembrane region close to the C-terminus (107). Very interesting recent work on different Taenia species (109,110) and E. granulosus (111) also demonstrated that these proteins are primarily located in the penetration glands of the nonactivated oncosphere and are distributed over the oncospheral parenchyma upon activation with low-pH/pepsin https://www.selleckchem.com/products/sch772984.html treatment (mimicking the transition to the intermediate host). Because Fn3 domains are typically found in extracellular matrix-associated proteins, it is conceivable that the EG95/45W proteins play a role in providing or organizing a primary matrix framework to which totipotent parasite stem cells (delivered by the oncosphere) can attach to undergo the early oncosphere–metacestode transition, although experimental evidence supporting this theory is still lacking. A close ortholog to EG95 has also already been identified in E. multilocularis (named EM95), and the respective recombinant Atezolizumab protein was effective in protecting mice against challenge infection with E. multilocularis oncospheres (112). Because this was, so far, the only report on these genes in E. multilocularis and because the overall genomic organization of the
EG95/45W encoding genes had not been determined in the other cestode species, we carried out respective analyses on the assembled E. multilocularis genome. When the EM95, EG95 and 45W sequences were used in tBLAST analyses, we could indeed identify a relatively large number (up to 15) of related genes dispersed over the genome, most of which were, however, transcriptionally
silent according to RNA-seq data and many contained inactivating mutations in their reading frames. Only five of the genes showed significant levels of transcription and only two of those, located on scaffold_159 (Em95; position 5963–4694) and scaffold_125 (Em95-2; 15880–14568) were closely related to the previously identified EM95 (112) and displayed the same Arachidonate 15-lipoxygenase conserved exon–intron structure (Figure 4). Intriguingly, in the RNA-seq transcription profiles, these oncosphere-specific genes displayed considerable levels of expression in regenerating primary cells but not in metacestode or protoscolex (Figure 5) which underscores the suitability of the E. multilocularis stem cell cultivation system to mimic the oncosphere–metacestode transition not only morphologically (36), but also concerning gene expression profiling. Two additional EM95-like genes that we identified, located on scaffold_104 (Emy162a; position 44001–45896) and scaffold_7 (Emy162b; 35094–33349) showed considerable homologies to the recently identified EMY162 antigen (113).