Undoubtedly, the most studied factor in Echinococcus is the so-called antigen B (AgB), a highly immunogenic lipoprotein and major component of hydatid cyst fluid (94). Although
there are several reports on Erastin solubility dmso immunomodulatory properties of AgB in vitro (94), and biochemical investigations that demonstrate binding of different hydrophobic ligands to AgB (95), the precise function of this protein in the biology of Echinococcus or in the immune response during echinococcosis is still unknown. Originally described as a 160 kDa lipoprotein, AgB was later shown to be built up of several 8 kDa monomers that are encoded by a gene family (96), and since the first full description of an AgB-encoding gene by Frosch et al. (97), there has been constant debate on how many of these genes are actually Selleckchem Panobinostat expressed in these parasites. By studies of Fernandez et al. (98), Chemale et al. (99), Arend et al. (100) and Mamuti et al. (101), the number of AgB subunit genes had grown to five in 2007 (named EmAgB1-EmAgB5 in E. multilocularis and EgAgB1-EgAgB5 in E. granulosus), whereas genomic Southern blot analyses indicated that there are at least seven loci
(102). Studies by Haag et al. (103) and Arend et al. (100) even suggested the presence of further AgB genes (up to 10 in E. granulosus and up to 110 copies in the related E. ortleppi) as well as a high degree of genetic polymorphism among those genes (even within protoscoleces that derived from one single cyst). These authors proposed that numerous AgB copies might be involved in gene conversion mechanisms through recombination processes and DNA rearrangements similar to the situation in protozoans such as Plasmodium sp. or trypanosomes (103). This theory was recently contradicted by Zhang et al. (104) who characterized AgB genes in E. granulosus isolates from different geographic origins and proposed the presence of 10 unique genes (or alleles) that are, however, highly homologous between these isolates and did not
show gross polymorphisms. To shed more light on the situation, we have BCKDHA analysed the presence and location of AgB genes in the current assemblies of the E. multilocularis and E. granulosus genomes. As described by Brehm (72), using the first assembly version of the E. multilocularis genome (19 000 contigs), a total of seven AgB loci appears to form a cluster on a distinct region of the genome. In the latest genome version (600 supercontigs), all these copies are now assembled into one continuous sequence fragment of 57 kbp that is present on scaffold_29 (Figures 2 and 3). The antigen B cluster is flanked by two genes, EmLDLR and EmMTA, which are highly conserved among cestodes.