The Echinococcus granulosus Antigen B Gene Family Comprises at Least 10 Unique Genes in Five Subclasses Which Are Differentially Expressed

Abstract

BackgroundAntigen B (EgAgB) is a major protein produced by the metacestode cyst of Echinococcus granulosus, the causative agent of cystic hydatid disease. This protein has been shown to play an important role in modulating host immune responses, although its precise biological function still remains unknown. It is generally accepted that EgAgB is comprised of a gene family of five subfamilies which are highly polymorphic, but the actual number of genes present is unknown.Methodology/Principal FindingsBased on published sequences for the family, we designed specific primers for each subfamily and used PCR to amplify them from genomic DNA isolated from individual mature adult worms (MAW) taken from an experimentally infected dog in China and individual larval protoscoleces (PSC) excised from a single hydatid cyst taken from an Australian kangaroo. We then used real-time PCR to measure expression of each of the genes comprising the five EgAgB subfamilies in all life-cycle stages including the oncosphere (ONC).Conclusions/SignificanceBased on sequence alignment analysis, we found that the EgAgB gene family comprises at least ten unique genes. Each of the genes was identical in both larval and adult E. granulosus isolates collected from two geographical areas (different continents). DNA alignment comparisons with EgAgB sequences deposited in GenBank databases showed that each gene in the gene family is highly conserved within E. granulosus, which contradicts previous studies claiming significant variation and polymorphism in EgAgB. Quantitative PCR analysis revealed that the genes were differentially expressed in different life-cycle stages of E. granulosus with EgAgB3 expressed predominantly in all stages. These findings are fundamental for determining the expression and the biological function of antigen B.

Recent Advances in the Immunology and Serological Diagnosis of Echinococcosis

“…AgB is a gene family containing at least 10 genes in 5 subfamilies (Shepherd et al, 1991;Fernandez et al, 1996;Chemale et al, 2001;Arend et al, 2004;Mamuti et al, 2007;Zhang et al, 2010), which are differentially expressed in different stages of E. granulosus (Mamuti et al, 2007;Zhang et al, 2010). Several AgB cDNAs, such as rAgB8/1 and rAgB8/2, have been cloned, expressed as recombinant proteins and used for diagnosis.…”

Immunoblotting with Human Native Antigen Shows Stage-Related Sensitivity in the Serodiagnosis of Hepatic Cystic Echinococcosis

“…Overall, these results are comparable with those reported in the literature using sheep hydatid fluid fractions, 28 although our test showed lower sensitivity compared with a commercial IB test routinely used for diagnostic purposes (Echinococcus Western Blot IgG, LDBIO, Lyon, France-Se 83% h-HCF-IB versus Se 98% commercial kit 29 ). The bands recognized by sera from CE patients (8,16,24, 34-50 kDa) belonged to the two main antigens present in the HCF, AgB (8,16, and 24 kDa), and Ag5 (34-50 kDa). Patients with cysts in active stages (CE1 and CE2) responded differently to h-HCF: sera of patients with CE1 cysts recognized inconsistently the AgB subunits, whereas sera of patients with cysts in the CE2 stage recognized all three subunits of AgB.…”

“…9,14,15 AgB is an immunogenic lipoprotein encoded by several genes 16 involved in several host-parasite interaction mechanisms, promoting parasite establishment and survival in the intermediate host. [17][18][19][20] There is also evidence that AgB genes are differentially expressed in the different stages of the parasite life cycle, and parasite tissues during development in the host.…”

“…[17][18][19][20] There is also evidence that AgB genes are differentially expressed in the different stages of the parasite life cycle, and parasite tissues during development in the host. 9,16,21,22 Ag5 is an immunogenic glycoprotein expressed in all stages of the parasite life cycle, and is secreted from the surface of the worm. 9,23 -25 Ag5 is present in elevated concentration in HCF, and it may have a relevant function in the development of the metacestode.…”

An Echinococcus multilocularis Antigen B3 Proteoform That Shows Specific Antibody Responses to Active-Stage Alveolar Echinococcosis

“…In E. granulosus, EgAgB3 was abundantly transcribed in the protoscolex (38), but secretion into the hydatid fluid was minimal at the protein level (25,39). The differential expression patterns of AgB3 in phylogenetically close neighbors imply that an as-yet-unknown transcriptional regulatory mechanism operates in different manners during the maturation of EmAgB3 and EgAgB3.…”