Comparative analysis of the diagnostic performance of six major Echinococcus granulosus antigens assessed in a double-blind, randomized multicenter study

Recent advances in the immunology and diagnosis of echinococcosis

Echinococcosis is a cosmopolitan zoonosis caused by adult or larval stages of cestodes belonging to the genus Echinococcus (family Taeniidae). The two major species of medical and public health importance are Echinococcus granulosus and Echinococcus multilocularis, which cause cystic echinococcosis and alveolar echinococcosis, respectively. Both cystic echinococcosis and alveolar echinococcosis are serious diseases, the latter especially so, with a high fatality rate and poor prognosis if managed inappropriately. This review highlights recent advances in immunity to infection and vaccination against both parasites in their intermediate and definitive hosts and procedures for diagnosis of cystic echinococcosis and alveolar echinococcosis, including the value of immunodiagnostic and DNA approaches. There is discussion also of progress in genomics and related technologies that is providing valuable insights on the functional biology of the Echinococcus organisms. These studies will underpin future research that will reveal a better understanding of the Echinococcus-host interplay, and suggest new avenues for the identification of additional targets for diagnosis, vaccination and chemotherapy.

Antigens for the immunodiagnosis of Echinococcus granulosus infection: An update

The taeniid tapeworm Echinococcus granulosus is the causative agent of the echinococcal disease, an important zoonosis with worldwide distribution. Accurate immunodiagnosis of the infection requires highly specific and sensitive antigens to be used in immunodiagnostic assays. The choice of an appropriate source of antigenic material is a crucial point in the improvement of the diagnostic features of tests, and must be based on the developmental stage of the parasite and the host. The most common antigenic sources used for the immunodiagnosis of echinococcal disease are hydatid cyst fluid, somatic extracts and excretory-secretory products from protoscoleces or adults of E. granulosus. Hydatid cyst fluid is the antigenic source of reference for immunodiagnosis of human hydatidosis, which is mainly based on the detection of antigens B and 5. Somatic extracts have been widely used in the serodiagnosis for E. granulosus infection in dogs and ruminant intermediate hosts, although in the last few years the detection of excretory-secretory products of the worm in faeces (coproantigens) have become the most reliable method for the detection of the parasite in the definitive host. This review emphasizes recent advances in the identification and characterization of novel antigens with potential for the immunodiagnosis of echinococcal disease. Progress in recombinant technologies and synthetic peptides are also discussed. The paper highlights the need to search for new antigenic components with high diagnostic sensitivity and specificity, a fact that remains a crucial task in the improvement of the immunodiagnosis of the disease.

Identification and intra-specific variability analysis of secreted and membrane-bound proteins from Echinococcus granulosus

Echinococcus granulosus, the etiological agent of cystic hydatid disease, exists as a series of strains or genotypes, differing in biological features. Many of the secreted and membrane-bound proteins (S/M) from helminth parasites are involved in the host-parasite interplay and constitute potential targets for diagnosis, anti-parasitic drugs and vaccines. A number of E. granulosus S/M proteins were identified using the signal sequence trap technique. Six out of seven cDNA fragments of these newly identified proteins showed nucleotide and amino acid sequence variation. Inter-strain variation was reported for other characterized S/M proteins as the vaccine target EG95 and the major hydatid cyst fluid antigen, Antigen B (AgB). AgB is highly polymorphic, 101 different sequences related to AgB were reported so far and were grouped in 5 genes (EgB1-EgB5) and one pseudogene (EgB2p) exclusive of G5, G6/G7 genotypes. The significance of AgB polymorphism and possible consequences in diagnostic performance are discussed. The diagnostic value of the new protein variants detected in E. granulosus strains could be determined through standardized inter-laboratory studies as the recently done by the South American Network for Hydatid Serology.