CONICET | Buscador de Institutos y Recursos Humanos

Echinococcus granulosus, the causative agent of cystic hydatid disease, exists as a number of strains (G1-G10) that differ in biological characters. One of the major antigens of the cyst hydatid fluid, the antigen B (AgB) is an oligomeric lipoprotein, used in diagnosis and possibly involved in the evasion of the host immune response. We used PCR-SSCP followed by sequencing to evaluate the intraspecific variation and expression profile of AgB gene family. Forty two genomic sequences were isolated and grouped in five genes (EgB1 to 5) by phylogenetic analysis. Sequences isolated from different clusters of strains grouped separately. EgB2 was present as a functional gene only in G1/G2 cluster of strains. G1 and G7 differed in their AgB expression pattern, while G1 transcribed all the AgB subunits, G7 did not transcribe neither AgB2, nor AgB5.The amino acid identity among AgB subunits (AgB1-5) ranges from 33 % to 73%. Most of the variability is concentrated in the N-terminal region. Since this region was shown to concentrate the immunoreactive B cell epitopes of the native molecule, the different type and abundance of expressed AgB isoforms in each strain could produce different efficiency in evading the immune response of each specific host. In situ hybridization analysis showed that AgB is expressed in the tegument of protoscoleces. Differential expression of AgB variants between individual protoscoleces of the same cyst is under analysis to search for intra-isolate variability. For this, RT-PCR assays on single protoscoleces were developed and monoclonal antibodies against some of the recombinant AgB subunits are being produced. Conclusiones: E. granulosus strains differ in the type and abundance of some of the AgB genes and in their expression patterns. Antigenic variation is suggested and is currently being analysed

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