Investigation of VAL family proteins (venom allergen-like protein) from Schistosoma mansoni

Abstract

Progress on schistosome research has, until recently, suffered from limited genomic information. This situation changed dramatically in October 2003 with the simultaneous publication of the Schistosoma mansoni (Verjovski et al., 2003) and Schistosoma japonicum (Hu et al., 2003) transcriptomes. Mining the database generated from S. mansoni transcriptome using Gene Ontology categorization, potentially surface-exposed or exported novel proteins were identified. Among the antigens tested as DNA vaccines, Antigen 5 gene showed better levels of worm burden reduction (31 %). The gene code a protein similar (42%) to the NaASP-2 vaccine candidate from Necator americanus, moreover presents similarity to allergen proteins (Venom Allergen Like Protein - VAL). Further searches for similar domains in the Schistosoma genomic data bank - Gene DB -revealed 23 paralogs genes from this new gene family. The present project aimed firstly to determine the gene expression profile from VAL - 4, 5, 6 e 22 through real time PCR assays. Thereafter, immunolocalize the respective proteins that we hypothesized to be located on schistosomulum secretions (VAL-4), on eggs and/or eggs secretions (VAL-5), on adult tegument (VAL-6) and on schistosomulum tegument (VAL-22). Afterwards, the immunoglobulin isotype profile against these proteins will be determined in the serum of schistosomiasis patients with chronic infection, resistant or susceptible to re-infection. Based on that information two of the four proteins will be selected for immunization and challenge assays in murine model, aimed to evaluate the immune response profile and worm burden reduction. (AU)