Serological screening of the Schistosoma mansoni adult worm proteome

Background New interventions tools are a priority for schistosomiasis control and elimination, as the disease is still highly prevalent. The identification of proteins associated with active infection and protective immune response may constitute the basis for the development of a successful vaccine and could also indicate new diagnostic candidates. In this context, post-genomic technologies have been progressing, resulting in a more rational discovery of new biomarkers of resistance and antigens for diagnosis. Methodology/Principal Findings Two-dimensional electrophoresed Schistosoma mansoni adult worm protein extracts were probed with pooled sera of infected and non-infected (naturally resistant) individuals from a S. mansoni endemic area. A total of 47 different immunoreactive proteins were identified by mass spectrometry. Although the different pooled sera shared most of the immunoreactive protein spots, nine protein spots reacted exclusively with the serum pool of infected individuals, which correspond to annexin, major egg antigen, troponin T, filamin, disulphide-isomerase ER-60 precursor, actin and reticulocalbin. One protein spot, corresponding to eukaryotic translation elongation factor, reacted exclusively with the pooled sera of non-infected individuals living in the endemic area. Western blotting of two selected recombinant proteins, major egg antigen and hemoglobinase, showed a similar recognition pattern of that of the native protein. Concluding/Significance Using a serological proteome analysis, a group of antigens related to the different infection status of the endemic area residents was identified and may be related to susceptibility or resistance to infection.
Author Summary Despite intensive efforts towards disease control, schistosomiasis is still highly prevalent in most endemic countries. Although effective treatment is available and widely used, it does not prevent reinfection, as it could be achieved with the use of a vaccine. Efforts to control and eradicate schistosomiasis rely on praziquantel, the only drug available for treatment. Therefore, the identification of antigens that can induce protective immunity is highly desirable, as well as the need for more sensitive assays, useful to detect low intensity infections and treatment follow-up. The occurrence of natural resistance in schistosome endemic areas suggests that there is protective immunity. However, the mechanisms involved in protection, or the proteins that induce this protective immunity, are not yet known. These proteins, once identified, may constitute the basis for a successful vaccine. In this study, we compared the profile of reactive proteins to the serum antibodies of infected and non-infected individuals residing in a schistosomiasis endemic area using two-dimensional western blotting. The association of proteomic and serological screening methodologies enabled the identification of immunogenic proteins of the parasite, which could be an informative source for the development of vaccines and new diagnostic assays. In this manuscript we describe the discovery of potential candidate proteins for subsequent testing as protective or diagnostic antigens.