BackgroundNew 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 FindingsTwo-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/SignificanceUsing 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.

Background: Schistosomiasis is an important parasitic disease, which affects more than 210 million people around the world. The control of schistosomiasis has been based on the use of the drug Praziquantel. While the use of the chemotherapy has an effect in the morbidity it does not prevent the re-infection. Therefore, the development of a long term protection based on vaccination is still an important priority. Another area that deserves attention is the search for new diagnostic candidates, where the deficiency of effective diagnostic assays has been related as one factor that contributes to transmission. The immunological mechanism that prevents the infection developed by individuals naturally resistant may indicate possible biomarker candidates. Genomic data for schistosomes have become increasingly available and postgenomic technologies have matured, proposing a more rational discovery of biomarkers.Methods: S. mansoni adult worm protein extract were probed with sera of infected individuals (INF) and non-infected individuals from endemic area (normal endemic, NE) using two dimensional electrophoresis coupled to western blot (2D-WE), and the pattern of spots recognized compared. Immunoreactive proteins were identified by mass spectrometry. All immunoreactive proteins identified were expressed in vitro to be used in a protein microarray experiment. Two of the recombinant proteins were probed with the pooled sera with which they were originally identified.Results: Immunoreactive profile showed that there is no correlation between the amount of adult worm protein expressed and their antigenicity pattern. Although both sera shared most of the immunoreactive proteins recognized, 8 protein spots reacted exclusively with the INF sera and 1 with the NE sera. A total of 47 different proteins were identified as immunoreactive and 27 of them were successfully expressed. Blot of two of the recombinant proteins confirmed the right identification of the immunogenic spot in the 2D-WE and also that the recombinant proteins maintained the immunogenic epitope present in the native protein. Conclusion:The association of two-dimensional electrophoresis and western blot had enabled a pre-screening of immunoantigenic proteins of the parasite, while the microarray technique will refine the list of potential candidates for subsequent testing as protective or diagnostic antigens.