Identification and Characterization of Antigenic Properties of Schistosoma japonicum Heat Shock Protein 90 alpha Derived Peptides

It is known that schistosome-derived antigens induce innate and adaptive immune responses that are essential for the formation of hepatic immunopathology. Here, we screened and synthesized four peptides derived from Schistosoma japonicum (S. japonicum) heat shock protein 90 alpha (Sjp90 alpha-1, -2, -3, and -4), which is widely expressed in adults and eggs of the genus S. japonicum and induces remarkable immune reactions. To define the antigenicity of these peptides, we stimulated splenocytes with peptides, and the results showed that only the Sjp90 alpha-1 peptide could predominately induce the activation of dendritic cells (DCs) and macrophages as well as alter the proportion of follicular helper T (Tth) cells. Next, CD4(+) T cells were purified and cocultured with mouse bonemarrow-derived DCs (BMDCs) with or without Sjp90 alpha-1 peptide stimulation in vitro, and the results showed that Sjp9O alpha-1-stimulated BMDCs can significantly induce CD4(+) T-cell differentiation into Tfh cells, while the direct stimulation of CD4(+) T cells with Sjp90 alpha-1 did not induce Tth cells, indicating that the Sjp90 alpha-1 peptide promotes Tfh cell differentiation depending on the presence of DCs. Furthermore, we selected and prepared an Sjp90 alpha-1-peptide-based antibody and illustrated that it has excellent reactivity with the immunizing peptide and detects a single band of 29 kDa corresponding to the Sjp90 alpha protein. The immunolocalization results showed that the protein recognized by this Sjp90 alpha-1-peptide-based antibody is present in the mature eggs and the tegument of adults, implying that the parasite-derived peptide has a potential interaction with the host immune system. Finally, we evaluated antipeptide IgG antibodies and revealed a significantly higher level of anti-Sjp90 alpha-1 peptide IgG antibodies in mice 3 weeks after S. japonicum infection. In conclusion, we illustrate that these synthetic peptides warrant further investigation by evaluating their antigen-specific immune response and their ability to efficiently induce Tth cells. Moreover, they may constitute a potentially helpful method for the laboratory diagnosis of schistosomiasis japonica.