Specific panallergen peptide of Sorghum polcalcin showing IgE response identified based on in silico and in vivo peptide mapping.

In India, Sorghum plant allergenicity was reported to be approximately 54.9%. Sorghum bicolor Polcalcin (Sorb PC) was identified as the panallergen but the specificity of this allergen is yet to be characterized. The present study was aimed to characterize the antigenic determinants of Sorb PC that are responsible for eliciting the IgE response. In silico modeling, simulation studies and docking of Sorb PC peptides (PC1-11) against IgG and IgE followed by in vivo evaluation was adopted. Peptide docking studies revealed PC 6 with highest G-score -12.85 against IgE followed by PC-11, 5, 1 and 7 (-10.91) peptides. The mice sensitized with PC7 peptide showed interleukin (IL) 4 (IL-4), IL-5, IL-12, TNF-a and GMCSF levels increased when compared with other peptides and controls, signifying a strong T helper type 2 (Th2)-based response. In tandem, the T helper type 1 (Th1) pathway was inhibited by low levels of cytokine IL-2, interferon gamma (IFN-gamma) and increased IL-10 levels justifying the role of PC7 in allergic IgE response. Considering the above data of overlapping peptides of PC6 and PC7, N-terminal part of the PC7 peptide (DEVQRMM) is found to play a crucial role in Sorghum Polcalcin allergenic response.