Adaptive immune responses of legumin nanoparticles

Legumin is one of the main storage proteins in the pea seeds (Pisum sativum L.) and the molecules of this protein have the capacity of binding together to form nanoparticles after aggregation and chemical cross-linkage with glutaraldehyde. The aim of this work was to study the adaptive immune response of legumin nanoparticles in rats. Following intradermal immunisation with the native protein legumin and legumin nanoparticles of about 250 nm, the humoral and cell-mediated immune responses were analysed in rats. The humoral responses against legumin and legumin nanoparticles were examined by western blot and ELISA analysis. Both techniques clearly showed that sera from rats immunised with legumin strongly expressed antibodies against this protein. On the contrary, serum samples from rats inoculated with legumin nanoparticles did not contain detectable amounts of antibodies. These results may be explained by a reduction on the antigenic epitopes of the protein induced by the glutaraldehyde used during the cross-linking step. Concerning the cell-mediated response, neither legumin nor legumin nanoparticles stimulated an immunogenic response. This absence of response of spleen lymphocytes for legumin and legumin nanoparticles may be explained by a cytostatic effect of legumin which was corroborated by the evaluation of the middle phase of cell apoptose. In fact, both legumin and legumin nanoparticles are potent inductors of a cytostatic phenomenon and showed a significant increase of the chromatin condensation (p < 0.05) as compared with control.