Identification of a Novel Protein Adjuvant Isolated from Abrus precatorius.

Agglutinin and toxin was isolated and purified from Abrus precatorius seeds using conventional biochemical techniques such as Sepharose 4B affinity chromatography, Sephadex G-100 gel filtration and analytical HPLC chromatography. The yield of purified agglutinin was 272 mg per 50 g of seeds which was composed of 8.0% agglutinin and 6.1% toxin. SDS gel electrophoresis of purified protein under reducing and non-reducing conditions of native and denatured protein revealed four bands with molecular weights ranging from 31 to 66 kDa by protein and glycoprotein staining procedures. The adjuvant property of abrus agglutinin was evaluated using rat as an animal model, in comparison with Freund's complete adjuvant. Ovalbumin was used as a test antigen and was injected along with Freund's complete adjuvant (Group I experimental animals) and along with denatured abrus protein (Group II experimental animals). The humoral response was compared between two groups of animals (Group I and II) for total (by sandwich ELISA) and specific response (by antibody capture assay). Group II animals which received denatured abrus protein along with test antigen showed a significantly higher IgG response of 23.0 +/- 2.37 mg ml[sup -1] (p < 0.001) when compared to Group I animals (14.0 +/- 2.50 mg ml[sup -1]). However, there was no statistically significant difference between Group I and Group II, with respect to specific IgG response to test antigen. Thus, the present investigation suggests that the denatured abrus agglutinin can be used as an effective alternative protein adjuvant. [ABSTRACT FROM AUTHOR]