Structural elucidation and immunoprophylactic studies of recombinant parasitic proteins for therapeutic intervention in human lymphatic filariasis

Abstract

Human lymphatic filariasis is an incapacitating vector borne disease and is the world s second leading cause of long-term disability. To worsen the condition there are no vaccines yet and vector control programs have limitations of insect resistance. The first part of the thesis deals with strategies to enhance the immunoprophylactic efficacy of filarial vaccine targets. The protection results correlates with humoral and cellular responses indicating the role of eukaryotic expression systems like P.pastoris in enhancing the immunogenicity of vaccine antigens. The second part of the thesis deals with X-ray crystallographic elucidation of Glutathione-S-transferase (GST) 3-D structure and conformational epitope analysis of Thioredoxin (TRX) 3-D structure for therapeutic intervention. The Wb-GST structure also revealed the presence of non-catalytic ligand binding sites (ligandin function) in the inter-subunit cleft, which can serve as a binding site for hydrophobic ligands. These crucial insights from structural data could be exploited for developing parasite-specific inhibitors. The recombinant Wb-TRX was sub-cloned, expressed and purification strategies were optimised for structural studies. Although TRX is a potential therapeutic target, it shares sequence homology with host enzyme which may lead to cross-reactivity. The current study for the first time reports that pichia expressed antigens combined with multiple-antigen mode is a promising vaccine strategy by virtue of ~80% reduction in worm burden. In regard with drug development approach, This is the first report on X-ray crystallographic determination of Wb-GST structure suggesting its potential as a drug target. Further, the study validates that the earlier reported protective epitopes (PC1) are a part of a dominant conformational epitope of Wb-TRX and also confirms its role in protective response by biochemical and structural analysis. newline newline newline