An efficient production of hybrid recombinant protein comprising non-structural proteins (NS 1 & NS 3) of bluetongue virus in prokaryotic expression system

Abstract

Strategic design and suitable purification techniques are of paramount importance in the production of recombinant proteins, if intended for use in a diagnostic assay. However, there is no single protocol that can be universally adopted for obtaining proteins in requisite quality and quantity across various platforms. In this study, we have targeted proteins of bluetongue virus (BTV), which is the causative agent of an arthropod-borne infectious disease in ruminants. Traditionally, serological diagnosis of the disease has rested upon either virus neutralization test or on an ELISA test that employed a recombinant structural (VP1, VP7) protein. Among the non-structural (NS) proteins of BTV, NS1 and NS3, are preferred candidate antigens in development of immuno-diagnostics as these provide the option for identifying recent/ongoing infection. However, the difficulty in production/purification of recombinant full length NS proteins of BTV in sufficient quantity and quality in various expression systems, due to inherent structural complexities, have restricted their wider applicability as immunodiagnostic reagents. To circumvent the difficulties associated with production/purification, we developed a novel NS1 and NS3 fusion gene (∼1302 bp) encoding for NS1 N-terminus (1M to G252 aa) and NS3 protein containing the N- and C-termini with a deletion of two hydrophobic domains along with intervening variable central domain (118A to A182 aa) of bluetongue virus 23. This construct was cloned, over-expressed and efficiently purified by single step affinity chromatography under unique denaturing/renaturing condition. The purified fusion protein was found suitable for detection of antibodies against BTV in an indirect ELISA (iELISA).