Acta Univ Latv (2009) 753: 33–42

Cloning and expression of a recombinant immunogenic truncated BBK32 protein of Borrelia afzelii

Abstract

Borrelia burgdorferi, the Lyme disease-causing spirochete, is often found associated with host connective tissue, where it interacts with components of the extracellular matrix, including fibronectin. BBK32 is a surface-expressed lipoprotein with fibronectin-binding ability of Borrelia burgdorferi. A fragment of the bbk32 gene of Borrelia afzelii strain ACAI encoding the N-terminus of the protein including the fibronectin-binding domain (designated BS4 in this study) was cloned end expressed in Echerichia coli under the control of arabinose promoter as six histidine-tagged protein. Expression for the target protein showed that BS4 was accumulated both in soluble and insoluble forms. The molecular weight of the recombinant protein was estimated by SDS-PAGE to be 35 kDa including the six histidine tag. The expressed protein was purified by Ni²⁺ affinity chromatography under denaturing conditions. The purified BS4 recombinant protein was evaluated as an antigen in the serology of Lyme disease. Western blot analysis of Lyme disease patient sera revealed that the recombinant truncated BBK32 protein has specific antigenic properties. The availability of recombinant immunogenic BBK32 protein provides a new opportunity for biochemical analysis of the protein, structure-function studies, examination of its role in microbial pathogenesis, and assessment of its diagnostic and vaccinogenic potential.