An optimized protocol for the expression of a recombinant protein fragment of human factor B used for the production of polyclonal antibodies

Abstract

Background: Complement is a critical component of the innate immunity bridging both arms of the immune system. Extensive trials are ongoing to develop therapeutics that target complement and hence alleviating complement-mediated disorders. Objectives: Here, we detail our attempts to express a recombinant protein fragment of human factor B (FBfr) in a high yield and solubility in addition to the production of polyclonal antibody against it. Methodology: We tested different expression conditions and host strains to express FBfr. Moreover, we used the expressed Fbfr to immunize rabbits for production of polyclonal antibody and tested its inhibitory properties against the alternative pathway by in vitro assays. Results: We successfully expressed an alternative complement pathway inhibitor FBfr in E. coli using an optimized protocol. The protein was antigenic and led to the production of a high titer of antibodies in sera of the immunized rabbits. The polyclonal antibody was shown to have a moderate inhibition of the alternative complement pathway activity. Conclusion: optimization of expression parameters can greatly improve the expression levels of recombinant proteins. These proteins can have a functional activity and be used for successful immunization process.