Development of a pilot-scale production process and characterization of a recombinant Japanese encephalitis virus envelope domain III protein expressed in Escherichia coli

Efficacy of genotype-matched vaccine against re-emerging genotype V Japanese encephalitis virus

Japanese encephalitis (JE), caused by the Japanese encephalitis virus (JEV), is a highly threatening disease with no specific treatment. Fortunately, the development of vaccines has enabled effective defense against JE. However, re-emerging genotype V (GV) JEV poses a challenge as current vaccines are genotype III (GIII)-based and provide suboptimal protection. Given the isolation of GV JEVs from Malaysia, China, and the Republic of Korea, there is a concern about the potential for a broader outbreak. Under the hypothesis that a GV-based vaccine is necessary for effective defense against GV JEV, we developed a pentameric recombinant antigen using cholera toxin B as a scaffold and mucosal adjuvant, which was conjugated with the E protein domain III of GV by genetic fusion. This GV-based vaccine antigen induced a more effective immune response in mice against GV JEV isolates compared to GIII-based antigen and efficiently protected animals from lethal challenges. Furthermore, a bivalent vaccine approach, inoculating simultaneously with GIII- and GV-based antigens, showed protective efficacy against both GIII and GV JEVs. This strategy presents a promising avenue for comprehensive protection in regions facing the threat of diverse JEV genotypes, including both prevalent GIII and GI as well as emerging GV strains.

Immunogenicity of Escherichia coli expressed envelope 2 protein of Chikungunya virus

Chikungunya fever, a re-emerging infection, is an arthropod-borne viral disease prevalent in different parts of the world, particularly Africa and South East Asia. Chikungunya virus envelope 2 protein is involved in binding to host receptors and it contains specific epitopes that elicit virus neutralizing antibodies. A highly immunogenic, recombinant Chikungunya virus envelope 2 protein was produced by bioreactor in Escherichia coli for development of a suitable diagnostic and vaccine candidate. This protein was refolded and further purified to achieve biologically active protein. The biological function of refolded and purified recombinant envelope 2 protein of Chikungunya virus was confirmed by its ability to generate envelope 2 specific antibodies with high titers in animal models. These findings suggest that recombinant envelope 2 protein of Chikungunya virus in combination with compatible adjuvant is highly immunogenic. Thus, recombinant envelope 2 protein can be a potential diagnostic reagent and vaccine candidate against Chikungunya virus infection.

Production of recombinant Chikungunya virus envelope 2 protein in Escherichia coli

Chikungunya, a mosquito-borne viral disease caused by Chikungunya virus (CHIKV), has drawn substantial attention after its reemergence causing massive outbreaks in tropical regions of Asia and Africa. The recombinant envelope 2 (rE2) protein of CHIKV is a potential diagnostic as well as vaccine candidate. Development of cost-effective cultivation media and appropriate culture conditions are generally favorable for large-scale production of recombinant proteins in Escherichia coli. The effects of medium composition and cultivation conditions on the production of recombinant Chikungunya virus E2 (rCHIKV E2) protein were investigated in shake flask culture as well as batch cultivation of Escherichia coli. Further, the fed-batch process was also carried out for high cell density cultivation of E. coli expressing rE2 protein. Expression of rCHIKV E2 protein in E. coli was induced with 1 mM isopropyl-beta-thiogalactoside (IPTG) at ~23 g dry cell weight (DCW) per liter of culture and yielded an insoluble protein aggregating to form inclusion bodies. The final DCW after fed-batch cultivation was ~35 g/l. The inclusion bodies were isolated, solubilized in 8 M urea and purified through affinity chromatography to give a final product yield of ~190 mg/l. The reactivity of purified E2 protein was confirmed by Western blotting and enzyme-linked immunosorbent assay. These results show that rE2 protein of CHIKV may be used as a diagnostic reagent or for further prophylactic studies. This approach of producing rE2 protein in E. coli with high yield may also offer a promising method for production of other viral recombinant proteins.

Production and purification of the multifunctional enzyme horseradish peroxidase

The oxidoreductase horseradish peroxidase (HRP) is used in numerous industrial and medical applications. In this review, we briefly describe this well-studied enzyme and focus on its promising use in targeted cancer treatment. In combination with a plant hormone, HRP can be used in specific enzyme-prodrug therapies. Despite this outstanding application, HRP has not found its way as a biopharmaceutical into targeted cancer therapy yet. The reasons therefore lie in the present low-yield production and cumbersome purification of this enzyme from its natural source. However, surface glycosylation renders the recombinant production of HRP difficult. Here, we compare different production hosts for HRP and summarize currently used production and purification strategies for this enzyme. We further present our own strategy of glycoengineering this powerful enzyme to allow recombinant high-yield production in Pichia pastoris and subsequent simple downstream processing.