The inhibition of aggregation of recombinant human consensus interferon-alpha mutant during Pichia pastoris fermentation

Unconventional microbial systems for the cost-efficient production of high-quality protein therapeutics

Both conventional and innovative biomedical approaches require cost-effective protein drugs with high therapeutic potency, improved bioavailability, biocompatibility, stability and pharmacokinetics. The growing longevity of the human population, the increasing incidence and prevalence of age-related diseases and the better comprehension of genetic-linked disorders prompt to develop natural and engineered drugs addressed to fulfill emerging therapeutic demands. Conventional microbial systems have been for long time exploited to produce biotherapeutics, competing with animal cells due to easier operation and lower process costs. However, both biological platforms exhibit important drawbacks (mainly associated to intracellular retention of the product, lack of post-translational modifications and conformational stresses), that cannot be overcome through further strain optimization merely due to physiological constraints. The metabolic diversity among microorganisms offers a spectrum of unconventional hosts, that, being able to bypass some of these weaknesses, are under progressive incorporation into production pipelines. In this review we describe the main biological traits and potentials of emerging bacterial, yeast, fungal and microalgae systems, by comparing selected leading species with well established conventional organisms with a long run in protein drug production.

Synthesis and expression of recombinant interferon alpha-5 gene in tobacco chloroplasts, a non-edible plant

The production of interferon alpha from microbial to mammalian expression system, have certain precincts in terms of cost, scalability, safety and authenticity. Modern biotechnology exploits transgenic crops to get large quantities of complex proteins in a cost-effective way. In order to overcome several challenges from biosafety point of view, the chloroplast transformation strategy is one of the best approaches since plastids are strictly maternally inherited in most of the cultivated species. In the present study the interferon alpha 5 gene was synthesized by using complex set of oligos. After sequence confirmation of the synthesized gene, the histidine residues along with the thrombin protease site were engineered upstream to the synthetic interferon alpha 5 gene. The recombinant fragment was then tethered with chloroplast light inducible promoter, rbcl followed by sequential cloning to develop chloroplast transformation vector to target the cassette into the inverted repeat region of plastome through two events of homologous recombination. The putative transgenic plants obtained through biolistic delivery method and as a result of antibiotic selection of bombarded leaves, were subjected to different rounds of selection and regeneration for homoplasmicity. The spectinomycin-resistant shoots were analyzed through Polymerase Chain Reaction and Sothern blotting. The expression of introduced synthetic genes was recorded using Enzyme Linked ImmunoSorbant Assay technique. It was experienced that mature leaves contained comparatively high levels of interferon compared to young and senescence leaves.

Inhibition of degradation and aggregation of recombinant human consensus interferon-alpha mutant expressed in Pichia pastoris with complex medium in bioreactor

The methylotrophic yeast Pichia pastoris has been used for the expression of many proteins. However, limitations such as protein degradation and aggregation became obvious when secreting heterologous protein-recombinant human consensus interferon-alpha mutant. Here, we investigate the effect of induction temperature on the yield and stability of interferon mutant expressed by P. patoris with buffered complex medium. The best results in terms of interferon mutant bioactivity and specific bioactivity were obtained when the microorganism was induced at 15 degrees C, which were 2.91 x 10(8) +/- 0.3 x 10(8) and 2.26 x 10(8 )+/- 0.23 x 10(8) IU mg(-1), respectively. At the same time, the cells grew fast owing to high AOX1-specific activity, and interferon mutant expression level reached 1.23 g l(-1), which was almost 30 times higher than that in the flask. Also, the proteolytic degradation of interferon mutant was inhibited completely because of lower protease bioactivity probably due to a reduced cell death rate at lower temperatures as well as protection of yeast extract and peptone in complex medium. In addition, interferon mutant aggregation was repressed significantly by the addition of Tween-80, and a specific bioactivity of 7.35 x 10(8) +/- 0.56 x 10(8) IU mg(-1) was obtained. These results should be applicable to other low-stability recombinant proteins expressed in P. pastoris.

Cloning recombinant consensus interferon with overlap extension polymerase chain reaction

AIM: To obtain the recombinant consensus interferon (cIFN) gene by overlap extension PCR and to express it using a prokaryotic expression system to identify its activities.

METHODS: Overlap extension PCR was performed to obtain the cIFN gene and to construct the high expression vector for the production of cIFN protein according the preferred codon of E.coli. The expression vector pRA-cIFN was transformed with BL21 (DE3) E.coli straining. The expression of cIFN was identified by SDS-PAGE and Western blotting and purified by metal-chelating chromatography, and refolded by stepwise dialysis method. Then, the immune and biological activities of cIFN were detected by ELISA, MTS chromometry and hemagglutination inhibition test.

RESULTS: The cIFN gene was obtained by overlap extension PCR. Its DNA length was 534 bp which is consistent with its theoretical length. SDS-PAGE and Western blotting showed that the pressed cIFN protein in E.coli BL21 (DE3) was in the form of inclusion bodies and its molecular weight was 23.3 kDa. We achieved the refolding of E.coli-expressed cIFN with a stepwise dialysis method. The biological activity of the refolded cIFN was detected by ELISA, MTS chromometry and hemagglutination inhibition test, showing that cIFN had obvious immunological activities, dose-dependent suppressive activity of PLC/PRF/5 cell proliferation and HBsAg secretion inhibitory activity.

CONCLUSION: Overlap extension PCR is a simple method to obtain the recombinant genes. cIFN protein produced in this study has significant anti-virus and anti-tumor cell proliferation activities.