Expression and purification of human interferon alpha 2a (IFNα2a) in the methylotrophic yeast Pichia pastoris

Human interferon alpha 2a (IFNα2a) is a secreted glycoprotein that exerts a wide spectrum of biological effects, such as triggering of antiviral, antitumor and immunosuppressive responses. IFNα2a is used as pharmaceutical polypeptide in chronic hepatitis C virus (HCV) infection, chronic myelogenous leukemia, advanced renal cell carcinoma, and metastatic malignant melanoma. So far, the pharmaceutical polypeptide of this cytokine is produced in prokaryotic expression systems (E. coli). Here we report the expression and purification of recombinant human IFNα2a in the methylotrophic yeast Pichia pastoris. The cDNA encoding for human IFNα2a, modified to bear the P. pastoris codon bias, was cloned into the pPinkα-HC vector in order to be expressed as a secreted protein upon induction. Proper expression and secretion of recombinant human IFNα2a (approximately 19 kDa) was confirmed by PCR-sequencing, SDS-PAGE and Western blot analysis following methanol-induced expression in a number of individual transformed strains. Purification of the recombinant protein was performed by affinity chromatography, achieving a robust yield of purified active form. The purified recombinant protein showed an impressive stability to thermal denaturation as observed by Differential Scanning Fluorimetry. The biological activity of the P. pastoris-produced IFNα2a was confirmed in A549 and HT29 cells by monitoring transcriptional up-regulation of a panel of known interferon-stimulated genes (ISGs). Our results document that the P. pastoris expression system is a suitable system for producing biologically functional IFNα2a in a secreted form.

Investigating the stabilisation of IFN-α2a by replica exchange molecular dynamics simulation

Current biopharmaceutical drugs are mainly a class of peptides or proteins that play an essential role in the treatment of many diseases. Such peptides/proteins are usually thermally unstable and may lose their bioactivity when exposed to ambient conditions. Therefore, they are not suitable for long-term storage. Lyophilisation is the most common method to prolong shelf life of solid peptide/protein drugs; however, the freeze-drying process can lead to irreversible damage. In the present study, human interferon-alpha 2a (IFN-α2a) was selected as a model protein drug; four disaccharides (β-lactose, β-maltose, sucrose, and trehalose) were selected as bioactive protectants. We investigated the effects of different protectants on IFN-α2a under various ambient conditions (vacuum, dry state, and aqueous solution) using replica exchange molecular dynamics simulation. The protective effect of β-maltose on IFN-α2a was the highest in aqueous solution and dry state, β-lactose showed a poor protective effect in all three conditions, the performance of sucrose was good in all conditions, and trehalose showed a better protective effect under vacuum conditions and in aqueous solution. Disaccharides form H-bonds with water, thereby preventing water from the tertiary structure of proteins. Trehalose forms strong H-bonds with water which explains its extraordinary stability.

Factors Affecting Relapse and Remission in Behçet's Uveitis Treated with Interferon Alpha2a

PURPOSE

To investigate factors affecting relapse and remission in patients with Behçet uveitis (BU) in the context of using the interferon alpha2a (IFNα2a) therapy.

METHODS

Clinical records were reviewed of 32 patients (totaling 54 eyes) presenting with severe BU who had been treated with IFNα2a therapy. Factors influencing relapsing-remitting course of BU during IFNα2a therapy and after the cessation of the agent were evaluated. Possible affecting factors of recurrence were age, gender, duration of the Behçet disease, time elapsed before starting the drug, number of relapses before the starting of IFNα2a, laterality, and presence of panuveitis.

RESULTS

Thirty patients (93.7%) responded to IFNα2a therapy. Annual attack rate before and after IFNα2a treatment was determined to be 4.03 ± 3.19 (attack per year) and 0.58 ± 1.07, respectively (P < 0.001). In univariable statistical evaluation, women tended to have a lower relapse risk than men. Multivariable analyses showed that age was the major factor determining relapse rate, while the effect of gender was not statistically significant (P = 0.196). The other probable influencing factors were not found to be statistically significant (P > 0.05). Increase in visual acuity observed during last examination compared to initial examination was determined to be statistically significant (P = 0.018).

CONCLUSIONS

Even if the female gender was evaluated as a good prognostic factor in univariable analyses, it was not assessed as an effective prognostic factor in multivariable analyses. Being aged may be regarded a good prognostic factor on the relapsing-remitting course of patients with BU who were treated with IFNα2a therapy.