Insufficient (Sub-native) Helix Content in Soluble/Solid Aggregates of Recombinant and Engineered Forms of IL-2 Throws Light on How Aggregated IL-2 is Biologically Active

Soluble expression of recombinant human interleukin-2 in Escherichia coli and its facile production

Recombinant human interleukin-2 (rhIL-2) represents one of the most difficult-to-produce cytokines in E. coli due to its extreme hydrophobicity and high tendency to formation of inclusion bodies. Refolding of rhIL-2 inclusion bodies always represents cumbersome downstream processes and low production efficiency. Herein, we disclosed a fusion strategy for efficiently soluble expression and facile production of rhIL-2 in E. coli Origami B (DE3) host. A two-tandem SUMO fusion partner (His-2SUMO) with a unique SUMO protease cleavage site at C-terminus was devised to fuse with the N-terminus of rhIL-2 and the fusion protein (His-2SUMO-rhIL-2) was almost completely expressed in a soluble from. The fusion partner could be efficiently removed by Ulp1 cleavage and the rhIL-2 was simply produced by a two-step Ni-NTA affinity chromatography with a considerable purity and whole recovery. The eventually obtained rhIL-2 was well-characterized and the results showed that the purified rhIL-2 exhibits a compact and ordered structure. Although the finally obtained rhIL-2 exists in a soluble aggregates form and the aggregation probably has been occurred during expression stage, the soluble rhIL-2 aggregates remain exhibit comparable bioactivity with the commercially available rhIL-2 drug formulation.

Inhibiting Protein Aggregation Using Cellulose Nanocrystal in MALDI-TOF MS Analysis: Improving the Sensitivity and Repeatability of Intact Protein in Pueraria

Protein aggregation can induce low sensitivity and poor repeatability of matrix-assisted laser desorption/ionization time-of-fight mass spectrometry (MALDI-TOF MS) analysis for intact protein. Herein, we introduced a strategy to decrease protein aggregation in the sample solution by using cellulose nanocrystal (CNC). The results indicated that protein granule size was effectively reduced by adding CNC to the sample solution. Through MALDI-TOF MS analysis, the signal-to-noise ratio of [M + H]+ peak increased 2-fold, and the detection of limit was <10 μg/mL for intact protein. The CNC also contributed to excellent point-to-point repeatability for MALDI-TOF MS analysis with the coefficient of variation (CV) of 10.0% with CNC vs 48.9% without CNC in Hb solution. Also, the repeatability of Pueraria protein ion signals was improved by using CNC, and the CV with and without CNC was 16.1% and 39.6%, respectively. Moreover, protein ion intensity exhibited great linear relationship (y = 53.04x - 3.474, R2 = 0.9936) with the concentrations (ranging from 0.1 to 10 mg/mL) when using CNC. Further investigation revealed that m/z 19,000 and m/z 21,000 peaks of Pueraria could be used for the adulteration analysis and post-translational modification research, demonstrating our method has the potential for broad applications.

Generation of IL-2-Fc-antibody conjugates by click chemistry

BACKGROUND

Immunocytokines (ICKs) are antibody directed cytokines produced by genetic fusion of an antibody to a cytokine.

METHODS

We now show that antibodies conjugated by click chemistry to interleukin-2 (IL-2)-Fc form fully active conjugates, and in one example, equivalent activity to a genetically produced ICK.

RESULTS

An IL-2-Fc fusion protein was optimized for click chemistry at hinge cysteines using protein stabilizing IL-2 mutations at Lys35 and Cys125 and Fc hinge mutations at Cys142 and Cys148. The IL-2-Fc fusion protein with K35E and C125S mutations with 3 intact hinge cysteines, designated as IL-2-Fc Par, was selected based on its minimal tendency to aggregate. IL-2-Fc-antibody clicked conjugates retained high IL-2 activity and bound target antigens comparable to parent antibodies. An IL-2-Fc-anti-CEA click conjugate showed comparable anti-tumor activity to an anti-CEA-IL-2 ICK in immunocompetent CEA transgenic mice bearing CEA positive orthotopic breast tumors. Significant increases in IFNγ+ /CD8+ and decreases in FoxP3+ /CD4+ T-cells were found for the clicked conjugate and ICK therapies, suggesting a common mechanism of tumor reduction.

CONCLUSION

The production of antibody targeted IL-2 therapy via a click chemistry approach is feasible with comparable activity to genetically produced ICKs with the added advantage of multiplexing with other monoclonal antibodies.

Molecular reshaping of phage-displayed Interleukin-2 at beta chain receptor interface to obtain potent super-agonists with improved developability profiles

Interleukin-2 (IL-2) engineered versions, with biased immunological functions, have emerged from yeast display and rational design. Here we reshaped the human IL-2 interface with the IL-2 receptor beta chain through the screening of phage-displayed libraries. Multiple beta super-binders were obtained, having increased receptor binding ability and improved developability profiles. Selected variants exhibit an accumulation of negatively charged residues at the interface, which provides a better electrostatic complementarity to the beta chain, and faster association kinetics. These findings point to mechanistic differences with the already reported superkines, characterized by a conformational switch due to the rearrangement of the hydrophobic core. The molecular bases of the favourable developability profile were tracked to a single residue: L92. Recombinant Fc-fusion proteins including our variants are superior to those based on H9 superkine in terms of expression levels in mammalian cells, aggregation resistance, stability, in vivo enhancement of immune effector responses, and anti-tumour effect.

Enhanced recombinant protein capture, purity and yield from crude bacterial cell extracts by N-Lauroylsarcosine-assisted affinity chromatography

BACKGROUND

Recombinant proteins cover a wide range of biomedical, biotechnological, and industrial needs. Although there are diverse available protocols for their purification from cell extracts or from culture media, many proteins of interest such as those containing cationic domains are difficult to purify, a fact that results in low yields of the final functional product. Unfortunately, this issue prevents the further development and industrial or clinical application of these otherwise interesting products.

RESULTS

Aiming at improving the purification of such difficult proteins, a novel procedure has been developed based on supplementing crude cell extracts with non-denaturing concentrations of the anionic detergent N-Lauroylsarcosine. The incorporation of this simple step in the downstream pipeline results in a substantial improvement of the protein capture by affinity chromatography, an increase of protein purity and an enhancement of the overall process yield, being the detergent not detectable in the final product.

CONCLUSION

By taking this approach, which represents a smart repurposing of N-Lauroylsarcosine applied to protein downstream, the biological activity of the protein is not affected. Being technologically simple, the N-Lauroylsarcosine-assisted protein purification might represent a critical improvement in recombinant protein production with wide applicability, thus smothering the incorporation of promising proteins into the protein market.

Surface cysteine to serine substitutions in IL-18 reduce aggregation and enhance activity

Background

Interleukin-18 (IL-18) is prone to form multimers resulting in inactive aggregates, making this cytokine unstable for clinical use. Therefore, mutations have been introduced into recombinant IL-18 to overcome this issue.

Methods

To prevent the formation of disulfide bonds between the IL-18 molecules, multiple mutations targeting surface cysteines (C38, C68, C76, and C127) were introduced into our previously modified human IL-18 double mutant E6K+T63A (IL-18 DM) by direct gene synthesis. The open reading frames of IL-18 wild-type (WT), IL-18 DM, and IL-18 multiple mutant E6K+T63A+C38S+C68S+C76S+C127S (IL-18 DM1234) were inserted in the pET28a expression vector and transformed into Escherichia coli Rosetta2 (DE3) pLysS cells for protein production. The inclusion bodies of WT and mutated IL-18 were extracted by sonication and refolded by stepwise dialysis using 8 M urea as the starting concentration. The refolded IL-18 proteins were tested for aggregation using the ProteoStat protein aggregation assay. Their activity was also investigated by treating NK-92MI cells with each IL-18 at concentrations of 75, 150, and 300 ng/ml with 0.5 ng/ml of human IL-12 and interferon-gamma (IFN-γ) levels in the supernatant were evaluated using ELISA. The structure of modified IL-18 was visualized using molecular dynamics (MD) simulations.

Results

IL-18 DM1234 exhibited the lowest aggregation signal, approximately 1.79- and 1.63-fold less than that of the WT and IL-18 DM proteins. Additionally, the IFN-γ inducing activity of IL-18 DM1234 was about 10 and 2.8 times higher than that of the WT and IL-18 DM, respectively. MD simulations revealed that binding site I of IL-18 DM1234 was altered mainly due to surface cysteine replacement with serine (C-to-S substitution). This is the first report showing that C-to-S substitutions in IL-18 improved its activity and stability, suggesting the use of this modified IL-18 for medical purposes in the future.

Purification and Conformational Characterization of a Novel Interleukin-2 Mutein

Toxicity of high-dose IL-2-based therapies have motivated the development of the IL-2 mutein, which has low expansion properties for regulatory T lymphocytes. The development of two variants (A and B) for the IL-2 mutein purification as well as a conformational comparative study by Circular dichroism (CD) and fluorescence spectroscopy of these products were evaluated. For the first time, in our center, were used of DTT and 2% SDS in the solubilization step to decrease the aggregates on intermediate product, which favors that disulfide bridges are correctly formed during re-folding. A molecular weight of 18 kDa to the monomeric form and of 25-37 kDa to the oligomeric species were estimated by SDS-PAGE. IL-2 mutein showed similar far-UV CD spectral characteristic typical of cytokines with 41% of α-helix content. Batches obtained by Process B showed similar conformational features according near-UV CD and FS studies. However, those obtained by Process A differed in their folding. IL-2 mutein showed that conformational features by near-UV CD were affected by 2% SDS, no variations on secondary structure were observed. Melting temperature values by far-UV CD were higher than 95 °C, indicating a high thermal stability. Finally, the drug product obtained by Process B showed similar conformational characteristics by near-UV CD and FS, and higher biological activity values (7.0 × 10³ ng/mL) in the cell proliferation assay with respect to Process A. Also, the recovery was 15% higher than in the Process A and exhibited a 78.48% of purity. Indeed, Process B was selected for the purification.

Directed evolution of super-secreted variants from phage-displayed human Interleukin-2

Selection from a phage display library derived from human Interleukin-2 (IL-2) yielded mutated variants with greatly enhanced display levels of the functional cytokine on filamentous phages. Introduction of a single amino acid replacement selected that way (K35E) increased the secretion levels of IL-2-containing fusion proteins from human transfected host cells up to 20-fold. Super-secreted (K35E) IL-2/Fc is biologically active in vitro and in vivo, has anti-tumor activity and exhibits a remarkable reduction in its aggregation propensity- the major manufacturability issue limiting IL-2 usefulness up to now. Improvement of secretion was also shown for a panel of IL-2-engineered variants with altered receptor binding properties, including a selective agonist and a super agonist that kept their unique properties. Our findings will improve developability of the growing family of IL-2-derived immunotherapeutic agents and could have a broader impact on the engineering of structurally related four-alpha-helix bundle cytokines.

Combining computational and experimental biology to develop therapeutically valuable IL2 muteins

High-dose IL2, first approved in 1992, has been used in the treatment of advanced renal cell carcinoma and melanoma. In these indications, IL2 induces long lasting objective responses in 5% to 20% of patients. However, toxicity and the unexpected expansion of regulatory T cells (Tregs) have limited its practical use and therapeutic impact, respectively. At the Center of Molecular Immunology in Havana, Cuba, a project was launched in 2005 to rationally design IL2 muteins that could be deployed in the therapy of cancer. The basic goal was to uncouple the pleiotropic effect of IL2 on different immune T cells, to obtain a mutein with a therapeutic index that was better than that achieved with wild type (wt) IL2. Using a combination of computational and experimental biology approaches, we predicted and developed two novel IL2 muteins with therapeutic potential. The first, designated no-alpha mutein, is an agonist of IL2R signaling with a reduced ability to expand Treg in vivo. In mice, the no-alpha mutein IL2 has higher antitumor activity and lower toxicity than wt IL2. It represents a potential best-in-class drug that has begun phase I/II clinical trials in solid tumors. The second, designated no-gamma mutein, is an antagonist of IL2R signaling, with some preferential affinity for Tregs. This mutein has antitumor activity in mice that likely derives from its ability to reduce Treg accumulation in vivo. It represents a first-in-class drug that offers a novel strategy to inhibit Treg activity in vivo.