A Structural In Silico Analysis of the Immunogenicity of L-Asparaginase from Penicillium cerradense

L-asparaginase is an essential drug used to treat acute lymphoid leukemia (ALL), a cancer of high prevalence in children. Several adverse reactions associated with L-asparaginase have been observed, mainly caused by immunogenicity and allergenicity. Some strategies have been adopted, such as searching for new microorganisms that produce the enzyme and applying protein engineering. Therefore, this work aimed to elucidate the molecular structure and predict the immunogenic profile of L-asparaginase from Penicillium cerradense, recently revealed as a new fungus of the genus Penicillium and producer of the enzyme, as a motivation to search for alternatives to bacterial L-asparaginase. In the evolutionary relationship, L-asparaginase from P. cerradense closely matches Aspergillus species. Using in silico tools, we characterized the enzyme as a protein fragment of 378 amino acids (39 kDa), including a signal peptide containing 17 amino acids, and the isoelectric point at 5.13. The oligomeric state was predicted to be a homotetramer. Also, this L-asparaginase presented a similar immunogenicity response (T- and B-cell epitopes) compared to Escherichia coli and Dickeya chrysanthemi enzymes. These results suggest a potentially useful L-asparaginase, with insights that can drive strategies to improve enzyme production.

Towards development of biobetter: L-asparaginase a case study

BACKGROUND

L-asparaginase (ASNase) has played a key role in the management of acute lymphoblastic leukaemia (ALL). As an amidohydrolase, it catalyzes the hydrolysis of L-asparagine, a crucial step in the treatment of ALL. Various ASNase variants have evolved from diverse sources since it was first used in paediatric patients in the 1960s. This review describes the available ASNase and approaches being used to develop ASNase as a biobetter candidate.

SCOPE OF REVIEW

The review discusses the Glycosylation and PEGylation techniques, which are frequently used to develop biobetter versions of the majority of the therapeutic proteins. Further, it explores current ASNase biobetters in therapeutic use and discusses the protein engineering and chemical modification approaches that were employed to reduce immunogenicity, extend protein half-life, and enhance protease stability of ASNase. Emerging strategies like immobilization and encapsulation are also highlighted as potential pathways for improving ASNase properties.

MAJOR CONCLUSIONS

The purpose of the development of ASNase biobetter is to achieve a novel therapeutic candidate that could improve catalytic efficiency, in vivo stability with minimum glutaminase (GLNase) activity and toxicity. Modification of ASNase by immobilization and encapsulation or by fusion technologies like Albumin fusion, Fc fusion, ELP fusion, XTEN fusion, etc. can be exploited to develop a novel biobetter candidate suitable for therapeutic approaches.

GENERAL SIGNIFICANCE

This review emphasizes the importance of biobetter development for therapeutic proteins like ASNase. Improved ASNase molecules have the potential to significantly advance the treatment of ALL and have broader implications in the pharmaceutical industry.

Expression and Biological Evaluation of an Engineered Recombinant L-asparaginase Designed by In Silico Method Based on Sequence of the Enzyme from Escherichia coli

Purpose

Medical usage of L-asparaginase (ASNase), the first-line of acute lymphoblastic leukemia treatment, is linked to allergic responses and toxicities, which necessitates the development of new bio-better ASNases. The aim of the current study was in silico design of a novel ASNase with predicted improved enzymatic properties using strategies encompassing sequence-function analysis of known ASNase mutants. Additionally, current study aimed to show that the new enzyme is active.

Methods

Based on 21 experimentally reported mutations for ASNase, a virtual library of mutated enzymes with all 7546 possible combinations of up to 4 mutations was generated. Three-dimensional models of proposed mutant enzymes were built and their in silico stabilities were calculated. The most promising mutant was selected for preparing a genetic construct suitable for expression of the designed ASNase in bacterial cells.

Results

Computational study predicted that Y176F/S241C double mutation of Escherichia coli ASNase may increase its folding stability. The designed ASNase was expressed in two different E. coli strains (Origami B(DE3) and BL21(DE3)pLysS) and then the soluble fractions prepared from the cell lysates of the host cells were used in enzyme activity assay. Results showed that enzyme activity of soluble fraction from Origami (95.4 ± 7.5 IU/0.1 mL) was four times higher than that of soluble fraction from pLysS (25.8 ± 2.5 IU/0.1 mL).

Conclusion

A novel functional double mutant ASNase with predicted improved enzymatic properties was designed and produced in E. coli. The results of the current study suggest a great commercial potential for the identified enzyme in pharmaceutical and industrial applications.

Engineering and Expression Strategies for Optimization of L-Asparaginase Development and Production

Genetic engineering for heterologous expression has advanced in recent years. Model systems such as Escherichia coli, Bacillus subtilis and Pichia pastoris are often used as host microorganisms for the enzymatic production of L-asparaginase, an enzyme widely used in the clinic for the treatment of leukemia and in bakeries for the reduction of acrylamide. Newly developed recombinant L-asparaginase (L-ASNase) may have a low affinity for asparagine, reduced catalytic activity, low stability, and increased glutaminase activity or immunogenicity. Some successful commercial preparations of L-ASNase are now available. Therefore, obtaining novel L-ASNases with improved properties suitable for food or clinical applications remains a challenge. The combination of rational design and/or directed evolution and heterologous expression has been used to create enzymes with desired characteristics. Computer design, combined with other methods, could make it possible to generate mutant libraries of novel L-ASNases without costly and time-consuming efforts. In this review, we summarize the strategies and approaches for obtaining and developing L-ASNase with improved properties.

Immune response induced by recombinant pres2/S-protein and a pres2-S-protein fused with a core 18-27 antigen fragment of hepatitis B virus compared to conventional HBV vaccine

Although comprehensive vaccination is the cornerstone of public health programs to control hepatitis B virus (HBV) infections, 5% of people who receive the existing vaccine do not develop proper immunity against HBV. To overcome this challenge, researchers have tried using various protein fragments encoded by the virus genome to achieve better immunization rates. An important antigenic component of HBsAg called the preS2/S or M protein has also received much attention in this area. The gene sequences of preS2/S and Core18-27 peptide were extracted from the GenBank (NCBI). Final gene synthesis was conducted with pET28. Groups of BALB/c mice were immunized with 10 μg/ml of recombinant proteins and 1 μg/ml CPG7909 adjuvant. Serum levels of IF-γ, TNF-α, IL-2, IL-4, and IL-10 were measured by ELISA assay method on spleen cell cultures on day 45, and IgG1, IgG2a, and total IgG titers obtained from mice serum were quantified on days 14 and 45. Statistical analysis did not show any significant difference between the groups regarding IF-γ level. There were, however, significant differences in terms of IL-2 and IL-4 levels between the groups receiving preS2/S-C18-27 with and without adjuvant and the groups receiving both preS2/S and preS2/S-C18-27 (Plus Recomb-Plus Recomb: the group of mice that received both preS2/S and preS2/S-C18-27 simultaneously). The strongest total antibody production was induced by immunization with both recombinant proteins without CPG adjuvant. The groups that received both preS2/S and preS2/S-C18-27, whether with or without adjuvant, were significantly different from those that received the conventional vaccine considering most abundant interleukins. This difference suggested that higher levels of efficacy can be achieved by the use of multiple virus antigen fragments rather than using a single fragment.

[Approaches for improving L-asparaginase expression in heterologous systems]

L-asparaginase (EC 3.5.1.1) is one of the most demanded enzymes used in the pharmaceutical industry as a drug and in the food industry to prevent the formation of toxic acrylamide. Researchers aimed to improve specific activity and reduce side effects to create safer and more potent enzyme products. However, protein modifications and heterologous expression remain problematic in the production of asparaginases from different species. Heterologous expression in optimized producer strains is rationally organized; therefore, modified and heterologous protein expression is enhanced, which is the main strategy in the production of asparaginase. This strategy solves several problems: incorrect protein folding, metabolic load on the producer strain and codon misreading, which affects translation and final protein domains, leading to a decrease in catalytic activity. The main approaches developed to improve the heterologous expression of L-asparaginases are considered in this paper.

Molecular Analysis of L-Asparaginases for Clarification of the Mechanism of Action and Optimization of Pharmacological Functions

L-asparaginases (EC 3.5.1.1) are a family of enzymes that catalyze the hydrolysis of L-asparagine to L-aspartic acid and ammonia. These proteins with different biochemical, physicochemical and pharmacological properties are found in many organisms, including bacteria, fungi, algae, plants and mammals. To date, asparaginases from E. coli and Dickeya dadantii (formerly known as Erwinia chrysanthemi) are widely used in hematology for the treatment of lymphoblastic leukemias. However, their medical use is limited by side effects associated with the ability of these enzymes to hydrolyze L-glutamine, as well as the development of immune reactions. To solve these issues, gene-editing methods to introduce amino-acid substitutions of the enzyme are implemented. In this review, we focused on molecular analysis of the mechanism of enzyme action and to optimize the antitumor activity.

Microbial production, molecular modification, and practical application of l-Asparaginase: A review

L-Asparaginase (L-ASNase, EC 3.5.1.1), an antitumor drug for acute lymphoblastic leukemia (ALL) therapy, is widely used in the clinical field. Similarly, L-ASNase is also a powerful and significant biological tool in the food industry to inhibit acrylamide (AA) formation. This review comprehensively summarizes the latest achievements and improvements in the production, modification, and application of microbial L-ASNase. To date, the expression levels and optimization of expression hosts such as Escherichia coli, Bacillus subtilis, and Pichia pastoris, have made significant progress. In addition, examples of successful modification of L-ASNase such as decreasing glutaminase activity, increasing the in vivo stability, and enhancing thermostability have been presented. Impressively, the application of L-ASNase as a food addition aid, as well as its commercialization in the pharmaceutical field, and cutting-edge biosensor application developments have been summarized. The presented results and proposed ideas could be a good guide for other L-ASNase researchers in both scientific and practical fields.

A potential type-II L-asparaginase from marine isolate Bacillus australimaris NJB19: Statistical optimization, in silico analysis and structural modeling

L-asparaginase is a cardinal biotherapeutic drug for treating acute lymphoblastic leukemia, which is highly prevalent in children worldwide. In the current investigation, L-asparaginase producing marine bacterial isolate, Bacillus australimaris NJB19 (MG734654), was observed to be producing extracellular glutaminase free L-asparaginase (13.27 ± 0.4 IU mL^-1). Production of L-asparaginase was enhanced by the Box-Behnken design approach that enumerated the significant variables affecting the enzyme production. The optimum levels of the derived variables resulted in 2.8-fold higher levels of the enzyme production (37.93 ± 1.06 IU mL^-1). An 1146 bp L-asparaginase biosynthetic gene of Bacillus australimaris NJB19 was identified and cloned in E. coli DH5α, fused with a histidine tag. The in silico analysis of the protein sequence revealed the presence of a signal peptide and classified it as a type II L-asparaginase. Toxic peptide prediction disclosed no toxin domain in the protein sequence, hence suggesting it as a non-toxic protein. The secondary structure analysis of the enzyme displayed a comparable percentage of alpha-helical and random coil structure, while 14.39% and 6.57% of amino acid residues were composed of extended strands and beta-turns, respectively. The functional sites in the three-dimensional structural model of the protein were predicted and interestingly had a few less conserved residues. Bacillus australimaris NJB19 identified in this study produces type-II L-asparaginase, known for its high affinity for asparagine and effectiveness against leukemic cells. Hence, these observations indicate the L-asparaginase, thus obtained, as a potentially significant and novel therapeutic drug.

Breast cancer targeted/ therapeutic with double and triple fusion Immunotoxins

Target-specific transport of therapeutic agents holds promise to increase the efficacy of cancer treatment by decreasing injury to normal tissues and post treatment problems. HER2 is a tumor cell surface marker that is expressed in 25-30 % of breast cancer patients. The significant role of HER2 in cancer development and its biological feature makes it a highly appealing goal for the therapeutic treatment of cancer targeted therapy using HER2 monoclonal antibody. This approach is currently used as a special treatment against breast cancer in some research. In the present study, HER2 monoclonal antibody (mAb), (Herceptin) fused to PE38 by recombinant DNA technology and a new recombinant IT was developed. The scFv(Herceptin)-PE-STXA and scFv(Herceptin)-PE fusions cloned in pET28a and recombinant protein expression was carried out and then the proteins were purified. MCF-7 and SKBR-3 cells were used as HER2-negative and HER2-positive breast cancer cells, respectively. The cytotoxicity of its evaluated using MTT assay. The cell ELISA was used to determine the binding ability of immunotoxins (ITs) to the cell receptor and internalization and apoptosis were also assessed. The results revealed that cell cytotoxicity occurred in SKBR-3 cells in a dose-dependent manner but not in MCF-7 cells. It is possible that this ITs can attach to HER2-positive breast cancer cells and then, internalize and eradicate cancer cells by apoptosis. Here, we concluded that the recombinant ITs have therapeutic potential against HER2-positive breast cancer.

Development of L-Asparaginase Biobetters: Current Research Status and Review of the Desirable Quality Profiles

L-Asparaginase (ASNase) is a vital component of the first line treatment of acute lymphoblastic leukemia (ALL), an aggressive type of blood cancer expected to afflict over 53,000 people worldwide by 2020. More recently, ASNase has also been shown to have potential for preventing metastasis from solid tumors. The ASNase treatment is, however, characterized by a plethora of potential side effects, ranging from immune reactions to severe toxicity. Consequently, in accordance with Quality-by-Design (QbD) principles, ingenious new products tailored to minimize adverse reactions while increasing patient survival have been devised. In the following pages, the reader is invited for a brief discussion on the most recent developments in this field. Firstly, the review presents an outline of the recent improvements on the manufacturing and formulation processes, which can severely influence important aspects of the product quality profile, such as contamination, aggregation and enzymatic activity. Following, the most recent advances in protein engineering applied to the development of biobetter ASNases (i.e., with reduced glutaminase activity, proteolysis resistant and less immunogenic) using techniques such as site-directed mutagenesis, molecular dynamics, PEGylation, PASylation and bioconjugation are discussed. Afterwards, the attention is shifted toward nanomedicine including technologies such as encapsulation and immobilization, which aim at improving ASNase pharmacokinetics. Besides discussing the results of the most innovative and representative academic research, the review provides an overview of the products already available on the market or in the latest stages of development. With this, the review is intended to provide a solid background for the current product development and underpin the discussions on the target quality profile of future ASNase-based pharmaceuticals.