Recombinant immunotherapeutics: current state and perspectives regarding the feasibility and market

Delivering monoclonal antibodies via inhalation: a systematic review of clinical trials in asthma and COPD

INTRODUCTION

Advances in understanding the pathophysiology of asthma and chronic obstructive pulmonary disease (COPD) led to investigation of biologic drugs targeting specific inflammatory pathways. No biologics are licensed for COPD while all the approved monoclonal antibodies (mAbs) for severe asthma treatment are systemically administered. Systemic administration is associated with low target tissue exposure and risk of systemic adverse events. Thus, delivering mAbs via inhalation may be an attractive approach for asthma and COPD treatment due to direct targeting of the airways.

AREAS COVERED

This systematic review of randomized control trials (RCTs) evaluated the potential role of delivering mAbs via inhalation in asthma and COPD treatment. Five RCTs were deemed eligible for a qualitative analysis.

EXPERT OPINION

Compared to systemic administration, delivering mAbs via inhalation is associated with rapid onset of action, greater efficacy at lower doses, minimal systemic exposure, and lower risk of adverse events. Although some of the inhaled mAbs included in this study showed a certain level of efficacy and safety in asthmatic patients, delivering mAbs via inhalation is still challenging and controversial. Further adequately powered and well-designed RCTs are needed to assess the potential role of inhaled mAbs in the treatment of asthma and COPD.

Challenges and progress towards industrial recombinant protein production in yeasts: A review

Recombinant proteins (RP) are widely used as biopharmaceuticals, industrial enzymes, or sustainable food source. Yeasts, with their ability to produce complex proteins through a broad variety of cheap carbon sources, have emerged as promising eukaryotic production hosts. As such, the prevalence of yeasts as favourable production organisms in commercial RP production is expected to increase. Yet, with the selection of a robust production host on the one hand, successful scale-up is dependent on a thorough understanding of the challenging environment and limitations of large-scale bioreactors on the other hand. In the present work, several prominent yeast species, including Saccharomyces cerevisiae, Pichia pastoris, Yarrowia lipolytica, Kluyveromyces lactis and Kluyveromyces marxianus are reviewed for their current state and performance in commercial RP production. Thereafter, the impact of principal process control parameters, including dissolved oxygen, pH, substrate concentration, and temperature, on large-scale RP production are discussed. Finally, technical challenges of process scale-up are identified. To that end, process intensification strategies to enhance industrial feasibility are summarized, specifically highlighting fermentation strategies to ensure sufficient cooling capacity, overcome oxygen limitation, and increase protein quality and productivity. As such, this review aims to contribute to the pursuit of sustainable yeast-based RP production.

Yeast Expression Systems: Overview and Recent Advances

Yeasts are outstanding hosts for the production of functional recombinant proteins with industrial or medical applications. Great attention has been emerged on yeast due to the inherent advantages and new developments in this host cell. For the production of each specific product, the most appropriate expression system should be identified and optimized both on the genetic and fermentation levels, considering the features of the host, vector and expression strategies. Currently, several new systems are commercially available; some of them are private and need licensing. The potential for secretory expression of heterologous proteins in yeast proposed this system as a candidate for the production of complex eukaryotic proteins. The common yeast expression hosts used for recombinant proteins' expression include Saccharomyces cerevisiae, Pichia pastoris, Hansenula polymorpha, Yarrowia lipolytica, Arxula adeninivorans, Kluyveromyces lactis, and Schizosaccharomyces pombe. This review is dedicated to discuss on significant characteristics of the most common methylotrophic and non-methylotrophic yeast expression systems with an emphasis on their advantages and new developments.

Established and Upcoming Yeast Expression Systems

Yeast was the first microorganism used by mankind for biotransformation of feedstock that laid the foundations of industrial biotechnology. Long historical use, vast amount of data, and experience paved the way for Saccharomyces cerevisiae as a first yeast cell factory, and still it is an important expression platform as being the production host for several large volume products. Continuing special needs of each targeted product and different requirements of bioprocess operations have led to identification of different yeast expression systems. Modern bioprocess engineering and advances in omics technology, i.e., genomics, transcriptomics, proteomics, secretomics, and interactomics, allow the design of novel genetic tools with fine-tuned characteristics to be used for research and industrial applications. This chapter focuses on established and upcoming yeast expression platforms that have exceptional characteristics, such as the ability to utilize a broad range of carbon sources or remarkable resistance to various stress conditions. Besides the conventional yeast S. cerevisiae, established yeast expression systems including the methylotrophic yeasts Pichia pastoris and Hansenula polymorpha, the dimorphic yeasts Arxula adeninivorans and Yarrowia lipolytica, the lactose-utilizing yeast Kluyveromyces lactis, the fission yeast Schizosaccharomyces pombe, and upcoming yeast platforms, namely, Kluyveromyces marxianus, Candida utilis, and Zygosaccharomyces bailii, are compiled with special emphasis on their genetic toolbox for recombinant protein production.

Improving Immunotherapy Through Glycodesign

Immunotherapy is revolutionizing health care, with the majority of high impact "drugs" approved in the past decade falling into this category of therapy. Despite considerable success, glycosylation-a key design parameter that ensures safety, optimizes biological response, and influences the pharmacokinetic properties of an immunotherapeutic-has slowed the development of this class of drugs in the past and remains challenging at present. This article describes how optimizing glycosylation through a variety of glycoengineering strategies provides enticing opportunities to not only avoid past pitfalls, but also to substantially improve immunotherapies including antibodies and recombinant proteins, and cell-based therapies. We cover design principles important for early stage pre-clinical development and also discuss how various glycoengineering strategies can augment the biomanufacturing process to ensure the overall effectiveness of immunotherapeutics.

Advances in Biomarker-Guided Therapy for Pediatric- and Adult-Onset Neuroinflammatory Disorders: Targeting Chemokines/Cytokines

The concept and recognized components of “neuroinflammation” are expanding at the intersection of neurobiology and immunobiology. Chemokines (CKs), no longer merely necessary for immune cell trafficking and positioning, have multiple physiologic, developmental, and modulatory functionalities in the central nervous system (CNS) through neuron–glia interactions and other mechanisms affecting neurotransmission. They issue the “help me” cry of neurons and astrocytes in response to CNS injury, engaging invading lymphoid cells (T cells and B cells) and myeloid cells (dendritic cells, monocytes, and neutrophils) (adaptive immunity), as well as microglia and macrophages (innate immunity), in a cascade of events, some beneficial (reparative), others destructive (excitotoxic). Human cerebrospinal fluid (CSF) studies have been instrumental in revealing soluble immunobiomarkers involved in immune dysregulation, their dichotomous effects, and the cells—often subtype specific—that produce them. CKs/cytokines continue to be attractive targets for the pharmaceutical industry with varying therapeutic success. This review summarizes the developing armamentarium, complexities of not compromising surveillance/physiologic functions, and insights on applicable strategies for neuroinflammatory disorders. The main approach has been using a designer monoclonal antibody to bind directly to the chemo/cytokine. Another approach is soluble receptors to bind the chemo/cytokine molecule (receptor ligand). Recombinant fusion proteins combine a key component of the receptor with IgG1. An additional approach is small molecule antagonists (protein therapeutics, binding proteins, and protein antagonists). CK neutralizing molecules (“neutraligands”) that are not receptor antagonists, high-affinity neuroligands (“decoy molecules”), as well as neutralizing “nanobodies” (single-domain camelid antibody fragment) are being developed. Simultaneous, more precise targeting of more than one cytokine is possible using bispecific agents (fusion antibodies). It is also possible to inhibit part of a signaling cascade to spare protective cytokine effects. “Fusokines” (fusion of two cytokines or a cytokine and CK) allow greater synergistic bioactivity than individual cytokines. Another promising approach is experimental targeting of the NLRP3 inflammasome, amply expressed in the CNS and a key contributor to neuroinflammation. Serendipitous discovery is not to be discounted. Filling in knowledge gaps between pediatric- and adult-onset neuroinflammation by systematic collection of CSF data on CKs/cytokines in temporal and clinical contexts and incorporating immunobiomarkers in clinical trials is a challenge hereby set forth for clinicians and researchers.

Employing Escherichia coli-derived outer membrane vesicles as an antigen delivery platform elicits protective immunity against Acinetobacter baumannii infection

Outer membrane vesicles (OMVs) have proven to be highly immunogenic and induced an immune response against bacterial infection in human clinics and animal models. We sought to investigate whether engineered OMVs can be a feasible antigen-delivery platform for efficiently inducing specific antibody responses. In this study, Omp22 (an outer membrane protein of A. baumannii) was displayed on E. coli DH5α-derived OMVs (Omp22-OMVs) using recombinant gene technology. The morphological features of Omp22-OMVs were similar to those of wild-type OMVs (wtOMVs). Immunization with Omp22-OMVs induced high titers of Omp22-specific antibodies. In a murine sepsis model, Omp22-OMV immunization significantly protected mice from lethal challenge with a clinically isolated A. baumannii strain, which was evidenced by the increased survival rate of the mice, the reduced bacterial burdens in the lung, spleen, liver, kidney, and blood, and the suppressed serum levels of inflammatory cytokines. In vitro opsonophagocytosis assays showed that antiserum collected from Omp22-OMV-immunized mice had bactericidal activity against clinical isolates, which was partly specific antibody-dependent. These results strongly indicated that engineered OMVs could display a whole heterologous protein (~22 kDa) on the surface and effectively induce specific antibody responses, and thus OMVs have the potential to be a feasible vaccine platform.

Mechanistic insight into the TH1-biased immune response to recombinant subunit vaccines delivered by probiotic bacteria-derived outer membrane vesicles

Recombinant subunit vaccine engineering increasingly focuses on the development of more effective delivery platforms. However, current recombinant vaccines fail to sufficiently stimulate protective adaptive immunity against a wide range of pathogens while remaining a cost effective solution to global health challenges. Taking an unorthodox approach to this fundamental immunological challenge, we isolated the TLR-targeting capability of the probiotic E. coli Nissle 1917 bacteria (EcN) by engineering bionanoparticlate antigen carriers derived from EcN outer membrane vesicles (OMVs). Exogenous model antigens expressed by these modified bacteria as protein fusions with the bacterial enterotoxin ClyA resulted in their display on the surface of the carrier OMVs. Vaccination with the engineered EcN OMVs in a BALB/c mouse model, and subsequent mechanism of action analysis, established the EcN OMV’s ability to induce self-adjuvanted robust and protective humoral and T_H1-biased cellular immunity to model antigens. This finding appears to be strain-dependent, as OMV antigen carriers similarly engineered from a standard K12 E. coli strain derivative failed to generate a comparably robust antigen-specific T_H1 bias. The results demonstrate that unlike traditional subunit vaccines, these biomolecularly engineered “pathogen-like particles” derived from traditionally overlooked, naturally potent immunomodulators have the potential to effectively couple recombinant antigens with meaningful immunity in a broadly applicable fashion.

A truncated receptor-binding domain of MERS-CoV spike protein potently inhibits MERS-CoV infection and induces strong neutralizing antibody responses: implication for developing therapeutics and vaccines

An emerging respiratory infectious disease with high mortality, Middle East respiratory syndrome (MERS), is caused by a novel coronavirus (MERS-CoV). It was first reported in 2012 in Saudi Arabia and has now spread to eight countries. Development of effective therapeutics and vaccines is crucial to save lives and halt the spread of MERS-CoV. Here, we show that a recombinant protein containing a 212-amino acid fragment (residues 377-588) in the truncated receptor-binding domain (RBD: residues 367-606) of MERS-CoV spike (S) protein fused with human IgG Fc fragment (S377-588-Fc) is highly expressed in the culture supernatant of transfected 293T cells. The purified S377-588-Fc protein efficiently binds to dipeptidyl peptidase 4 (DPP4), the receptor of MERS-CoV, and potently inhibited MERS-CoV infection, suggesting its potential to be further developed as a therapeutic modality for treating MERS-CoV infection and saving the patients' lives. The recombinant S377-588-Fc is able to induce in the vaccinated mice strong MERS-CoV S-specific antibodies, which blocks the binding of RBD to DPP4 receptor and effectively neutralizes MERS-CoV infection. These findings indicate that this truncated RBD protein shows promise for further development as an effective and safe vaccine for the prevention of MERS-CoV infection.

With or without sugar? (A)glycosylation of therapeutic antibodies

Antibodies and antibody-based drugs are currently the fastest-growing class of therapeutics. Over the last three decades, more than 30 therapeutic monoclonal antibodies and derivatives thereof have been approved for and successfully applied in diverse indication areas including cancer, organ transplants, autoimmune/inflammatory disorders, and cardiovascular disease. The isotype of choice for antibody therapeutics is human IgG, whose Fc region contains a ubiquitous asparagine residue (N297) that acts as an acceptor site for N-linked glycans. The nature of these glycans can decisively influence the therapeutic performance of a recombinant antibody, and their absence or modification can lead to the loss of Fc effector functions, greater immunogenicity, and unfavorable pharmacokinetic profiles. However, recent studies have shown that aglycosylated antibodies can be genetically engineered to display novel or enhanced effector functions and that favorable pharmacokinetic properties can be preserved. Furthermore, the ability to produce aglycosylated antibodies in lower eukaryotes and bacteria offers the potential to broaden and simplify the production platforms and avoid the problem of antibody heterogeneity, which occurs when mammalian cells are used for production. In this review, we discuss the importance of Fc glycosylation focusing on the use of aglycosylated and glyco-engineered antibodies as therapeutic proteins.

Progress towards the 'Golden Age' of biotechnology

Biotechnology uses substances, materials or extracts derived from living cells, employing 22 million Europeans in a € 1.5 Tn endeavour, being the premier global economic growth opportunity this century. Significant advances have been made in red biotechnology using pharmaceutically and medically relevant applications, green biotechnology developing agricultural and environmental tools and white biotechnology serving industrial scale uses, frequently as process feedstocks. Red biotechnology has delivered dramatic improvements in controlling human disease, from antibiotics to overcome bacterial infections to anti-HIV/AIDS pharmaceuticals such as azidothymidine (AZT), anti-malarial compounds and novel vaccines saving millions of lives. Green biotechnology has dramatically increased food production through Agrobacterium and biolistic genetic modifications for the development of 'Golden Rice', pathogen resistant crops expressing crystal toxin genes, drought resistance and cold tolerance to extend growth range. The burgeoning area of white biotechnology has delivered bio-plastics, low temperature enzyme detergents and a host of feedstock materials for industrial processes such as modified starches, without which our everyday lives would be much more complex. Biotechnological applications can bridge these categories, by modifying energy crops properties, or analysing circulating nucleic acid elements, bringing benefits for all, through increased food production, supporting climate change adaptation and the low carbon economy, or novel diagnostics impacting on personalized medicine and genetic disease. Cross-cutting technologies such as PCR, novel sequencing tools, bioinformatics, transcriptomics and epigenetics are in the vanguard of biotechnological progress leading to an ever-increasing breadth of applications. Biotechnology will deliver solutions to unimagined problems, providing food security, health and well-being to mankind for centuries to come.

Protein G, protein A and protein A-derived peptides inhibit the agitation induced aggregation of IgG

Controlling and preventing aggregation is critical to the development of safe and effective antibody drug products. The studies presented here test the hypothesis that protein A and protein G inhibit the agitation-induced aggregation of IgG. The hypothesis is motivated by the enhanced conformational stability of proteins upon ligand binding and the specific binding affinity of protein A and protein G to the Fc region of IgG. The aggregation of mixed human IgG from pooled human plasma was induced by agitation alone or in the presence of (i) protein A, (ii) protein G or (iii) a library of 24 peptides derived from the IgG-binding domain of protein A. Aggregation was assessed by UV spectroscopy, SDS-PAGE, high performance size-exclusion chromatography (HP-SEC), dynamic light scattering (DLS) and fluorescence spectroscopy. Additional information on IgG-ligand interactions was obtained using differential scanning fluorimetry (DSF) and competitive binding studies. The results demonstrate that protein A provides near-complete inhibition of agitation-induced aggregation, while protein G and two peptides from the peptide library show partial inhibition. The findings indicate that the IgG protein A-binding site is involved in the agitation-induced aggregation of IgG, and suggest a dominant role of colloidal interactions.

Industrial production of recombinant therapeutics in Escherichia coli and its recent advancements

Nearly 30% of currently approved recombinant therapeutic proteins are produced in Escherichia coli. Due to its well-characterized genetics, rapid growth and high-yield production, E. coli has been a preferred choice and a workhorse for expression of non-glycosylated proteins in the biotech industry. There is a wealth of knowledge and comprehensive tools for E. coli systems, such as expression vectors, production strains, protein folding and fermentation technologies, that are well tailored for industrial applications. Advancement of the systems continues to meet the current industry needs, which are best illustrated by the recent drug approval of E. coli produced antibody fragments and Fc-fusion proteins by the FDA. Even more, recent progress in expression of complex proteins such as full-length aglycosylated antibodies, novel strain engineering, bacterial N-glycosylation and cell-free systems further suggests that complex proteins and humanized glycoproteins may be produced in E. coli in large quantities. This review summarizes the current technology used for commercial production of recombinant therapeutics in E. coli and recent advances that can potentially expand the use of this system toward more sophisticated protein therapeutics.

Daedalus: a robust, turnkey platform for rapid production of decigram quantities of active recombinant proteins in human cell lines using novel lentiviral vectors

A key challenge for the academic and biopharmaceutical communities is the rapid and scalable production of recombinant proteins for supporting downstream applications ranging from therapeutic trials to structural genomics efforts. Here, we describe a novel system for the production of recombinant mammalian proteins, including immune receptors, cytokines and antibodies, in a human cell line culture system, often requiring <3 weeks to achieve stable, high-level expression: Daedalus. The inclusion of minimized ubiquitous chromatin opening elements in the transduction vectors is key for preventing genomic silencing and maintaining the stability of decigram levels of expression. This system can bypass the tedious and time-consuming steps of conventional protein production methods by employing the secretion pathway of serum-free adapted human suspension cell lines, such as 293 Freestyle. Using optimized lentiviral vectors, yields of 20–100 mg/l of correctly folded and post-translationally modified, endotoxin-free protein of up to ~70 kDa in size, can be achieved in conventional, small-scale (100 ml) culture. At these yields, most proteins can be purified using a single size-exclusion chromatography step, immediately appropriate for use in structural, biophysical or therapeutic applications.

Conformational and aggregation properties of a PEGylated alanine-rich polypeptide

The conformational and aggregation behavior of PEG conjugates of an alanine-rich polypeptide (PEG-c17H6) were investigated and compared to that of the polypeptide equipped with a deca-histidine tag (17H6). These polypeptides serve as simple and stimuli-responsive models for the aggregation behavior of helix-rich proteins, as our previous studies have shown that the helical 17H6 self-associates at acidic pH and converts to β-sheet structures at elevated temperature under acidic conditions. In the work here, we show that PEG-c17H6 also adopts a helical structure at ambient/subambient temperatures, at both neutral and acidic pH. The thermal denaturation behavior of 17H6 and PEG-c17H6 is similar at neutral pH, where the alanine-rich domain has no self-association tendency. At acidic pH and elevated temperature, however, PEGylation slows β-sheet formation of c17H6, and reduces the apparent cooperativity of thermally induced unfolding. Transmission electron microscopy of PEG-c17H6 conjugates incubated at elevated temperatures showed fibrils with widths of ∼20-30 nm, wider than those observed for fibrils of 17H6. These results suggest that PEGylation reduces β-sheet aggregation in these polypeptides by interfering, only after unfolding of the native helical structure, with interprotein conformational changes needed to form β-sheet aggregates.

miR-34a confers chemosensitivity through modulation of MAGE-A and p53 in medulloblastoma

Recent studies have established miR-34a as a key effector of the p53 signaling pathway and have implicated its role in multiple cancer types. Here, we establish that miR-34a induces apoptosis, G2 arrest, and senescence in medulloblastoma and renders these cells more sensitive to chemotherapeutic agents. These effects are mediated in part by the direct post-transcriptional repression of the oncogenic MAGE-A gene family. We demonstrate that miR-34a directly targets the 3' untranslated regions of MAGE-A genes and decreases MAGE-A protein levels. This decrease in MAGE-A results in a concomitant increase in p53 and its associated transcriptional targets, p21/WAF1/CIP1 and, importantly, miR-34a. This establishes a positive feedback mechanism where miR-34a is not only induced by p53 but increases p53 mRNA and protein levels through the modulation of MAGE-A genes. Additionally, the forced expression of miR-34a or the knockdown of MAGE-A genes by small interfering RNA similarly sensitizes medulloblastoma cells to several classes of chemotherapeutic agents, including mitomycin C and cisplatin. Finally, the analysis of mRNA and micro-RNA transcriptional profiles of a series of primary medulloblastomas identifies a subset of tumors with low miR-34a expression and correspondingly high MAGE-A expression, suggesting the coordinate regulation of these genes. Our work establishes a role for miR-34a in modulating responsiveness to chemotherapy in medulloblastoma and presents a novel positive feedback mechanism involving miR-34a and p53, via direct targeting of MAGE-A.