Conjugation to 10 kDa Linear PEG Extends Serum Half-Life and Preserves the Receptor-Binding Ability of mmTRAIL with Minimal Stimulation of PEG-Specific Antibodies

Phage-derived proteins: Advancing food safety through biocontrol and detection of foodborne pathogens

The emergence of antimicrobial-resistant foodborne pathogens poses a continuous health risk and economic burden as they can easily spread through contaminated food. Therefore, the demand for new antimicrobial agents to address this problem is steadily increasing. Similarly, the development of rapid, sensitive, and accurate pathogen detection tools is a prerequisite for ensuring food safety. Phage-derived proteins have become innovative tools for combating these pathogens because of their potent antimicrobial activity and host specificity. Phage proteins are relatively free from regulation compared to phages per se, and there are no concerns about the transduction of harmful genes. With recent progress in next-generation sequencing technology, the analysis of phage genomes has become more accessible, and numerous phage proteins with potential for biocontrol and detection have been identified. This review provides a comprehensive overview of phage protein research on food safety from 2006 to the present, a pivotal period marked by the certification of phages as Generally Recognized As Safe (GRAS). Emphasizing recent advancements, we investigated the diverse applications of various phage proteins for biocontrol and detection purposes. While highlighting the successful implementation of these proteins, we also address the current bottlenecks and propose strategies to overcome these challenges. By summarizing the current state of research on phage-derived proteins, this review contributes to a deeper understanding of their potential as effective antimicrobial agents and tools for detecting foodborne pathogens.

PEGylation Prolongs the Half-Life of Equine Anti-SARS-CoV-2 Specific F(ab')2

Therapeutic antibodies-F(ab')₂ obtained from hyperimmune equine plasma could treat emerging infectious diseases rapidly because of their high neutralization activity and high output. However, the small-sized F(ab')₂ is rapidly eliminated by blood circulation. This study explored PEGylation strategies to maximize the half-life of equine anti-SARS-CoV-2 specific F(ab')₂. Equine anti-SARS-CoV-2 specific F(ab')₂ were combined with 10 KDa MAL-PEG-MAL in optimum conditions. Specifically, there were two strategies: Fab-PEG and Fab-PEG-Fab, F(ab')₂ bind to a PEG or two PEG, respectively. A single ion exchange chromatography step accomplished the purification of the products. Finally, the affinity and neutralizing activity was evaluated by ELISA and pseudovirus neutralization assay, and ELISA detected the pharmacokinetic parameters. The results displayed that equine anti-SARS-CoV-2 specific F(ab')₂ has high specificity. Furthermore, PEGylation F(ab')₂-Fab-PEG-Fab had a longer half-life than specific F(ab')₂. The serum half-life of Fab-PEG-Fab, Fab-PEG, and specific F(ab')₂ were 71.41 h, 26.73 h, and 38.32 h, respectively. The half-life of Fab-PEG-Fab was approximately two times as long as the specific F(ab')₂. Thus far, PEGylated F(ab')₂ has been prepared with high safety, high specificity, and a longer half-life, which could be used as a potential treatment for COVID-19.

Single domain antibodies derived from ancient animals as broadly neutralizing agents for SARS-CoV-2 and other coronaviruses

With severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as an emergent human virus since December 2019, the world population is susceptible to coronavirus disease 2019 (COVID-19). SARS-CoV-2 has higher transmissibility than the previous coronaviruses, associated by the ribonucleic acid (RNA) virus nature with high mutation rate, caused SARS-CoV-2 variants to arise while circulating worldwide. Neutralizing antibodies are identified as immediate and direct-acting therapeutic against COVID-19. Single-domain antibodies (sdAbs), as small biomolecules with non-complex structure and intrinsic stability, can acquire antigen-binding capabilities comparable to conventional antibodies, which serve as an attractive neutralizing solution. SARS-CoV-2 spike protein attaches to human angiotensin-converting enzyme 2 (ACE2) receptor on lung epithelial cells to initiate viral infection, serves as potential therapeutic target. sdAbs have shown broad neutralization towards SARS-CoV-2 with various mutations, effectively stop and prevent infection while efficiently block mutational escape. In addition, sdAbs can be developed into multivalent antibodies or inhaled biotherapeutics against COVID-19.

A higher dose of PEGylated gold nanoparticles reduces the accelerated blood clearance phenomenon effect and induces spleen B lymphocytes in albino mice

Polyethylene glycol (PEG) is a multifunctional polymer that has many uses in medical and biological applications. Recently, PEG has been mainly used in developing nanomaterial-based drug delivery systems (DDS). PEG is characterized by its high solubility, biological inertness, and ability to escape from immune cells (stealthiness) after systemic injection. The most challenging problem for PEGylated nanomaterials is their rapid elimination from the bloodstream after repeated doses of systemic injection, called accelerated blood clearance (ABC). Therefore, in this study, the effect of PEGylated nanomaterial dose concentration on ABC induction will be investigated using quantitative, histological, and immunohistochemical analyses. A higher dose concentration (2 mg/kg) of PEGylated gold nanoparticles (PEG-coated AuNPs) reduced the ABC phenomenon when intravenously injected into mice preinjected with the same dose. In contrast, a lower dose concentration (< 1 mg/kg) significantly induced the ABC phenomenon by the rapid elimination of the second dose of PEG-coated AuNPs from the bloodstream. To explain the relationship between the dose concentration (from PEG and AuNPs) and the induction of ABC, the biodistribution of PEG-coated AuNPs in liver and spleen [reticuloendothelial systems (RES)-rich organs] was investigated. The injected dose of PEG-coated AuNPs accumulated mainly in the hepatic Kupffer cells and hepatocytes. Similarly, spleen red pulp received a higher amount of the injected dose of PEG-coated AuNPs. However, the biodistriution profiles of PEG-coated AuNPs after the first and second dose for different dose concentrations varied in RES-rich organs. Additionally, the number of B lymphocytes, which have an important role in producing anti-PEG immunoglobulin (Ig)M, was affected by the repeated dose of PEG-coated AuNPs in the spleen. Therefore, for effective nanomaterial-based DDS development, dose optimization of PEG molecules that express PEGylated nanomaterials is important to reduce the ABC phenomenon effect. The ideal concentration of PEG molecules used to coat nanomaterials and the role of RES-rich organs must be determined to control the ABC phenomenon effect of PEGylated nanomaterials.

Improving Targeted Delivery and Antitumor Efficacy with Engineered Tumor Necrosis Factor-Related Apoptosis Ligand-Affibody Fusion Protein

Tumor necrosis factor-related apoptosis ligand (TRAIL) is a promising protein candidate for selective apoptosis of a variety of cancer cells. However, the short half-life and a lack of targeted delivery are major obstacles for its application in cancer therapy. Here, we propose a simple strategy to solve the targeting problem by genetically fusing an anti-HER2 affibody to the C-terminus of the TRAIL. The fusion protein TRAIL-affibody was produced as a soluble form with high yield in recombinant Escherichia coli. In vitro studies proved that the affibody domain promoted the cellular uptake of the fusion protein in the HER2 overexpressed SKOV-3 cells and improved its apoptosis-inducing ability. In addition, the fusion protein exhibited higher accumulation at the tumor site and greater antitumor effect than those of TRAIL in vivo, indicating that the affibody promoted the tumor homing of the TRAIL and then improved the therapeutic efficacy. Importantly, repeated injection of high-dose TRAIL-affibody showed no obvious toxicity in mice. These results demonstrated that the engineered TRAIL-affibody is promising to be a highly tumor-specific and targeted cancer therapeutic agent.

Sheward D, Karl V, Perez Vidakovics L, Murrell B, McInerney GM, Hanke L. Picomolar SARS-CoV-2 Neutralization Using Multi-Arm PEG Nanobody Constructs

Multivalent antibody constructs have a broad range of clinical and biotechnological applications. Nanobodies are especially useful as components for multivalent constructs as they allow increased valency while maintaining a small molecule size. We here describe a novel, rapid method for the generation of bi- and multivalent nanobody constructs with oriented assembly by Cu-free strain promoted azide-alkyne click chemistry (SPAAC). We used sortase A for ligation of click chemistry functional groups site-specifically to the C-terminus of nanobodies before creating C-to-C-terminal nanobody fusions and 4-arm polyethylene glycol (PEG) tetrameric nanobody constructs. We demonstrated the viability of this approach by generating constructs with the SARS-CoV-2 neutralizing nanobody Ty1. We compared the ability of the different constructs to neutralize SARS-CoV-2 pseudotyped virus and infectious virus in neutralization assays. The generated dimers neutralized the virus similarly to a nanobody-Fc fusion variant, while a 4-arm PEG based tetrameric Ty1 construct dramatically enhanced neutralization of SARS-CoV-2, with an IC₅₀ in the low picomolar range.

Customizing a Tridomain TRAIL Variant to Achieve Active Tumor Homing and Endogenous Albumin-Controlled Release of the Molecular Machine In Vivo

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an attractive antitumor drug candidate for precision cancer therapy due to its superior selective cytotoxicity in a variety of tumor cells. However, the clinical application of TRAIL in cancer therapy has been limited by its poor tumor-homing capacities and short half-life. Herein, we designed a tridomain TRAIL variant, Z-ABD-TRAIL, by sequentially fusing the platelet-derived growth factor receptor beta (PDGFRβ)-specific affibody Z_PDGFRβ and an albumin-binding domain (ABD) to the N-terminus of TRAIL. The fusion protein Z-ABD-TRAIL was produced as a soluble protein with high yield in Escherichia coli (E. coli). The Z_PDGFRβ domain provided Z-ABD-TRAIL with PDGFRβ-binding properties and thus promoted its tumor homing via the engagement of PDGFRβ-expressing pericytes on tumor microvessels. ABD-mediated binding of Z-ABD-TRAIL to albumin in the blood endowed TRAIL with long-lasting (>72 h for Z-ABD-TRAIL vs <0.5 h for TRAIL) abilities to kill tumor cells. Although the in vitro cytotoxicity of Z-ABD-TRAIL in tumor cells was similar to that of the parent TRAIL, the in vivo tumor uptake, apoptosis-inducing ability, and antitumor effect of Z-ABD-TRAIL were much greater than those of TRAIL, indicating that Z_PDGFRβ-mediated tumor homing and ABD-introduced albumin binding significantly improved the pharmacodynamics of TRAIL. In addition, repeated injection of high-dose Z-ABD-TRAIL showed no obvious acute toxicity in mice. These results demonstrate that the newly designed tridomain Z-ABD-TRAIL is a promising agent for precision cancer therapy.

Site-Specific PEGylation of Anti-Mesothelin Recombinant Immunotoxins Increases Half-life and Antitumor Activity

Recombinant immunotoxins (RIT) are chimeric proteins containing an Fv that binds to tumor cells, fused to a fragment of Pseudomonas exotoxin (PE) that kills the cell. Their efficacy is limited by their short half-life in the circulation. Chemical modification with polyethylene glycol (PEG) is a well-established method to extend the half-lives of biologics. Our goal was to engineer RITs with an increase in half-life and high cytotoxic activity. We introduced single cysteines at different locations in five anti-mesothelin RITs and employed site-specific PEGylation to conjugate them to 20-kDa PEG. Because our previous PEGylation method using β-mercaptoethanol reduction gave poor yields of PEG-modified protein, we employed a new method using tris(2-carboxyethyl)phosphine to reduce the protein and could PEGylate RITs at approximately 90% efficiency. The new proteins retained 19% to 65% of cytotoxic activity. Although all proteins are modified with the same PEG, the radius of hydration varies from 5.2 to 7.1, showing PEG location has a large effect on protein shape. The RIT with the smallest radius of hydration has the highest cytotoxic activity. The PEGylated RITs have a 10- to 30-fold increase in half-life that is related to the increase in hydrodynamic size. Biodistribution experiments indicate that the long half-life is due to delayed uptake by the kidney. Antitumor experiments show that several PEG-RITs are much more active than unmodified RIT, and the PEG location greatly affects antitumor activity. We conclude that PEGylation is a useful approach to improve the half-life and antitumor activity of RITs.

Accelerated Clearance of Ultrasound Contrast Agents Containing Polyethylene Glycol is Associated with the Generation of Anti-Polyethylene Glycol Antibodies

Emerging evidence suggests that the immune system can recognize polyethylene glycol (PEG), leading to the accelerated blood clearance (ABC) of PEGylated particles. Our aim here was to study the generation of anti-PEG immunity and changes in PEGylated microbubble pharmacokinetics during repeated contrast-enhanced ultrasound imaging in rats. We administered homemade PEGylated microbubbles multiple times over a 28-d period and observed dramatically accelerated clearance (4.2 × reduction in half-life), which was associated with robust anti-PEG IgM and anti-PEG IgG antibody production. Dosing animals with free PEG as a competition agent before homemade PEGylated microbubble administration significantly prolonged microbubble circulation, suggesting that ABC was largely driven by circulating anti-PEG antibodies. Experiments with U.S. Food and Drug Administration-approved Definity microbubbles similarly resulted in ABC and the generation of anti-PEG antibodies. Experiments repeated with non-PEGylated Optison microbubbles revealed a slight shift in clearance, indicating that immunologic factors beyond anti-PEG immunity may play a role in ABC, especially of non-PEGylated agents.