The multiple arrays of a PD1-derived peptide on chromatin specifically bind to PD-L1 and induce doxorubicin resistance in cancer cell lines.

Programmed cell death-1 (PD-1) and its ligand 1 (PD-L1) have been extensively studied to block the activation of the PD-1 axis immune checkpoint pathway on T cells. However, recent evidence suggests that PD-1-independent PD-L1 pathways in cancer cells and macrophages are important in cellular proliferation and survival of those cell types but the underlying mechanism is little understood. To recapitulate the binding of multiple PD-1 to the high levels of PD-L1 expression on cancer cell membranes, recombinant histones carrying a PD-1 receptor-derived peptide (PDR) were prepared and used to assemble a PDR-displayed nucleosome array. PDR-displayed chromatin showed physiologically spaced nucleosomes, unaffected by N-terminal histone tails and biotinylated DNA modifications. PDR-displayed chromatin exhibited selective binding to the breast cancer cell line with high PD-L1 expression, MDA-MB-231, where saturated binding occurred within 3 h, comparable to well-known antigen-antibody reactions. Notably, PDR-displayed chromatin enhanced resistance to doxorubicin in PD-L1-overexpressed cancer cells, revealing a PD-L1 level-dependent effect on cell survival upon chemotherapy. Our study sheds light on the potential of PDR-displayed chromatin as a tool to induce chemoresistance in cancer cells without employing anti-PD-L1 antibodies or soluble PD-1 receptors. Further investigation into the underlying signaling pathways and therapeutic applications is warranted, positioning PDR-displayed chromatin as a valuable tool for understanding PD-L1-mediated intracellular signaling pathways in cancer cells with high PD-L1 expression.

Recent Advances and Mechanisms of Phage-Based Therapies in Cancer Treatment.

The increasing interest in bacteriophage technology has prompted its novel applications to treat different medical conditions, most interestingly cancer. Due to their high specificity, manipulability, nontoxicity, and nanosize nature, phages are promising carriers in targeted therapy and cancer immunotherapy. This approach is particularly timely, as current challenges in cancer research include damage to healthy cells, inefficiency in targeting, obstruction by biological barriers, and drug resistance. Some cancers are being kept at the forefront of phage research, such as colorectal cancer and HCC, while others like lymphoma, cervical cancer, and myeloma have not been retouched in a decade. Common mechanisms are immunogenic antigen display on phage coats and the use of phage as transporters to carry drugs, genes, and other molecules. To date, popular phage treatments being tested are gene therapy and phage-based vaccines using M13 and λ phage, with some vaccines having advanced to human clinical trials. The results from most of these studies have been promising, but limitations in phage-based therapies such as reticuloendothelial system clearance or diffusion inefficiency must be addressed. Before phage-based therapies for cancer can be successfully used in oncology practice, more in-depth research and support from local governments are required.

Repurposing a drug targeting peptide for targeting antimicrobial peptides against Staphylococcus.

OBJECTIVES: Targeted therapies seek to selectively eliminate a pathogen without disrupting the resident microbial community. However, with selectivity comes the potential for developing bacterial resistance. Thus, a diverse range of targeting peptides must be made available. RESULTS: Two commonly used antimicrobial peptides (AMPs), plectasin and eurocin, were genetically fused to the targeting peptide A12C, which selectively binds to Staphylococcus species. The targeting peptide did not decrease activity against the targeted Staphylococcus aureus and Staphylococcus epidermidis, but drastically decreased activity against the nontargeted species, Enterococcus faecalis, Bacillus subtilis, Lactococcus lactis and Lactobacillus rhamnosus. This effect was equally evident across two different AMPs, two different species of Staphylococcus, four different negative control bacteria, and against both biofilm and planktonic forms of the bacteria. CONCLUSIONS: A12C, originally designed for targeted drug delivery, was repurposed to target antimicrobial peptides. This illustrates the wealth of ligands, both natural and synthetic, which can be adapted to develop a diverse array of targeting antimicrobial peptides.

The next generation of biopanning: next gen sequencing improves analysis of bacterial display libraries.

BACKGROUND: Bacterial surface display libraries are a popular tool for novel ligand discovery due to their ease of manipulation and rapid growth rates. These libraries typically express a scaffold protein embedded within the outer membrane with a short, surface-exposed peptide that is either terminal or is incorporated into an outer loop, and can therefore interact with and bind to substrates of interest. RESULTS: In this study, we employed a novel bacterial peptide display library which incorporates short 15-mer peptides on the surface of E. coli, co-expressed with the inducible red fluorescent protein DsRed in the cytosol, to investigate population diversity over two rounds of biopanning. The naive library was used in panning trials to select for binding affinity against 3D printing plastic coupons made from polylactic acid (PLA). Resulting libraries were then deep-sequenced using next generation sequencing (NGS) to investigate selection and diversity. CONCLUSIONS: We demonstrated enrichment for PLA binding versus a sapphire control surface, analyzed population composition, and compared sorting rounds using a binding assay and fluorescence microscopy. The capability to produce and describe display libraries through NGS across rounds of selection allows a deeper understanding of population dynamics that can be better directed towards peptide discovery.

Intracellular delivery of messenger RNA by recombinant PP7 virus-like particles carrying low molecular weight protamine.

BACKGROUND: Cell-penetrating peptides (CPPs) have been widely used as carriers to transport different molecules into living cells, whereas messenger RNAs (mRNAs) have been utilized as target molecules for the prevention and treatment of various diseases. However, the instability of CPPs and mRNAs has limited their application. Bacteriophage PP7 virus-like particles (VLPs) may protect peptides and RNAs from degradation through displaying foreign peptides on their surface and encapsidating RNA linked with the pac site. RESULTS: In this study, the cDNA of the PP7 coat protein single-chain dimer carrying low molecular weight protamine (LMWP) and the cDNA of green fluorescent protein (GFP) were inserted into two multiple cloning sites of pETDuet-1, respectively. PP7 VLPs carrying the LMWP peptide and GFP mRNA were subsequently expressed in Escherichia coli BL21 (DE3) with high yield and thermal stability, and were easily purified. The VLPs were also non-replicative, non-infectious, and non-toxic. Moreover, they penetrated the mouse prostate cancer cells RM-1 after 24 h incubation. Last, PP7 VLPs carrying the LMWP could encapsidate the GFP mRNA, which was translated into mature protein in mammalian cells. CONCLUSIONS: Recombinant PP7 VLPs can be used simultaneously as a targeted delivery vector for both peptides and mRNA due to their abilities to package RNA and display peptides.

Peptide Synthesis on a Next-Generation DNA Sequencing Platform.

Methods for displaying large numbers of peptides on solid surfaces are essential for high-throughput characterization of peptide function and binding properties. Here we describe a method for converting the >10(7) flow cell-bound clusters of identical DNA strands generated by the Illumina DNA sequencing technology into clusters of complementary RNA, and subsequently peptide clusters. We modified the flow-cell-bound primers with ribonucleotides thus enabling them to be used by poliovirus polymerase 3D(pol) . The primers hybridize to the clustered DNA thus leading to RNA clusters. The RNAs fold into functional protein- or small molecule-binding aptamers. We used the mRNA-display approach to synthesize flow-cell-tethered peptides from these RNA clusters. The peptides showed selective binding to cognate antibodies. The methods described here provide an approach for using DNA clusters to template peptide synthesis on an Illumina flow cell, thus providing new opportunities for massively parallel peptide-based assays.

Identification of putative bone anabolic peptides targeting adherent plasma membrane.

Bone matrix provides unknown essential cues for osteoblast lineage cells to develop, grow, repair and remodel bones via adherent plasma membrane. Because of its tight sealing with bone matrix in vivo and culture surface in vitro as well, the adherent plasma membrane has been unveiled target of investigation to date. Herein, we report a new approach to explore the adherence plasma membrane of osteoblasts with biofunctional peptide candidates in a bacterial peptide library. To accomplish this, human osteoblast like hFOB 1.19 cells were cultured on porous filter with 8 µm pore through which bacterial peptides were allowed to meet the membrane for affinity selection. The affinity-selected peptides were coated on culture plate to further evaluate their influence on osteoblastic cell adhesion, as well as expressions of osteoblast differentiation markers, alkaline phosphatase and osteocalcin. Finally, the serial screenings identified two prominent active peptides that enhanced the differentiation markers nearly to the same level as a control peptide of bone morphogenetic protein-2. Osteogenic activity is expected for the peptides when immobilized on bone implant surface.

Construction of a high efficiency copper adsorption bacterial system via peptide display and its application on copper dye polluted wastewater.

For the construction of an efficient copper waste treatment system, a cell surface display strategy was employed. The copper adsorption ability of recombinant bacterial strains displaying three different copper binding peptides were evaluated in LB Luria-Bertani medium (LB), artificial wastewater, and copper phthalocyanine containing textile dye industry wastewater samples. Structural characteristics of the three peptides were also analyzed by similarity-based structure modeling. The best binding peptide was chosen for the construction of a dimeric peptide display and the adsorption ability of the monomeric and dimeric peptide displayed strains were compared. The dimeric peptide displayed strain showed superior copper adsorption in all three tested conditions (LB, artificial wastewater, and textile dye industry wastewater). When the strains were exposed to copper phthalocyanine dye polluted wastewater, the dimeric peptide display [543.27 µmol/g DCW dry cell weight (DCW)] showed higher adsorption of copper when compared with the monomeric strains (243.53 µmol/g DCW).

Screening and characterization of anti-SEB peptides using a bacterial display library and microfluidic magnetic sorting.

Bacterial peptide display libraries enable the rapid and efficient selection of peptides that have high affinity and selectivity toward their targets. Using a 15-mer random library on the outer surface of Escherichia coli (E.coli), high-affinity peptides were selected against a staphylococcal enterotoxin B (SEB) protein after four rounds of biopanning. On-cell screening analysis of affinity and specificity were measured by flow cytometry and directly compared to the synthetic peptide, off-cell, using peptide-ELISA. DNA sequencing of the positive clones after four rounds of microfluidic magnetic sorting (MMS) revealed a common consensus sequence of (S/T)CH(Y/F)W for the SEB-binding peptides R338, R418, and R445. The consensus sequence in these bacterial display peptides has similar amino acid characteristics with SEB peptide sequences isolated from phage display. The Kd measured by peptide-ELISA off-cell was 2.4 nM for R418 and 3.0 nM for R445. The bacterial peptide display methodology using the semiautomated MMS resulted in the discovery of selective peptides with affinity for a food safety and defense threat. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Extraction of Modified Adeno-Associated Virus-Like Particles Displaying Peptides on Their Surface.

Virus-like particles (VLPs) of the adeno-associated virus (AAV) can be produced using the baculovirus expression vector system. Insertion of small peptides on the surface of the AAV or AAV VLPs has been used to redirect the AAV to different target tissues and for vaccine development. Usually, the VLPs self-assemble intracellularly, and an extraction step must be performed before purification. Here, we describe the method we have used to extract AAV VLPs from insect cells successfully with peptide insertions on their surface.

ShuffleAnalyzer: A Comprehensive Tool to Visualize DNA Shuffling.

DNA shuffling is a powerful technique for generating synthetic DNA via recombination of homologous parental sequences. Resulting chimeras are often incorporated into complex libraries for functionality screenings that identify novel variants with improved characteristics. To survey shuffling efficiency, subsequences of chimeras can be computationally assigned to their corresponding parental counterpart, yielding insight into frequency of recombination events, diversity of shuffling libraries and actual composition of final variants. Whereas tools for parental assignment exist, they do not provide direct visualization of the results, making the analysis time-consuming and cumbersome. Here we present ShuffleAnalyzer, a comprehensive, user-friendly, Python-based analysis tool that directly generates graphical outputs of parental assignments and is freely available under a BSD-3 license (https://github.com/joerg-swg/ShuffleAnalyzer/releases). Besides DNA shuffling, peptide insertions can be simultaneously analyzed and visualized, which makes ShuffleAnalyzer a highly valuable tool for integrated approaches often used in synthetic biology, such as AAV capsid engineering in gene therapy applications.

Using display technologies to identify macrocyclic peptide antibiotics.

Antibiotic resistant bacterial infections are now a leading cause of global mortality. While drug resistance continues to spread, the clinical antibiotic pipeline has become bare. This discord has focused attention on developing new strategies for antimicrobial discovery. Natural macrocyclic peptide-based products have provided novel antibiotics and antibiotic scaffolds targeting several essential bacterial cell envelope processes, but discovery of such natural products remains a slow and inefficient process. Synthetic strategies employing peptide display technologies can quickly screen large libraries of macrocyclic sequences for specific target binding and general antibacterial potential providing alternative approaches for new antibiotic discovery. Here we review cell envelope processes that can be targeted with macrocyclic peptide therapeutics, outline important macrocyclic peptide display technologies, and discuss future strategies for both library design and screening.

Exploring the Landscape of the PP7 Virus-like Particle for Peptide Display.

Self-assembling virus-like particles (VLPs) can tolerate a wide degree of genetic and chemical manipulation to their capsid protein to display a foreign molecule polyvalently. We previously reported the successful incorporation of foreign peptide sequences in the junction loop and onto the C-terminus of PP7 dimer VLPs, as these regions are accessible for surface display on assembled capsids. Here, we report the implementation of a library-based approach to test the assembly tolerance of PP7 dimer capsid proteins to insertions or terminal extensions of randomized 15-mer peptide sequences. By performing two iterative rounds of assembly-based selection, we evaluated the degree of favorability of all 20 amino acids at each of the 15 randomized positions. Deep sequencing analysis revealed a distinct preference for the inclusion of hydrophilic peptides and negatively charged amino acids (Asp and Glu) and the exclusion of positively charged peptides and bulky and hydrophobic amino acid residues (Trp, Phe, Tyr, and Cys). Within the libraries tested here, we identified 4000 to 22,000 unique 15-mer peptide sequences that can successfully be displayed on the surface of the PP7 dimer capsid. Overall, the use of small initial libraries consisting of no more than a few million members yielded a significantly larger number of unique and assembly-competent VLP sequences than have been previously characterized for this class of nucleoprotein particle.

MS2 Virus-like Particles as a Versatile Peptide Presentation Platform: Insights into the Deterministic Abilities for Accommodating Heterologous Peptide Lengths.

Virus-like particles (VLPs) are nanostructures with the potential to present heterologous peptides at high density, thereby triggering heightened immunogenicity. RNA bacteriophage MS2 VLPs are a compelling delivery platform among them. However, a notable hurdle arises from the immune response toward MS2 coat protein, swiftly eliminating subsequent vaccinations via the same vector. Although larger inserts effectively mask carrier epitopes, current research predominantly focuses on displaying short conserved peptides (<30 aa). A systematic evaluation regarding the deterministic ability of MS2 VLPs as a platform for presenting heterologous peptides remains a gap. In light of this, we employed the "single-chain dimer" paradigm to scrutinize the tolerance of MS2 VLPs for peptide/protein insertions. The results unveiled functional MS2 VLP assembly solely for inserts smaller than 91 aa. Particularly noteworthy is the largest insertion achieved on the MS2 VLPs to date: the RNA helicase A (RHA) dsRNA-binding domains (dsRBD1). Attempts to introduce additional linkers or empty coat subunits fail to augment the expression level or assembly of the MS2 VLPs displaying dsRBD1, affirming 91 aa as the upper threshold for exogenous protein presentation. By illuminating the precise confines of MS2 VLPs in accommodating distinct peptide lengths, our study informs the selection of appropriate peptide and protein dimensions. This revelation not only underscores the scope of MS2 VLPs but also establishes a pivotal reference point, facilitating the strategic manipulation of MS2 VLPs to design next-generation epitope/antibody-based therapeutics.

Discovery of Antimicrobial Peptide Macrocycles Through Bacterial Display.

Peptide macrocycles exhibit great ability to inhibit bacterial growth making them a promising new avenue for antimicrobial discovery. Surface Localized Antimicrobial Display (SLAY) is a platform allowing the high-throughput screening of large peptide libraries of diverse length, composition, or structure for their antimicrobial activity, including macrocyclic peptides cyclized through disulfide bonding. Here we describe the procedure for the design and construction of a SLAY peptide library and the process for screening that library for antimicrobial potential.

CasPlay provides a gRNA-barcoded CRISPR-based display platform for antibody repertoire profiling.

Protein display technologies link proteins to distinct nucleic acid sequences (barcodes), enabling multiplexed protein assays via DNA sequencing. Here, we develop Cas9 display (CasPlay) to interrogate customized peptide libraries fused to catalytically inactive Cas9 (dCas9) by sequencing the guide RNA (gRNA) barcodes associated with each peptide. We first confirm the ability of CasPlay to characterize antibody epitopes by recovering a known binding motif for a monoclonal anti-FLAG antibody. We then use a CasPlay library tiling the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) proteome to evaluate vaccine-induced antibody reactivities. Using a peptide library representing the human virome, we demonstrate the ability of CasPlay to identify epitopes across many viruses from microliters of patient serum. Our results suggest that CasPlay is a viable strategy for customized protein interaction studies from highly complex libraries and could provide an alternative to phage display technologies.

Phage display and other peptide display technologies.

Phage display technology, which is based on the presentation of peptide sequences on the surface of bacteriophage virions, was developed over 30 years ago. Improvements in phage display systems have allowed us to employ this method in numerous fields of biotechnology, as diverse as immunological and biomedical applications, the formation of novel materials and many others. The importance of phage display platforms was recognized by awarding the Nobel Prize in 2018 'for the phage display of peptides and antibodies'. In contrast to many review articles concerning specific applications of phage display systems published in recent years, we present an overview of this technology, including a comparison of various display systems, their advantages and disadvantages, and examples of applications in various fields of science, medicine and the broad sense of biotechnology. Other peptide display technologies, which employ bacterial, yeast and mammalian cells, as well as eukaryotic viruses and cell-free systems, are also discussed. These powerful methods are still being developed and improved; thus, novel sophisticated tools based on phage display and other peptide display systems are constantly emerging, and new opportunities to solve various scientific, medical and technological problems can be expected to become available in the near future.

Sprayable nanomicelle hydrogels and inflammatory bowel disease patient cell chips for development of intestinal lesion-specific therapy.

All-in-one treatments represent a paradigm shift in future medicine. For example, inflammatory bowel disease (IBD) is mainly diagnosed by endoscopy, which could be applied for not only on-site monitoring but also the intestinal lesion-targeted spray of injectable hydrogels. Furthermore, molecular conjugation to the hydrogels would program both lesion-specific adhesion and drug-free therapy. This study validated this concept of all-in-one treatment by first utilizing a well-known injectable hydrogel that underwent efficient solution-to-gel transition and nanomicelle formation as a translatable component. These properties enabled spraying of the hydrogel onto the intestinal walls during endoscopy. Next, peptide conjugation to the hydrogel guided endoscopic monitoring of IBD progress upon adhesive gelation with subsequent moisturization of inflammatory lesions, specifically by nanomicelles. The peptide was designed to mimic the major component that mediates intestinal interaction with Bacillus subtilis flagellin during IBD initiation. Hence, the peptide-guided efficient adhesion of the hydrogel nanomicelles onto Toll-like receptor 5 (TLR5) as the main target of flagellin binding and Notch-1. The peptide binding potently suppressed inflammatory signaling without drug loading, where TLR5 and Notch-1 operated collaboratively through downstream actions of tumor necrosis factor-alpha. The results were produced using a human colorectal cell line, clinical IBD patient cells, gut-on-a-chip, a mouse IBD model, and pig experiments to validate the translational utility.

VLP-factory™ and ADDomer© : Self-assembling Virus-Like Particle (VLP) Technologies for Multiple Protein and Peptide Epitope Display.

Virus-like particles (VLPs) play a prominent role in vaccination as safe and highly versatile alternatives to attenuated or inactivated viruses or subunit vaccines. We present here two innovations, VLP-factory™ and ADDomer© , for creating VLPs displaying entire proteins or peptide epitopes as antigens, respectively, to enable efficient vaccination. For producing these VLPs, we use MultiBac, a baculovirus expression vector system (BEVS) that we developed for producing complex protein biologics in insect cells transfected with an engineered baculovirus. VLPs are protein assemblies that share features with viruses but are devoid of genetic material, and thus considered safe. VLP-factory™ represents a customized MultiBac baculovirus tailored to produce enveloped VLPs based on the M1 capsid protein of influenza virus. We apply VLP-factory™ to create an array of influenza-derived VLPs presenting functional mutant influenza hemagglutinin (HA) glycoprotein variants. Moreover, we describe MultiBac-based production of ADDomer© , a synthetic self-assembling adenovirus-derived protein-based VLP platform designed to display multiple copies of pathogenic epitopes at the same time on one particle for highly efficient vaccination. © 2021 The Authors. Basic Protocol 1: VLP-factory™ baculoviral genome generation Basic Protocol 2: Influenza VLP array generation using VLP-factory™ Basic Protocol 3: Influenza VLP purification Basic Protocol 4: ADDomer© BioBrick design, expression, and purification Basic Protocol 5: ADDomer© candidate vaccines against infectious diseases.

[Preparation of anti-hCG antibody-like molecule by using a RAD peptide display system].

By using an RAD peptide display system derived from the ATPase domain of recombinase RadA of Pyrococcus furiosus, an anti-hCG antibody-like molecule was prepared by grafting an hCG-binding peptide to the RAD scaffold. After linking to sfGFP gene, a gene of hCG peptide-grafted RAD was synthesized and cloned into a bacterial expression vector (pET30a-RAD/hCGBP-sfGFP). The vector was transformed into Escherichia coli, and expression of the fusion protein was induced. After isolation and purification of the fusion protein, its binding affinity and specificity to hCG were determined by using a process of immunoabsorption followed by GFP fluorescence measurement. A comparison of hCG-binding activity with a similarly grafted single-domain antibody based on a universal scaffold was performed. The measurement of hCG-binding affinity and specificity revealed that the grafted RAD has an optimally high binding affinity and specificity to hCG, which are better than the grafted single-domain antibody. Moreover, the affinity and specificity of grafted RAD molecule are comparable to those of a commercial monoclonal antibody. In addition, the hCG-binding peptide-grafted RAD molecule has a relatively high biochemical stability, making it a good substitute for antibody with potential application.