P53 Peptide Research Articles

In vitro enhancement of Zika virus infection by preexisting West Nile virus antibodies in human plasma-derived immunoglobulins revealed after P2 binding site-specific enrichment.

Human immunoglobulin preparations contain a diverse range of polyclonal antibodies that reflect past immune responses against pathogens encountered by the blood donor population. In this study, we examined a panel of intravenous immunoglobulins (IGIVs) manufactured over the past two decades (1998-2020) for their capacity to neutralize or enhance Zika virus (ZIKV) infection in vitro. These IGIVs were selected specifically based on their production dates in relation to the occurrences of two flavivirus outbreaks in the U.S.: the West Nile virus (WNV) outbreak in 1999 and the ZIKV outbreak in 2015. As demonstrated by enzyme-linked immunosorbent assay (ELISA) experiments, IGIVs made before the ZIKV outbreak already harbored antibodies that bind to various peptides across the envelope protein of ZIKV because of the WNV outbreak. Using phage display, the most dominant binding site was mapped precisely to the P2 peptide between residues 211 and 230 within domain II, where BF1176-56, an anti-ZIKV monoclonal antibody, also binds. When tested in permissive Vero E6 cells for ZIKV neutralization, the IGIVs, even after undergoing rigorous enrichment for P2 binding specificity, failed, as did BF1176-56. Meanwhile, BF1176-56 enhanced ZIKV infection in both FcγRII-expressing K562 cells and human peripheral blood mononuclear cells. However, for enhancement by the IGIVs to be detected in these cells, a substantial increase in their P2 binding specificity was required, thus linking the P2 site with ZIKV enhancement in vitro. Our findings warrant further study of the significance of elevated levels of anti-WNV antibodies in IGIVs, considering that various mechanisms operating in vivo may modulate ZIKV infection outcomes.IMPORTANCEWe investigated the capacity of intravenous immunoglobulins manufactured previously over two decades (1998-2020) to neutralize or enhance Zika virus infection in vitro. West Nile virus antibodies in IGIVs could not neutralize Zika virus initially; however, once the IGIVs were concentrated further, they enhanced its infection. These findings lay the groundwork for exploring how preexisting WNV antibodies in IGIVs could impact Zika infection, both in vitro and in vivo. Our observations are historically significant, since we tested a panel of IGIV lots that were carefully selected based on their production dates which covered two major flavivirus outbreaks in the U.S.: the WNV outbreak in 1999 and the ZIKV outbreak in 2015. These findings will facilitate our understanding of the interplay among closely related viral pathogens, particularly from a historical perspective regarding large blood donor populations. They should remain relevant for future outbreaks of emerging flaviviruses that may potentially affect vulnerable populations.

Discovery of novel HER2 targeting peptide-camptothecin conjugates with effective suppression for selective cancer treatment

Due to the strong selectivity and permeability of tumor tissue, anti-cancer peptide-drug conjugates (PDCs) can accumulate high concentration of toxic payloads at the target, effectively killing tumor cells. This approach holds great promise for tumor-targeted treatment. In our previous study, we identified the optimal peptide P1 (NPNWGRSWYNQRFK) targeting HER2 from pertuzumab, a monoclonal antibody that blocks the HER2 signaling pathway. Here, a series of PDCs were constructed through connecting P1 and CPT with different linkers. Among these, Z8 emerged as the optimal compound, demonstrating good antitumor activity and targeting ability in biological activity tests. Z8 exhibited IC50 values of 1.04 ± 0.24 μM and 1.91 ± 0.71 μM against HER2-positive SK-BR-3 and NCI-N87 cells, respectively. Moreover, superior antitumor activity and higher biosafety of Z8 were observed compared to the positive control CPT in vivo, suggesting a novel idea for the construction of PDCs.

Preclinical evaluation of Tc-99m p5+14 peptide for SPECT detection of cardiac amyloidosis.

Amyloid deposition is a cause of restrictive cardiomyopathy. Patients who present with cardiac disease can be evaluated for transthyretin (TTR)-associated cardiac amyloidosis using nuclear imaging with 99mTc-labeled pyrophosphate (PYP); however, light chain-associated (AL) cardiac amyloid is generally not detected using this tracer. As an alternative, the amyloid-binding peptide p5+14 radiolabeled with iodine-124 has been shown to be an effective pan-amyloid radiotracer for PET/CT imaging. Here, a 99mTc-labeled form of p5+14 peptide has been prepared to facilitate SPECT/CT imaging of cardiac amyloidosis. A synthesis method suitable for clinical applications has been used to prepare 99mTc-labeled p5+14 and tested for peptide purity, product bioactivity, radiochemical purity and stability. The product was compared with99mTc-PYP for cardiac SPECT/CT imaging in a mouse model of AA amyloidosis and for reactivity with human tissue sections from AL and TTR patients. The 99mTc p5+14 tracer was produced with >95% yields in radiopurity and bioactivity with no purification steps required and retained over 95% peptide purity and >90% bioactivity for >3 h. In mice, the tracer detected hepatosplenic AA amyloid as well as heart deposits with uptake ~5 fold higher than 99mTc-PYP. 99mTc p5+14 effectively bound human amyloid deposits in the liver, kidney and both AL- and ATTR cardiac amyloid in tissue sections in which 99mTc-PYP binding was not detectable. 99mTc-p5+14 was prepared in minutes in >20 mCi doses with good performance in preclinical studies making it suitable for clinical SPECT/CT imaging of cardiac amyloidosis.

Abstract 4101: Immune inhibition of murine colorectal cancer by a p53 peptide mucosal vaccine

Abstract Colorectal cancer (CRC) is among the most common cancers with high morbidity and mortality for patients despite multi-modality treatment options. Immune checkpoint inhibitors often have impact in the 15% of CRC patients with microsatellite instability-high status CRCs but have limited utility in the remaining 85% of CRC patients. Given the presence of p53 mutations in CRC, we pursued a vaccine approach against tumor cells expressing murine CRC Trp53 codon 270 missense alleles (codon 273 mutation in human cancer) using a combination of R270H p53 peptide, wild type p53 recombinant protein and used a mucosal adjuvant (MA) to drive epithelial immune responses. The vaccine (p53/MA) was studied in a CDX2-CreERT2 (tamoxifen-induced Cre-Lox) transgenic mouse CRC model where tumors arise in the cecum and proximal colon epithelium following combined ApcΔ580, KrasG12D, and Trp53R270H mutations (AKP model). The p53/MA vaccine treatment was administered intranasally to the mice at defined time points after tamoxifen tumor induction. p53/MA vaccinated animals had increased anti-p53 IgG (p<0.01), IgG2a (p<0.01), and IgG2b (p<0.001) in sera compared to control mice. The treatment enhanced antigen-specific Th1 and Th17 cellular immune responses, as shown by increasing of IFN-ɤ (p<0.05), IL-17a (p<0.01) and IL-2 (p<0.01) both in splenocytes and draining lymph nodes measured by Luminex assay. Vaccinated mice also showed significant more cells producing IFN-ɤ (p<0.001) and IL-17a (p<0.001) as analyzed by ELISpot. Importantly, the immunized animals had decreased tumor size/volume (p<0.001) and prolonged survival (p<0.05) compared to control animals that received only saline or MA respectively. Tumors from vaccinated mice also showed more mononuclear cell infiltrates than tumors from the control animals. In conclusion, novel p53/MA vaccinations can induce significant p53-specific immune responses and anti-tumor effects in the mouse AKP CRC model. Citation Format: Suhe Wang, Zhengyi Cao, Katarzyna W. Janczak, Ying Feng, Maranne Green, Eric R. Fearon, James R. Baker Jr. Immune inhibition of murine colorectal cancer by a p53 peptide mucosal vaccine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4101.

Efficient production of isomaltulose using engineered Yarrowia lipolytica strain facilitated by non-yeast signal peptide-mediated cell surface display.

Isomaltulose is a 'generally recognized as safe' ingredient and is widely used in the food, pharmaceutical and chemical industries. The exploration and development of efficient technologies is essential for enhancing isomaltulose yield. In the present study, a simple and efficient surface display platform mediated by a non-yeast signal peptide was developed in Yarrowia lipolytica and utilized to efficiently produce isomaltulose from sucrose. We discovered that the signal peptide SP1 of sucrose isomerase from Pantoea dispersa UQ68J (PdSI) could guide SIs anchoring to the cell surface of Y. lipolytica, demonstrating a novel and simple cell surface display strategy. Furthermore, the PdSI expression level was significantly increased through optimizing the promoters and multi-site integrating genes into chromosome. The final strain gained 451.7 g L-1 isomaltulose with a conversion rate of 90.3% and a space-time yield of 50.2 g L-1 h-1. The present study provides an efficient way for manufacturing isomaltulose with a high space-time yield. This heterogenous signal peptide-mediated cell surface display strategy featured with small fusion tag (approximately 2.2 kDa of SP1), absence of enzyme leakage in fermentation broth and ample room for optimization, providing a convenient way to construct whole-cell biocatalysts to synthesize other products and broadening the array of molecular toolboxes accessible for engineering Y. lipolytica. © 2024 Society of Chemical Industry.

Design, Synthesis, and Anticancer Activity of N‐1 Terminal Segment of α‐(2, 5,7‐Tri‐tert‐butylindol‐3‐yl)alanine‐Incorporated Short Peptides

AbstractUsing a minimallised approach,we designed and synthesized N‐terminal modified peptides W‐KRGNKWLA‐CONH2 (P1) and W‐ARGDGGNGRGA‐CONH2 (P2) using Fmoc‐Chemistry solid phase peptide synthesis protocol. High‐performance liquid chromatograms and mass spectrometry (LCMS and analytical HPLC) were employed to determine the purity and molecular weight of the peptide. Surface tension measurements are used to evaluate peptide surface activity. The primary structure of the peptideis anlaysed by NMR spectroscopy. Circular dichroism studies demonstrate that the secondary structure of the peptide changes minimally when it attached to anionic lipid bilayers (POPC : POPG). According to a steady‐state fluorescence experiment, peptides P1 and P2 preferentially interact with anionic (POPC : POPG) lipid bilayers rather than zwitterionic (POPC) lipid bilayers. The peptide P2 interacts preferentially with anionic lipid membranes and has an anticancer effect due to RGD and NGR binding motifs. The cytotoxicity of the MTT experiment demonstrated that both normal and cancerous cells could lower peptide concentrations below their IC50 levels. Molecular docking also supports in‐vitro anticancer research. Both peptides P1 and P2 were non‐toxic to vero cells and appeared to be more promising as it demonstrated wide spectrum anticancer activity.

Antibacterial Peptides derived from Capra hircus Goat Milk Casein

AbstractMilk is a popular source of antimicrobial peptides (AMPs). Therefore, this study aimed to investigate antibacterial activity of fractions and peptides derived from casein hydrolysate. Casein protein was hydrolyzed using the trypsin enzyme and the hydrolyzate was fractionated with a strong cationic exchange (scx) cartridge at a pH 3–9 buffer. The results showed that the pH 5–8 fraction demonstrated antibacterial activity against Staphylococcus aureus and Escherichia coli. The pH 6 fraction had the greatest activity against S. aureus and E. coli, with inhibition zone of 8.00 and 2.00 mm, respectively. Peptides in the pH 6 fraction, namely YNVPQLEIVPK (P1), KENINELSK (P2), GLSPEVPNENLLR (P3), and YLGYLEQLLK (P4) were tested for the activity against S. aureus and E. coli. Based on the results, synthetic peptide P1, P2, P3, and P4 have activity against S. aureus and E. coli. Peptide P3 showed higher activity than others with an inhibition zone of 4.55 and 6.60 mm in S. aureus and E. coli, respectively. Peptide P4 showed an amphipathic structure and good physicochemical properties as a cell‐penetrating peptide. A strong interaction was also observed between peptide P4 and enzyme MurC with a binding affinity of −6.6 kcal/mol.

The hormonal control of parturition.

Parturition is a complex physiological process that must occur in a reliable manner and at an appropriate gestation stage to ensure a healthy newborn and mother. To this end, hormones that affect the function of the gravid uterus, especially progesterone (P4), 17β-estradiol (E2), oxytocin (OT), and prostaglandins (PGs), play pivotal roles. P4 via the nuclear P4 receptor (PR) promotes uterine quiescence and for most of pregnancy exerts a dominant block to labor. Loss of the P4 block to parturition in association with a gain in prolabor actions of E2 are key transitions in the hormonal cascade leading to parturition. P4 withdrawal can occur through various mechanisms depending on species and physiological context. Parturition in most species involves inflammation within the uterine tissues and especially at the maternal-fetal interface. Local PGs and other inflammatory mediators may initiate parturition by inducing P4 withdrawal. Withdrawal of the P4 block is coordinated with increased E2 actions to enhance uterotonic signals mediated by OT and PGs to promote uterine contractions, cervix softening, and membrane rupture, i.e., labor. This review examines recent advances in research to understand the hormonal control of parturition, with focus on the roles of P4, E2, PGs, OT, inflammatory cytokines, and placental peptide hormones together with evolutionary biology of and implications for clinical management of human parturition.

NCAM mimetic peptide P2 synergizes with bone marrow mesenchymal stem cells in promoting functional recovery after stroke

The neural cell adhesion molecule (NCAM) promotes neural development and regeneration. Whether NCAM mimetic peptides could synergize with bone marrow mesenchymal stem cells (BMSCs) in stroke treatment deserves investigation. We found that the NCAM mimetic peptide P2 promoted BMSC proliferation, migration, and neurotrophic factor expression, protected neurons from oxygen-glucose deprivation through ERK and PI3K/AKT activation and anti-apoptotic mechanisms in vitro. Following middle cerebral artery occlusion (MCAO) in rats, P2 alone or in combination with BMSCs inhibited neuronal apoptosis and induced the phosphorylation of ERK and AKT. P2 combined with BMSCs enhanced neurotrophic factor expression and BMSC proliferation in the ischemic boundary zone. Moreover, combined P2 and BMSC therapy induced translocation of nuclear factor erythroid 2-related factor, upregulated heme oxygenase-1 expression, reduced infarct volume, and increased functional recovery as compared to monotreatments. Treatment with LY294002 (PI3K inhibitor) and PD98059 (ERK inhibitor) decreased the neuroprotective effects of combined P2 and BMSC therapy in MCAO rats. Collectively, P2 is neuroprotective while P2 and BMSCs work synergistically to improve functional outcomes after ischemic stroke, which may be attributed to mechanisms involving enhanced BMSC proliferation and neurotrophic factor release, anti-apoptosis, and PI3K/AKT and ERK pathways activation.

Eliminating senescent cells by white adipose tissue-targeted senotherapy alleviates age-related hepatic steatosis through decreasing lipolysis.

Cellular senescence is an important risk factor in the development of hepatic steatosis. Senolytics present therapeutic effects on age-related hepatic steatosis without eliminating senescent hepatocytes directly. Therefore, it highlights the need to find senolytics' therapeutic targets. Dysfunction of adipose tissue underlies the critical pathogenesis of lipotoxicity in the liver. However, the correlation between adipose tissue and hepatic steatosis during aging and its underlying molecular mechanism remains poorly understood. We explored the correlation between white adipose tissue (WAT) and the liver during aging and evaluated the effect of lipolysis of aged WAT on hepatic steatosis and hepatocyte senescence. We screened out the ideal senolytics for WAT and developed a WAT-targeted delivery system for senotherapy. We assessed senescence and lipolysis of WAT and hepatic lipid accumulation after treatment. The results displayed that agingaccelerated cellular senescence and facilitated lipolysis of WAT. Free fatty acids (FFAs) generated by WAT during aging enhanced hepatic steatosis and induced hepatocyte senescence. The combined usage of dasatinib and quercetin was screened out as the ideal senolytics to eliminate senescent cells in WAT. To minimize non-specific distribution and enhance the effectiveness of senolytics, liposomes decorated with WAT affinity peptide P3 were constructed for senotherapy in vivo. In vivo study, WAT-targeted treatment eliminated senescent cells in WAT and reduced lipolysis, resulting in the alleviation of hepatic lipid accumulation and hepatocyte senescence when compared to non-targeted treatment, providing a novel tissue-targeted, effective and safe senotherapy for age-related hepatic steatosis.

Lysosome-targeting chimeras containing an endocytic signaling motif trigger endocytosis and lysosomal degradation of cell-surface proteins.

Lysosome-targeting degradation technologies have emerged as a promising therapeutic strategy for the selective depletion of target extracellular and cell-surface proteins by harnessing a cell-surface effector protein such as lysosome-targeting receptors (LTRs) or transmembrane E3 ligases that direct lysosomal degradation. We recently developed a lysosome-targeting degradation platform termed signal-mediated lysosome-targeting chimeras (SignalTACs) that functions independently of an LTR or E3 ligase; these are engineered fusion proteins comprising a target binder, a cell-penetrating peptide (CPP), and a lysosomal sorting signal motif (P1). Herein, we present the next-generation SignalTACs containing a single endocytic signal that bypasses the need for a CPP. We demonstrate that the fusion with a 10-amino acid endocytic signaling peptide (P3) derived from the cation-independent mannose-6-phosphate receptor (CI-M6PR) induces robust internalization and lysosomal degradation of the target protein. The P3-based SignalTAC exhibited enhanced antitumor efficacy compared to the parent antibody. We envision that the fusion of the endocytic signaling peptide P3 to a target binder may allow the construction of an effective degrader for membrane-associated targets. Furthermore, mechanistic studies identified different drivers for the activities of the P3- and P1-based SignalTACs, which is expected to provide crucial insights toward the harnessing of the intrinsic signaling pathways to direct protein trafficking and degradation.

Unraveling the Effects of Cationic Peptides on Vesicle Structures: Insights into Peptide-Membrane Interactions.

Antimicrobial resistance is a pressing global health issue, with millions of lives at risk by 2050, necessitating the development of alternatives with broad-spectrum activity against pathogenic microbes. Antimicrobial peptides provide a promising solution by combating microbes, modulating immunity, and reducing resistance development through membrane and intracellular targeting. PuroA, a synthetic peptide derived from the tryptophan-rich domain of puroindoline A, exhibits potent antimicrobial activity against various pathogens, while the rationally designed P1 peptide demonstrates enhanced antimicrobial activity with its specific composition. This paper investigates the concentration-dependent effects of these cationic peptides on distinct types of vesicles representing strong-negative bacterial cell membranes (S-vesicles), weak-negative bacterial cell membranes (W-vesicles), and mammalian cell membranes (M-vesicles). To investigate the interactions between the peptides and vesicles, small-angle neutron scattering experiments were conducted. The cationic peptides, PuroA and P1, interact with S-vesicles through electrostatic interactions, leading to distinct effects. PuroA accumulates on the vesicle surface, increasing Rcore and Rtotal, aligning with the carpet model. P1 disrupts the vesicle structure at higher concentrations, consistent with the detergent model. Neither peptide significantly affects W-vesicles, emphasizing the role of charge. In uncharged M-vesicles, both peptides decrease Rcore and Rtotal and increase tshell, indicating peptide insertion and altered bilayer properties. These findings provide valuable insights into peptide-membrane interactions and their impact on vesicle structures. Furthermore, the implications of these findings extend to the potential development of innovative antimicrobial agents and drug delivery systems that specifically target bacterial and mammalian membranes. This research contributes to the advancement of understanding peptide-membrane interactions and lays the foundation for the design of approaches for targeting membranes in various biomedical applications.

Prediction and identification of HLA-A*0201-restricted epitopes from cancer testis antigen CT23

ABSTRACT Cancer-testis antigen CT23 is a class of tumor-associated antigens (TAA) characterized by restricted expression in male germ cells and a variety of tumor tissues. Numerous studies have shown that CT23 is closely related to tumor cell viability, proliferation, metastasis and invasion. CT23 is immunogenic and can cause specific immune response in tumor patients. Therefore, it is considered to be one of the best target antigens for designing therapeutic tumor vaccines and T-cell-mediated tumor immunotherapy. In this study, we initially obtained seven HLA-A*0201-restricted CT23 epitope candidate peptides through the T cell epitope prediction program. Subsequently, a T2 cell binding assay revealed the potential binding of all candidate peptides with HLA-A2 molecules. Notably, peptide P7 (ALLVLCYSI) exhibited the highest affinity, as evidenced by a fluorescence index (FI) of 2.19. Dendritic cells (DCs) loaded with CT23 candidate peptide can stimulate CD8+T cell activation and proliferation, and compared with other candidate peptides, candidate peptide P7 is superior. The cytotoxic T lymphocytes (CTLs) stimulated by the peptide P7 had killing effect on tumor cells (HLA-A*0201+, CT23+), but no killing effect on tumor cells (HLA-A*0201−, CT23+). The CTLs induced by the peptide P7 also had a specific killing effect on T2 cells bearing the peptide P7. In summary, our findings suggest that the CT23 peptide P7 (ALLVLCYSI) can induce immune responses and holds potential for tumor-specific CTL therapy.

Modulating Liquid-Liquid Phase Separation of Nck Adaptor Protein against Enteropathogenic Escherichia coli Infection.

Signaling proteins often form biomolecular condensates through liquid-liquid phase separation (LLPS) during intracellular signal transduction. Modulating the LLPS property of intracellular protein condensates will redirect intracellular signals and provide a potential way to regulate cellular physiology. Phosphorylation of multiple tyrosine residues of the transmembrane receptor nephrin is known to drive the LLPS of the adaptor protein Nck and neuronal Wiskott-Aldrich Syndrome protein (N-WASP) and form the Nck signaling complex. Phosphorylation of the translocated intimin receptor (Tir) in the host cell may recruit this enteropathogenic Escherichia coli (EPEC) virulence factor to the Nck signaling complex and lead to the entry of EPEC into the intestine cell. In this work, we first identified a phosphotyrosine (pY)-containing peptide 3pY based on the sequence similarity of nephrin and Tir; 3pY promoted the LLPS of Nck and N-WASP, mimicking the role of phosphorylated nephrin. Next, we designed a covalent blocker of Nck, peptide p1 based on the selected pY peptides, which site-selectively reacted with the SH2 domain of Nck (Nck-SH2) at Lys331 through a proximity-induced reaction. The covalent reaction of p1 with Nck blocked the protein binding site of Nck-SH2 and disintegrated the 3pY/Nck/N-WASP condensates. In the presence of membrane-translocating peptide L17E, p1 entered Caco-2 cells in the cytosol, reduced the number of Nck puncta, and rendered Caco-2 cells resistant to EPEC infection. Site-selective covalent blockage of Nck thereby disintegrates intracellular Nck condensates, inhibits actin reorganization, and shuts down the entrance pathway of EPEC. This work showcases the promotion or inhibition of protein phase separation by synthetic peptides and the use of reactive peptides as LLPS disruptors and signal modulators.

Alzheimer’s disease linked amyloid beta 1‐42 exerts product feedback inhibition on gamma‐secretase impairing downstream signaling cascades

AbstractBackgroundΓ‐secretases are proteolytic switches at the membrane regulating multiple signaling cascades. Their dysfunction, resulting in enhanced generation of longer amyloid β (Aβ) peptides from the amyloid precursor protein (APP), leads to neurodegeneration in the context of Alzheimer’s disease (AD), while their inhibition causes neurodegenerative phenotypes in mice and cognitive worsening in AD patients treated with γ‐secretase inhibitors. The accumulation of Aβ in the brain is the earliest pathological hallmark of AD. Based on the proven affinity of Aβ peptides for γ‐secretases, we hypothesized that elevations in Aβ levels would promote an inhibitory‐feedback mechanism on γ‐secretases and impair downstream cell signaling events.MethodWe conducted rigorous kinetic analyses of γ‐secretase activity in the presence of a series of Aβ and p3 peptides, by quantifying the levels of intracellular domains generated from different γ‐secretase substrates in cell‐free assays. In addition, we determined the effects of these peptides on endogenous γ‐secretase activity in living neurons, using a ratiometric FRET‐based reporter and western blot analysis of the levels of immediate γ‐secretase substrates. Furthermore, we assessed the impact of Aβ and p3 peptides on γ‐secretase‐mediated, p75‐ and TrkA‐dependent downstream signaling via immunostaining for an apoptotic marker: cleaved caspase 3. Finally, we evaluated the impact of Aβ peptides on APP processing in synaptosome fractions derived from mouse brains.ResultOur analyses showed that human Aβ42 inhibited γ‐secretase activity and accordingly caused accumulation of unprocessed γ‐secretase substrates in neuronal cells, i.e. CTFs of APP, p75 and pan‐cadherin. Remarkably, neither murine Aβ42 nor human p3 (17‐42) peptides exerted the inhibition. In TrkA signaling deficient PC12 cells and basal forebrain cholinergic neurons, Aβ1‐42‐mediated inhibition of γ‐secretase led to the accumulation of unprocessed p75‐CTFs and potentiated p75‐dependent cell death, mimicking the effects of γ‐secretase inhibitors.ConclusionWe demonstrate that the pathologically relevant human Aβ1‐42 exerts product feedback inhibition on γ‐secretases, leading to dysregulation of downstream cellular signaling. These findings provide a novel conceptual framework for investigations of Aβ toxicity in the context of γ‐secretase‐dependent homeostatic signaling and raise the possibility that Aβ42‐mediated inactivation of these enzymes contributes to AD development.

Heterobivalent Peptide Agonists Comprising Covalently Linked Protease Activated Receptor 1 and Protease Activated Receptor 3 Peptides Mimic the Cytoprotective Cell Signaling Activities of Activated Protein C

Introduction: Activated protein C (APC) exhibits both anticoagulant and cytoprotective cell signaling actions, including anti-inflammatory and anti-apoptotic activities and endothelial barrier stabilization. Extensive in vitro and in vivo data for APC's cell signaling benefits identified requirements for two G-protein coupled receptors (GPCR), protease-activated receptor (PAR) PAR1 and PAR3 which are cleaved by APC at the noncanonical sites (R46 and R41, respectively). Agonism of PARs following proteolysis of the N-terminal tail is driven by the newly revealed N-terminus and related synthetic peptides, e.g., for APC, PAR1 peptides (P1) beginning with N47 or PAR3 peptides (P3) beginning with G42. We found that the non-canonical P1-47-66 and P3-42-65 peptides mimic APC in that each is anti-inflammatory by reducing NLRP3-driven caspase-1 activity in human THP-1 cells (Healy LD et al, J Thromb Haemost 2021;19:269-280). Remarkably, these two peptides act synergistically to attenuate activity of caspase-1 at low concentrations where either peptide alone has little activity. Thus, we undertook studies of P1 peptides that were covalently linked to P3 peptides for ability to mimic APC's anti-inflammatory and endothelial barrier stabilization actions. Methods: Monocytes (THP-1 cells) were differentiated into macrophages using PMA, then pretreated with APC or peptides prior to stimulation with lipopolysaccharide and adenosine triphosphate to induce caspase-1 whose activity was measured using a luminescent caspase-1 substrate. Endothelial barrier stability was monitored for transendothelial electrical resistance (TEER) using an electric cell-substrate sensing system (iCelligence apparatus) when cultured human EAhy926 or murine aortic endothelial cells (EC) were exposed to thrombin treatment (0.25 nM) plus or minus treatment with P1 and/or P3 peptides or G10-related peptides. Synthetic P1 and P3 sequence-derived peptides of various compositions were made, and bivalent P1:P3 peptides were made using oligo-Gly-peptide linkers containing from 4 to 14 Gly residues. Results: Using THP-1 cell anti-inflammatory assays for various peptides, studies showed that P1-47-55 was as potent as P1-47-66 and that the N-terminal N47 was essential. In anti-inflammatory activity assays, some P3 peptides shorter than P3-42-65 (e.g., P3-44-54, P3-51-65, and P3-51-59) were as active as P3-42-65. Remarkably, this is the first example for any PAR-agonist peptide that does not require a native-like sequence with an intact free alpha-amino N-terminus to agonize the PAR response. For bivalent P1:P3 studies, we covalently linked P3-47-55 to P3-51-65 using oligo-Gly linkers with 4-14 Gly residues. In anti-inflammatory activity assays, the maximal activity was seen for a 10-Gly linker. The bivalent peptide comprising P1-47-55-[Gly(10 residues)]-P3-51-65, designated as the G10 peptide, was much more potent than any P1 peptide or P3 peptide in anti-inflammatory THP-1 cell assays in dose-response studies. In TEER studies of thrombin-challenged EAhy926 EC where APC markedly attenuates thrombin-induced endothelial barrier dysfunction, P1-47-55 and the G10 peptide mimicked APC's protective actions. In dose-response studies, the G10 peptide was much more potent than the P1-47-55 peptide or any combination of P1-47-55 with a P3 peptide. The P3 peptides alone were very weak. In TEER studies of thrombin-challenged murine aortic EC where murine APC markedly attenuates thrombin-induced endothelial barrier dysfunction, the G10 peptide comprising murine PAR sequences mimicked murine APC's protective actions. Conclusions: Covalent linkage of a PAR1-derived peptide agonist to a PAR3-derived peptide agonist using a 10-Gly-residue linker provided the first heterobivalent PAR peptide GPCR agonist. This heterobivalent G10 peptide potently mimicked APC's cytoprotective activities of anti-inflammation and endothelial barrier stabilization. Molecular mechanisms for G10 likely involve both orthosteric and allosteric effects for PAR1 and PAR3 which can form heterodimers. Given APC's beneficial cell signaling effects in many preclinical injury models and given the increasing usage of peptide-based drugs, studies of the G10 peptide for beneficial APC-mimicking effects may help to identify important directions for future translational research.

Early Development and Pre-Clinical Evaluation of a Fluorine-18 Labeled Peptide p5+14 for PET/CT Imaging of Cardiac Amyloidosis

Background:Systemic amyloidosis is a rare protein misfolding disorder, where patients can present with varied symptoms due to the diverse organ involvement. This is particularly true of patients with light chain associated (AL) amyloidosis, which makes early and accurate diagnosis challenging. Currently there are no FDA-approved methods that allow visualization of amyloidosis in patients. Nuclear imaging is a promising method for early detection of amyloid. We have developed a novel amyloid-reactive peptide, designated p5+14, capable of binding AL, as well as other types of amyloid, via multivalent electrostatic interactions. Peptide p5+14 has been successfully radiolabeled with radioiodine and technetium-99m and evaluated clinically, labeled with iodine-124, in a PET/CT imaging study of patients with amyloidosis (NCT03678259). While there are numerous advantages to using I-124 as the radionuclide for amyloid imaging, fluorine is a viable alternative for detecting cardiac amyloidosis. Fluorine-18 has a shorter half-life (108 min as compared to 4.2 days) thus reducing the internal radiation dose to patients. Moreover, F-18 is the most common nuclide used in PET imaging. We have previously generated a 18F-labeled variant of p5+14; however, the reaction was inefficient and not translatable. Here we present a novel development strategy for generating 18F labeled p5+14 using a commercially available precursor that can bind AL amyloid and perform initial characterization of the reagent in a murine model of inflammation-associated systemic AA amyloidosis. Methods: Isotopic exchange chemistry using a silicon-fluoride-acceptor (SiFA) method was used to label peptide p5+14 with F-18. The peptide precursor was purchased from Almac Life Sciences (Penicuik, UK). 18F was purchased from PetNet (Siemens Healthineers, Knoxville, TN) and prepared for reaction according to standard methods. After drying, F-18 (1000 - 1900 MBq ) was dissolved in anhydrous acetonitrile and the pH neutralized before the addition of peptide precursor. Radiolabeling was performed at room temperature for 5 min. After standard purification of the product, radiochemical purity studies demonstrated that it was stable, with no significant loss of F-18 for at least 5 hours. Radiofluorinated p5+14 was assessed in bioactivity “pulldown” assays to ensure binding to synthetic AL amyloid-like fibrils and human AL amyloid extracts. The radiolabeled peptide was also diluted in PBS and injected IV in the lateral tail vein of mice with severe systemic AA amyloidosis. After 1 h, mice were euthanized small animal PET/CT imaging performed and tissue biodistribution measurements were conducted using an automated Wizard 3 gamma counter (1480 Wallac Gamma Counter, Perkin-Elmer). Results: Using optimized synthesis conditions, the non-decay corrected radiochemical yield was 55±4.5%. Radiochemical purity was 99±1% at end of synthesis. Peptide purity was shown to be 93.7±4.9% by assessed using HPLC. Radiochemical stability was similarly evaluated using an HLPC method and remained >97.5% radiochemical purity at 5 hours after synthesis. The binding of 18F-p5+14 to synthetic AL amyloid like fibrils composed of a l6 variable domain was 96.2%, mimicking data using the radioiodinated peptide, and 87.2% to human AL amyloid extracts. Background binding to control beads was 17.4%. In mice, accumulation of 18F-peptide in the liver and spleen, the organs with most AA amyloid deposits in this mouse model, was readily evident in PET images taken 1 h post injection. There was also evidence of hepatic clearance of the peptide, manifest as a prominent gall bladder in the images. There was no accumulation of F-18 in bone, indicating positive in vivo stability. Imaging of amyloid-free wild type mice showed rapid clearance with radioactivity in the urinary bladder, gall bladder and gastrointestinal tract with little or no hepatosplenic radiotracer retention. Conclusion: Radiofluorination of peptides, such as p5+14, has been made more efficient through the use of novel precursors amenable to isotopic exchange. 18F-peptide binds amyloid effectively and may serve as a next generation radiotracer for the detection of cardiac amyloid by PET/CT imaging. Acknowledgments: EW is a doctoral student in the Comparative and Experimental Medicine Program. This study was supported by the Amyloidosis and Cancer Theranostics Program and the UTGSM.

Longitudinal PET/CT Imaging with Iodine ( 124I) Evuzamitide Reveals Organ Response to Plasma Cell Immunotherapy in a Patient with AL Amyloidosis

Background:Iodine-124-evuzamitide is a novel amyloidophilic peptide (p5+14), labeled with iodine-124, for detecting amyloid by positron emission/x-ray computed tomographic (PET/CT) imaging ( Pharmaceuticals 2023 Apr 21;16(4):629). PET is an inherently quantitative modality and thus 124I-evuzamitide may be useful for monitoring disease progression and response to therapy. Amyloid deposits can impact any organ in patients with light chain-associated amyloidosis (AL); thus, tissue-specific changes in amyloid load, based on PET/CT imaging, may be informative. Currently, response to therapy is assessed by anatomic imaging and measurement of serum or urinary biomarkers. However, the correlation between these metrics and concomitant changes in amyloid load remains enigmatic. Here, we report a case of a patient with AL amyloidosis, on long-term daratumumab therapy, who underwent longitudinal 124I-evuzamitide PET/CT imaging over 4 years (NCT03678259 and NCT05968846). Patient and Methods: A 70-year-old male presented with abnormal liver function tests, notably an elevated serum alkaline phosphatase (ALK) of 465 IU/L. Biopsies of both the liver and celiac nodes revealed the characteristic apple-green birefringence of Congo red stain, indicating the presence of amyloid. The patient began daratumumab immunotherapy 14 months prior to his enrollment in the 124I-evuzamitide imaging study and over the 4-year course of serial imaging. During this time, regular serial serum biomarkers were evaluated as standard of care. PET/CT images were acquired at 0, 23, and 45 months. For each imaging session, the patient received 2 mCi iodine-124-labeled tracer via intravenous injection and was imaged at 5 h post injection. Image data were assessed for visual uptake of radiotracer and quantified by manual 2D region-of-interest analysis where the semi-quantitative mean standard uptake value ratio (SUVR mean) was calculated using blood pool as the reference tissue. Results: Over the 45 months of evaluation, there was a 59% and 73% reduction in 124I-evuzamitide SUVR in the liver and spleen. This was accompanied by decreases in the weight-scaled organ volume (cc/kg) for both the liver (15.2%) and spleen (30.0%) based on segmentation of the organ volume from CT images. This reduction in radiotracer uptake coincided with a sustained decrease in serum FLC, from 38.3 mg/L to 19.1 mg/L, and a positive liver response, where ALK levels dropped from ~200 IU/L to ~120 IU/L. In contrast, renal radiotracer uptake increased slightly in the context of stable creatinine levels, and a modest decline in eGFR. Cardiac uptake of 124I-evuzamitide remained positive and relatively stable, concordant with serum NT-proBNP levels. These data suggest that organ-specific amyloid response, in the context of a sustained hematologic response, may occur independently and at different rates. Conclusion: Previous reports have demonstrated the resolution of AL amyloid. However, this is the first report using an amyloid-binding radiotracer, capable of visualizing all major organs including the heart, demonstrating the complex pattern of organ response and regression of AL amyloid in the context of concurrent biomarker improvement and changes in organ volume. PET/CT imaging using 124I-evuzamitide may, therefore, play a valuable role in both diagnosing amyloidosis and monitoring changes in organ-specific amyloid load. Additional longitudinal imaging studies are needed to support this clinical application.

Screening and identification of B cell epitope within the major capsid protein L1 of HPV 52, using monoclonal antibodies

The L1 protein of Human papillomavirus (HPV), the main capsid protein, induces the formation of neutralizing antibodies. In this study, HPV52 L1 protein was induced to be expressed. Monoclonal antibody (mAb) 6A7 against L1 protein were screened by cell fusion techniques. Western Blot and immunofluorescence assay (IFA) demonstrated the specificity of the mAb. The L1 protein was truncated for prokaryotic expression (N1∼N7) and Dot-ELISA showed that 6A7 recognized N3 (aa 200–350). The immunodominant regions were truncated again for expression, with 6A7 recognizing N6 (aa 251–305). The N6 proteins were further truncated and then were constructed an four-segment eukaryotic expression vector. IFA showed that 6A7 could recognize amino acid 262–279. Amino acid 262–279 was selected to be truncated into short peptides P1 and P2. Finally, Peptide-ELISA and Dot-ELISA showed that the epitope regions of mAb 6A7 were amino acid 262–273. The mAbs with defined epitopes can lay the foundation for the analysis of antigenic epitope characteristics and promote the development of epitope peptide vaccines.

Efficacy of the Vaccine Candidate Based on the P0 Peptide against Dermacentor nitens and Ixodes ricinus Ticks.

The control of ticks through vaccination offers a sustainable alternative to the use of chemicals that cause contamination and the selection of resistant tick strains. However, only a limited number of anti-tick vaccines have reached commercial realization. In this sense, an antigen effective against different tick species is a desirable target for developing such vaccines. A peptide derived from the tick P0 protein (pP0) conjugated to a carrier protein has been demonstrated to be effective against the Rhipicephalus microplus, Rhipicephalus sanguineus, and Amblyomma mixtum tick species. The aim of this work was to assess the efficacy of this peptide when conjugated to the Bm86 protein against Dermacentor nitens and Ixodes ricinus ticks. An RNAi experiment using P0 dsRNA from I. ricinus showed a dramatic reduction in the feeding of injected female ticks on guinea pigs. In the follow-up vaccination experiments, rabbits were immunized with the pP0-Bm86 conjugate and challenged simultaneously with larvae, nymphs, and the adults of I. ricinus ticks. In the same way, horses were immunized with the pP0-Bm86 conjugate and challenged with D. nitens larva. The pP0-Bm86 conjugate showed efficacies of 63% and 55% against I. ricinus and D. nitens ticks, respectively. These results, combined with previous reports of efficacy for this conjugate, show the promising potential for its development as a broad-spectrum anti-tick vaccine.