Engineering a Low-Immunogenic Mirror-Image VHH against Vascular Endothelial Growth Factor.

Immunogenicity is a major caveat of protein therapeutics. In particular, the long-term administration of protein therapeutic agents leads to the generation of antidrug antibodies (ADAs), which reduce drug efficacy while eliciting adverse events. One promising solution to this issue is the use of mirror-image proteins consisting of d-amino acids, which are resistant to proteolytic degradation in immune cells. We have recently reported the chemical synthesis of the enantiomeric form of the variable domain of the antibody heavy chain (d-VHH). However, identifying mirror-image antibodies capable of binding to natural ligands remains challenging. In this study, we developed a novel screening platform to identify a d-VHH specific for vascular endothelial growth factor A (VEGF-A). We performed mirror-image screening of two newly constructed synthetic VHH libraries displayed on T7 phage and identified VHH sequences that effectively bound to the mirror-image VEGF-A target (d-VEGF-A). We subsequently synthesized a d-VHH candidate that preferentially bound the native VEGF-A (l-VEGF-A) with submicromolar affinity. Furthermore, immunization studies in mice demonstrated that this d-VHH elicited no ADAs, unlike its corresponding l-VHH. Our findings highlight the utility of this novel d-VHH screening platform in the development of protein therapeutics exhibiting both reduced immunogenicity and improved efficacy.

Design and Synthesis of Monobody Variants with Low Immunogenicity.

Mirror-image proteins (d-proteins) are promising scaffolds for drug discovery because of their high proteolytic stability and low immunogenic properties. Facile and reproducible processes for the preparation of functional d-proteins are required for their application in therapeutic biologics. In this study, we designed and synthesized a novel monobody variant with two cysteine substitutions that facilitate the synthetic process via sequential native chemical ligations and improve protein stability by disulfide bond formation. The synthetic anti-GFP monobody in this model study exhibited good binding affinity to the target enhanced green fluorescent protein. In vivo administration of the synthetic anti-GFP monobody (l-monobody) to mice induced antidrug antibody (ADA) production, whereas no ADA production was observed following immunization with the mirror-image anti-GFP monobody (d-monobody). These results suggest that the synthetic d-monobody is a non-antibody protein scaffold with low immunogenic properties.

Mirror-Image Single-Domain Antibody for a Novel Nonimmunogenic Drug Scaffold.

Immunogenic responses by protein therapeutics often lead to reduced therapeutic effects and/or adverse effects via the generation of neutralizing antibodies and/or antidrug antibodies (ADA). Mirror-image proteins of the variable domain of the heavy chain of the heavy chain antibody (VHH) are potential novel protein therapeutics with high-affinity binding to target proteins and reduced immunogenicity because these mirror-image VHHs (d-VHHs) are less susceptible to proteolytic degradation in antigen-presenting cells (APCs). In this study, we investigated the preparation protocols of d-VHHs and their biological properties, including stereoselective target binding and immunogenicity. Initially, we established a facile synthetic process of two model VHHs [anti-GFP VHH and PMP12A2h1 (monomeric VHH of caplacizumab)] and their mirror-image proteins by three-step native chemical ligations (NCLs) from four peptide segments. The folded synthetic VHHs (l-anti-GFP VHH and l-PMP12A2h1) bound to the target proteins (EGFP and vWF-A1 domain, respectively), while their mirror-image proteins (d-anti-GFP VHH and d-PMP12A2h1) showed no binding to the native proteins. For biodistribution studies, l-VHH and d-VHH with single radioactive indium diethylenetriamine-pentaacid (111In-DTPA) labeling at the C-terminus were designed and synthesized by the established protocol. The distribution profiles were essentially similar between l-VHH and d-VHH, in which the probes accumulated in the kidney within 15 min after intravenous administration in mice, because of the small molecular size of VHHs. Comparative assessment of the immunogenicity responses revealed that d-VHH-induced levels of ADA generation were significantly lower than those of native VHH, regardless of the peptide sequences and administration routes. The resulting scaffold investigated should be applicable in the design of d-VHHs with various C-terminal CDR3 sequences, which can be identified by screening using display technologies.

Construction of a T7 phage random peptide library by combining seamless cloning with in vitro translation.

T7 phage libraries displaying random peptides are powerful tools for screening peptide sequences that bind to various target molecules. The T7 phage system has the advantage of less biased peptide distribution compared to the M13 phage system. However, the construction of T7 phage DNA is challenging due to its long 36 kb linear DNA. Furthermore, the diversity of the libraries depends strongly on the efficiency of commercially available packaging extracts. To address these issues, we examined the combination of seamless cloning with cell-free translation systems. Seamless cloning technologies have been widely used to construct short circular plasmid DNA, and several recent studies showed that cell-free translation can achieve more diverse phage packaging. In this study, we combined these techniques to construct four libraries (CX7C, CX9C, CX11C and CX13C) with different random regions lengths. The libraries thus obtained all showed diversity > 109 plaque forming units (pfu). Evaluating our libraries with an anti-FLAG monoclonal antibody yielded the correct epitope sequence. The results indicate that our libraries are useful for screening peptide epitopes against antibodies. These findings suggest that our system can efficiently construct T7 phage libraries with greater diversity than previous systems.

Characterization of novel antibodies that recognize sialylated keratan sulfate and lacto-N-fucopentaose I on human induced pluripotent cells: comparison with existing antibodies.

This report describes the isolation and characterization of two new antibodies, R-6C (IgM) and R-13E (IgM), which were generated in C57BL/6 mice (Mus musculus) using the Tic (JCRB1331) human induced pluripotent cell (hiPSC) line as an antigen, and their comparisons with two existing antibodies, R-10G (IgG1) and R-17F (IgG1). Their epitopes were studied by western blotting after various glycosidase digestions, binding analyses using enzyme-linked immunosorbent assays (ELISAs) and microarrays with various synthetic oligosaccharides. The minimum epitope structures identified were: Siaα2-3Galß1-3GlcNAc(6S)ß1-3Galß1-4GlcNAc(6S)ß1 (R-6C), Fucα1-2Galß1-3GlcNAcß1-3Galß1 (R-13E), Galß1-4GlcNAc(6S)ß1-3Galß1-4GlcNAc(6S)ß1 (R-10G), and Fucα1-2Galß1-3GlcNAß1-3Galß1-4Glc (lacto-N-fucopentaose I) (R-17F). Most glycoprotein epitopes are expressed as O-glycans. The common feature of these epitopes is the presence of an N-acetyllactosamine type 1 structure (Galß1-3GlcNAc) at their nonreducing termini, followed by a type 2 structure (Galß1-4GlcNAc); this arrangement comprises a type 1-type 2 motif. This motif is also shared by TRA-1-60, a traditional onco-fetal antigen. In contrast, the R-10G epitope has a type 2-type 2 motif. Among these antibodies, R-17F and R-13E exhibit cytotoxic activity toward hiPSCs. R-17F and R-13E exhibit extremely high similarity in the amino acid sequences in their complementarity-determining regions (CDRs), which is consistent with their highly similar glycan recognition. These antibodies are excellent tools for investigating the biological functions of glycoconjugates in hiPSCs/hESCs; they could be useful for the selection, isolation and selective killing of such undifferentiated pluripotent stem cells.

Efficient antigen delivery by dendritic cell-targeting peptide via nucleolin confers superior vaccine effects in mice.

Efficient delivery of subunit vaccines to dendritic cells (DCs) is necessary to improve vaccine efficacy, because the vaccine antigen alone cannot induce sufficient protective immunity. Here, we identified DC-targeting peptides using a phage display system and demonstrated the potential of these peptides as antigen-delivery carriers to improve subunit vaccine effectiveness in mice. The fusion of antigen proteins and peptides with DC-targeting peptides induced strong antigen-specific IgG responses, even in the absence of adjuvants. In addition, the DC-targeting peptide improved the distribution of antigens to DCs and antigen presentation by DCs. The combined use of an adjuvant with a DC-targeting peptide improved the effectiveness of the vaccine. Furthermore, nucleolin, located on the DC surface, was identified as the receptor for DC-targeting peptide, and nucleolin was indispensable for the vaccine effect of the DC-targeting peptide. Overall, the findings of this study could be useful for developing subunit vaccines against infectious diseases.

THE EFFICACY OF MARINE NATURAL PRODUCTS AGAINST PLASMODIUM FALCIPARUM.

Malaria remains one of the most important infectious diseases in the world. In 2017 alone, approximately 219 million people were infected with malaria, and 435,000 people died of this disease. Plasmodium falciparum, which causes falciparum malaria, is becoming resistant to artemisinin (ART) in Southeast Asia; therefore, new antimalarial drugs are urgently needed. Some excellent antimalarial drugs, such as quinine and ART, were originally obtained from plants. Hence, we analyzed the antimalarial effects of marine natural products to find new antimalarial agents. We used a malaria growth inhibition assay to determine the antimalarial ability and half-maximal inhibitory concentration (IC50) values of the marine organism-derived compounds. Three compounds (kapakahine A, kapakahine B, and kulolide-1) showed antimalarial effects, and one (kapakahine F) showed selective antimalarial effects on the Dd2 clone. Although the IC50 values obtained for these compounds were greater than that of ART, their potency against P. falciparum is sufficient to warrant further investigation of these compounds as possible drug leads.

Tumor vasculature-targeted 10B delivery by an Annexin A1-binding peptide boosts effects of boron neutron capture therapy.

BACKGROUND: p-Boronophenylalanine (10BPA) is a powerful 10B drug used in current clinical trials of BNCT. For BNCT to be successful, a high (500 mg/kg) dose of 10BPA must be administered over a few hours. Here, we report BNCT efficacy after rapid, ultralow-dose administration of either tumor vasculature-specific annexin A1-targeting IFLLWQR (IF7)-conjugated 10BPA or borocaptate sodium (10BSH). METHODS: (1) IF7 conjugates of either 10B drugs intravenously injected into MBT2 bladder tumor-bearing mice and biodistribution of 10B in tumors and normal organs analyzed by prompt gamma-ray analysis. (2) Therapeutic effect of IF7-10B drug-mediated BNCT was assessed by either MBT2 bladder tumor bearing C3H/He mice and YTS-1 tumor bearing nude mice. RESULTS: Intravenous injection of IF7C conjugates of either 10B drugs into MBT2 bladder tumor-bearing mice promoted rapid 10B accumulation in tumor and suppressed tumor growth. Moreover, multiple treatments at ultralow (10-20 mg/kg) doses of IF7-10B drug-mediated BNCT significantly suppressed tumor growth in a mouse model of human YTS-1 bladder cancer, with increased Anxa1 expression in tumors and infiltration by CD8-positive lymphocytes. CONCLUSIONS: We conclude that IF7 serves as an efficient 10B delivery vehicle by targeting tumor tissues via the tumor vasculature and could serve as a relevant vehicle for BNCT drugs.

Development of an orally-administrable tumor vasculature-targeting therapeutic using annexin A1-binding D-peptides.

We previously reported that IF7 peptide, which binds to the annexin A1 (ANXA1) N-terminus, functions as a tumor vasculature-targeted drug delivery vehicle after intravenous injection. To enhance IF7 stability in vivo, we undertook mirror-image peptide phage display using a synthetic D-peptide representing the ANXA1 N-terminus as target. We then identified peptide sequences, synthesized them as D-amino acids, and designated the resulting peptide dTIT7, which we showed bound to the ANXA1 N-terminus. Whole body imaging of mouse brain tumor models injected with near infrared fluorescent IRDye-conjugated dTIT7 showed fluorescent signals in brain and kidney. Furthermore, orally-administered dTIT7/geldanamycin (GA) conjugates suppressed brain tumor growth. Ours is a proof-of-concept experiment showing that ANXA1-binding D-peptide can be developed as an orally-administrable tumor vasculature-targeted therapeutic.

Nullscript inhibits Cryptosporidium and Toxoplasma growth.

Cryptosporidium and Toxoplasma are parasites that have caused problems worldwide. Cryptosporidium causes severe watery diarrhoea and may be fatal in immunocompromised patients and in infants. Nitazoxanide is the only agent currently approved by the FDA, but its efficacy is limited. Toxoplasmosis is also a problem in the immunocompromised, as currently available treatment options have limited efficacy and patient tolerance can be poor. In the present investigation, we screened libraries of epigenetic compounds to identify those that inhibited C. parvum growth. Nullscript was identified as a compound with an inhibitory effect on C. parvum and T. gondii growth, and was less toxic to host cells. Nullscript was also able to significantly decrease oocyst excretion in C. parvum-infected SCID mice.

Overcoming the blood-brain barrier by Annexin A1-binding peptide to target brain tumours.

BACKGROUND: Annexin A1 is expressed specifically on the tumour vasculature surface. Intravenously injected IF7 targets tumour vasculature via annexin A1. We tested the hypothesis that IF7 overcomes the blood-brain barrier and that the intravenously injected IF7C(RR)-SN38 eradicates brain tumours in the mouse. METHODS: (1) A dual-tumour model was generated by inoculating luciferase-expressing melanoma B16 cell line, B16-Luc, into the brain and under the skin of syngeneic C57BL/6 mice. IF7C(RR)-SN38 was injected intravenously daily at 7.0 µmoles/kg and growth of tumours was assessed by chemiluminescence using an IVIS imager. A similar dual-tumour model was generated with the C6-Luc line in immunocompromised SCID mice. (2) IF7C(RR)-SN38 formulated with 10% Solutol HS15 was injected intravenously daily at 2.5 µmoles/kg into two brain tumour mouse models: B16-Luc cells in C57BL/6 mice, and C6-Luc cells in nude mice. RESULTS: (1) Daily IF7C(RR)-SN38 injection suppressed tumour growth regardless of cell lines or mouse strains. (2) Daily injection of Solutol-formulated IF7C(RR)-SN38 led into complete disappearance of B16-Luc brain tumour in C57BL/6 mice, whereas this did not occur in C6-Luc in nude mice. CONCLUSIONS: IF7C(RR)-SN38 crosses the blood-brain barrier and suppresses growth of brain tumours in mouse models. Solutol HS15-formulated IF7C(RR)-SN38 may have promoted an antitumour immune response.

Distinct Cell Surface Expression Patterns of N-Glycosylation Site Mutants of AMPA-Type Glutamate Receptor under the Homo-Oligomeric Expression Conditions.

The AMPA-type glutamate receptor (AMPAR) is a homotetrameric or heterotetrameric ion channel composed of various combinations of four subunits (GluA1-4), and its abundance in the synapse determines the strength of synaptic activity. The formation of oligomers in the endoplasmatic reticulum (ER) is crucial for AMPAR subunits' ER-exit and translocation to the cell membrane. Although N-glycosylation on different AMPAR subunits has been shown to regulate the ER-exit of hetero-oligomers, its role in the ER-exit of homo-oligomers remains unclear. In this study, we investigated the role of N-glycans at GluA1N63/N363 and GluA2N370 in ER-exit under the homo-oligomeric expression conditions, whose mutants are known to show low cell surface expressions. In contrast to the N-glycosylation site mutant GluA1N63Q, the cell surface expression levels of GluA1N363Q and GluA2N370Q increased in a time-dependent manner. Unlike wild-type (WT) GluA1, GluA2WT rescued surface GluA2N370Q expression. Additionally, the expression of GluA1N63Q reduced the cell surface expression level of GluA1WT. In conclusion, our findings suggest that these N-glycans have distinct roles in the ER-exit of GluA1 and GluA2 homo-oligomers; N-glycan at GluA1N63 is a prerequisite for GluA1 ER-exit, whereas N-glycans at GluA1N363 and GluA2N370 control the ER-exit rate.

Screening of a library of traditional Chinese medicines to identify compounds and extracts which inhibit Toxoplasma gondii growth.

Toxoplasma gondii can cause severe encephalitis in immunocompromised patients. Although pyrimethamine and sulphadiazine have been standard therapeutic agents for the treatment of acute toxoplasmosis, they have toxic side effects. Therefore, there is a need to identify new drugs that are less toxic. Some traditional Chinese medicines (TCMs) have shown good efficacy in controlling T. gondii replication in mouse models. Here, we screened a natural product library comprising TCMs with the aim of identifying compounds and extracts with anti-toxoplasmosis activities. We found several hit compounds and extracts that could be candidates for new drugs against T. gondii infection.

Screening of a library of traditional Chinese medicines to identify anti-malarial compounds and extracts.

BACKGROUND: Malaria is a major infectious disease in the world. In 2015, approximately 212 million people were infected and 429,000 people were killed by this disease. Plasmodium falciparum, which causes falciparum malaria, is becoming resistant to artemisinin (ART) in Southeast Asia; therefore, new anti-malarial drugs are urgently needed. Some excellent anti-malarial drugs, such as quinine or ART, were originally obtained from natural plants. Hence, the authors screened a natural product library comprising traditional Chinese medicines (TCMs) to identify compounds/extracts with anti-malarial effects. METHODS: The authors performed three assays: a malaria growth inhibition assay (GIA), a cytotoxicity assay, and a malaria stage-specific GIA. The malaria GIA revealed the anti-malarial ability and half-maximal inhibitory concentrations (IC50) of the natural products, whereas the malaria stage-specific GIA revealed the point in the malaria life cycle where the products exerted their anti-malarial effects. The toxicity of the products to the host cells was evaluated with the cytotoxicity assay. RESULTS: Four natural compounds (berberine chloride, coptisine chloride, palmatine chloride, and dehydrocorydaline nitrate) showed strong anti-malarial effects (IC50 < 50 nM), and low cytotoxicity (cell viability > 90%) using P. falciparum 3D7 strain. Two natural extracts (Phellodendri cortex and Coptidis rhizoma) also showed strong antiplasmodial effects (IC50 < 1 µg/ml), and low cytotoxicity (cell viability > 80%). These natural products also demonstrated anti-malarial capability during the trophozoite and schizont stages of the malaria life cycle. CONCLUSIONS: The authors identified four compounds (berberine chloride, coptisine chloride, palmatine chloride, and dehydrocorydaline nitrate) and two extracts (Phellodendri cortex and Coptidis rhizoma) with anti-malarial activity, neither of which had previously been described. The IC50 values of the compounds were comparable to that of chloroquine and better than that of pyrimethamine. These compounds and extracts derived from TCMs thus show promise as potential future anti-malarial drugs.

A Cytotoxic Antibody Recognizing Lacto-N-fucopentaose I (LNFP I) on Human Induced Pluripotent Stem (hiPS) Cells.

We have generated a mouse monoclonal antibody (R-17F, IgG1 subtype) specific to human induced pluripotent stem (hiPS)/embryonic stem (ES) cells by using a hiPS cell line as an antigen. Triple-color confocal immunostaining images of hiPS cells with R-17F indicated that the R-17F epitope was expressed exclusively and intensively on the cell membranes of hiPS cells and co-localized partially with those of SSEA-4 and SSEA-3. Lines of evidence suggested that the predominant part of the R-17F epitope was a glycolipid. Upon TLC blot of total lipid extracts from hiPS cells with R-17F, one major R-17F-positive band was observed at a slow migration position close to that of anti-blood group H1(O) antigen. MALDI-TOF-MS and MS(n) analyses of the purified antigen indicated that the presumptive structure of the R-17F antigen was Fuc-Hex-HexNAc-Hex-Hex-Cer. Glycan microarray analysis involving 13 different synthetic oligosaccharides indicated that R-17F bound selectively to LNFP I (Fucα1-2Galß1-3GlcNAcß1-3Galß1-4Glc). A critical role of the terminal Fucα1-2 residue was confirmed by the selective disappearance of R-17F binding to the purified antigen upon α1-2 fucosidase digestion. Most interestingly, R-17F, when added to hiPS/ES cell suspensions, exhibited potent dose-dependent cytotoxicity. The cytotoxic effect was augmented markedly upon the addition of the secondary antibody (goat anti-mouse IgG1 antibody). R-17F may be beneficial for safer regenerative medicine by eliminating residual undifferentiated hiPS cells in hiPS-derived regenerative tissues, which are considered to be a strong risk factor for carcinogenesis.

Functional assay using lectin gene targeting technologies (over-expression).

Function of lectin depends on its amino acid sequence of carbohydrate-recognition domain (CRD), conformation, and extracellular/intracellular localization. Altering lectin gene expression by over-expression or knockdown is a powerful tool for analyzing its cellular function. Here, we describe a method of lectin gene over-expression, taking a C-type lectin, mannan-binding protein (MBP), as an example. Carbohydrate-binding ability of MBP, its subcellular localization, and functional co-localization with ligand glycoprotein are assayed comparing with an inactive mutant MBP.

Synthetic di-sulfated iduronic acid attenuates asthmatic response by blocking T-cell recruitment to inflammatory sites.

Identification of carbohydrate sequences that determine affinity to specific chemokines is a critical step for strategies to interfere with chemokine-mediated leukocyte trafficking. Here, we first characterized the development of allergic asthma in Tie2-dependent and inducible Ext1-knockout (Tie2-Ext1(iKO)) mice. We showed that heparan sulfate is essential for leukocyte recruitment in the peribronchial region and bronchoalveolar lavage fluid (BALF), and is crucial for induction of airway hyperresponsiveness. Our glycan microarray showed a unique affinity profile of chemokine CCL20 to substructures of heparin and heparin-like oligo/di/monosaccharides. Among them, we identified a synthetic and not naturally occurring monosaccharide, 2,4-O-di-sulfated iduronic acid (Di-S-IdoA), as a potential inhibitor for CCL20-heparan sulfate interaction. Mice injected with Di-S-IdoA via tail vain or nasal inhalation showed attenuated leukocyte recruitment into inflammatory sites and BALF. These results demonstrate a critical role of chemokine-heparan sulfate interaction in the asthma development and Di-S-IdoA as a potential drug for asthma treatment.

Carbohydrate sequence of the prostate cancer-associated antigen F77 assigned by a mucin O-glycome designer array.

Monoclonal antibody F77 was previously raised against human prostate cancer cells and has been shown to recognize a carbohydrate antigen, but the carbohydrate sequence of the antigen was elusive. Here, we make multifaceted approaches to characterize F77 antigen, including binding analyses with the glycolipid extract of the prostate cancer cell line PC3, microarrays with sequence-defined glycan probes, and designer arrays from the O-glycome of an antigen-positive mucin, in conjunction with mass spectrometry. Our results reveal F77 antigen to be expressed on blood group H on a 6-linked branch of a poly-N-acetyllactosamine backbone. We show that mAb F77 can also bind to blood group A and B analogs but with lower intensities. We propose that the close association of F77 antigen with prostate cancers is a consequence of increased blood group H expression together with up-regulated branching enzymes. This is in contrast to other epithelial cancers that have up-regulated branching enzymes but diminished expression of H antigen. With knowledge of the structure and prevalence of F77 antigen in prostate cancer, the way is open to explore rationally its application as a biomarker to detect F77-positive circulating prostate cancer-derived glycoproteins and tumor cells.