An immunocytokine consisting of a TNFR2 agonist and TNFR2 scFv enhances the expansion of regulatory T cells through TNFR2 clustering.

Regulatory T cells (Tregs) are lymphocytes that play a central role in peripheral immune tolerance. Tregs are promising targets for the prevention and suppression of autoimmune diseases, allergies, and graft-versus-host disease, and treatments aimed at regulating their functions are being developed. In this study, we created a new modality consisting of a protein molecule that suppressed excessive immune responses by effectively and preferentially expanding Tregs. Recent studies reported that tumor necrosis factor receptor type 2 (TNFR2) expressed on Tregs is involved in the proliferation and activation of Tregs. Therefore, we created a functional immunocytokine, named TNFR2-ICK-Ig, consisting of a fusion protein of an anti-TNFR2 single-chain Fv (scFv) and a TNFR2 agonist TNF-α mutant protein, as a new modality that strongly enhances TNFR2 signaling. The formation of agonist-receptor multimerization (TNFR2 cluster) is effective for the induction of a strong TNFR2 signal, similar to the TNFR2 signaling mechanism exhibited by membrane-bound TNF. TNFR2-ICK-Ig improved the TNFR2 signaling activity and promoted TNFR2 cluster formation compared to a TNFR2 agonist TNF-α mutant protein that did not have an immunocytokine structure. Furthermore, the Treg expansion efficiency was enhanced. TNFR2-ICK-Ig promotes its effects via scFv, which crosslinks receptors whereas the agonists transmit stimulatory signals. Therefore, this novel molecule expands Tregs via strong TNFR2 signaling by the formation of TNFR2 clustering.

Development of a 1:1-binding biparatopic anti-TNFR2 antagonist by reducing signaling activity through epitope selection.

Conventional bivalent antibodies against cell surface receptors often initiate unwanted signal transduction by crosslinking two antigen molecules. Biparatopic antibodies (BpAbs) bind to two different epitopes on the same antigen, thus altering crosslinking ability. In this study, we develop BpAbs against tumor necrosis factor receptor 2 (TNFR2), which is an attractive immune checkpoint target. Using different pairs of antibody variable regions specific to topographically distinct TNFR2 epitopes, we successfully regulate the size of BpAb-TNFR2 immunocomplexes to result in controlled agonistic activities. Our series of results indicate that the relative positions of the two epitopes recognized by the BpAb are critical for controlling its signaling activity. One particular antagonist, Bp109-92, binds TNFR2 in a 1:1 manner without unwanted signal transduction, and its structural basis is determined using cryo-electron microscopy. This antagonist suppresses the proliferation of regulatory T cells expressing TNFR2. Therefore, the BpAb format would be useful in designing specific and distinct antibody functions.

Bivalent structure of a TNFR2-selective and agonistic TNF-α mutein Fc-fusion protein enhances the expansion activity of regulatory T cells.

Recently, TNF receptor type 2 (TNFR2) signaling was found to be involved in the proliferation and activation of regulatory T cells (Tregs), a subpopulation of lymphocytes that suppress immune responses. Tregs mediate peripheral immune tolerance, and the disruption of their functions causes autoimmune diseases or allergy. Therefore, cell expanders or regulators of Tregs that control immunosuppressive activity can be used to treat these diseases. We focused on TNFR2, which is preferentially expressed on Tregs, and created tumor necrosis factor-α (TNF-α) muteins that selectively activate TNFR2 signaling in mice and humans, termed R2agoTNF and R2-7, respectively. In this study, we attempted to optimize the structure of muteins to enhance their TNFR2 agonistic activity and stability in vivo by IgG-Fc fusion following single-chain homo-trimerization. The fusion protein, scR2agoTNF-Fc, enhanced the expansion of CD4+CD25+ Tregs and CD4+Foxp3+ Tregs and contributed to their immunosuppressive activity ex vivo and in vivo in mice. The prophylactic administration of scR2agoTNF-Fc suppressed inflammation in contact hypersensitivity and arthritis mouse models. Furthermore, scR2-7-Fc preferentially expanded Tregs in human peripheral blood mononuclear cells via TNFR2. These TNFR2 agonist-Fc fusion proteins, which have bivalent structures, are novel Treg expanders.

A Proximity-Induced Fluorogenic Reaction Triggered by Antibody-Antigen Interactions with Adjacent Epitopes.

Proximity-induced chemical reactions are site-specific and rapid by taking advantage of their high affinity and highly selective interactions with the template. However, reactions induced solely by antibody-antigen interactions have not been developed. Herein, we propose a biepitopic antigen-templated chemical reaction (BATER) as a novel template reaction. In BATER, reactive functional groups are conjugated to two antibodies that interact with two epitopes of the same antigen to accelerate the reaction. We developed a method for visualizing the progress of BATER using fluorogenic click chemistry for optimal antibody selection and linker design. The reaction is accelerated in the presence of a specific antigen in a linker length-dependent manner. The choice of the antibody epitope is important for a rapid reaction. This design will lead to various applications of BATER in living systems.

Synthesis of multivalent fatty acid-conjugated antisense oligonucleotides: Cell internalization, physical properties, and in vitro and in vivo activities.

Herein, we describe the design and synthesis of multi-conjugatable fatty acid monomer phosphoramidites and their conjugation to antisense oligonucleotides (ASOs). Multivalent long-chain fatty acid conjugation improved the cellular uptake of ASOs but decreased in vitro activity due to alterations in physical properties and cellular localization. In addition, multivalently fatty acid-conjugated ASOs showed different organ specificity compared with that of unconjugated ASO in in vivo experiment. Although optimization of the linker structure between the fatty acid moiety and the ASO may be required, divalent long-chain fatty acid conjugation provides a new approach to increase endocytosis, thereby potentially improving the activity of therapeutic ASOs.

Anti-PD-1 antibodies recognizing the membrane-proximal region are PD-1 agonists that can down-regulate inflammatory diseases.

The PD-1 receptor triggers a negative immunoregulatory mechanism that prevents overactivation of immune cells and subsequent inflammatory diseases. Because of its biological significance, PD-1 has been a drug target for modulating immune responses. Immunoenhancing anti-PD-1 blocking antibodies have become a widely used cancer treatment; however, little is known about the required characteristics for anti-PD-1 antibodies to be capable of stimulating immunosuppressive activity. Here, we show that PD-1 agonists exist in the group of anti-PD-1 antibodies recognizing the membrane-proximal extracellular region in sharp contrast to the binding of the membrane-distal region by blocking antibodies. This trend was consistent in an analysis of 81 anti-human PD-1 monoclonal antibodies. Because PD-1 agonist antibodies trigger immunosuppressive signaling by cross-linking PD-1 molecules, Fc engineering to enhance FcγRIIB binding of PD-1 agonist antibodies notably improved human T cell inhibition. A PD-1 agonist antibody suppressed inflammation in murine disease models, indicating its clinical potential for treatment of various inflammatory disorders, including autoimmune diseases.

Synthesis and physical and biological properties of 1,3-diaza-2-oxophenoxazine-conjugated oligonucleotides.

The artificial nucleobase 1,3-diaza-2-oxophenoxazine (tCO) and its derivative G-clamp strongly bind to guanine and, when incorporated into double-stranded DNA, significantly increase the stability of the latter. As the phenoxazine skeleton is a constituent of major pharmaceuticals, we hypothesized that oligonucleotides (ONs) containing phenoxazine bases would induce property changes related to intracellular uptake and migration in tissues. In this study, we designed and synthesized a novel G-clamp-linker antisense oligonucleotide (ASO) in which a G-clamp base with a flexible linker was introduced into the 5'-end of an ASO targeting mouse long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (mMALAT1). Compared to unconjugated ASO, the G-clamp-linker ASO induced significantly more effective knockdown of mMALAT1 in mouse skeletal muscle. The ASOs conjugated with 2'-deoxyribonucleotide(s) bearing a tCO nucleobase at the 5'-end exhibited a similar knockdown effect in skeletal muscle. Thus, it may be possible to improve therapeutic effects against skeletal muscle diseases, such as muscular dystrophy, by using ONs with incorporated phenoxazine nucleobases.

Identification of biomarkers of chronic kidney disease among kidney-derived proteins.

BACKGROUND: Chronic kidney disease (CKD) has few objective symptoms, and it is difficult to make an early diagnosis by using existing methods. Therefore, new biomarkers enabling diagnosis of renal dysfunction at an early stage need to be developed. Here, we searched for new biomarkers of CKD by focusing on kidney-derived proteins that could sensitively reflect that organ's disease state. METHODS: To identify candidate marker proteins, we performed a proteomics analysis on renal influx and efflux blood collected from the same individual. RESULTS: Proteomics analysis revealed 662 proteins in influx blood and 809 in efflux. From these identified proteins, we selected complement C1q as a candidate; the plasma C1q level was significantly elevated in the renal efflux of donors. Moreover, the plasma concentration of C1q in a mouse model of diabetic nephropathy was significantly increased, in association with increases in blood glucose concentration and urinary protein content. Importantly, we demonstrated that the tendency of C1q to increase in the plasma of CKD patients was correlated with a decrease in their estimated glomerular filtration rate. CONCLUSION: Overall, our results indicate that our approach of focusing on kidney-derived proteins is useful for identifying new CKD biomarkers and that C1q has potential as a biomarker of renal function.

ACE2-like carboxypeptidase B38-CAP protects from SARS-CoV-2-induced lung injury.

Angiotensin-converting enzyme 2 (ACE2) is a receptor for cell entry of SARS-CoV-2, and recombinant soluble ACE2 protein inhibits SARS-CoV-2 infection as a decoy. ACE2 is a carboxypeptidase that degrades angiotensin II, thereby improving the pathologies of cardiovascular disease or acute lung injury. Here we show that B38-CAP, an ACE2-like enzyme, is protective against SARS-CoV-2-induced lung injury. Endogenous ACE2 expression is downregulated in the lungs of SARS-CoV-2-infected hamsters, leading to elevation of angiotensin II levels. Recombinant Spike also downregulates ACE2 expression and worsens the symptoms of acid-induced lung injury. B38-CAP does not neutralize cell entry of SARS-CoV-2. However, B38-CAP treatment improves the pathologies of Spike-augmented acid-induced lung injury. In SARS-CoV-2-infected hamsters or human ACE2 transgenic mice, B38-CAP significantly improves lung edema and pathologies of lung injury. These results provide the first in vivo evidence that increasing ACE2-like enzymatic activity is a potential therapeutic strategy to alleviate lung pathologies in COVID-19 patients.

COVID-19 cynomolgus macaque model reflecting human COVID-19 pathological conditions.

The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global threat to human health and life. A useful pathological animal model accurately reflecting human pathology is needed to overcome the COVID-19 crisis. In the present study, COVID-19 cynomolgus monkey models including monkeys with underlying diseases causing severe pathogenicity such as metabolic disease and elderly monkeys were examined. Cynomolgus macaques with various clinical conditions were intranasally and/or intratracheally inoculated with SARS-CoV-2. Infection with SARS-CoV-2 was found in mucosal swab samples, and a higher level and longer period of viral RNA was detected in elderly monkeys than in young monkeys. Pneumonia was confirmed in all of the monkeys by computed tomography images. When monkeys were readministrated SARS-CoV-2 at 56 d or later after initial infection all of the animals showed inflammatory responses without virus detection in swab samples. Surprisingly, in elderly monkeys reinfection showed transient severe pneumonia with increased levels of various serum cytokines and chemokines compared with those in primary infection. The results of this study indicated that the COVID-19 cynomolgus monkey model reflects the pathophysiology of humans and would be useful for elucidating the pathophysiology and developing therapeutic agents and vaccines.

Production of IgG1-based bispecific antibody without extra cysteine residue via intein-mediated protein trans-splicing.

A major class of bispecific antibodies (BsAbs) utilizes heterodimeric Fc to produce the native immunoglobulin G (IgG) structure. Because appropriate pairing of heavy and light chains is required, the design of BsAbs produced through recombination or reassembly of two separately-expressed antigen-binding fragments is advantageous. One such method uses intein-mediated protein trans-splicing (IMPTS) to produce an IgG1-based structure. An extra Cys residue is incorporated as a consensus sequence for IMPTS in successful examples, but this may lead to potential destabilization or disturbance of the assay system. In this study, we designed a BsAb linked by IMPTS, without the extra Cys residue. A BsAb binding to both TNFR2 and CD30 was successfully produced. Cleaved side product formation was inevitable, but it was minimized under the optimized conditions. The fine-tuned design is suitable for the production of IgG-like BsAb with high symmetry between the two antigen-binding fragments that is advantageous for screening BsAbs.

Highly susceptible SARS-CoV-2 model in CAG promoter-driven hACE2-transgenic mice.

COVID-19, caused by SARS-CoV-2, has spread worldwide with dire consequences. To urgently investigate the pathogenicity of COVID-19 and develop vaccines and therapeutics, animal models that are highly susceptible to SARS-CoV-2 infection are needed. In the present study, we established an animal model highly susceptible to SARS-CoV-2 via the intratracheal tract infection in CAG promoter-driven human angiotensin-converting enzyme 2-transgenic (CAG-hACE2) mice. The CAG-hACE2 mice showed several severe symptoms of SARS-CoV-2 infection, with definitive weight loss and subsequent death. Acute lung injury with elevated cytokine and chemokine levels was observed at an early stage of infection in CAG-hACE2 mice infected with SARS-CoV-2. Analysis of the hACE2 gene in CAG-hACE2 mice revealed that more than 15 copies of hACE2 genes were integrated in tandem into the mouse genome, supporting the high susceptibility to SARS-CoV-2. In the developed model, immunization with viral antigen or injection of plasma from immunized mice prevented body weight loss and lethality due to infection with SARS-CoV-2. These results indicate that a highly susceptible model of SARS-CoV-2 infection in CAG-hACE2 mice via the intratracheal tract is suitable for evaluating vaccines and therapeutic medicines.

Characterization of a TNFR2-Selective Agonistic TNF-α Mutant and Its Derivatives as an Optimal Regulatory T Cell Expander.

Regulatory T cells (Tregs) are a subpopulation of lymphocytes that play a role in suppressing and regulating immune responses. Recently, it was suggested that controlling the functions and activities of Tregs might be applicable to the treatment of human diseases such as autoimmune diseases, organ transplant rejection, and graft-versus-host disease. TNF receptor type 2 (TNFR2) is a target molecule that modulates Treg functions. In this study, we investigated the role of TNFR2 signaling in the differentiation and activation of mouse Tregs. We previously reported the generation of a TNFR2-selective agonist TNF mutant, termed R2agoTNF, by using our unique cytokine modification method based on phage display. R2agoTNF activates cell signaling via mouse TNFR2. In this study, we evaluated the efficacy of R2agoTNF for the proliferation and activation of Tregs in mice. R2agoTNF expanded and activated mouse CD4+CD25+ Tregs ex vivo. The structural optimization of R2agoTNF by internal cross-linking or IgG-Fc fusion selectively and effectively enhanced Treg expansion in vivo. Furthermore, the IgG-Fc fusion protein suppressed skin-contact hypersensitivity reactions in mice. TNFR2 agonists are expected to be new Treg expanders.

Structural optimization of a TNFR1-selective antagonistic TNFα mutant to create new-modality TNF-regulating biologics.

Excessive activation of the proinflammatory cytokine tumor necrosis factor-α (TNFα) is a major cause of autoimmune diseases, including rheumatoid arthritis. TNFα induces immune responses via TNF receptor 1 (TNFR1) and TNFR2. Signaling via TNFR1 induces proinflammatory responses, whereas TNFR2 signaling is suggested to suppress the pathophysiology of inflammatory diseases. Therefore, selective inhibition of TNFR1 signaling and preservation of TNFR2 signaling activities may be beneficial for managing autoimmune diseases. To this end, we developed a TNFR1-selective, antagonistic TNFα mutant (R1antTNF). Here, we developed an R1antTNF derivative, scR1antTNF-Fc, which represents a single-chain form of trimeric R1antTNF with a human IgG-Fc domain. scR1antTNF-Fc had properties similar to those of R1antTNF, including TNFR1-selective binding avidity, TNFR1 antagonistic activity, and thermal stability, and had a significantly extended plasma t1/2in vivo In a murine rheumatoid arthritis model, scR1antTNF-Fc and 40-kDa PEG-scR1antTNF (a previously reported PEGylated form) delayed the onset of collagen-induced arthritis, suppressed arthritis progression in mice, and required a reduced frequency of administration. Interestingly, with these biologic treatments, we observed an increased ratio of regulatory T cells to conventional T cells in lymph nodes compared with etanercept, a commonly used TNF inhibitor. Therefore, scR1antTNF-Fc and 40-kDa PEG-scR1antTNF indirectly induced immunosuppression. These results suggest that selective TNFR1 inhibition benefits the management of autoimmune diseases and that R1antTNF derivatives hold promise as new-modality TNF-regulating biologics.

GPC1 specific CAR-T cells eradicate established solid tumor without adverse effects and synergize with anti-PD-1 Ab.

Current xenogeneic mouse models cannot evaluate on-target off-tumor adverse effect, hindering the development of chimeric antigen receptor (CAR) T cell therapies for solid tumors, due to limited human/mouse cross-reactivity of antibodies used in CAR and sever graft-versus-host disease induced by administered human T cells. We have evaluated safety and antitumor efficacy of CAR-T cells targeting glypican-1 (GPC1) overexpressed in various solid tumors. GPC1-specific human and murine CAR-T cells generated from our original anti-human/mouse GPC1 antibody showed strong antitumor effects in xenogeneic and syngeneic mouse models, respectively. Importantly, the murine CAR-T cells enhanced endogenous T cell responses against a non-GPC1 tumor antigen through the mechanism of antigen-spreading and showed synergistic antitumor effects with anti-PD-1 antibody without any adverse effects in syngeneic models. Our study shows the potential of GPC1 as a CAR-T cell target for solid tumors and the importance of syngeneic and xenogeneic models for evaluating their safety and efficacy.

Antibodies against adenovirus fiber and penton base proteins inhibit adenovirus vector-mediated transduction in the liver following systemic administration.

Pre-existing anti-adenovirus (Ad) neutralizing antibodies (AdNAbs) are a major barrier in clinical gene therapy using Ad vectors and oncolytic Ads; however, it has not been fully elucidated which Ad capsid protein-specific antibodies are involved in AdNAb-mediated inhibition of Ad infection in vivo. In this study, mice possessing antibodies specific for each Ad capsid protein were prepared by intramuscular electroporation of each Ad capsid protein-expressing plasmid. Ad vector-mediated hepatic transduction was efficiently inhibited by more than 100-fold in mice immunized with a fiber protein-expressing plasmid or a penton base-expressing plasmid. An Ad vector pre-coated with FX before administration mediated more than 100-fold lower transduction efficiencies in the liver of warfarinized mice immunized with a fiber protein-expressing plasmid or a penton base-expressing plasmid, compared with those in the liver of warfarinized non-immunized mice. These data suggest that anti-fiber protein and anti-penton base antibodies bind to an Ad vector even though FX has already bound to the hexon, and inhibit Ad vector-mediated transduction. This study provides important clues for the development of a novel Ad vector that can circumvent inhibition with AdNAbs.

Development of a detection method for antisense oligonucleotides in mouse kidneys by matrix-assisted laser desorption/ionization imaging mass spectrometry.

RATIONALE: Oligonucleotide therapeutics have recently gained much attention, but its pharmacokinetic evaluation methods are still not sufficient, and, in particular, more tools are needed to evaluate their tissue distribution and metabolites. We developed a matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS)-based method to evaluate the tissue distribution of oligonucleotide therapeutics. METHODS: We used an antisense oligonucleotide containing locked nucleic acids (LNA-A). Various washing protocols were examined using mouse kidney homogenate sections. Next, we applied a two-step matrix preparation strategy. As a first step, 3-hydroxypicolinic acid (3-HPA) matrix containing citrate and amines was sprayed using an airbrush and subsequently 3-HPA matrix containing citrate only was sprayed using the ImagePrep. Finally, kidney sections prepared from LNA-A-dosed mice were treated with our optimized method and analyzed with MALDI-IMS. RESULTS: The selected washing method made it possible to detect LNA-A with MALDI-IMS and, furthermore, our developed matrix pretreatment method enhanced signal intensity approximately two-fold. MALDI-IMS revealed that LNA-A localized in a portion presumed to be the renal cortex. We also obtained information on LNA-A metabolites, which showed the same distribution profile as LNA-A in kidneys. CONCLUSIONS: This study shows that MALDI-IMS can be applied to evaluate the tissue distribution of oligonucleotide therapeutics. Our method can evaluate the tissue distribution along with metabolites and has the potential to help the development of novel oligonucleotide therapeutics.

Modifying the Surface of Silica Nanoparticles with Amino or Carboxyl Groups Decreases Their Cytotoxicity to Parenchymal Hepatocytes.

We previously reported that unmodified silica nanoparticles with diameters of 70 nm (nSP70) induced liver damage in mice, whereas nSP70 modified with carboxyl or amino groups did not. In addition, we have found that both unmodified and modified nSP70s localize in both Kupffer cells and parenchymal hepatocytes. We therefore evaluated the contributions of nSP70 uptake by these cell populations to liver damage. To this end, we pretreated mice with gadolinium (III) chloride hydrate (GdCl3) to prevent nSP70 uptake by Kupffer cells, subsequently injected the mice with either type of nSP70, and then assessed plasma levels of alanine aminotransferase (ALT). In mice given GdCl3, unmodified nSP70 increased ALT levels. From these data, we hypothesized that in GdCl3-treated mice, the unmodified nSP70 that was prevented from entering Kupffer cells was shunted to parenchymal hepatocytes, where it induced cytotoxicity and increased liver damage. In contrast, GdCl3 pretreatment had no effect on ALT levels in mice injected with surface-modified nSP70s, suggesting that modified nSP70s spared parenchymal hepatocytes and thus induced negligible liver damage. In cytotoxicity analyses, the viability of a parenchymal hepatocyte line was greater when exposed to surface-modified nSP70s than to unmodified nSP70s. These findings imply that the decreased liver damage associated with surface-modified compared with unmodified nSP70 is attributable to decreased cytotoxicity to parenchymal hepatocytes.

A trimeric structural fusion of an antagonistic tumor necrosis factor-α mutant enhances molecular stability and enables facile modification.

Tumor necrosis factor-α (TNF) exerts its biological effect through two types of receptors, p55 TNF receptor (TNFR1) and p75 TNF receptor (TNFR2). An inflammatory response is known to be induced mainly by TNFR1, whereas an anti-inflammatory reaction is thought to be mediated by TNFR2 in some autoimmune diseases. We have been investigating the use of an antagonistic TNF mutant (TNFR1-selective antagonistic TNF mutant (R1antTNF)) to reveal the pharmacological effect of TNFR1-selective inhibition as a new therapeutic modality. Here, we aimed to further improve and optimize the activity and behavior of this mutant protein both in vitro and in vivo Specifically, we examined a trimeric structural fusion of R1antTNF, formed via the introduction of short peptide linkers, as a strategy to enhance bioactivity and molecular stability. By comparative analysis with R1antTNF, the trimeric fusion, referred to as single-chain R1antTNF (scR1antTNF), was found to retain in vitro molecular properties of receptor selectivity and antagonistic activity but displayed a marked increase in thermal stability. The residence time of scR1antTNF in vivo was also significantly prolonged. Furthermore, molecular modification using polyethylene glycol (PEG) was easily controlled by limiting the number of reactive sites. Taken together, our findings show that scR1antTNF displays enhanced molecular stability while maintaining biological activity compared with R1antTNF.

Distribution of Silver Nanoparticles to Breast Milk and Their Biological Effects on Breast-Fed Offspring Mice.

Recent rodent studies have shown that nanoparticles are distributed to breast milk, and more-detailed safety information regarding nanoparticle consumption by lactating mothers is required. Here, we used mice to investigate the safety of nanoparticle use during lactation. When Ag and Au nanoparticles were intravenously administered to lactating mice, the nanoparticles were distributed to breast milk without producing apparent damage to the mammary gland, and the amount of Ag nanoparticles distributed to breast milk increased with decreasing particle size. Orally administered Ag nanoparticles were also distributed to breast milk and subsequently to the brains of breast-fed pups. Ten-nanometer Ag nanoparticles were retained longer in the pups' brains than in their livers and lungs. Nevertheless, no significant behavioral changes were observed in offspring breast-fed by dams that had received orally administered 10 nm Ag nanoparticles. These data provide basic information for evaluating the safety of nanoparticle use during lactation.