High-Affinity Decoy PD-1 Mutant Screened from an Epitope-Specific Cell Library

Immunotherapy with anti-programmed cell death protein-1(PD-1)/programmed cell death ligand-1(PDL1)monoclonal antibodies has become routine in the treatment of many kinds of human cancers,such as lung cancer,intestinal cancer,and melanoma.The PD-1/PD-L1 pathway inhibits T cell activation in the micro-environment,making it an attractive target against cancer.Wild-type(WT)PD-1 ectodomain has been shown to have difficulty blocking PD-1/PD-L1 mixture formation due to its low affinity.The present work uses three-dimensional(3D)crystal complex structures to analyze the interaction by which PD-1 binds to PD-L1 or PD-L2.It also reports on a theoretical study of the binding mode between PD-1 and its clinical antibody Opdivo.Based on the theoretical binding analysis of PD-1 and its ligands(i.e.,PD-L1 and PD-L2)or antibody(Opdivo),a small-content,epitope-oriented mammalian cell library was established for PD-1.After three rounds of cell sorting,the decoy PD-1 mutant 463,which presented a higher affinity than WT PD-1 to the PD-L1(the affinity has increased by almost three orders of magnitude)was screened out.It exhibited an inhibitory effect against PD-1 to prevent it from forming mixtures with PD-L1,which was similar to the effect of the commercial anti-PD-L1 antibody atezolizumab(ATE).The median effective concentration(EC50)value of the decoy mutant was 0.031 μg·mL^(-1) in comparison with 0.063 μg·mL^(-1) for ATE;both values were much lower than that of WT PD-1,at 2.571 μg·mL^(-1).The 463 decoy mutant reversed the inhibitory function of PD-1 in T cell activation;furthermore,10 mg·kg^(-1) of 463 inhibited about 75%of tumor growth in vivo in a MC38 transgenic xenograft mice model,which was similar to the activity of ATE.More interestingly,an even lower dose of 463(2 mg·kg^(-1))showed a better effect than 10 mg·kg^(-1) of WT PD-1.This work offers the decoy 463 with an improved curative effect,which holds potential to become a good option against PD-1/PD-L1-related cancers.

A Novel Human Antibody,HF,against HER2/erb-B2 Obtained by a Computer-Aided Antibody Design Method

Fully human antibodies have minimal immunogenicity and safety profiles.At present,most potential antibody drugs in clinical trials are humanized or fully human.Human antibodies are mostly generated using the phage display method(in vitro)or by transgenic mice(in vivo);other methods include B lymphocyte immortalization,human–human hybridoma,and single-cell polymerase chain reaction.Here,we describe a structure-based computer-aided de novo design technology for human antibody generation.Based on the complex structure of human epidermal growth factor receptor 2(HER2)/Herceptin,we first designed six short peptides targeting the potential epitope of HER2 recognized by Herceptin.Next,these peptides were set as complementarity determining regions in a suitable immunoglobulin frame,giving birth to a novel anti-HER2 antibody named "HF,"which possessed higher affinity and more effective anti-tumor activity than Herceptin.Our work offers a useful tool for the quick design and selection of novel human antibodies for basic mechanical research as well as for imaging and clinical applications in immune-related diseases,such as cancer and infectious diseases.

Binding Activity Difference of Anti-CD20 scFv-Fc Fusion Protein Derived from Variable Domain Exchange

Two novel engineered antibody fragments binding to antigen CD20 were generated by fusing a murine IgM-type anti-CD20 singie-chain Fv fragment （scFv） to the human IgG1 CH2 （i.e., Cγ2） and CH3 （i.e., Cγ3） domains with the human IgG1 hinge （i.e. Hγ）. Given the relationship between structure and function of protein, the 3-D structures of the two engineered antibody fragments were modeled using computer-aided homology modeling method. Furthermore, the relationship between 3-D conformation and their binding activity was evaluated theoretically. Due to the change of active pocket formed by CDRs, the HL23 （VH-Linker-VL-Hγ-Cγ2-Cγ3） remained its activity because of its preserved conformation, while the binding activity of the LH23 （VL-Linker-VH-Hγ-Cγ2-Cγ3） was impaired severely. Experimental studies by flow cytometry and fluorescence microscopy showed that HL23 possessed significantly superior binding activity to CD20-expressing target cells than LH23. That is to say, the order of variable regions could influence the binding activity of the fusion protein to CD20^＋ cell lines, which was in accordance with the theoretical results. The study highlights the potential relationship between the antibody binding activity and their 3-D conformation, which appears to be worthwhile in providing direction for future antibody design of recombinant antibody.

Neddylation is required for herpes simplex virus type I （HSV- 1）-induced early phase interferon-beta production

Type I interferons such as interferon-beta （IFN-β） play essential roles in the host innate immune response to herpes simplex virus type I （HSV-1） infection. The transcription of type I interferon genes is controlled by nuclear factor-κB （NF-κB） and interferon regulatory factor （IRF） family members including IRF3. NF-κB activation depends on the phosphorylation of inhibitor of κB （IκB）, which triggers its ubiqitination and degradation. It has been reported that neddylation inhibition by a pharmacological agent MLN4924 potently suppresses lipopolysaccharide （LPS）-induced proinflammatory cytokine production with the accumulation of phosphorylated IκBa. However, the role of neddylation in type I interferon expression remains unknown. Here, we report that neddylation inhibition with MLN4924 or upon UBA3 deficiency led to accumulation of phosphorylated IκBa, impaired IκBa degradation, and impaired NF-κB nuclear translocation in the early phase of HSV-1 infection even though phosphorylation and nuclear translocation of IRF3 were not affected. The blockade of NF-κB nuclear translocation by neddylation inhibition becomes less efficient at the later time points of HSV-1 infection. Consequently, HSV- 1-induced early phase IFN-β production significantly decreased upon MLN4924 treatment and UBA3 deficiency. NF-κB inhibitor JSH-23 mimicked the effects of neddylation inhibition in the early phase of HSV-1 infection. Moreover, the effects of neddylation inhibition on HSV-1-induced early phase IFN-c production diminished in the presence of NF-κB inhibitor JSH-23. Thus, neddylation contributes to HSV-l-induced early phase IFN-β production through, at least partially, promoting NF-κB activation.

Characterization of a Novel Anti-DR5 Monoclonal Antibody WD1 with the Potential to Induce Tumor Cell Apoptosis

TNF-related apoptosis-inducing ligand （TRAIL） is a TNF family member capable of inducing apoptosis. Death receptor 5 （DR 5） is a key receptor of TRAIL and plays an important role in TRAIL-induced apoptosis. To prepare monoclonal antibodies （mAbs） against DR5, cDNA encoding soluble DR5 （sDR5） was firstly amplified by reverse transcriptase-polymerase chain reaction （RT-PCR） with specific primers, and then inserted into a prokaryotic expression vector pET-30a. The recombinant plasmid was expressed in Escherichia coli strain BL21 （DE3）, and sDR5 was purified by nickel affinity chromatography. As an antigen, sDR5 was used to immunize mice. Hybridomas secreting antibodies against sDR5 were identified. One positive done was selected to produce antibody, WD1. ELISA and immunofluorescence demonstrated that WD1 could bind recombinant sDR5 and membranebound DR5 （mDR5） on Jurkat and Molt-4 cells. ATPLite assays showed that Jurkat and Molt-4 cells were sensitive to the antibody in a dose dependent manner. The Annexin V/PI assays and Giemsa＇s staining both showed that WD1 could induce Jurkat cell apoptosis efficiently. Transient transfection of 293T cells and indirect immunofluorescence assay demonstrated that mAb （WD1） couldn＇t cross-react with DR4. Our findings indicated that the novel antibody, WD1 could act as a direct agonist, bind DR5 characteristically, and initiate efficient apoptotic signaling and tumor regression. Thus, WD1 would be a leading candidate for potential cancer therapeutics. Cellular ＆ Molecular Immunology.

Selection and characterization of the novel anti-human PD-1 FV78 antibody from a targeted epitope mammalian cell-displayed antibody library

Currently,display-based methods are well established and widely used in antibody engineering for affinity maturation and structural stability improvement.We obtained a novel anti-human programmed death 1(PD-1)antibody using computer-aided design and a mammalian cell display technology platform.We used computer-aided modeling and distance geometry methods to predict and assign the key residues that contributed to the binding of human PD-L1 to PD-1.Then,we analyzed the sequence of nivolumab(an anti-human PD-1 antibody,referred to as MIL75 in the article)to determine the template for antibody design and library construction.We identified a series of potential substitutions on the obtained template and constructed a virtual epitope-targeted antibody library based on the physicochemical properties and each possible location of the assigned key residues.The virtual antibody libraries were displayed on the surface of mammalian cells as the antigen-binding fragments of full-length immunoglobulin G.Then,we used flow cytometry and sequencing approaches to sort and screen the candidates.Finally,we obtained a novel anti-human PD-1 antibody named FV78.FV78 competitively recognized the PD-1 epitopes that interacted with MIL75 and possessed an affinity comparable to MIL75.Our results implied that FV78 possessed equivalent bioactivity in vitro and in vivo compared with MIL75,which highlighted the probability and prospect of FV78 becoming a new potential antibody therapy.

cAMP Modulates Macrophage Development by Suppressing M-CSF-Induced MAPKs Activation

M-CSF is a key cytokine in macrophage development by inducing MAPKs activation, and cAMP can inhibit MAPKs activation induced by inflammatory stimuli. To explore the effects of cAMP on M-CSF-induced MAPKs activation and on macrophage development, the model of bone marrow-derived murine macrophages （BMMs） was used. The effects of cAMP on M-CSF-induced MAPKs activation were analyzed by Western blotting assay, and the effects of cAMP on CD14 and F4/80 expression during macrophage development were examined by FACS analysis. Macrophage morphology showed the successful establishment of the model of macrophage development. Western blotting assay revealed that M-CSF activated ERK, JNK and p38 in both mature and immature macrophages, and cAMP inhibited M-CSF-induced ERK, JNK and p38 activation in a time-dependent manner. FACS analysis revealed that macrophage development was impaired with cAMP pretreatment. In conclusion, cAMP modulates macrophage development by suppressing M-CSF-induced MAPKs activation. Cellular ＆ Molecular Immunology.

Potent anti-angiogenesis and anti-tumor activity of a nove human anti-VEGF antibody, MIL60

Angiogenesis is crucial for tumor development, growth and metastasis. Vascular endothelial growth factor （VEGF） has been implicated in promoting solid tumor growth and metastasis via stimulating tumor-associated angiogenesis, and blocking the activity of VEGF can starve tumors. Avastin, which is a humanized anti-VEGF antibody, has been successfully applied in clinics since 2004. However, the price of Avastin is extremely high for Chinese people. Here, we report a novel human anti-VEGF neutralizing antibody, MIL60, which shows an affinity comparable to that of Avastin （the KD value of MIL60 was 44.5 pM, while that of Avastin was 42.7 pM）. MIL60 displays favorable actions in inhibiting VEGF-triggered endothelial cell proliferation （the IC5o value of M IL60 was 31-6.4 ng/ml and that of Avastin was 47--.8.1 ng/ml）, migration （8 pg/ml or 0.8 pg/ml MIL60 versusthe control： P〈O.05） and tube formation （2 I^g/ml or 0.2 lzg/ml MIL60 versusthe control： P〈O.05） viathe VEGFR2 signaling pathway. Moreover, MIL60 was shown to inhibit tumor growth and angiogenesis in vivo in xenograft models of human colon carcinoma and ovarian cancer using immunotherapy and immunohistochemistry analysis （MIL60 versus N.S.： P=0.0007; Avastin versus N.S.： P=0.00046）. These data suggest that MIL60 is a potential therapeutic, anti-angiogenic agent. Our work provides a novel anti-VEGF antibody, which can be considered an anti-tumor antibody candidate and a new option for patients with various cancers.

Active regions' setting of the extracellular ligand-binding domain of human interleukin-6 receptor

The reliable three dimensional (3-D) structure of the extracellular ligand-binding domain (V106-P322) of human interleukin-6 receptor (hlL-6R) has been constructed by means of computer-guided homology modeling techniques using the crystal structure of the extracellular ligand-binding region (K52-L251) of human growth hormone receptor (hGHR) as templet. The space location of some key residues which influence the combination ability between the receptor and the ligand has been observed and the effects of point mutagenesis of the four conservative cysteine residues on the space conformation are analyzed. The results show that the space conformation of the side-chain carboxyl of E305 plays a key role in the ligand-binding ability. Furthermore, the space conformation of the side-chain carboxyl of E305 is very important for the electrostatic potential complementarity between hlL-6R and hlL-6 according to the docking method.

Human IgG1 C_γ1 Domain Is Crucial for the Bioactivity of the Engineered Anti-CD20 Antibodies

In this study, we discussed the necessity of human IgG1 Cγ1 domain for recombinant antibody using computeraided homology modeling method and experimental studies. The heavy （VH） and light （VL） chain variable regions of 1-28, a murine IgM-type anti-CD20 mAb, were ligated by linker peptide （Gly4Ser）3 to form the single-chain Fv fragment （scFv）. Then, the engineered antibody （LH1-3） was generated by fusing scFv with the entire IgG1 heavy constant regions. The 3-D structure of LH1-3 was modeled using computer-aided homology modeling method and the binding activity of LH1-3 was evaluated theoretically. Compared to the 3-D structure of the Fv fragment of the parent antibody, the conformation of the active pocket of LH1-3 was remained because of the rigid support of Cγ1. Further experimental results of flow cytometry showed that the engineered anti-CD20 antibody possessed specifically binding activity to CD20-expressing target cells. The anti-CD20 antibody fragments could also mediate complement-dependent cytotoxicity （CDC） of human B-lymphoid cell lines. Our study highlights some interests and advantages of a methodology based on the homology modeling and analysis of molecular structural properties.

SHP limits TLR signaling, an inducible transcriptional corepressor

Toll-like receptor(TLR)signaling stimulated by diverse microbial components plays a pivotal role in innate immunity by eliciting a powerful proinflammatory response that is essential for pathogen elimination.However,uncontrolled inflammation can result in tissue damage.Thus,TLR signaling has to be tightly controlled to maintain immune balance in the organism.The paradigm for modulating TLR signaling seems to center on the canonical nuclear factor-kB(NF-kB)pathway,most likely because of the central role of NF-kB in the production of various proinflammatory cytokines.1 In a recent issue of Nature Immunology,Yuk et al.have reported the identification of a novel endogenous NF-kB inhibitor in TLR signaling—small heterodimer partner(SHP)2 Interestingly,SHP functions in a self-regulating system:TLR signaling induces the expression of SHP in macrophages through Ca21-dependent activation of AMP-activated protein kinase(AMPK),which has anti-inflammatory effects3 SHP in turn decreases the expression of proinflammatory cytokines such as tumor necrosis factor-a(TNF-a)by physically binding to two key components of the canonical NF-kB pathway,namely,RelA/p65 and TNF receptorassociated factor 6(TRAF6)This work demonstrates an essential role for SHP in the negative control of TLR signaling and provides a novel underlying molecular mechanism.

Functional Identification of the Stable Transfection C5aR Cell Line Molt-4

The complement C5 anaphylatoxin receptor is a member of the seven transmembrane-spanning G protein-coupled receptor superfamily that signals through Gcxi and Gtz16. C5aR is mostly expressed on neutrophils, macrophages and endothelial cells. C5a and C5aR interaction plays an important role in numerous biological effects such as in vivo cytokine storm which results in inflammatory damage. Considering the limitation of collection of human peripheral blood neutrophils and their short half life, the stably transfected cell line for studying the biological effects of C5aR is needed. In this study, we transfected C5aR gene into Molt-4 cell line and examined the function of ectopic C5aR. Our results showed stable expression of the C5aR in Molt-4 cell line and their interaction with human C5a induced ERKI/2 phosphorylation, Ca＋＋ influx. This stable transfected cell line may provide a useful tool for studying signal pathways related to C5a and C5aR interplay and antibody development specific for C5aR. Cellular ＆ Molecular Immunology.