Fusion protein of CDR mimetic peptide with Fc inhibit TNF-α induced cytotoxicity

Construction and bacteriostatic effect analyses of a recombinant thermostable Newcastle disease virus expressing cecropin AD

Cecropin AD (CAD), a hybrid antimicrobial peptide composed of the first 11 residues of cecropin A and last 26 residues of cecropin D, is a promising antibiotic candidate. Therefore, an efficient and convenient method for producing CAD is necessary for commercial applications. The Newcastle disease virus (NDV) has been widely used as a platform for gene delivery and exogenous protein expression. In this study, we constructed a recombinant NDV that expresses CAD. To obtain high expression of the CAD peptide, tandem repeats of the cad gene were inserted into the genomes of the thermostable NDV strain TS09-C using reverse genetic technology. The thermostable recombinant NDV, namely rTS-CAD3, showed thermostability and growth kinetics similar to those of their parental strain. A bacteriostatic test showed that rTS-CAD3 inhibited Staphylococcus aureus (gram-positive bacteria) and Escherichia coli (gram-negative bacteria) in vitro. We further determined the bacteriostatic effects of rTS-CAD3 expressed CAD against S. aureus in skin wound infections. The results showed that rTS-CAD3 subcutaneously injection improved wound healing and reduced S. aureus decolonization. In summary, our results indicate that the rTS-CAD3 expressing CAD peptide is a potent antimicrobial agent against S. aureus and E. coli and may be applied to accelerate wound healing in farm animals.

Downsizing antibodies: Towards complementarity-determining region (CDR)-based peptide mimetics

Monoclonal antibodies emerged as an important therapeutic drug class with remarkable specificity and binding affinity. Nonetheless, these heterotetrameric immunoglobulin proteins come with high manufacturing and therapeutic costs which can take extraordinary proportions, besides other limitations such as their limited in cellulo access imposed by their molecular size (ca. 150 kDa). These drawbacks stimulated the development of downsized functional antibody fragments (ca. 15-50 kDa), together with smaller synthetic peptides (ca. 1-3 kDa) derived from the antibodies' crucial complementarity-determining regions (CDR). Despite the general lack of success in the literal translation of CDR loops in peptide mimetics, rational structure-based and computational approaches have shown their potential for obtaining functional CDR-based peptide mimetics. In this review, we describe the efforts made in the development of antibody and nanobody paratope-derived peptide mimetics with particular focus on the used design strategies, in addition to highlighting the challenges associated with their development.

In vitro display evolution of the PURE system-expressed TNFα-binding unnatural cyclic peptide containing an N-methyl-d-amino acid

Tumor necrosis factor-alpha (TNFα) is a multifunctional cytokine associated with inflammation, immune responses, and autoimmune diseases including rheumatoid arthritis, inflammatory bowel disease, and psoriasis. In the present study, we performed in vitro selection, systematic evolution of ligands by exponential enrichment (SELEX) against human TNFα from mRNA-displayed peptide library prepared with Escherichia coli-reconstituted cell-free transcription/translation system (PURE system) and cyclized by N-chloroacetyl-N-methyl-d-phenylalanine incorporated by genetic code expansion (sense suppression). We identified a novel TNFα-binding thioether-cyclized peptide that contains an N-methyl-d-phenylalanine. Since cyclic structure and presence of an N-methyl-d-amino acid can increase proteolytic stability, the TNFα binding peptide has potential to be used for therapeutic, research and diagnostic applications.

A novel anti-TNF scFv constructed with human antibody frameworks and antagonistic peptides

The introduction of TNF inhibitors has revolutionized the treatment of some chronic inflammatory diseases, e.g., rheumatoid arthritis and Crohn's disease. However, immunogenicity is one of the important mechanisms behind treatment failure, and generally, switching to another TNF inhibitor will be the first choice for patients and doctors, which results in unmet need for novel anti-TNF agents. Small antibody molecules with less number of epitope may be valuable in less immunogenicity. In this study, with the help of computer-guided molecular design, single-chain variable fragment (scFv) TSA2 was designed using consensus frameworks of human antibody variable region as scaffold to display anti-TNF antagonistic peptides. TSA2 showed evidently improved bioactivity over TSA1 (anti-TNF scFv explored before) and almost similar activity as S-Remicade (the scFv form of Remicade, anti-TNF antibody approved by FDA), especially in inhibiting TNF-induced cytotoxicity and NF-κB activation. Human antibody consensus frameworks with less immunogenicity have been used in the designing of VH domain antibody, scFv TSA1 and TSA2. A serial of TNF-related works convinced us that the novel design strategy was feasible and could be used to design inhibitors targeting more other molecules than TNF-α. More importantly, these designed inhibitors derived from computer modeling may form a virtual antibody library whose size depends on the number of candidate antagonistic peptides. It will be molecular-targeted virtual antibody library because of the specific antagonistic peptides and the potential antibodies could be determined by virtual screening and then confirmed by biologic experiments.

Development and characterization of a fully functional small anti-HER2 antibody

The penetrating of monoclonal antibodies (mAbs) into solid tumor may be hampered by their large size. The antibody mimetics, composed of two complementarity-determining regions (CDRs) through a cognate framework region (FR), have been demonstrated to have the capacity to penetrate tumors superior to its parental intact IgG. In this study, we used CDR and FR sequences from the humanized anti-HER2 monoclonal antibody trastuzumab to design four antibody mimetics. Then these antibody mimetics were fused to human IgG Fc to generate mimetics-Fc small antibodies. One of the four mimetics-Fc antibodies binds well to HER2-overexpressing SK-BR3 cells and effectively inhibits the binding of trastuzumab. This mimetics-Fc, denoted as HMTI-Fc, was shown to be effective in mediating antibody-dependent cellular cytotoxicity and exhibit an antiproliferative effect in SK-BR3 cells. To our knowledge, the HMTI-Fc antibody shown here is the smallest fully functional antibody and may have a potential for treatment of cancer.

Small antibody mimetics comprising two complementarity-determining regions and a framework region for tumor targeting

Here we show that fusion of two complementarity-determining regions (CDRs), VHCDR1 and VLCDR3, through a cognate framework region (VHFR2) yields mimetics that retain the antigen recognition of their parent molecules, but have a superior capacity to penetrate tumors. The antigen-recognition abilities of these approximately 3 kDa mimetics surpass those of comparable fragments lacking the framework region. In vivo activities of the mimetics suggests that the structural orientation of their CDRs approximates the conformation of the CDRs in the complex of the parent antibody with antigen. We linked the antibody mimetics to the bacterial toxin colicin Ia to create fusion proteins called "pheromonicins," which enable targeted inhibition of tumor growth. In mice bearing human malignant tumors, pheromonicins directed against tumor-specific surface markers show greater capacity to target and penetrate tumors than their parent antibodies. Rational recombination of selected VH/VL binding sites and their framework regions might provide useful targeting moieties for cytotoxic cancer therapies.

A novel human scFv fragment against TNF-α from de novo design method

Anti-TNF antibody has been an effective therapeutic strategy for the diseases related to aberrant production of TNF-alpha, such as rheumatoid arthritis (RA) and Crohn's disease. The limitations of large molecule inhibitors in the therapy of these diseases prompted the search for other potent novel TNF-alpha antagonists. Antagonistic peptides, derived directly or designed rationally from complementarity-determining regions (CDRs) of neutralizing antibodies against TNF-alpha, have been demonstrated for their ability of inhibiting TNF-alpha. However, their activity is very low. In this study, to increase the affinity and bioactivity, human antibody variable region was used as scaffold to display antagonistic peptides, which were designed on the interaction between TNF-alpha and its neutralizing monoclonal antibody (mAb Z12). Based on the previously designed domain antibody (framework V(H)5), framework V(kappa)1 was used as light chain scaffold. On the basis of computer-guided molecular design method, a novel human scFv fragment (named as TSA1) was designed. Theoretical analysis showed that TSA1 could bind to TNF-alpha with more hydrogen bonds and lower binding free energy than the designed domain antibody. The biological experiments demonstrated that TSA1 could directly bind with TNF-alpha, competitively inhibit the binding of mAb Z12 to TNF-alpha and block the binding of TNF-alpha to TNFR I and TNFR II. TSA1 could also inhibit TNF-induced cytotoxicity on L929 cells and TNF-mediated NF-kappaB activation on HEK-293T cells. The bioactivity of TSA1 was significantly increased over the domain antibody. This study indicated that the framework of antibody variable region could serve as an ideal scaffold for displaying the peptides and provides a novel strategy to design TNF-alpha inhibitors with the ability to block the deleterious biological effects of TNF-alpha.

A novel domain antibody rationally designed against TNF-alpha using variable region of human heavy chain antibody as scaffolds to display antagonistic peptides

Neutralizing of TNF-alpha has been proved effective in treatment of some autoimmune diseases, e.g. rheumatoid arthritis and Crohn's disease. Low molecular weight synthetic peptides can mimic the binding sites of TNF-alpha receptors and block the activity of TNF-alpha. In order to stabilize the conformation, increase the affinity and bioactivity, in this study, heavy chain variable region of human antibody was used as a scaffold to simultaneously display three peptides, which were designed on the interaction between TNF-alpha and it's neutralizing monoclonal antibody. On the basis of the structural character and physical-chemical property of the families of seven kinds of heavy chain variable regions (VH) in human antibodies, the fifth type of VH was screened as scaffold to display the antagonist peptide. Based on the computer-guided molecular design method, a novel domain antibody against TNF-alpha (named as ATD5) was designed as TNF-alpha antagonist. The theoretical study showed that ATD5 was more stable than displayed antagonist peptide. The binding activity with TNF-alpha was higher than free peptides. After expression and purification in Escherichia coli, ATD5 could bind directly with TNF-alpha and inhibit the binding of TNF-alpha to its two receptors, TNFR1 and TNFR2. ATD5 could also reduce the TNF-alpha-mediated cytotoxicity and inhibit TNF-alpha-mediated caspase activation on L929 cells in a dose dependent manner. The activity of ATD5 was significantly stronger than three peptides displayed by ATD5. This study provides a novel strategy for the development of new TNF-alpha inhibitors. This study demonstrates that it is possible to screen potential antagonists of TNF-alpha using in vitro analysis systems in combination with the computer-aided modeling method.

De novo design TNF-α antagonistic peptide based on the complex structure of TNF-α with its neutralizing monoclonal antibody Z12

Tumor necrosis factor-alpha (TNF-alpha) antagonists have become therapeutic drugs for immunological diseases including rheumatoid arthritis, inflammatory bowel disease, Crohn's disease, etc. Low molecular weight synthetic peptides can mimic the binding sites of TNF-alpha receptors and block the activity of TNF-alpha. Based on the 3-D complex structure of TNF-alpha with its neutralizing monoclonal antibody (Mab) Z12, an antagonistic peptide (AP) was rationally de novo designed. The designed AP possessed similar structural character and potential bioactivity with Mab Z12. AP could competitively inhibit the binding of Mab Z12 to TNF-alpha, TNF-alpha-meditated caspase activation and TNF-alpha-induced cytotoxicity on murine L929 cells with a dose-dependent fashion. This study highlights the potential of computation-aided method for the design of novel peptides with the ability to block the deleterious biological effects of TNF-alpha.