Patent Grant
11912751
None. The nucleotide and amino acid sequences are submitted as ASCII text file via EFS-Web.
Traditionally, immunosuppressive drugs constitute the first-line therapy for many types of immune disorders, immune dysregulation, and autoimmune diseases (AID) [1]. Although these drugs help diminish disease pathology, they are associated with severe toxicity and are associated with a high risk of opportunistic infections [2-3] and other life-threatening complications among patients [4-6]. The introduction of targeted-based therapies has advanced the treatment of immune disorders and AID [7,8] and targeted-based biological agents such as infliximab [9] have recently become the interest for standard treatments, particularly in cases where first-line therapies fail to manage the disease [10-11].
Some potential ways to regulate the immune response are the TGF-B proteins. TGF-B proteins belong to the transforming growth factor family that includes three mammalian isoforms—TGF-B1, TGF-B2, and TGF-B3 that are produced by white blood cell lineages and are involved in modulating immune response and in maintaining immune tolerance [12-14]. TGF-B isoforms are pleiotropic cytokines that control various physiological processes such as cell growth, cell proliferation, cell differentiation, and morphogenesis [15-17], but the immune-specific regulatory effects of TGF-B proteins in various effector cells and how they act in concert with other cytokines still need to be elucidated [13,18-23].
Immune checkpoints are regulators of the immune system which are critical for self-tolerance, thereby preventing the indiscriminate attack of cells by the immune system [24]. Among the best known immune checkpoint is PD1 (Programmed Death 1) which has two ligands, Programmed Death Ligand—PD-L1 and PD-L2. These PD-L immune-regulatory ligands play important roles in maintaining peripheral tolerance by downregulating immune effector functions through binding with PD-1 receptors expressed by various cells of the innate and adaptive immune systems [24-26]. Defective PD-1/PD-L pathways correlate with the occurrence of various types of immune disorders, immune dysregulation, and autoimmune diseases [27]. Understanding the molecular biology of PD-L ligands has only recently developed, including studies of PD-1-deficient mice which were found to negatively regulate effector T cell functions and developed autoimmune symptoms [28]. The immune regulating activity of the PD-1/PD-L pathways has been shown in clinical settings for cancer immunotherapy utilizing antibodies that block the binding of these proteins to enhance immune response [29-30]. Another important checkpoint with clinical importance is CTLA-4 (Cytotoxic T-Lymphocyte-Associated protein 4) also called CD152, which binds to 2 distinct ligands, CD80 and CD86, leading to their removal from opposing cells; CTLA-4 acts as an immune regulatory mechanism by directly reducing the ability of APC to stimulate via CD28 and the activity of CTLA-4 on Treg cells serves to control T cell proliferation [31].
Recently, bispecific T cell engager (BiTE) technology has emerged as a new class of immunotherapy for cancer by increasing immune reactions targeted to tumor associated antigens [32]. This involves mainly the fusion of two scFvs (single-chain variable fragments) that recognize T cell marker and cancer antigen, allowing the recognition of cancer by cytotoxic T cells; this BiTE− mediated cell-to-cell contact may be an important mechanism to elicit regulatory T cell-mediated contact-dependent immune regulation. Various molecular mechanisms of immune regulation mediated by cell-to-cell contact were previously described [33] and appear to play important roles in the tolerogenic property of regulatory T cells with consequences in immune therapies of cancer [34]. Fusion proteins that incorporate antibody domains including anti-PDL1, anti TGF-beta receptor II, anti-TGF-beta, have been developed to enhance anti-cancer immunotherapy [35-37].
In contrast to the previously described BiTE technologies for cancer immunotherapy that use antibody domains, we now describe In this invention a different action and use of a new type of fusion protein that can play an important role in modulating immune responses in immune disorders and autoimmune diseases. We disclose the characterization of the biological activities of a novel bifunctional T regulatory cell engaging TGF-B/immune checkpoint fusion protein, using as proof of concept a TGF-B1/PD-L1 pair. When we created a new gene and protein fusion of these two ligands, we found that they worked in concert in a BiTE-like mechanism to favor Treg-mediated contact-dependent immune regulation. A dimeric form of TGF-B was constructed, linked by a flexible linker. We found that this fusion protein bound receptors of TGF-B1 and PD-L1 that are expressed by both regulatory and effector cells and opens up opportunities for controlling immune responses. The potential for further development as immune regulatory therapy was evaluated by assessing the downregulation pattern of NF-kB1 activation including its target genes, its ability to suppress the growth of activated effector-like Jurkat cell, and the subsequent analysis of expression patterns of inflammatory and regulatory-associated markers. The BiTE mechanisms were evaluated further by measuring the frequency of cell-to-cell contact. Our data demonstrate the potential applications of TGF-B/immune checkpoint bifunctional fusion proteins with anti-inflammatory activity that represent a new class of therapy for Immune disorders, immune dysregulation, and autoimmune diseases. As proof of concept, a TGF-B1/PD-L1 fusion pair was used to demonstrate the immune regulatory activity of the fusion protein.
Keywords:
TGF-beta; Immune checkpoint; PD-L1; fusion protein; T regulatory cells; Immune disorders, immune dysregulation, autoimmune diseases
Molecular crosstalk between effector immune cells and inhibitory cytokines as well as interactions with regulatory cells are mechanisms by which the immune response is regulated and controlled [7-8]. In immune disorders, immune dysregulation, and autoimmune diseases (AID), the failure of these regulatory checkpoints against autoreactive immune cells characterize the pathogenesis and progression of the disease. This invention describes the construction of TGF-B/immune checkpoint proteins, tested using a TGF-B1/PD-L1 fusion pair, that act in concert to maintain tolerance for self-antigens by stimulating regulatory cells and to regulate the activities of effector cells. The binding activity and bioactivity of this bifunctional TGF-B1/PD-L1 fusion protein were characterized with emphasis on assessing its therapeutic potential for treatment of immune disorders and autoimmune diseases. The functional components of the fusion protein comprising a TGF-B1 ligand in dimeric form and a PD-L1 domain functionally bind their respective receptors, inhibit NF-kB activation in Secreted Embryonic Alkaline Phosphatase (SEAP) reporter assays, and collaborate to downregulate NF-kB-responsive genes. The fusion protein selectively suppressed the growth of PHA/IFN-γ-activated effector-like Jurkat T cells with subsequent upregulation of Foxp3 and downregulation of NF-kB1 and IL-6. The receptor expression of these ligands suggests their utilization as bispecific T cell engager (BiTE) for Treg-mediated contact-dependent immune regulation. We also demonstrated that our fusion protein elicited a high frequency of cell-to-cell contact that induced upregulation of Treg-associated markers (Foxp3 and IL2RA) in a cellular co-culture set-up. These findings lend support for the concept of redirecting BiTE technology to treat immune disorders, immune dysregulation, and autoimmune diseases. By combining the activity of these two ligands, this fusion of TGF-B and immune checkpoint protein acts to modulate inflammatory signals and represents a new class of therapy for autoimmunity. As proof of concept, we used a TGF-B1/PD-L1 fusion pair.
Purpose of Invention:
To develop bifunctional T regulatory engaging fusion genes and proteins using a TGF-B domain in dimeric form consisting of TGF-B1 and as fusion pair, a domain consisting of PD-L1, that has applications for immune modulation and therapy for immune disorders, immune dysregulation, and autoimmune diseases.
Description of Problem(s) that this Invention Solves:
Immune disorders, immune dysregulation, and autoimmune diseases are conditions that are very complex and highly heterogeneous, presenting major challenges to clinical management. There are more than 80 clinical subtypes of immune diseases and current immunotherapies are only implicated for certain types. Overall, there are very few immunotherapies available for autoimmune diseases.
The technology described in this invention of a TGF-B domain fused with an immune checkpoint domain provides a unique solution that could help alleviate the shortage of therapies available for immune disorders, immune dysregulation, and autoimmune diseases.
Description—how the Invention is an Improvement Over Existing Technology:
This invention is an improvement over the existing technology in the creation/construction of a bifunctional protein with a TGF-B domain fused with an immune checkpoint domain, demonstrated by a TGF-B1/PD-L1 fusion protein that presents a more specific, more effective, and less toxic form of immunotherapy compared to the existing treatments available for: a) patients with immune disorders, immune dysregulation, and autoimmune diseases, b) patients who are unable to tolerate toxicities of existing immune therapies, c) patients who have developed resistance to current immune therapies, and d) patients who suffer from toxic side-effects of immune therapies.
Individuals and Business Demographics that would Use this Invention:
There are several potential applications for the immune-regulatory activity of this novel TGF-B/Immune checkpoint fusion gene and protein, including treatment for:
This invention offers to its users a new form of immune therapy with greater efficacy, less toxicity, and greater affordability in the long term management of patients.
The Applicant has attached the following illustrations of the aforementioned invention:
A) Schematic representation of fusion gene construct expressed under the control of a CMV promoter. TGF-B1 (SEQ ID NO: 2) was dimerized into TGF-B1 dimer (SEQ ID NO: 21) by fusing two monomers with a flexible peptide linker (GGGGS)3 (SEQ ID NO: 20) and fused with the PD-L1 extracellular domain (SEQ ID NO: 6) using a rigid peptide linker A(EAAAK)2A (SEQ ID NO: 27). B) SDS-PAGE profile of HEK 293 cells transfected with pCDNA3.1+/TP (containing the fusion gene) or pCDNA3.1+ only (empty control vector) following 48 hrs of lipofection. Black arrow indicates expected molecular size of the fusion product (˜70 kDa). C) Immunoprecipitation (IP) of fusion protein using magnetic beads coupled with either anti-PD-L1 or anti-TGF-B1 antibodies. D) Molecular weight comparison between the fusion protein immunoprecipitated with either anti-PD-L1 or anti-TGF-B1 antibodies and mammalian-derived full-length PD-L1 protein using SDS-PAGE. E) Schematic representation of the TGF-B1/PD-L1 fusion protein (SEQ ID NO: 13).
A) Predicted TGF-B1 structure (upper) and elucidated NMR solution structure of TGF-B1 (PDB ID: 1KLD) (lower) showing the dimer form (SEQ ID NO: 21) on the left and the monomeric form (SEQ ID NO: 2) on the right. B) Secondary structure comparison of the fingertip domains of TGF—B1 (SEQ ID NO: 2) which are involved in receptor binding. All structures were predicted to be the same in both except residue 97 (marked with *) in Finger 4.
A) Immunoprecipitation of TGFBR1 from cancer cell lines using anti-TGFBR1-coupled magnetic beads. AMLK cells yielded presence of band at the desired molecular weight of 53 kDa which coincide with the size of TGFBR1. B) Western blot analysis of co-IP between fusion protein and their target receptors, TGFBR1 and PD-1. Presence of signal in the desired molecular sizes (70 kDa for fusion protein, 53 kDa for TGFBR1 and 45 kDa for PD-1) suggested the interaction of fusion protein domains with their physiological receptors. C) SDS-PAGE profile of co-IP using fusion protein and PD-1, presence of bands corresponding to sizes of both proteins indicated presence of interaction.
A) Dot blot analysis following co-IP and reverse co-IP assays showing the absence of interaction between fusion protein and TGFBR1 (TR=pCDNA3.1+/TP-transfected cells; UT=untransfected). Co—IP with anti-TGF-B1-coupled magnetic beads failed to produce signal of TGFBR1 which is consistent with the use of anti-TGFBR1-coupled beads. B) Normalized OD450 nm reading in capture ELISA to identify interaction between plate-coated TGFBR1 with TGF-B1 of the fusion protein. Data are presented as mean value from plate readings of six wells and error bars represent+/−SD. Statistical analysis using one-way analysis of variance (ANOVA) revealed no statistical differences (ns) among the set-ups. C) SDS-PAGE profile of co-IP experiment using AMLK cell lysate and fusion protein. Three potential co-receptors bind TGF-B1 with molecular sizes of 53 kDa, 120 kDa, >250 kDa. D) Dot blot detection of TGFBR1 following co-IP in
A) Dot blot analysis following co-IP and reverse co-IP assays showing the presence of interaction between fusion protein and PD-1 (TR=pCDNA3.1+/TP-transfected cells; UT=untransfected). Co—IP with anti-PD-L1-coupled magnetic beads resulted in the detection of PD-1 signal which is consistent with the use of anti-PD-1-coupled beads. B) Capture ELISA assay where PD1 was coated on the substrate allowing the binding with PD-L1 domain of fusion protein. Detection proceeded by probing the TGF-B1 domain of the fusion protein with anti-TGF-B1 antibody. Data are presented as mean value from plate readings of six wells and error bars represent +/−SD. Significance was determined by one-way analysis of variance (ANOVA). **p-value<0.01. C) Heat map signature of fold change expression of TGF-B1 and PD-L1-target genes in AMLK by treatment of cells with 50 ng/mL of PD-L1 (SEQ ID NO: 6), TGF-B1 (SEQ ID NO: 2), and fusion protein (SEQ ID NO: 13) for 36 hrs. D) Line plot of gene expression profile in C capturing the combinatorial expression values of genes from TGF-B1 (SEQ ID NO: 2), and PD-L1 (SEQ ID NO: 6), by the fusion protein (SEQ ID NO: 13), suggesting the functional activation of both signaling in fusion protein.
A) Immunofluorescence staining of AMLK cells visualizing the expression of both TGFBR1 and PD-1. B) Cq values of gene expression analysis by qRT-PCR in response to treatment of fusion protein, TGFB-1 and PD-L1 by AMLK cells. Beta actin expression was used as control. Experiment was performed in duplicate. Statistical analysis was performed using Analysis of Variance (ANOVA). ns=not significant.
A) Immunofluorescence staining of TGFBR1+PD-1+TLR2-expressing HEK293 cells with endogenous expression of TGFBR1 and a transgenic expression of a full-length human PD1 protein. TLR2 pathway induces NF-kB-mediated secretion of embryonic alkaline phosphatase (SEAP) which served as reported of NF-kB activation in response to challenge with mycobacteria-containing Freund's complete adjuvant (FCA). B) Percent inhibition of SEAP secretion by transgenic TLR2-expressing HEK293 cells treated with 1:100 dilution of FCA after 24 hrs. Fusion protein treated samples were normalized over treatment without fusion protein as mentioned in materials and methods section. Pre-incubation of cells with blocking antibodies specific to receptor targets (PD-1 Ab and TGFBR1 Ab) of fusion proteins served to assess receptor-ligand specificity of SEAP readings. C) Fold-change expression of NF-kB-target genes, c-myc and bcl2 in the presence of fusion protein or pretreatment of receptor blocking antibodies. Broken line represents comparative expression of untreated set-up. +TP=with fusion protein; IB PD1/+TP=with anti-PD-1 blocking; IB TR/+TP=with anti-TGFBR1 blocking. Expression values were derived from Cq values obtained in duplicates. D) Normalized raw optical density reading (655 nm) of SEAP secretion in higher FCA dilutions (1:1000, 10000, 50000, 100000). +TP=with fusion protein; −TP=without fusion protein; IB PD1/+TP=with anti-PD-1 blocking; IB TR/+TP=with anti-TGFBR1 blocking. E) Percent inhibition of SEAP secretion in higher dilutions. All data are presented as mean value (D) or percentage as derived from the formula indicated in materials and method section (B, E) from plate readings of eight wells and error bars represent+/−SD. Multiple comparison of significance was determined by Tukey's HSD test. *p-value<0.05; **p-value<0.01; ns=not significant.
A) Normalized OD655 nm reading of SEAP secretion by mycobacteria-challenged TLR-expressing HEK-Blue cells using 1:100 dilution of FCA after 24 hrs. Pre-incubation of cells with blocking antibodies specific to receptor targets (PD-1 Ab and TGFBR1 Ab) of fusion proteins served to assess receptor-ligand specificity of SEAP readings. B) Percent inhibition of SEAP secretion in higher dilutions (1:1000, 1:10000, 1:50000, 1:100,000). C) Total cell count of PHA/IFN-γ-activated Jurkat cells following cultures after 3, 5 and 7 days. Cell count was assayed using trypan blue staining. D) Percent growth suppression of activated Jurkat T cells derived from viable cell count data in
A) Viable cell count of PHA/IFN-γ activated and non-activated Jurkat T cells in response to treatment with fusion protein assayed using trypan blue staining. Cells treated with receptor-specific antibodies PD-1 Ab or TGFBR1 Ab served as activity controls. B) Time-dependent growth suppression of activated Jurkat cells after 3, 5 and 7 days of culture. Data (in A and B) are presented as mean value of three independent experiment and error bars represent+/−SD. Significance was determined by two-tailed unpaired Student's t-tests. *p-value<0.05; **B<0.01; ns=not significant. C) Gene expression analysis of nfkb1 and foxp3 in activated Jurkat cells cultured in the presence (+TP) or absence (−TP) of fusion protein (SEQ ID NO: 13) after 24 and 72 hrs. Horizontal axis was set to 1 (normalized to non-activated cells). All data >1 was considered upregulated while <1 was considered down regulated. RNA expression was validated using westernblot analysis utilizing lysates of cells treated after 72 hrs. B-actin served as loading control. D) Westernblot analysis of intracellular IL-6 in PHA/IFN-γ activated Jurkat cells after 72 hrs of culture. B-actin served as loading control.
A) Cellular retention assay to measure frequency of cell-to-cell contact. Target cells were coated on a poly-L-lysine-coated substrate and were treated with or without the fusion protein. Binding cells were added in 1:1 (target: binding) ratio followed by gentle washing. Total cell count was determined, and bona fide cellular retention count was derived by normalizing the cells with a “no binding cell” set-up. B) Normalized retention count. Data are presented as mean value from plate counts in eight wells and error bars represent+/−SD. Multiple comparison of significance was determined by Tukey's HSD test. *p-value<0.05; **p-value<0.01. C) Size exclusion assay similar in
A) Treg-independent control of effector functions by inhibition of NF-kB activation, suppression of cell growth and upregulation of Treg-associated markers such as Foxp3. These mechanisms are well-studied physiological consequences of signaling pathway elicited by both TGF-B1 and PD-L1.
B) Proposed BiTE-like mechanism of the fusion protein (SEQ ID NO: 13) to encourage Treg-mediated contact-dependent immune regulation. C) Molecular mechanisms of immunosuppression by Tregs which could potentially be enhanced by the fusion protein
Table 1. Primer pairs used in gene expression analysis. Sequence ID No is indicated for each primer sequence.
Table 2. Fold change expression of immune related genes in AMLK cells treated with treated with fusion protein (SEQ ID NO: 13), TGF-B1(SEQ ID NO: 2) and PD-L1 (SEQ ID NO: 6).
1.0 Description of the Binding Activity and Functions of the Domains of the Fusion Protein:
This invention presents a description of a bifunctional gene and protein with a TGF-B domain fused with an immune checkpoint domain, demonstrated by a novel TGF-B1/PD-L1 fusion protein (SEQ ID NO: 13), the characterization of its bioactivity, and exploitation of its therapeutic potential for autoimmunity. In this patent application, the proof of concept using a new combination of TGF-B1 (SEQ ID NO: 2) and PD-L1 ligands (SEQ ID NO: 6) in a fusion protein ID NO: 13), is designed to act in concert to maintain tolerance for self-antigens by stimulating regulatory cells and to regulate the activities of effector cells.
First, the TGF-B1 and PD-L1 domains were demonstrated to functionally bind their respective receptors and inhibit NF-kB activation in our SEAP reporter assay which collaborate with the downregulation of NF-kB-responsive genes.
Next, the fusion protein treatment was shown to selectively suppress the growth of PHA/IFN-γ-activated effector-like Jurkat T cells with subsequent upregulation of Foxp3 and downregulation of NF-kB1 and IL-6. The receptor expression of these ligands suggests their utilization as bispecific T cell engager (BiTE) for Treg-mediated contact-dependent immune regulation.
The fusion protein described herein elicited a high frequency of cell-to-cell contact and upregulated Treg-associated markers (Foxp3 and IL2RA) in a cellular co-culture set-up.
1.1 Description of the Parts and Components of the Fusion Protein:
The functional components of the fusion gene and protein are: (1) TGF-B ligand (SEQ ID NO: 2) which is important in maintaining tolerance for self-antigens by stimulating regulatory cells; (2) an immune checkpoint domain (PD-L1, SEQ ID NO: 6) that is a crucial gatekeeper in regulating the activities of effector cells; (3) a flexible peptide linker (SEQ ID NO: 20) used to link two TGF-B domains resulting in a dimeric TGF-B construct, wherein the flexible linker is preferred for a configuration of the dimeric form of the TGF-B ligand binding to the PD-1 receptor; and (4) a rigid peptide linker (SEQ ID NO: 27) for connecting the dimeric PDF-B ligand (SEQ ID NO: 21) to the immune checkpoint domain
In detail, the components and characteristics of the fusion protein are:
Experiments with the TGF-B1/PD-L1 fusion protein (SEQ ID NO: 13) show that these two ligands work in concert to regulate immune reactions by: a) exploiting the ability of the TGF-B1 ligand to maintain tolerance for self-antigens by stimulating regulatory cells, and at the same time, b) exploiting the ability of the PD-L1 ligand to act as an immune gatekeeper in regulating the activities of effector cells.
1.3 Summary of Fusion Protein Binding Activity and Functions:
The TGF-B/Immune checkpoint fusion protein exemplified by TGF-B1/PD-L1 fusion protein (SEQ ID NO: 13) was comprised of TGF-B1 and PD-L1 domains that bound to their respective receptors, inhibited NF-kB activation, and collaborated to downregulate NF-kB-responsive genes. The TGF-B1/PD-L1 fusion protein selectively suppressed the growth of PHA/IFN-γ-activated effector-T cells to regulate immune reactions.
1.4 Unique Features of Invention:
AMLK cells and Jurkat T cells were maintained in RPMI-1640 (Gibco, Calif., USA) while HEK 293 cells and HEK-Blue TLR2-expressing cells (PlasmoTestTM, Invivogen, Calif., USA) were maintained in DMEM basal medium (Gibco, Calif., USA). All media were supplemented with 10% FBS (fetal bovine serum), 1 mM L-glutamine, 1 mM sodium pyruvate, 1.5 g/L sodium bicarbonate, 50 U/mL penicillin and 50 μg/mL streptomycin. Jurkat T cell activation and induction of PD1 expression were performed by adding 1 μg/mL of PHA or phytohemagglutinin (L1668, Sigma-Aldrich, MO, USA) and 0.1 μg/mL IFN-γ (SRP3058, Sigma-Aldrich, MO, USA) in the medium. All experiments with HEK-Blue TLR2-expressing cells were performed with the addition of 100 μg/mL NormocinTM (PlasmoTestTM, Invivogen, Calif., USA) to prevent mycoplasma contamination. Cells were cultured at 37° C. with 5% CO2.
2.2. Antibodies and Proteins
Active PD1 protein (ab214141), anti-PD-L1 (ab210931), anti-CD25 (ab9496) and FITC anti-mouse IgG (ab97022) were obtained from Abcam (CA, USA). PD-L1 (10084-HNAH) and TGF-beta 1 (10804-HNAC) proteins were purchased from Sino Biological Inc (Wayne, Pa., USA). Anti-TGFBR1 (sc518018), HRP-conjugated anti-murine IgGk (sc516102) were obtained from Santa Cruz Biotechnology (USA). Anti-TGF-B1 (525301), anti-PD-1 (367402), FITC anti-CD25 (356106), FITC anti-PD-1 (329904), anti-Foxp3 (320001), anti-B-actin (643801), anti-IL-6 and avidin-conjugated HRP (430504) were purchased from Biolegend (CA, USA). Anti-NF-KB1 (p105/p50, NBP2-22178) was obtained from Novus Biologicals.
2.3. Immunoprecipitation (IP)
TGFBR1 was isolated from AMLK cells using a modified protein extraction buffer using 100 mM EDTA instead of 2 μM TCEP. Purification of TGFBR1 was performed using DynabeadsTM M-280 (Invitrogen, USA) covalently coupled with anti-TGFBR1 following the manufacturer's suggested protocol. Magnetic separation was carried out using DYNAL® (Invitrogen, Calif., USA). Protein quantification was performed using a Qubit 2.0 protein assay (Invitrogen, Calif., USA). The same procedure was used to IP fusion protein using magnetic beads coupled with either anti-TGF-B1, anti-PD-1, or anti-PD-L1.
2.4. Co-Immunoprecipitation (Co-IP) and Reverse Co-IP
Each receptor targets (PD1 or TGFBR1) were combined separately with purified fusion protein in 1:1 ratio (for co-IP using AMLK lysate, a 2:1 lysate to fusion protein ratio was used) in a maximum of 50 μL PBS reaction volume, incubated for 15 mins at room temperature with gentle shaking. For co-IP, magnetic beads coupled with anti-PD-L1 or anti-TGF-B1 was used. For reverse co-IP, anti-PD1 or anti-TGFBR1 was used. Antibody-coupled beads were added in 25 μL volume. The reactions were incubated for 30 mins at room temperature with constant shaking. The tubes were placed on a magnetic rack and washing was performed using PBS three times and the protein complexes were eluted using 20 μL of 100 mM glycine-HCl (pH 3.0) for 1 min followed by neutralization using 2 μL of 1M Tris-HCl (pH 8.8). IgG kappa anti-CD25 antibody served as an isotype control.
2.5. SDS-PAGE Analysis
At least 1 μg of protein samples were mixed in a 1:1 ratio with 2× Laemmli buffer (#1610737, Bio-Rad, Calif., USA) followed by 15 mins of boiling. Samples were run in NuPAGETM 10% Bis-Tris Gels (Invitrogen, Calif., USA) using MOPS-SDS buffer [50 mM MOPS, 50 mM Tris, 1 mM EDTA, 0.1% (w/v) SDS] at 250 V for 30 mins. Gels were stained with Coomasie brilliant blue followed by overnight washing with a destaining solution (50% water, 40% methanol, 10% glacial acetic acid).
2.6. Immunoblot Analysis
For western blot, proteins were electroblotted onto a nitrocellulose membrane at 100 V for 1 hr. For dot blot, proteins were blotted on nitrocellulose membrane and were incubated for 30 mins at room temperature. Membranes were washed in deionized sterile water for 1 min and were directly blocked with 2% (w/v) BSA at 37° C. for 1 hr. Washing was performed thrice using PBS-T (PBS with 0.01% Tween-20). All detection followed the indirect format. Antibodies were added in 1:1000 dilution of PBS-B (PBS with 0.1% BSA) and incubated for 1 hr at room temperature. After washing, HRP-conjugated anti-murine IgGk antibody or avidin-conjugated HRP was added in 1:10,000 dilution of PBS-B and incubated for 1 hr at room temperature with constant shaking. Following washing, 1 mL of DAB substrate (D22185, Invitrogen, USA) was poured on the membrane. The reaction was stopped by adding excess PBS.
2.7. Capture ELISA
Ninety-six well ELISA plate was coated with 100 μL of either PD1 or TGFBR1 (1 μg/mL) for 16 hrs at 4° C. Coated wells were washed with PBS-T and blocked with 2% (w/v) BSA for 1 hr at 37° C. Fusion protein (1 μg/mL and 2 μg/mL) were diluted in PBS and 100 μl of these solutions were transferred into designated wells followed by incubation at room temperature for 1 hr. For detection of binding between TGF-B1 and TGFBR1, anti-PD-L1 was used as the primary antibody; while in the detection of PD-L1 binding with PD1, an anti-TGF-B1 antibody was used. Primary antibodies were added in 1:1000 dilution in PBS-B and incubated for 1 hr at room temperature. Following washing with PBS-T, HRP-conjugated anti-murine IgGk antibody was added in 1:10,000 dilution of PBS-B and incubated for 1 hr at room temperature. After washing, TMB peroxidase substrate (#555214, BD Biosciences, Calif., USA) and stop solution were added sequentially. Optical density (OD) reading was recorded at 450 nm. Normalization control used was the lack of receptor coating, a negative control was without the addition of the fusion protein, and antibody specificity controls included isotype anti-CD25 antibody without primary antibody.
2.8. Immunofluorescence Staining
CD25 expression in Jurkat cells was visualized using FITC-conjugated anti-CD25. Expression of PD1 and TGFBR1 in AMLK and HEK-Blue TLR2 cells were visualized using FITC-conjugated anti-PD1 and pre-mixed (1:1 ratio for 1 hr at room temperature) anti-TGFBR1 antibody with FITC-conjugated anti-mouse IgG antibody. Approximately 1×106 cells were collected by centrifugation followed by resuspension in 100 μL of PBS containing 1:100 dilution of antibody and incubated at 4° C. for 30 mins. Washing with PBS-T was performed twice by centrifugation at 500×g for 3 mins. Cells were incubated in 25 μL of PBS with or without 0.5 μg/mL Hoechst 33342 (H3570, Thermo Scientific, MA, USA) for 5 mins at room temperature. Cells were washed once with PBS and allowed to attach on poly-L-lysine coated slides before visualization under a fluorescence microscope.
2.9. Lipofection and Stable Transfection
TLR2-expressing HEK Blue cells (1×106) were seeded in 6-well plates and cultured for 24 hrs. Lipofection with pCMV3-PD1 construct proceeded using Lipofectamine® 2000 (Invitrogen, Calif., USA) following the manufacturer's protocol using a 5 μg vector DNA to 10 μL Lipofectamine ratio. After 72 hrs of culture, transfected cells were selectively grown in the presence of 500 μg/mlof G418 (Invivogen, Calif., USA) for 1 week. Cells were then serially diluted into single cells in a 96-well plate to isolate stably transfected single-cell clones that homogenously express PD1 protein. Successful transfection and expression were assayed using immunofluorescence staining.
2.10. NF-κB-Induced—Secreted Embryonic Alkaline Phosphatase (SEAP) Assay
The absence of endotoxin was first examined in the isolated fusion protein using LAL assay (L00350, Genscript, USA). Lipofected HEK-Blue TLR2 cells were seeded in 96-well plates with 1×105 cell density per well. After 24 hrs, the medium was replaced with HEK Blue Detection Medium (PlasmoTestTM, Invivogen, Calif., USA) and the cells were challenged with an increasing dilution of mycobacteria-containing FCA (Freund's Complete Adjuvant) (#77140, Thermo Scientific, MA, USA) in 1:100, 1:1000, 1:10000, 1:50000 and 1:100000 dilutions. Cells were either directly treated with 50 ng/mL fusion protein or pre-incubated first with either 1 μg/mL of anti-PD1 or anti-TGFBR1 antibodies. Cells without FCA challenge served as the normalization control. After 24 hrs of incubation, NF-κB-induced secreted embryonic alkaline phosphatase (SEAP) activity was assessed by measuring optical density (OD) absorbance at 655 nm. Percent inhibition was derived using the formula: [(OD(−)TP− ODexperimental)/OD(−)TP*100].
2.11. Growth Suppression Assay
The growth suppression activity of fusion protein in PHA/IFN-γ-activated Jurkat cells was performed by incubating 100 ng/mL of fusion protein within a week. Growth suppression was compared to PD1-blocked (pre-incubated with 1 μg/mL anti-PD-1 antibody) and TGFBR1-blocked cells (pre-incubated with 1 μg/mL anti-TGFBR1 antibody) with untreated activated and non-activated cells as controls. Cell viability and cell count were assayed using trypan blue staining assisted by automated cell counter CountessTM (Invitrogen, Calif., USA) after 3, 5, and 7 days. Cells were fed every 3 days. Percent growth suppression was derived using the formula: [(untreated count—fusion protein-treated count)/untreated Jurkat cells)]*100.
2.12. Gene Expression Analysis
AMLK cells (1.0×107) were cultured in 6-well plates and treated with 50 ng/mL of either fusion protein or commercially available TGF-B1 or PD-L1 for 32 hrs. Receptor-reconstituted HEK-Blue TRL2-expressing cells (1.0×106) were cultured in 12-well plates and treated directly with 50 ng/mL fusion protein or following pre-incubation of receptor-specific antibodies. Jurkat cells (activated and non-activated, 1.0×106 each) were cultured in 6-well plates with supplementation of 50 ng/mL of fusion protein for 24 and 72 hrs. Set-ups without fusion protein served as control. RNA extraction proceeded with RNeasy® Mini Kit (Qiagen, Germany). For all samples, 1 μg of RNA was converted to cDNA using either M-MuLV Reverse Transcription kit (NewEngland Biolabs) or iScriptTM cDNA synthesis kit (Bio-Rad, Calif., USA) following the manufacturer's protocol. Gene expression analysis was carried out using either M-MuLV Reverse Transcription kit (NewEngland Biolabs) or iScriptTM cDNA synthesis kit (Bio-Rad, Calif., USA) following the manufacturer's protocol. Gene expression analysis was carried out using SsoFastTM EvaGreen® Supermix (Bio-Rad, Calif., USA) with CFX96TM Real-Time PCR Detection System using primer pairs shown in Table 1. Amplification parameters include an initial denaturation at 96° C. for 30 sec followed by 40 cycles of denaturation at 96° C. for 5 sec, annealing and extension at 60° C. for 60 sec. Expression levels were presented as fold change values.
2.13. Cellular Retention Assay
TGFBR1+PD1+HEK293 cells (5×105) were seeded into 96-well plates coated with 50 μg/mL poly-L-lysine (ScienCell, Calif., USA) and incubated for 10 mins on ice. Unwanted binding sites were blocked with 20% (v/v) FBS for 5 mins. Fusion protein (2 μg/mL) was added next and incubated for 10 mins followed by the addition of 5×105 TGFBR1+PD1− HEK293 cells and incubated further for 20 mins. The wells were gently washed once with 200 μL PBS to remove non-binding cells. Cellular retention was recorded as a measure of the total number of counted cells using trypan blue staining. Reverse retention assay was performed by first coating the substrate with the TGFBR1+PD1− cells followed by the addition of the TGFBR1+PD1+ cells. Without fusion protein, PD1-blocked and TGFBR1-blocked set-ups served as controls. Retention count was normalized using the count of HEK only (no binding partner) set-up.
2.14. Cellular Size-Exclusion Assay
TGFBR1+PD1+HEK293 cells (5×105) were mixed with the same cell density of TGFBR1+PD1-cells in 0.5 mL of PBS with or without receptor blocking antibodies (anti-PD1 and anti-TGFBR1) and incubated for 10 mins on ice. Approximately, 0.5 mL of 2 μg fusion protein was added and incubated for 20 more mins. The solution was transferred into a new conical tube through a 20 μm cell strainer mesh. Cell count was determined using trypan blue staining. Set-up without fusion protein served as a negative control.
2.15. Fluorescence-Assisted Cell Counting
Initially, 1×104 of each activated and non-activated Jurkat T cells were separately stained with 0.5 μg/mL Rhodamine B (#83689, Sigma-Aldrich, MO, USA) and 0.5 μg/mL Hoechst 33342, respectively for 10 mins. Cells were washed with PBS and collected by centrifugation. Cells were mixed (1:1 ratio) in 100 μL PBS with 200 ng of fusion protein for 15 mins. The solution was transferred into poly-L-lysine-coated 96-well plates and cells were allowed to settle for 10 mins before paired-cell counting.
2.16. Co-Culture Assay
A 1:1 ratio (1×106 each) of non-activated and PHA/IFN-γ activated Jurkat T cells were co-cultured in 24-well plates with 1 μg/mlof the fusion protein in the presence or absence of receptor blocking antibodies (anti-PD1 and anti-TGFBR1) for 24 hrs. Foxp3 expression was assayed by immunoblot and qRT-PCR. IL2Ra (CD25) was assayed quantitatively using Qubit 2.0 using excitation430-495 nm/emission510-580 nm filters.
2.17. Data Analysis
Statistical analyses were performed using Data Analysis Software (Microsoft, WA, USA) and Prism 5 software (GraphPad Software, Calif., USA). P-values less than 0.05 were considered significant. All analyses and p-values are described in figure legends.
3. Detailed Description of the Invention.
3.0 Summary—Fusion Gene and Protein Design, Construction, and Experimental Results:
The fusion TGF-B/checkpoint gene and protein constructs were based upon the DNA (SEQ ID NO: 2) and amino acid (SEQ ID NO: 14) sequences of the TGF-B1 ligand the PD-L1 immune checkpoint domain (SEQ ID NO: 6), and selected flexible peptide linker (GGGGS)3 linker (SEQ ID NO: 20) and a rigid peptide linker A(EAAAK)2A (SEQ ID NO: 27). The details of the ligand/receptor binding domain sequences are presented in the Sequence Listing:
The Nucleotide and Amino Acid Sequence Listings—the Patentln Software was used to input nucleotide and amino acid sequences listings, and presented in ASCII text file, hereby directing its entry into the application and disclosing the Sequence Listing as follows:
In an embodiment of the fusion protein, a TGF-B1/PD-L1 fusion protein (SEQ ID NO: 13) was molecularly designed and constructed with the fusion gene of TGF-B1 (SEQ ID NO: 2) (NM_000660.6) and PD-L1 (SEQ ID NO: 6) (NM_014143.3) using an overlap extension PCR strategy. A dimeric TGF-B1 (SEQ ID NO: 21) was successfully developed by incorporating a flexible (GGGGS)3 linker (SEQ ID NO: 20) between two monomeric units of PD-L1 (SEQ ID NO: 6) (GenBank accession: MN688294) and linked with a rigid linker A(EAAAK)2A (SEQ ID NO: 27) upstream of the PD-L1 domain (SEQ ID NO: 6) (GenBank accession: MN688295) as graphically represented in
The fusion gene (SEQ ID NO: 1) was cloned into a pCDNA3.1+ mammalian expression vector (pCDNA3.1+/TP) and the fusion gene with vector construct was transfected into HEK293 (Human Embryonic Kidney) cells by lipofection. After 48 hrs, cell lysates of transfected cells were analyzed. The presence of a thicker 70 kDa protein band (
The fusion protein (SEQ ID NO: 13) was immunoprecipitated from the lysate using magnetic beads with covalently coupled antibodies against PD-L1 and TGF-B1, and we verified that this 70 kDa protein was the desired fusion product. SDS-PAGE analysis (
3.1. Development of TGF-B/Checkpoint Fusion Proteins—Based Upon Ligand/Receptor Binding Domains.
Selected Domains for construction of the fusion protein. The Sequence Listing indicates the DNA and Amino Acid domains selected from the gene and protein structures of:
In some embodiments, the DNA and amino acid sequences of the TGF-B1 domain, partly or wholly overlap with the enumerated DNA (SEQ ID NO: 2) and amino acid (SEQ ID NO: 14) sequences or represent variants of the DNA (SEQ ID NO: 2) and amino acid (SEQ ID NO: 14) sequences capable of binding to its receptor.
In some embodiments, the flexible peptide linker SEQ ID NO: 20 is a variant of the enumerated DNA (SEQ ID NO: 5) and amino acid (SEQ ID NO: 20) sequences or composed of linkers with different amino acid lengths and sequences, while retaining flexible characteristics, wherein the conformation of the TGF-B ligand allows binding to TGF-B receptors.
In some embodiments, the DNA and amino acid sequences of the PD-L1 domain, partly or wholly overlap with the enumerated DNA (SEQ ID NO: 6) and amino acid (SEQ ID NO: 17) sequences or represent variants of the DNA (SEQ ID NO: 6) and amino acid (SEQ ID NO: 17) sequences capable of binding to its receptor.
In some embodiments, the flexible peptide linker is a variant of SEQ ID NO: 20 or composed of linkers with different amino acid lengths and sequences, while retaining flexible characteristics, wherein the conformation of the TGF-B ligand allows binding to TGF-B receptors.
In some embodiments, the rigid peptide linker is a variant of SEQ ID NO: 27 or composed of linkers with different amino acid lengths and sequences, while preventing allosteric interference between the linked TGF-B ligand and the immune checkpoint domain, wherein the conformation of the fusion protein allows binding to TGF-B and immune checkpoint receptors, respectively. 3.2. The dimeric TGF-B1 domain (SEQ ID NO: 21) of the fusion protein binds to TGF-B1 receptors only in the presence of co-receptors as shown by co-immunoprecipitation (co-IP) and immunoblot with TGFBR1 from leukemic cells.
Dimerization of endogenous TGF-B1 is needed to assume its active form, which may consist of homodimers but mature TGF-B dimers may also form heterodimers of TGF-B1 with other TGF-B monomers including TGF-B2 and TGF-B3 [38-39]. We recreated the dimer (SEQ ID NO: 21) by linking two monomers with (GGGGS)3 linker (SEQ ID NO: 20) which is used to link functional scFvs. Comparison of the predicted structure of fused TGF-B1 with an NMR-derived structure (PDB ID:1KLD) using Phyre2 revealed a more concave configuration in the former (
“Fingertip” structures responsible for receptor binding are shown (
TGF-B1 signals through oligomerization with type I and type II receptors [38-39]. Binding studies suggested the chronologic interaction first of a type II receptor such as TGFBR2 followed by association of type I receptors such as TGFBR1. These co-receptor binding experiments were important to confirm the proper conformation of dimeric TGF-B ligand fused to an immune checkpoint domain. First, it was established that the fusion protein was unable to bind TGFBR1, by itself, in the absence of co-receptors. This lack of direct interaction of between the fusion protein (SEQ ID NO: 13) and TGFBR1 was tested (
The result of capture ELISA experiments revealed no significant difference in the binding readout of set-ups with the fusion protein (+TP) and the controls (
3.3. PD-L1 Domain (SEQ ID NO: 6) of the TGF-B1/PD-L1 Fusion Protein (SEQ ID NO: 13) Binds PD1 Receptor.
Next, PD-1 binding by the fusion protein was examined using the same co-precipitation experiments; for this experiment, a commercially available active PD-1 protein was used. As control, the absence of endogenous PD-L1 expression (molecular weight is within 45-70 kDa depending on glycosylation state) in transfected (TR) cells (
3.4. Expression of Immune-Related Genes was Coordinated Through Actions of the TGF-B1/PD-L1 Fusion Protein (SEQ ID NO: 13).
To support findings of these protein-protein interaction, experiments we done separately treating TGFBR1+PD-1+leukemic (AMLK) cells (
3.5. TGF-B1/PD-L1 Fusion Protein (SEQ ID NO: 13) Inhibits Inflammatory Gene NF-κB Activation and Signaling.
As a potent activator of inflammatory genes, NF-κB signaling plays a critical role in inflammation and is believed to contribute strongly in the pathology of immune dysregulation and autoimmune diseases [33-34]. As an initial assay to evaluate the potential use of our fusion protein as anti-inflammatory therapy, the fusion protein's ability to suppress NF-κB activation was tested by challenging commercially available human TLR2-expressing HEK-Blue cells with Freund's Complete Adjuvant (FCA). In this system, the Secreted Embryonic Alkaline Phosphatase (SEAP) gene is expressed under the control of NF-κB-responsive promoter and the activation of TLR2 signaling by FCA induced SEAP secretion in the culture. TLR-2 is sensitive to bacteria-derived molecules, although mammalian cells were used, it was confirmed in these experiments that endotoxins were absent in the fusion protein preparations used in all in-vitro assays.
As expected, TGFBR1 but not PD-1 was expressed by these cells due to the cell type-specific expression of the latter, revealed by immunofluorescence staining (
After reconstituting the receptors of TGF-B1 and PD-L1, the cells were treated with 1:100 dilution of FCA in the presence of commercially available anti-mycoplasma agent, Normocin to prevent false-positive reading. The optical density (OD) at 655 nm was measured after 24 hrs to measure SEAP secretion in the culture supernatants. Cells treated with fusion protein showed 73.66% inhibition of SEAP secretion relative to the untreated set-up (
To correlate the functionality of this NF-κB signaling inhibition, the expression of NF-κB target genes, c-Myc, and Bcl2 was evaluated. Consistent with NF-kB downregulation, these genes were found to be downregulated in fusion protein-treated (+TP) set-up relative to untreated (broken line), suggesting the downregulation of NF-κB signaling by the fusion protein. Treatment with receptor-specific antibodies nearly restored the expression profile similar to the untreated (
3.6. The TGF-B1/PD-L1 Fusion Protein (SEQ ID NO: 13) does not Abrogate NF-κB Signaling in the Presence of a Low Concentration of Inflammatory Signals
The concentration-dependence of NF-κB signaling inhibition of fusion protein was tested by increasing FCA dilution to 1:1,000, 1:10,000, 1:50,000 and 1:100,000. After 24 hrs, we found significant reduction in SEAP secretion of cells treated with fusion protein (+TP=0.3473) compared to the control (−TP=0.6773) in 1:1,000 dilution. This significant reduction was constantly observed in the rest of other dilutions, demonstrating additional evidence of the potential anti-inflammatory activity of our fusion protein (
Decreasing the inflammatory trigger did not abrogate SEAP secretion even at 100,000-fold dilution of FCA. Treatment with receptor-specific antibodies resulted in SEAP secretion that was higher in those set-ups compared to +TP alone, suggesting receptor-specific activities. Significant inhibition was only observed in 1:1,000 FCA dilution (IB PD1/+TP=26.34%, IB TR/+TP=25.53% and +TP=47.83%) (
3.7. TGF-B1/PD-L1 Fusion Protein (SEQ ID NO: 13) Selectively Suppressed Growth of Activated Jurkat T Cells by.
The functional consequences of receptor binding by fusion protein were evaluated in response to the growth of activated effector-like Jurkat T cells which have an endogenous expression of TGF-B receptors. The induction of PD-1 expression in Jurkat cells was accomplished with PHA and IFN-γ. Although PHA alone was found to induce mitogenic effects on lymphocytes, its proliferative effects on Jurkat cells were negligible. Co-activation of effector phenotype was done with a pro-inflammatory stimulant such IFN-γ in nanogram concentration. This activation was used to assess the immune downregulation activity of fusion protein against activated effector T cells. Viable cell count was assayed using trypan blue staining assisted with an automated cell counter. After 3 days of culture, a significant reduction of viable cell count of activated (PHA/IFN-γ-treated) Jurkat cells was observed compared to non-activated cells (804,000 vs. 1,126,000) in the presence of fusion protein (
3.8. The Constructed Fusion Protein (SEQ ID NO: 13) Counteracts Effector Activation and Sustains Cell Growth Suppression in Activated Jurkat T Cells
To determine whether the suppression in cell growth is temporary or constant, activated Jurkat cells were cultured with the fusion protein (+TP) for 1 week and the growth response was compared to cultures in the absence of fusion protein (−TP) after 3, 5, and 7 days.
3.9. TGF-B1/PD-L1 Protein (SEQ ID NO: 13) Induces Reversal of PHA/IFN-γ Activation and Induction of Regulatory T Cell Differentiation.
Further experiments indicated that the reduction in cell viability was a result of the induction of T cell anergy as a consequence of PD-1/PD-L1 pathway activation or metabolic termination for induced Treg (iTreg) differentiation elicited by TGF-B1 signaling. First, we correlated the cell count data from the seven days culture experiment above. A significant increase in cell count was observed in −TP, IB TR/+TP, and IB PD1/+TP. Comparable cell count was observed in +TP (
Next, the expression levels of nfkb1 and foxp3 were measured to assess iTreg induction. After 24 hrs of culture, in +TP and −TP, the upregulation of nkfb1 was observed which plays a vital role in both regulatory and effector functions of T cells. However, nfkb1 expression in +TP set-up (6.521-fold expression) was lower compared to −TP (15.846-fold expression) (
3.10. Bi-Functional Bridging of the TGF-B1/PD-L1 Fusion Protein (SEQ ID NO: 13) Mediates Cell-to-Cell Interaction.
Bi-specific scFv or BiTE (bispecific T cell engager) technology facilitates the interaction of cytotoxic lymphocytes with cancer cells to induce tumor killing. TGF-B1 receptors are expressed on regulatory T cells while high PD1 expression was observed in activated effector cells systems. Meanwhile, activated regulatory T cells also express PD1; and TGF-B1 receptors were also found on effector cells. The molecular design of the fusion protein can act similarly as BiTE to potentially facilitate Treg-mediated contact-dependent immune regulation by cell-to-cell contact.
This bi-functional bridging activity was evaluated in a cellular retention assay by measuring the frequency of interaction between TGFBR1+PD1+ and TGFBR1+PD1− HEK293 cells (
While most BiTE platforms strategize on cell-to-cell contact to induce tumor killing by effector T cells, the design of the TGF-B1/PD-L1 fusion protein and the molecular expression of receptor targets could favor the recognition of effector T cells by the regulatory cells. To partially test this hypothesis, PHA/IFN-γ-activated and non-activated Jurkat T cells were separately labeled with Rhodamine B and Hoechst 33342, respectively before mixing in the presence or absence of our fusion protein. The results showed a higher pairing count (
4. Descriptions of the Subject Matter and Significance of this Invention:
Molecular crosstalk between effector immune cells and inhibitory cytokines or contact with regulatory cells are important mechanisms by which the immune response is regulated and controlled. These mechanisms are crucial in maintaining tolerance for self-antigens, preventing the onset of autoimmune disease (AID). TGF-B1 ligands can exert immunosuppressive properties by enhancing regulatory T cell activities whereas and PD-L1 can act by modulating the activation state of effector cells. TGF-B1 may be an important molecular target for autoimmune diseases such as inflammatory bowel diseases, type 1 diabetes, lupus, and other autoimmune diseases. Although the immunoregulatory activity of PD-L1 has been described a few decades ago, its application as a therapeutic target for AID is only in its early stages. Meanwhile, advancements in cancer immunotherapy have brought new classes of biologics that have shown encouraging clinical outcomes such as the BiTE or bispecific T cell engager. This strategy mediates the recognition of cancer by cytotoxic lymphocytes due to the dual specificity of the two scFvs against a cancer-associated antigen and a T cell surface marker. This cell-to-cell contact seems to capture Treg-mediated contact-dependent immune regulation that could be harnessed potentially as a strategy to downregulate autoreactive cells in AID. To validate these concepts, we a bifunctional TGF-B1/PD-L1 fusion protein was constructed. The description herein indicates the potential therapeutic applications of this fusion protein as an approach to treat immune dysregulation and autoimmune diseases (
Critical to the pathogenesis of immune dysregulation and autoimmune diseases, NF-kB is a transcription factor that is considered as a master regulator of immune response that targets many genes encoding pro-inflammatory proteins and that is known to be pathologically activated in many autoimmune conditions [3-5]. Many immunosuppressive drugs act on various stages of NF-kB signaling pathway and can be considered as an important biomarker to evaluate immunosuppressive properties of many biological therapies [7-11]. The experimental results detailed herein indicate that activation of signaling pathways by these two ligands led to the downregulation of NF-kB signaling. Consistent with this, 73.66% relative inhibition of NF-kB activation was observed in SEAP reporter assays which collaborates to downregulate NF-kB-target genes, c-myc, and bcl2.
The activation of NF-kB is indispensable to the effector phenotype of T cells [10-11]. The biological activity of TGF-B1/PD-L1 fusion protein was tested to determine the correlation of NF-kB-dependent c-myc and bcl2 downregulation Jurkat T cells. The hypothesis being tested was whether the downregulation of these cell growth-promoting and anti-apoptotic proteins results in the suppression of cell growth and viability of stimulated effector cells. Several stimulatory molecules such as PMA, ionomycin, polyclonal CD3, and CD28 antibodies were used to induced T cell expansion, but PHA and IFN-γ were most consistent in inducing PD-1 expression in Jurkat T cells and were both found to activate NF-kB signaling. Consistent with the inhibition of NF-kB activation in reporter cells, only those stimulated with PHA and IFN-γ were found suppressed in terms of cell viability, and no significant increase in cell count was observed within 7 days of culture. Although the response in non-activated cells may be due to lack of PD-1 expression, receptor blocking using anti-TGFBRI or anti-PD-1 antibodies resulted in comparable cell viability and cell count, suggesting receptor-ligand-specific outcomes. This induction of reduced viability and unresponsiveness to stimuli may indicate passive regulation of immune response by TGF-B1 and PD-L1 signaling to control autoreactivity (
Regulatory T cells are considered indispensable to maintain immune tolerance (
There are more than 80 clinical subtypes of immune disorders and autoimmune diseases [1,10]. The majority of therapeutically approved biological drugs for autoimmune diseases address only a few of these types. Modes of action by these targeted-based therapies include depleting specific T and B cell subsets, neutralizing activities of inflammatory factors, or mediating receptor-ligand interactions. However, the long-term efficacy and sustained safety of these treatments are still in question. In addition to the deleterious side effects of small molecule drugs, efforts to create a more strategic therapy is valuable for immune disorders. In addition to its immune regulatory activity, the TGF-B1/PD-L1 fusion protein was tested in dose-dependent and time-dependent experiments to determine dose-controlled modulation of immune reactions that would be important in clinical safety. The TGF-B1/PD-L1 was shown to have NF-kB activation which has a permissive activity of around 30% regardless of the concentration of inflammatory triggers. This NF-kB-dependent c-myc and bcl2 downregulation increased over 7 days and approximately 50% of growth inhibition was observed with the fusion protein treatment. Although these data were derived in vitro, the use of an appropriate model and the execution of a comprehensive dosing experiment to assess avoidance of complete immunosuppression that would be important in adjustments of clinical dosing.
Aside from immune cells, other tissues of the body express TGF beta 1 receptors [12]. Being a pleiotropic cytokine, TGF beta 1 plays a role in the growth and differentiation of many cells of the body. In some tissues, TGF beta 1 promotes fibrosis and could potentially be involved in cancer progression. Many cancer treatment adjuvants include the sequestration or downregulation of TGF beta 1 activities. The biological half-life and potential tissue-distribution of the fusion protein are important factors to consider in therapeutic applications. Experiments on dosing are also a crucial part of physiological assessments of the toxicity of this recombinant protein. In the context of controlling tissue-specific autoreactivity, the distribution of the fusion protein may help in tissue recovery while allowing potential control of tissue/organ-reactive immune cells as cooperatively induced by the immunosuppressive activities of TGF beta 1 and PD-L1.
Recently, efforts by scientists to create and advance treatments for cancer have encouraged the spur of many immunotherapies that are now revolutionizing the way various cancers are treated. Chimeric antigen receptor T cell (CAR-T) therapy has been used to direct depletion of certain immune cells causing chronic inflammation which are now tested in clinical trials. Another platform, the BiTE (bispecific T cell engager) technology has been creating a milestone in cancer therapy.
Using a different approach, the current invention points to the potential application of fusion protein as BiTE technology for immune disorders and autoimmunity. The structural, receptor-binding ability and biological activity of TGF-B1/PD-L1 fusion protein described herein demonstrates its potential for immune regulation and control based upon several experimental observations. There was efficient binding to receptors expressed by both effector and regulatory cells. Further, the fusion of these two ligands enhanced Treg-mediated contact-dependent immune regulation through a BiTE-like mechanism (
The molecular bioactivity of the fusion protein with the endogenous receptors are important for designs of potential therapeutic applications. The results of the biochemical and molecular assays herein demonstrate the similarity of our fusion protein with the endogenous unfused forms in terms of receptor binding, functional induction of gene signatures including cellular consequences of cell signaling activation. The experimental results using the fusion protein also point to the molecular signaling crosstalk between these proteins that are only beginning to be unraveled. Although Tregs represent a strategic target in AID, discouraging results have been produced in clinical settings so far. The fusion protein may represent a new class of therapy that could potentially help advance this regulatory cell-based targeted therapy in autoimmunity. The TGF-B and immune checkpoint domains of fusion protein work cooperatively to elicit both Treg-dependent and -independent mechanisms (
There are several potential applications for the immune-regulatory activity of this novel TGF-B/Immune checkpoint fusion gene and protein, including treatment for:
[A] US 2013/0039911 A1 (Bedi et al., published 14 Feb. 2013).
Bedi at al., disclose a fusion protein with only one copy of TGF-B1 with the same sequence as instant SEQ ID NO: 14, a flexible linker with the same sequence a instant SEQ ID NO: 20, an immunoglobulin Fcv domain, and PD-L1 sequence the same as instant SEQ ID NO: 17. However, Bedi et al. do not disclose nor suggest a rigid peptide linker as indicated in the instant SEQ ID NO: 27, nor do they disclose or suggest a TGF-B1 homodimer linked by a flexible linker as indicated in the instant SEQ ID NO: 20. Thus, the instant application is free of prior art.
The subject matter of this patent application was not supported by U.S. Federal, U.S. State, Philippine Government, or any other Government-sponsored research or development program.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20130039911 | Bedi | Feb 2013 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20210238245 A1 | Aug 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62968664 | Jan 2020 | US |
