GB1275, a first-in-class CD11b modulator: rationale for immunotherapeutic combinations in solid tumors.

Resistance to immune checkpoint inhibitors (ICI) and other anticancer therapies is often associated with the accumulation of myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) in the tumor microenvironment (TME). Therefore, targeting MDSC recruitment or function is of significant interest as a strategy to treat patients with ICI-resistant cancer. The migration and recruitment of MDSCs to the TME is mediated in part by the CD11b/CD18 integrin heterodimer (Mac-1; αMß2), expressed on both MDSCs and TAMs. However, inhibition or blockade of CD11b/CD18 has had limited success in clinical trials to date, likely since saturation of CD11b requires doses that are not clinically tolerable with the agents tested so far. Interestingly, activation of CD11b with leukadherin-1 was found to reduce macrophage and neutrophil migration in animal models of inflammatory conditions. Preclinical studies with GB1275, a salt form of leukadherin-1, demonstrated that activation of CD11b improves the antitumor immune response and enhances the response to immunotherapy in mouse models of pancreatic adenocarcinoma, breast cancer and lung cancer. Based on the promising results from preclinical studies, a phase 1/2 clinical study (NCT04060342) of GB1275 in patients with advanced solid tumor types known to be resistant or less likely responsive to immuno-oncology therapies, including pancreatic, breast, prostate, and microsatellite-stable colorectal cancer, is ongoing. In this review, we examine targeting MDSCs as a therapeutic approach in cancer therapy, with a special focus on GB1275 preclinical studies laying the rationale for the phase 1/2 clinical study.

Targeted Delivery of LXR Agonist Using a Site-Specific Antibody-Drug Conjugate.

Liver X receptor (LXR) agonists have been explored as potential treatments for atherosclerosis and other diseases based on their ability to induce reverse cholesterol transport and suppress inflammation. However, this therapeutic potential has been hindered by on-target adverse effects in the liver mediated by excessive lipogenesis. Herein, we report a novel site-specific antibody-drug conjugate (ADC) that selectively delivers a LXR agonist to monocytes/macrophages while sparing hepatocytes. The unnatural amino acid para-acetylphenylalanine (pAcF) was site-specifically incorporated into anti-CD11a IgG, which binds the α-chain component of the lymphocyte function-associated antigen 1 (LFA-1) expressed on nearly all monocytes and macrophages. An aminooxy-modified LXR agonist was conjugated to anti-CD11a IgG through a stable, cathepsin B cleavable oxime linkage to afford a chemically defined ADC. The anti-CD11a IgG-LXR agonist ADC induced LXR activation specifically in human THP-1 monocyte/macrophage cells in vitro (EC50-27 nM), but had no significant effect in hepatocytes, indicating that payload delivery is CD11a-mediated. Moreover, the ADC exhibited higher-fold activation compared to a conventional synthetic LXR agonist T0901317 (Tularik) (3-fold). This novel ADC represents a fundamentally different strategy that uses tissue targeting to overcome the limitations of LXR agonists for potential use in treating atherosclerosis.

Immunological evaluation of ß-thalassemia major patients receiving oral iron chelator deferasirox.

OBJECTIVE: To determine the immune abnormalities and occurrence of infections in transfusion-dependent ß-thalassemia major patients receiving oral iron chelator deferasirox (DFX). STUDY DESIGN: An observational study. PLACE AND DURATION OF STUDY: Hematology Clinics, King Khalid University Hospital, Riyadh, Saudi Arabia, from July to December 2010. METHODOLOGY: Seventeen patients with ß-thalassemia major (12 females, median age 26 years) receiving deferasirox (DFX) for a median duration of 27 months were observed for any infections and had their immune status determined. Immune parameters studied included serum immunoglobulins and IgG subclasses, serum complement (C3 and C4) and anti-nuclear antibody (ANA) level, total B and T-lymphocytes, CD4+ and CD8+ counts, CD4+/CD8+ ratio, and natural killer (NK) cells. Immunological parameters of the patients were compared with age, gender, serum ferritin level and splenectomy status. Lymphocyte subsets were also compared with age and gender matched normal controls. RESULTS: A considerable reduction in serum ferritin was achieved by DFX from a median level of 2528 to 1875 µmol/l. Serum IgG levels were increased in 7 patients. Low C4 levels were found in 9 patients. Total B and T-lymphocytes were increased in 14 patients each, while CD4+, CD8+ and NK cells were increased in 13, 12 and 11 patients respectively. Absolute counts for all lymphocyte subsets were significantly higher compared to the normal controls (p ² 0.05 for all parameters). Raised levels of IgG were associated with older age, female gender, splenectomized status and higher serum ferritin levels but this did not reach statistical significance except for the higher ferritin levels (p=0.044). Increased tendency to infections was not observed. CONCLUSION: Patients with ß-thalassemia major receiving DFX exhibited significant immune abnormalities. Changes observed have been described previously, but could be related to DFX. The immune abnormalities were not associated with increased tendency to infections.

Detection of paeoniflorin and albiflorin by immunostaining technique using anti-paeoniflorin monoclonal antibody.

INTRODUCTION: Paeoniae radix is one of the most important crude drugs used in Kampo medicines (KMs). A part of its pharmaceutical properties is due to the presence of paeoniflorin (PF) and albiflorin (AF). OBJECTIVE: For the specific and easy identification of PF and AF, an immunostaining technique was developed using anti-PF monoclonal antibody (MAb). METHODOLOGY: PF and AF were treated with a NaIO4 solution and reacted with bovine serum albumin (BSA) preparing PF- and AF-BSA conjugates on the polyethersulphone (PES) membrane. Anti-PF MAb was bound and then antibody labelled with peroxidase directed against anti-PF MAb. Finally, a substrate was added and then PF and AF were detected. RESULTS: Anti-PF MAb recognised not only PF but also AF when 10 µg was present on the PES membrane. As little as 0.5 µg of PF and AF were still detected under immunostaining. Various Paeoniae radix samples and KMs were qualitatively analysed, and total amounts of PF and AF were visually detected by immunostaining technique. This method was applied to investigate the distribution of PF and AF in fresh peony root using immunoblotting by transferred from peony root to the PES membrane. CONCLUSION: The technique permitted the visualisation of PF and AF on PES membrane using immunostaining. The immunostaining technique established would be a powerful tool for probing the sources of PF and AF in plant extracts.

Retinoid agonist Am80-enhanced neutrophil bactericidal activity arising from granulopoiesis in vitro and in a neutropenic mouse model.

Despite advances in the therapeutic use of recombinant granulocyte colony-stimulating factor (G-CSF) to promote granulopoiesis of human hematopoietic stem cells (HSCs), neutropenia remains one of the most serious complications of cancer chemotherapy. We discovered that retinoid agonist Am80 (tamibarotene) is more potent than G-CSF in coordinating neutrophil differentiation and immunity development. Am80-induced neutrophils (AINs) either in vitro or in neutropenic mouse model displayed strong bactericidal activities, similar to those of human peripheral blood neutrophils (PBNs) or mouse peripheral blood neutrophils (MPBNs) but markedly greater than did G-CSF­induced neutrophils (GINs). In contrast to GINs but similar to PBNs, the enhanced bacterial killing by AINs accompanied both better granule maturation and greater coexpression of CD66 antigen with the integrin ß2 subunit CD18. Consistently, anti-CD18 antibody neutralized Am80-induced bactericidal activities of AINs. These studies demonstrate that Am80 is more effective than G-CSF in promoting neutrophil differentiation and bactericidal activities, probably through coordinating the functional interaction of CD66 with CD18 to enhance the development of neutrophil immunity during granulopoiesis. Our findings herein suggest a molecular rationale for developing new therapy against neutropenia using Am80 as a cost-effective treatment option.

Isolation of alpaca anti-hapten heavy chain single domain antibodies for development of sensitive immunoassay.

Some unique subclasses of Camelidae antibodies are devoid of the light chain, and the antigen binding site is comprised exclusively of the variable domain of the heavy chain (VHH). Although conventional antibodies dominate current assay development, recombinant VHHs have a high potential as alternative reagents for the next generation of immunoassay. We expressed VHHs from an immunized alpaca and developed a VHH-based immunoassay using 3-phenoxybenzoic acid (3-PBA), a major metabolite of pyrethroid insecticides as a model system. A phage VHH library was constructed, and seven VHH clones were selected by competitive binding with 3-PBA. The best immunoassay developed with one of these VHHs showed an IC(50) of 1.4 ng/mL (limit of detection (LOD) = 0.1 ng/mL). These parameters were further improved by using the phage borne VHH, IC(50) = 0.1 ng/mL and LOD = 0.01 ng/mL. Both assays showed a similar tolerance to methanol and dimethylsulfoxide up to 50% in assay buffer. The assay was highly specific to 3-PBA and its 4-hydroxylated derivative, 4-hydroxy 3-PBA, (150% cross reactivity) with negligible cross reactivity with other tested structural analogues, and the recovery from spiked urine sample ranged from 80 to 112%. In conclusion, a highly specific and sensitive VHH for 3-PBA was developed using sequences from immunized alpaca and phage display technology for antibody selection.

The effect of synthetic retinoid, Am80, on T helper cell development and antibody production in murine collagen-induced arthritis.

Retinoids are known to promote T helper (Th)2 and regulatory T cell (Treg) differentiation, and suppress Th1 and Th17 in vitro. Am80, a synthetic retinoid, is reported to ameliorate collagen-induced arthritis (CIA). The aims of this study are to determine the effects of Am80 on CIA in detail, and on Th development and antibody (Ab) production in vivo. Murine CIA was induced by immunization with bovine type II collagen (CII) at days 1 and 22. Treatment with Am80 from day 1 to 35 significantly lowered clinical arthritis score, suppressed cellular infiltration and bone destruction in the joint, decreased interleukin (IL)-17 and increased interferon (IFN)-gamma production by CII-stimulated splenocytes, and decreased proportion of Foxp3(+) splenic CD4 T cells and serum anti-CII Ab levels. Thus, Am80 inhibited Th17 and Treg and enhanced Th1 differentiation in vivo. In contrast, Am80 applied from day 15 to 35 did not alter arthritis score, IL-17 or IFN-gamma production by CII-stimulated splenocytes, but decreased the proportion of Foxp3(+) splenic CD4 T cells and serum anti-CII Ab levels. Am80 exhibits inhibitory effects on CIA and might regulate both Th development and Ab production in vivo. Decreased Th17 by treatment with Am80 might be responsible for the attenuation of arthritis.

Magnetic bead-based phage anti-immunocomplex assay (PHAIA) for the detection of the urinary biomarker 3-phenoxybenzoic acid to assess human exposure to pyrethroid insecticides.

Noncompetitive immunoassays are advantageous over competitive assays for the detection of small molecular weight compounds. We recently demonstrated that phage peptide libraries can be an excellent source of immunoreagents that facilitate the development of sandwich-type noncompetitive immunoassays for the detection of small analytes, avoiding the technical challenges of producing anti-immunocomplex antibody. In this work we explore a new format that may help to optimize the performance of the phage anti-immunocomplex assay (PHAIA) technology. As a model system we used a polyclonal antibody to 3-phenoxybenzoic acid (3-PBA) and an anti-immunocomplex phage clone bearing the cyclic peptide CFNGKDWLYC. The assay setup with the biotinylated antibody immobilized onto streptavidin-coated magnetic beads significantly reduced the amount of coating antibody giving identical sensitivity (50% saturation of the signal (SC(50))=0.2-0.4ng/ml) to the best result obtained with direct coating of the antibody on ELISA plates. The bead-based assay tolerated up to 10 and 5% of methanol and urine matrix, respectively. This assay system accurately determined the level of spiked 3-PBA in different urine samples prepared by direct dilution or clean-up with solid-phase extraction after acidic hydrolysis with overall recovery of 80-120%.

Emerging strategies to treat chronic immune thrombocytopenic purpura.

Immune thrombocytopenic purpura (ITP) is a fairly common hematological disorder and is a minor disease for many affected patients; most are in good health, and many can tolerate low platelet counts without the need for treatment. For the majority of patients who do undergo treatment, first-line therapies, including corticosteroids, are effective in increasing platelet counts, although long-term use can be associated with adverse effects. Second-line therapies, such as immunosuppressants, have been largely untested in controlled studies of ITP patients. Like first-line therapies, splenectomy is effective for many patients; however, it is frequently avoided by physicians who prefer the use of alternative drug therapies due to concerns about safety risks and is often declined by patients reluctant to undergo surgery. Thus, approaches to avoid or defer the use of splenectomy have been actively pursued. An anti-CD20 antibody, rituximab, can limit the production of autoantibodies, but reactivated viral infections have been reported with its use. Agents that directly stimulate platelet production, such as thrombopoietin (TPO) receptor-binding agents, have shown promise in clinical trials of ITP patients as well as in hepatitis C virus-infected individuals with thrombocytopenia. Two TPO receptor agonists in advanced clinical development--eltrombopag and AMG 531--are discussed here. Both eltrombopag and AMG 531 appear to be effective in raising platelet counts and both have been well tolerated in clinical trials to date. However, potential safety issues with thrombopoietic growth factors include thrombocytosis, rebound thrombocytopenia, and increased bone marrow fibrosis. Further testing will determine which safety issues--if any--are of clinical concern.

Phage-borne peptidomimetics accelerate the development of polyclonal antibody-based heterologous immunoassays for the detection of pesticide metabolites.

Competitive immunoassays for the detection of small analytes, such as pesticides and their metabolites, use haptens that compete with the target compounds for binding to the antibody. This competing hapten can be either the same as the immunizing hapten (homologous assay) or structurally modified mimics of the immunizing hapten (heterologous assay). Polyclonal antibody-based heterologous immunoassays have shown superior sensitivities to homologous ones, butthe synthesis of heterologous haptens may be time-consuming, requiring expertise in synthetic chemistry. In this work we demonstrate that phage display peptide libraries can be used as a source of phage-borne peptidomimetics to facilitate the development of sensitive heterologous assays. Different strategies for the isolation of these peptides were explored using two metabolites of pyrethroid insecticides. The sensitivities of the best competitive phage heterologous enzyme-linked immunosorbent assays were 13 fold and 100 fold better than the homologous assay, for the glycine conjugate of trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid and 3-phenoxybenzoic acid, respectively. The phage particles were highly versatile as tracer reagents, allowing the use of enzymatic, chemiluminescent, or immuno-polymerase chain reaction detection. The data presented here shows a new systematic procedure that enables the fast generation of several competing haptens for the rapid development of sensitive heterologous immunoassays.

Construction and expression of a single chain Fv fragment against pharmacologically active paeoniflorin in Escherichia coli, and its potential use in an enzyme-linked immunosorbent assay.

A recombinant single chain variable-fragment (scFv) antibody against paeoniflorin (PF) was produced using the hybridoma cell line C31B9. Variable regions of heavy (V (H)) and light (V (L)) chain antibody genes were directly cloned from cDNA resources of hybridoma C31B9 and assembled using splicing by overlap extension (SOE)-PCR using a (Gly (4)Ser) (3) linker DNA. The constructed scFv genes were cloned into pET28a vectors for the generation of recombinant proteins in Escherichia coli. Most of the recombinant proteins were expressed in inclusion bodies. The yield of refolded and purified scFv was 1.89 mg per 100 mL of cell culture. The recombinant scFv displayed cross-reactivity as its mother monoclonal antibody (MAb) C31B9. Therefore, the newly expressed scFv protein was applied to quantitative ELISA to determine the total paeoniflorin (PF) and albiflorin (Alb) concentrations in peony root samples. Using PF as a standard compound, the full linear range of the assay was extended from 0.78 to 25 microg/mL. The results obtained by ELISA employing both the recombinant scFv and the original MAbC31B9 showed a reasonably good agreement with each other.

Angiotensin receptor blockers suppress antigen-specific T cell responses and ameliorate collagen-induced arthritis in mice.

OBJECTIVE: The renin-angiotensin system plays an important role in the regulation of cardiovascular, renal, and endocrine functions. Recent studies have demonstrated that angiotensin II has proinflammatory effects that may contribute to the pathogenesis of immune-mediated diseases. We used the collagen-induced arthritis (CIA) model to investigate the influence of angiotensin II receptor blockers (ARBs) on antigen-specific immune responses and determine whether ARBs have preventive or therapeutic effects on the development of arthritis. METHODS: We administered ARBs (olmesartan, candesartan, and telmisartan) to mice and evaluated antigen-specific T cell proliferation and cytokine production following immunization with ovalbumin (OVA) or type II collagen in Freund's complete adjuvant (CFA) or aluminum hydroxide (alum). Next, we induced CIA in DBA/1 mice and administered olmesartan. The severity and incidence of arthritis were scored according to clinical manifestations, and joint tissue sections were examined histopathologically. RESULTS: ARBs severely suppressed lymphocyte proliferation and interferon-gamma production in mice immunized with OVA or type II collagen in CFA. Olmesartan also suppressed lymphocyte proliferation in mice immunized with ovalbumin in alum. In the CIA model, olmesartan reduced the mean arthritis score and the incidence of severe arthritis, even when it was administered only after disease onset. Histopathologic findings for joint destruction were improved in olmesartan-treated mice. CONCLUSION: ARBs suppressed antigen-specific immune responses for Th1 and Th2 in vivo. Furthermore, olmesartan suppressed the development of severe arthritis and joint destruction in the CIA model. These findings suggest that ARBs may have therapeutic potential in rheumatoid arthritis.

Immunobiological [correction of Immunobioloical] activity of a new benzyl benzoate from the aerial parts of Solidago virga-aurea var. gigantea.

The chromatographic separation of the hexane soluble fraction of the methanol extract of the aerial parts of Solidago virga-aurea var. gigantea M(IQ*) (Compositae) led to the isolation of a new benzylbenzoate (1) together with four known benzylbenzoates (2-5). Their structures were determined as 2-methoxybenzyl-2-hydroxybenzoate (1), benzyl-2-hydroxy-6-methoxybenzoate (2), 2-methoxybenzyl-2,6-dimethoxybenzoate (3), 2-methoxybenzyl-2-methoxy-6-hydroxybenzoate (4), and benzyl-2,6-dimethoxybenzoate (5). Their structures were established by spectroscopic methods. Biological effects of compounds, 1 and 2, were investigated in vitro using mouse peritoneal macrophages. The benzylbenzoates (1 and 2) could serve as immunotherapeutic agents by stimulating macrophage functions, with potential use in the treatment of infectious diseases.

Anti-sulfonylbenzoate antibodies as a tool for the detection of nucleotide-binding proteins for functional proteomics.

Proteins that bind ATP and GTP are important cellular components. We developed an immunological approach to selectively tag nucleotide-binding proteins based on the use of 5'-[4-(fluorosulfonyl)benzoyl]adenosine and 5'-[4-(fluorosulfonyl)benzoyl]guanosine affinity tags and an antibody against 4-(sulfonyl)benzoate. Detection follows affinity labeling, gel electrophoresis, and ester bond cleavage to expose the epitope. Trial analyses of labeled proteins from lymphoid cells identified multiple ATP-binding proteins, including chaperones, actin, kinases, an RNA splicing factor, a membrane ATPase, and ATP synthase.

Protective efficacy of a DNA influenza virus vaccine is markedly increased by the coadministration of a Schiff base-forming drug.

Effective vaccination against heterologous influenza virus infection remains elusive. Immunization with plasmid DNA (pDNA) expressing conserved genes from influenza virus is a promising approach to achieve cross-variant protection. However, despite having been described for more than a decade, pDNA vaccination still requires further optimization to be applied clinically as a standard vaccination approach. We have recently described a simple and efficient approach to enhance pDNA immunization, based on the use of tucaresol, a Schiff base-forming drug. In this report we have tested the ability of this drug to increase the protection conferred by pDNA vaccination against influenza virus infection. Our results demonstrate that a significant protection was achieved in two strains of mice by using the combination of pDNA and tucaresol. This protection was associated with an elevated humoral and cellular response and a switch in the type of the T helper cell (Th) immune response from type 2 to type 1. This vaccine combination represents a promising strategy for designing a clinical study for the protection from influenza and similar infections.

A quantitative ELISA using monoclonal antibody to survey paeoniflorin and albiflorin in crude drugs and traditional Chinese herbal medicines.

This work describes an immunochemical approach for the quality control of Paeoniae Radix by an enzyme-linked immunosorbent assay (ELISA) based on determination of the total concentration of paeoniflorin (PF) and albiflorin (Alb), which are major bioactive constituents in Paeoniae Radix. Four hybridromas secreting monoclonal antibodies against PF and Alb were produced by fusing splenocytes from a mouse immunized by a PF-bovine serum albumin (BSA) conjugate with the hypoxanthine-aminopterin-thymidine (HAT)-sensitive mouse myeloma cell line, P3-X63-Ag8-653. A relatively higher reactivity of monoclonal antibodies (MAbs) with PF and Alb than oxypaeoniflorin (OP) and benzoylpaeoniflorin (BP) was observed, while other monoterpenes and benzoic acid did not cross-react. When PF was used as a standard, the assay can cover a measuring range of 20-600 ng/ml for PF and Alb. A series of Paeoniae Radix samples have been determined, and the results showed good agreement with that determined by traditional high-performance liquid chromatography (HPLC). The developed competitive ELISA was 100 times more sensitive than the HPLC method. Meanwhile, fifteen Chinese traditional prescriptions were determined by the competitive ELISA.

Marked enhancement of the antigen-specific immune response by combining plasmid DNA-based immunization with a Schiff base-forming drug.

Although plasmid DNA (pDNA)-based immunization has proven efficacy, the level of immune responses that is achieved by this route of vaccination is often lower than that induced by traditional vaccines, especially for primates and humans. We report here a simple and potent method to enhance pDNA-based vaccination by using two different plasmids encoding viral or bacterial antigens. This method is based on coadministration of low concentrations of a recently described immunopotentiating, Schiff base-forming drug called tucaresol which has led to significant augmentation of antigen-specific humoral and cellular immune responses. Our data suggest that enhancement of the immune response with tucaresol might provide a powerful tool for the further development of pDNA-based immunization for humans.

Comparison of IgE antibody concentrations to pyromellitic dianhydride-modified laminin and human serum albumin in sera of exposed workers with respiratory complaints.

BACKGROUND: Acid anhydrides are used in a variety of industrial branches because of their highly reactive anhydride groups. Adverse effects of anhydride exposure include toxic/irritative effects as well as IgE- and IgG-mediated respiratory disorders. It was the aim of this study to examine the usefulness of conjugates of pyromellitic dianhydride (PMDA) and laminin, a respiratory tract protein, for the in vitro diagnosis of sensitization to PMDA. METHODS: Sera of PMDA-exposed workers (n = 9) and nonexposed controls (n = 8) were tested with an enzyme allergosorbent test (EAST). Human laminin and human serum albumin (HSA) were derivatized with PMDA and used as solid-phase in a commercial assay. RESULTS: Seven out of 9 exposed workers revealed elevated IgE antibody concentrations (>0.35 kU/l) against laminin-PMDA whereas 5 of 9 subjects had elevated IgE antibody concentrations to HSA-PMDA. All 9 workers had elevated IgE antibody concentrations in at least one of the two tests. Of the 4 workers who complained of shortness of breath, 3 were positive for laminin-PMDA and 2 for HSA-PMDA. All of the nonexposed subjects were negative (<0.35 kU/l) for laminin-PMDA. CONCLUSION: PMDA-modified laminin could provide an additional diagnostic tool for the detection of sensitization to PMDA.