Antibody Binding Affinity Research Articles

Endometrial cancer patients have high affinity antibodies for estrogen metabolite-receptor aggregate: A potential biomarker for EC.

Elevated levels of 16α-hydroxyestrone (16α-OHE1 ) have been described in endometrial cancer (EC) and estrogen receptors (ER) expressed in endometrial tissue, but research on their combined role is lacking. We aimed to investigate the affinity and binding specificity of EC antibodies against the 16α-OHE1 -ERα aggregate in the serum of EC patients. Specificities of EC antibodies were also evaluated according to various clinical characteristics found in these cancer patients. The binding specificity and affinity of EC antibodies against 16α-OHE1 -ERα in the serum of 120 EC patients were evaluated by direct binding and competition ELISA and quantitative precipitation titration. Binding of EC antibodies was also determined according to various clinical characteristics in EC patients through competition ELISA. Antibodies from EC patients demonstrated high recognition of 16α-OHE1 -ERα compared to ERα (P < 0.05) or 16α-OHE1 (P < 0.001). The relative affinity of EC IgG was 1.49 × 10-7 M, 1.34 × 10-6 M and 1.13 × 10-6 M for 16α-OHE1 -ERα, ERα and 16α-OHE1 , respectively. Several factors, such as obesity, postmenopausal status, use of hormonal therapy, ER and progesterone receptor (PR) status, low 2-OHE1 /16α-OHE1 ratio, chemotherapy and hypertension, augment the production of antibodies against 16α-OHE1 -ERα in EC patients. 16α-OHE1 -ERα is a high-affinity antigen for EC antibodies in the serum of EC patients and might function as a biomarker for this disease. Furthermore, several factors enhanced the production of antibodies against 16α-OHE1 -ERα in the sera of these EC patients.

The trimer to monomer transition of Tumor Necrosis Factor-Alpha is a dynamic process that is significantly altered by therapeutic antibodies

The cytokine tumor necrosis factor-alpha (TNF-α) readily forms homotrimers at sub-nM concentrations to promote inflammation. For the treatment of inflammatory diseases with upregulated levels of TNF-α, a number of therapeutic antibodies are currently used as scavengers to reduce the active TNF-α concentration in patients. Despite their clinical success, the mode-of-action of different antibody formats with regard to a stabilization of the trimeric state is not entirely understood. Here, we use a biosensor with dynamic nanolevers to analyze the monomeric and trimeric states of TNF-α together with the binding kinetics of therapeutic biologics. The intrinsic trimer-to-monomer decay rate k = 1.7 × 10−3 s−1 could be measured directly using a microfluidic system, and antibody binding affinities were analyzed in the pM range. Trimer stabilization effects are quantified for Adalimumab, Infliximab, Etanercept, Certolizumab, Golimumab for bivalent and monovalent binding formats. Clear differences in trimer stabilization are observed, which may provide a deeper insight into the mode-of-action of TNF-α scavengers.

Genomic Sequencing and Analysis of Eight Camel-Derived Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Isolates in Saudi Arabia.

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe respiratory illness in humans; the second-largest and most deadly outbreak to date occurred in Saudi Arabia. The dromedary camel is considered a possible host of the virus and also to act as a reservoir, transmitting the virus to humans. Here, we studied evolutionary relationships for 31 complete genomes of betacoronaviruses, including eight newly sequenced MERS-CoV genomes isolated from dromedary camels in Saudi Arabia. Through bioinformatics tools, we also used available sequences and 3D structure of MERS-CoV spike glycoprotein to predict MERS-CoV epitopes and assess antibody binding affinity. Phylogenetic analysis showed the eight new sequences have close relationships with existing strains detected in camels and humans in Arabian Gulf countries. The 2019-nCov strain appears to have higher homology to both bat coronavirus and SARS-CoV than to MERS-CoV strains. The spike protein tree exhibited clustering of MERS-CoV sequences similar to the complete genome tree, except for one sequence from Qatar (KF961222). B cell epitope analysis determined that the MERS-CoV spike protein has 24 total discontinuous regions from which just six epitopes were selected with score values of >80%. Our results suggest that the virus circulates by way of camels crossing the borders of Arabian Gulf countries. This study contributes to finding more effective vaccines in order to provide long-term protection against MERS-CoV and identifying neutralizing antibodies.

Gold nanoparticles morphology does not affect the multivalent presentation and antibody recognition of Group A Streptococcus synthetic oligorhamnans.

The development of novel delivery systems capable of enhancing the antibody binding affinity and immunoactivity of short length saccharide antigens is at the forefront of modern medicine. In this regard, gold nanoparticles (AuNPs) raised great interest as promising nano-vaccine platform, as they do not interfere with the desired immune response and their surface can be easily functionalized, enabling the antigen multivalent presentation. In addition, the nanoparticles morphology can have a great impact on their biological properties. Gram-positive Group A Streptococcus (GAS) is a bacterium responsible for many infections and represents a priority healthcare concern, but a universal vaccine is still unavailable. Since all the GAS strains have a cell wall characterized by a common polyrhamnose backbone, this can be employed as alternative antigen to develop an anti-GAS vaccine. Herein, we present the synthesis of two oligorhamnoside fragments and their corresponding oligorhamnoside-AuNPs, designed with two different morphologies. By competitive ELISA we assessed that both symmetric and anisotropic oligorhamnan nanoparticles inhibit the binding of specific polyclonal serum much better than the unconjugated oligosaccharides.

Establishment and Application of Engineered NIH 3T3 Cell Line with Stable Human RAGE Expression

Abstract Aim NIH3T3 cell line with expression of human receptor for advanced glycation end-products (hRAGE) transduced with lentivirus vectors was used to analyze affinity, biological activity, and/or molecular mechanisms of molecules targeting the hRAGE pathway. Method The DNA fragment coding for hRAGE gene was integrated into the genome of NIH3T3 cells using lentivirus transduction. Cells expressing hRAGE were selected with puromycin, and the level of hRAGE expression was analyzed by Western blot. To establish a stable cell line, colonies of hRAGE-expressing cells were generated, and the level of RAGE expression in each engineered cell line was analyzed within 20 generations. Flow cytometry assay was used to verify affinity of anti-hRAGE antibody binding to hRAGE on the surface of engineered cells. The engineered NIH3T3 cell line was applied to assess effects of anti-hRAGE blocking antibody on amyloid β-induced cells apoptosis by CCK-8 assay. Results The engineered NIH3T3 cell line (hRAGE-NIH3T3) could stably express human RAGE. Commercial anti-RAGE polyclonal antibody could recognize and bind to human RAGE on the surface of hRAGE-NIH3T3 but not original NIH3T3 cells. In addition, hRAGE-NIH3T3 was more sensitive to RAGE pathway-dependent stimulation. Our data show that the hRAGE-NIH3T3 cell line established is an excellent tool in the study of RAGE-targeting molecules based on the cellular level, biological function, and RAGE-mediated molecular mechanisms.

Digital Receptor Occupancy Assay in Quantifying On- and Off-Target Binding Affinities of Therapeutic Antibodies.

While monoclonal antibodies are the fastest-growing class of therapeutic agents, we lack a method that can directly quantify the on- and off-target binding affinities of newly developed therapeutic antibodies in crude cell lysates. As a result, some therapeutic antibody candidates could have a moderate on-target binding affinity but a high off-target binding affinity, which not only gives a reduced efficacy but triggers unwanted side effects. Here, we report a single-molecule counting method that precisely quantifies antibody-bound receptors, free receptors, and unbound antibodies in crude cell lysates, termed digital receptor occupancy assay (DRO). Compared to the traditional flow cytometry-based binding assay, DRO assay enables direct and digital quantification of the three molecular species in solution without the additional antibodies for competitive binding. When characterizing the therapeutic antibody, cetuximab, using DRO assay, we found the on-target binding ratio to be 65% and the binding constant (Kd) to be 2.4 nM, while the off-target binding causes the binding constant to decrease by 0.3 nM. Other than cultured cells, the DRO assay can be performed on tumor mouse xenograft models. Thus, DRO is a simple and highly quantitative method for cell-based antibody binding analysis which can be broadly applied to screen and validate new therapeutic antibodies.

Binding Affinities Studies of Nitrated Model Peptides to Monoclonal Anti-3-nitrotyrosine Antibody

Tyrosine nitration has been shown to be an important oxidative protein modification and play a crucial role in pathophysiological conditions, associated with oxidative stress, such as atherosclerosis and neurodegenerative disease. For a better understanding of nitration mechanism, the identification and the quantification of nitration sites represents an important research goal. Due to (i) the low levels of nitration in native proteins, (ii) structural changes induced by nitration and (iii) the specificity of anti � 3 nitro tyrosine antibodies the method which may provide the identification of nitration sites in proteins represent a challenging experimental task. In this work we have used synthetic nitrated tyrosine containing peptides to determine antibody-binding affinities and specificity of different tyrosine residue (Tyr33, Tyr98, Tyr107and Tyr122) in Eosinophil cationic proteins (ECP). The highest affinity of nitrated ECP peptides to the monoclonal antibody (anti-3NT) was obtained for the only in vivo nitrated identified residue Tyr33(0.082 �M); in contrast, all other three nitrated residues at Tyr98, Tyr107 and Tyr122) showed significant lower affinity being imbedded in the ECP protein structure as similar resulted by molecular computational modeling.

Site-specific N-glycan Analysis of Antibody-binding Fc γ Receptors from Primary Human Monocytes

FcγRIIIa (CD16a) and FcγRIIa (CD32a) on monocytes are essential for proper effector functions including antibody dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP). Indeed, therapeutic monoclonal antibodies (mAbs) that bind FcγRs with greater affinity exhibit greater efficacy. Furthermore, post-translational modification impacts antibody binding affinity, most notably the composition of the asparagine(N)-linked glycan at N162 of CD16a. CD16a is widely recognized as the key receptor for the monocyte response, however the post-translational modifications of CD16a from endogenous monocytes are not described. Here we isolated monocytes from individual donors and characterized the composition of CD16a and CD32a N-glycans from all modified sites. The composition of CD16a N-glycans varied by glycosylation site and donor. CD16a displayed primarily complex-type biantennary N-glycans at N162, however some individuals expressed CD16a V158 with ∼20% hybrid and oligomannose types which increased affinity for IgG1 Fc according to surface plasmon resonance binding analyses. The CD16a N45-glycans contain markedly less processing than other sites with >75% hybrid and oligomannose forms. N38 and N74 of CD16a both contain highly processed complex-type N-glycans with N-acetyllactosamine repeats and complex-type biantennary N-glycans dominate at N169. The composition of CD16a N-glycans isolated from monocytes included a higher proportion of oligomannose-type N-glycans at N45 and less sialylation plus greater branch fucosylation than we observed in a recent analysis of NK cell CD16a. The additional analysis of CD32a from monocytes revealed different features than observed for CD16a including the presence of a predominantly biantennary complex-type N-glycans with two sialic acids at both sites (N64 and N145).

Association of variability in antibody binding affinity with a clinical course of anti-MAG neuropathy

Anti-myelin-associated glycoprotein (MAG) neuropathy is mediated by the binding of IgM M-proteins to the human natural killer-1 epitope of several glycoconjugates, including MAG and phosphacan. We recently reported that IgM M-proteins with a higher ratio of anti-phosphacan titer to anti-MAG titer (P/M ratio) were associated with a progressive clinical course. Herein, we investigated the temporal variability of the P/M ratio. The results showed that P/M ratios in worsened cases were significantly increased relative to stable or improved cases. Thus, temporal variability in the specificity of IgM M-proteins may be related to the disease course of anti-MAG neuropathy.

Engineering High Affinity and Cleavage Resistant CD16 to Augment ADCC of Placental Hematopoietic Stem Cells-Derived Natural Killer Cells

Background: Celularity, Inc. is developing human placental hematopoietic stem cells-derived, cryopreserved, off-the-shelf, ex-vivo expanded and allogenic natural killer (PNK) cells for various hematological malignancies and solid tumors. NK cells play a central role in antibody dependent cell mediated cytotoxicity (ADCC) through Fc receptor CD16 in monoclonal antibody mediated anti-tumor therapies. Two allelic forms of CD16 have been identified. The 158Val/Val form has shown to have higher IgG binding affinity compared to the 158Phe/Phe form.1 The high IgG binding allele are found in about 10-20% of the normal population.2,3 In addition, activation of NK cells induces CD16 shedding by matrix metalloprotease ADAM17 at 197Ser, thus limiting ADCC responses. A single mutation (Ser197Pro) prevents CD16 shedding and increases ADCC activity in NK cells.4 Since the antibody binding affinity and CD16 expression of PNK could vary with different donors, we hypothesize that expressing a high affinity (158Val) and proteinase cleavage resistant (197Pro) CD16 variant (CD16VP) augments anti-tumor ADCC activity. Methods: Lentivirus expressing CD16VP was used to transduce human placental CD34+ cells. After transduction, the cells were cultured in the presence of cytokines including thrombopoietin, SCF, Flt3 ligand, IL-7, IL-15 and IL-2, for 35 days to generate PNK-CD16VP cells. Non-transduced PNK cells (NT) served as a control. Expression of CD16VP was evaluated by activating cells with PMA/ionomycin to induce CD16 cleavage (CD16 shedding assay) followed by immunostaining with CD16 antibody and analyzed using flowcytometry. ADCC of PNK-CD16VP cells was assessed against Daratumumab (anti-CD38) or Rituximab (anti-CD20) opsonized lymphoma cell lines at various effector to target (E:T) ratios. IgG was used as ADCC control. In vivo anti-tumor activity was assessed in a Daudi disseminated Xenograft model in NSG mice. Luciferase-expressing Daudi cells (3x106) were intravenously (IV) administered at day 0, followed by PNK-CD16VP cells (10x106) IV at day 1 and day 3, and Daratumumab at day 3. Tumor burden in mice was monitored by Bioluminescence Imaging (BLI). Statistical differences between the groups were calculated using paired t-test using Prism. Results: Lentiviral transduction of CD16VP achieved high expression efficiency in multiple placental CD34+ donors. These cells expanded [7095 ± 2998 folds (n=8)] and differentiated into PNK cells (&amp;gt;90% CD56+CD3-) at day 35. PNK-CD16VP expressed 64.6 ± 10.3% (n=8) of CD16, while the NT expressed 12.1 ± 3.3% (n=8) CD16. PMA/ionomycin induced &amp;gt;89% shedding of CD16 in NT cells, while significantly less (&amp;lt;11%) CD16 shedding was observed in PNK-CD16VP cells. These results indicated that CD16VP was expressed and maintained throughout the culture process. In vitro ADCC assay demonstrated improved anti-tumor activity of PNK-CD16VP cells over NT cells against Daratumumab or Rituximab opsonized lymphoma cell lines. At 10:1 E:T ratio PNK-CD16VP cells elicited higher cytotoxicity compared to NT: 47 ± 13% against Daratumumab opsonized Daudi cells versus 25 ± 5% (n=5; p&amp;lt;0.05); 30 ± 13% against Daratumumab opsonized HS-Sultan cells versus 21 ± 14% (n=3; p&amp;lt;0.05); 30 ± 7% against Daratumumab opsonized Sudhl6 cells versus 16 ± 10% (n=3; p&amp;lt;0.05). Improved ADCC activities in PNK-CD16VP were also observed in other cell lines including Raji and Sudhl4 with Daratumumab and Rituximab antibodies. PNK-CD16VP were used to test anti-tumor ADCC in vivo using a disseminated Daudi Xenograft model. The preliminary data demonstrated that PNK-CD16VP combined with Daratumumab reduced BLI signal (&amp;gt;50%) compared to vehicle or Daratumumab alone at day 10 after treatment. This observation suggested that PNK-CD16VP demonstrated in vivo ADCC anti-tumor activity. Conclusions: In this study, we genetically modified PNK to express high affinity and cleavage resistant CD16 variant using lentivirus. The PNK-CD16VP cells demonstrated enhanced ADCC function against lymphoma cell lines in vitro and in vivo. Further development of PNK-CD16VP for immune-oncology therapeutics is warranted.

Recurrent Patterns of Clonal Evolution in Relapsed-Refractory DLBCL Following Treatment with R-CHOP

Introduction Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma and is characterized by its genetic and clinical heterogeneity. Patients can develop DLBCL de novo or as a transformation from other lymphoid malignancies, most commonly follicular lymphoma. For patients with relapsed/refractory DLBCL (rrDLBCL), prognosis is extremely poor with 2-year overall survival of 20-40%. While numerous treatments are under investigation to improve patient outcomes, the success of these treatments has been limited as the genetic mechanisms underpinning treatment resistance are largely unknown. Identifying genomic alterations which contribute to relapse may improve salvage therapy for patients with rrDLBCL or allow patients to be stratified prior to frontline treatment. Methods To identify genomic alterations which contribute to R-CHOP resistance, we previously collected samples from patients enrolled in four clinical trials exploring candidate salvage therapies for patients with rrDLBCL as well as a retrospective rrDLBCL cohort, totalling 193 cases (133 de-novo DLBCL, 60 transformed). Plasma samples were collected from each patient upon relapse along with diagnostic tissue biopsies where available. A combination of exome sequencing and target-panel sequencing of lymphoma associated genes was performed on circulating tumour DNA and tissue biopsies (if available). Mutations implicated in R-CHOP resistance were identified through two complimentary strategies. First, the mutation frequency of recurrently mutated genes across de novo rrDLBCL samples was compared to a cohort of unrelated diagnostic DLBCL cases (n=1691) to identify genes enriched for mutations. Second, the genomic landscape and tumor clonal structure was compared prior to and following R-CHOP to identify mutations in each patient that underwent clonal expansion following therapy. Anti-CD20 antibody binding affinity of MS4A1 mutants was evaluated using flow cytometry on transfected CHO-S cells. Results We have identified five genes enriched for mutations in our rrDLBCL cohort relative to diagnostic DLBCL: KMT2D (Mutated in 49%, Q=0.0385), TP53 (47%, Q=1.07x10-9), FOXO1 (11%, Q=0.0727), NFKBIE (11%, Q=0.0385), and MS4A1 (8%, Q=0.0522). Consistent with its characterization as a poor prognostic marker, mutations in TP53 were typically present at diagnosis and remained stable following R-CHOP therapy for both de novo and transformed DLBCL (23/27 cases, 85%). Recurrent mutations affecting Arg248 of TP53 (6.8%, Q=0.0413) were also clonally stable and have previously been associated with poor overall survival across several cancer types. The histone methyltransferase KMT2D is dominated by nonsense and frameshift mutations which were stable or underwent clonal expansion following R-CHOP (17/19, 89%). Recurrent missense mutations in MS4A1 targeted the small loop and adjacent transmembrane domains of CD20, including several patients with a Tyr86 mutation. Transfected cells carrying Tyr86Cys or Leu66Arg mutations were not bound by rituximab or other anti-CD20 antibodies including obinituzumab and ofatumumab. Subclonal populations containing MS4A1 mutations underwent clonal expansion (6 cases) or were stable (1 case) following treatment, including one case with multiple MS4A1 mutations in distinct subclonal populations which both underwent clonal expansion. In another unique case, a series of ctDNA samples were available prior to and following R-CHOP and salvage therapy, where we again observed convergent evolution of two mutually exclusive clonal subpopulations containing MS4A1 mutations. The first subpopulation underwent clonal expansion following frontline therapy but was extinguished following salvage therapy, while the other subpopulation underwent clonal expansion following salvage therapy and harboured a transmembrane domain mutation. Conclusion Mutations in TP53 and truncating mutations in KMT2D are generally present prior to treatment and will be investigated as biomarkers of treatment failure. Additional mutations are not always present at diagnosis, but their emergence can be detected in ctDNA and relapsed tissue, specifically mutations in MS4A1. As mutations in MS4A1 attenuate rituximab binding and are recurrently associated with clonal expansion, they likely impart a selective advantage and lead to resistance against anti-CD20 antibodies. Disclosures Michaud: Epizyme: Employment. Daigle:Epizyme: Employment. Jain:Kite/Gilead: Consultancy. Kuruvilla:Roche: Honoraria; Astra Zeneca: Honoraria; Novartis: Honoraria; Merck: Honoraria; Karyopharm: Honoraria; Gilead: Honoraria; Celgene: Honoraria; BMS: Honoraria; Amgen: Honoraria; Seattle Genetics: Consultancy; Roche: Consultancy; Merck: Consultancy; Karyopharm: Consultancy; Gilead: Consultancy; Janssen: Research Funding; Roche: Research Funding; BMS: Consultancy; Abbvie: Consultancy; Seattle Genetics: Honoraria; Janssen: Honoraria. Assouline:Abbvie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Speakers Bureau. Scott:NanoString: Patents &amp; Royalties: Named inventor on a patent licensed to NanoSting [Institution], Research Funding; Celgene: Consultancy; Roche/Genentech: Research Funding; Janssen: Consultancy, Research Funding. Johnson:BD Biosciences: Other: Provided a significant proportion of the antibodies used in this project free of cost.; Merck: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Abbvie: Consultancy, Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel fees, gifts, and others, Research Funding; Seattle Genetics: Honoraria; Lundbeck: Employment, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel fees, gifts, and others, Research Funding.

Termination of bleeding by a specific, anticatalytic antibody against plasmin

BackgroundExcessive, plasmin‐mediated fibrinolysis augments bleeding and contributes to death in some patients. Current therapies for fibrinolytic bleeding are limited by modest efficacy, low potency, and off‐target effects. ObjectivesTo determine whether an antibody directed against unique loop structures of the plasmin protease domain may have enhanced specificity and potency for blocking plasmin activity, fibrinolysis, and experimental hemorrhage. MethodsThe binding specificity, affinity, protease cross‐reactivity and antifibrinolytic properties of a monoclonal plasmin inhibitor antibody (Pi) were examined and compared with those of epsilon aminocaproic acid (EACA), which is a clinically used fibrinolysis inhibitor. ResultsPi specifically recognized loop 5 of the protease domain, and did not bind to other serine proteases or nine other non‐primate plasminogens. Pi was ~7 logs more potent in neutralizing plasmin cleavage of small‐molecule substrates and >3 logs more potent in quenching fibrinolysis than EACA. Pi was similarly effective in blocking catalysis of a small‐molecule substrate as α2‐antiplasmin, which is the most potent covalent inhibitor of plasmin, and was a more potent fibrinolysis inhibitor. Fab or chimerized Fab fragments of Pi were equivalently effective. In vivo, in a humanized model of fibrinolytic surgical bleeding, Pi significantly reduced bleeding to a greater extent than a clinical dose of EACA. ConclusionsA mAb directed against unique loop sequences in the protease domain is a highly specific, potent, competitive plasmin inhibitor that significantly reduces experimental surgical bleeding in vivo.

Removal of N-Linked Glycosylation Enhances PD-L1 Detection and Predicts Anti-PD-1/PD-L1 Therapeutic Efficacy

Reactivation of Tcell immunity by PD-1/PD-L1 immune checkpoint blockade has been shown to be a promising cancer therapeutic strategy. However, PD-L1 immunohistochemical readout is inconsistent with patient response, which presents a clinical challenge to stratify patients. Because PD-L1 is heavily glycosylated, we developed a method to resolve this by removing the glycan moieties from cell surface antigens via enzymatic digestion, a process termed sample deglycosylation. Notably, deglycosylation significantly improves anti-PD-L1 antibody binding affinity and signal intensity, resulting in more accurate PD-L1 quantification and prediction of clinical outcome. This proposed method of PD-L1 antigen retrieval may provide a practical and timely approach to reduce false-negative patient stratification for guiding anti-PD-1/PD-L1 therapy.

Differences in the Binding Affinity of an HIV-1 V2 Apex-Specific Antibody for the SIVsmm/mac Envelope Glycoprotein Uncouple Antibody-Dependent Cellular Cytotoxicity from Neutralization.

As a consequence of their independent evolutionary origins in apes and Old World monkeys, human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency viruses of the SIVsmm/mac lineage express phylogenetically and antigenically distinct envelope glycoproteins. Thus, HIV-1 Env-specific antibodies do not typically cross-react with the Env proteins of SIVsmm/mac isolates. Here we show that PGT145, a broadly neutralizing antibody to a quaternary epitope at the V2 apex of HIV-1 Env, directs the lysis of SIVsmm/mac-infected cells by antibody-dependent cellular cytotoxicity (ADCC) but does not neutralize SIVsmm/mac infectivity. Amino acid substitutions in the V2 loop of SIVmac239 corresponding to the epitope for PGT145 in HIV-1 Env modulate sensitivity to this antibody. Whereas a substitution in a conserved N-linked glycosylation site (N171Q) eliminates sensitivity to ADCC, a lysine-to-serine substitution in this region (K180S) increases ADCC and renders the virus susceptible to neutralization. These differences in function correlate with an increase in the affinity of PGT145 binding to Env on the surface of virus-infected cells and to soluble Env trimers. To our knowledge, this represents the first instance of an HIV-1 Env-specific antibody that cross-reacts with SIVsmm/mac Env and illustrates how differences in antibody binding affinity for Env can differentiate sensitivity to ADCC from neutralization.IMPORTANCE Here we show that PGT145, a potent broadly neutralizing antibody to HIV-1, directs the lysis of SIV-infected cells by antibody-dependent cellular cytotoxicity but does not neutralize SIV infectivity. This represents the first instance of cross-reactivity of an HIV-1 Env-specific antibody with SIVsmm/mac Env and reveals that antibody binding affinity can differentiate sensitivity to ADCC from neutralization.

Abstract 1149: Systems pathology by Optra 30 color multiplex immunofluorescence automated whole slide imaging system integrated with image analysis

Abstract Background A paradigm shift from single marker immunohistochemistry (IHC) to multiplexing in molecular histopathology has helped better understand the cellular composition and heterogeneity of sub population of cells in tissues. Presently, one needs to manually exchange filters after each multiplex scan for capturing all fluorophores per staining round. This is very cumbersome and inefficient, as this process requires rescanning the same slide multiple times. Moreover, visual assessment and quantification of biomarkers is limited by inter and intra-observer variability. We hereby present an automated multispectral whole-slide imaging system integrated with image analysis for detection of upto 30-color multiplex assay with spectral unmixing and cell segmentation functionality. Material and Methods Multiplex IHC whole slide imaging Formalin Fixed Paraffin Embedded rat brain; indirect IHC stained sections with 10 antibodies using photostable fluorophores were obtained. The staining was based on antigenic integrity and antibody binding affinity. Optra's multispectral fluorescent whole slide scanning process was optimized to image sensitive antigens in early cycles and robust antigens in latter cycles. The fully automated fluorescence scanning system imaged weakly expressing biomarkers in the visible range (480-620 nm), highly expressing targets in the violet/blue (405-440 nm), far-red (650-680 nm) and NIR (700-800 nm) range across the entire usable light spectrum (350-800 nm). ResultsWe could simultaneously detect up to 30 biomarkers within a single tissue section, using 12 staining-imaging-stripping cycles, with 10 antibodies screened per cycle. Software measures enabled separation of spectrally overlapping markers in the multiplex assay. A computer-controlled X-Y-Z stage used autofocusing at 20X/40X magnification. Integrated image analysis solution performed comprehensive evaluation of antigens of interest with accurate quantification of the target proteins based on parameters including but not limited to hue value/width, intensity threshold scoring, morphological characterization, pixel-count thresholding and color saturation. Conclusion This proposed solution is efficient compared to the current imaging methods to tackle the aforementioned image acquisition and image analysis challenges associated with multiplexing assays. Note: This abstract was not presented at the meeting. Citation Format: Abhi Gholap, Anagha P. Jadhav, Suraj Somwanshi, Gurunath Kamble, Isha Doshi, Jiaoti Huang. Systems pathology by Optra 30 color multiplex immunofluorescence automated whole slide imaging system integrated with image analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1149.

Perlecan-targeted nanoparticles for drug delivery to triple-negative breast cancer.

Aim:We previously developed two antibodies that bind to a cell surface protein, perlecan, overexpressed in triple-negative breast cancer (TNBC). The goal of this study was to investigate these antibodies as targeting ligands for nanoparticle-mediated drug delivery.Methods:Paclitaxel-loaded poly(D,L-lactide-co-glycolide) nanoparticles were functionalized with antibodies using thiol–maleimide chemistry. Effect of antibody functionalization on therapeutic efficacy of drug-loaded nanoparticles was investigated using in vitro and in vivo models of TNBC.Results:The antibodies were covalently conjugated to nanoparticles without affecting antibody binding affinity or nanoparticle properties. Perlecan-targeted nanoparticles showed improved cell uptake, retention, cytotoxicity in vitro and enhanced tumor growth inhibition in vivo.Conclusion:The data presented here indicates that perlecan-targeted nanoparticles can improve tumor drug delivery to TNBC.

Abstract 1551: First in class immunotherapy targeting Galectin-9 promotes T-cell activation and anti-tumor response against pancreatic cancer and other solid tumors

Abstract Background: Pancreatic adenocarcinoma (PDA) is one of the deadliest forms of cancer, with a five-year survival rate at or below seven percent. Current immunotherapies show promise in treating other cancers, but success remains elusive for pancreatic cancer. Poor prognosis in pancreatic cancer is invariably linked to immune dysfunction. We have shown that in PDA, Galectin-9 (Gal-9) plays a significant role in facilitating a tumor-permissive immune microenvironment. Specifically, Gal-9 modulates immunosuppression via binding to multiple partner molecules (TIM-3, Dectin-1, CD44, CD206 etc). In light of these findings, we have developed and characterized first-in-class, therapeutic monoclonal antibodies to target Gal-9 and impede tumor growth. Methods: A proprietary synthetic, human antibody library was screened via phage display to identify high-affinity antibodies cross-reactive with human, cynomolgus and rodent Gal-9, to enable efficacy and toxicity studies. We used surface plasmon resonance and bead-based assays to measure antibody binding affinity. ELISA and cell-based approaches were used to demonstrate antibody blockade of Gal-9 binding to known ligands, inferring potential therapeutic efficacy. Efficacy in multiple IgG formats were assayed using KPC (Pdx1Cre; KrasG12D; Tp53R172H)-derived cancer cells implanted orthotopically into the pancreas of C57BL/6 mice. Patient-derived organotypic tumor spheroids (PDOTs) derived from PDA and other GI tumors, which recapitulate complex tumor architecture, were treated with anti-Gal-9 antibodies and resulting immune profile was analyzed via flow cytometry. Results: Our lead clinical candidate Gal-9 antibodies exhibit specific binding towards mouse, cynomolgus and human Gal-9 with KDvalues in the sub nanomolar range. These antibodies potently block Gal-9 interactions with known ligands such as CD206 and Dectin-1. These antibodies also inhibit Gal-9 mediated apoptosis of Jurkat cells. Mice bearing orthotopic pancreatic tumors treated with Gal-9 antibodies induced significant reduction in tumor size (p&amp;lt;0.005) compared with relevant controls. Immune profiling showed increased T cell activation and modulation of the monocytic compartment towards an immune permissive state. PDOTs showed similar immune profiles including an increase in type 1 inflammatory cytokines and effector T cell activation. Conclusions: Our Gal-9 lead therapeutic antibody has been identified, characterized and is being further assessed in expanding pre-clinical efficacy, molecular and safety studies in preparation for an IND filing. Our data demonstrate novel cancer immune biology with therapeutic implications of a first-in-class monoclonal antibody against Gal-9 to reverse immunosuppressive mechanisms contributing to tumor growth immune escape in pancreatic cancer and other solid tumors. Citation Format: Linxiao Chen, Wei Wang, Akiko Koide, Joseph Bolen, George Miller, Shohei Koide. First in class immunotherapy targeting Galectin-9 promotes T-cell activation and anti-tumor response against pancreatic cancer and other solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1551.

Broadly resistant HIV-1 against CD4-binding site neutralizing antibodies.

Recently identified broadly neutralizing antibodies (bnAbs) show great potential for clinical interventions against HIV-1 infection. However, resistant strains may impose substantial challenges. Here, we report on the identification and characterization of a panel of HIV-1 strains with broad and potent resistance against a large number of bnAbs, particularly those targeting the CD4-binding site (CD4bs). Site-directed mutagenesis revealed that several key epitope mutations facilitate resistance and are located in the inner domain, loop D, and β23/loop V5/β24 of HIV-1 gp120. The resistance is largely correlated with binding affinity of antibodies to the envelope trimers expressed on the cell surface. Our results therefore demonstrate the existence of broadly resistant HIV-1 strains against CD4bs neutralizing antibodies. Treatment strategies based on the CD4bs bnAbs must overcome such resistance to achieve optimal clinical outcomes.

Epitope approach in molecular imprinting of antibodies

Herein an approach to prepare molecularly imprinted polymer nanoparticles (nanoMIPs) with specific binding affinity for antibodies is reported. The process relied on the covalent immobilization of the template (whole immunoglobulin G (IgG), Fc domain of human IgG and peptide epitope) onto the surface of a solid support, polymerization and affinity separation of nanoMIPs. The binding between nanoMIPs and their corresponding templates was analyzed and evaluated as being in sub-nanomolar and nano-molar range. The nanoMIPs prepared for Fc domain and epitope demonstrated a specific recognition of both human and goat IgGs, therefore they could be considered as a synthetic analogue of protein A and benefit from its intrinsic stability, short time and low cost of preparation.

Multifunctional iron oxide-carbon hybrid nanoparticles for targeted fluorescent/MR dual-modal imaging and detection of breast cancer cells

An efficient method for the highly sensitive and specific detection of cancer cells is crucial for the early diagnosis of cancer. In this work, we propose a one-pot approach to fabricating magnetic-fluorescent iron oxide-carbon hybrid nanomaterials (MCNP) with excellent stable, high quantum yield and excellent magnetic properties for breast cancer cells recognition and detection via magnetic resonance and multicolour fluorescence imaging. MCNPs were efficiently synthesised via one-pot, multi-component reactions of FeCl3, FeCl2•4H2O, citric acid and ethylenediamine in diethylene glycol. The MCNPs showed strong excitation wavelength-dependent fluorescence in the blue-red region with a high quantum yield of 58.4%, and they presented higher stability and T2 relaxivity than pure iron oxide nanoparticles. After conjugating with CD44 monoclonal antibodies, the fabricated targeting nanoprobe, MCNPs-CD44, demonstrated a specific fluorescence/MRI dual imaging contrast effect in 4T1 breast cancer cells. Biological transmission electron microscope imaging showed a significant preferential uptake of the nanoparticle conjugates by the 4T1 cells. By taking advantage of the high binding affinity and specificity of the CD44 antibodies to the overexpressed CD44 on the cancer cell surface, the developed MCNPs-CD44 probe distinguished 4T1 breast cancer cells from normal cells and detected as low as a few hundred cancer cells, thus indicating the potential application of multifunctional nanocomposites in the MR diagnosis and fluorescence positioning of breast cancer at cellular-level resolution.