Distinct Monoclonal Antibodies Research Articles

A Pan-Ebolavirus Monoclonal Antibody Cocktail Provides Protection Against Ebola and Sudan Viruses.

Filoviruses, including ebolaviruses and marburgviruses, can cause severe and often fatal disease in humans. Over the past several years, antibody therapy has emerged as a promising strategy for the treatment of filovirus disease. Here, we describe 2 distinct cross-reactive monoclonal antibodies (mAbs) isolated from mice immunized with recombinant vesicular stomatitis virus-based filovirus vaccines. Both mAbs recognized the glycoproteins of multiple different ebolaviruses and exhibited broad but differential in vitro neutralization activities against these viruses. By themselves, each mAb provided partial to full protection against Ebola virus in mice, and in combination, the mAbs provided 100% protection against Sudan virus challenge in guinea pigs. This study identified novel mAbs that were elicited through immunization and able to provide protection from ebolavirus infection, thus enriching the pool of candidate therapeutics for treating Ebola disease.

Evaluating multiproduct chromatography Protein A resinreuse for monoclonal antibodies in biopharmaceutical manufacturing.

In good manufacturing practice (GMP) facilities in the biopharmaceutical industry, chromatography resins are largely underutilized during purification of single drug products during clinical production. Chromatography resins are dedicated to a specific product and disposed of, after only a fraction of their lifetime due to concerns of potential product carryover from one program to another. In this study, we follow a resin lifetime methodology typically used for commercial submissions and apply it to determine the feasibility of purifying different products on a Protein A MabSelect PrismA™ resin. Three distinct monoclonal antibodies were used as model molecules. Column performance was monitored through chromatogram profiles, yield, clearance capability of selected media components, pressure and product quality. A protein carryover study was designed to demonstrate that the column cleaning procedures reduced protein carryover to safe cleanliness levels regardless of multiple product contact cycles and the order in which the mAbs are captured. Data show that up to 90 total cycles (30 cycles per antibody), there was negligible protein carryover and impact on process performance. Product quality was consistent, with the only meaningful trends found for the leached Protein A ligand, without affecting the conclusion of the study. While the study was restricted to three antibodies, the proof of concept for resin reuse was demonstrated.

Biolayer Interferometry Analysis for a Higher Throughput Quantification of In-Process Samples of a Rotavirus Vaccine.

Rotavirus A infection is a global leading cause of severe acute gastroenteritis associated with life-threatening diarrheal episodes in infants and young children. The disease burden is being reduced, namely due to a wider access to rotavirus vaccines. However, there is a demand to expand rotavirus vaccination programs, and to achieve this, it is critical to improve high-throughput in-process product quality control and vaccine manufacturing monitoring. Here, we present the development of an analytical method for the quantification of rotavirus particles contained in a licensed vaccine. The binding of rotavirus proteins to distinct glycoconjugate receptors and monoclonal antibodies was evaluated using biolayer interferometry analysis, applied on an Octet platform. The antibody strategy presented the best results with a linear response range within 2.5 × 107–1.0 × 108 particles·mL−1 and limits of detection and quantification of 2.5 × 106 and 7.5 × 106 particles·mL−1, respectively. Method suitability for the quantification of in-process samples was shown using samples from different manufacturing stages and their titers were comparable with the approved CCID(50) method. This cell-free method enables a fast and high-throughput analysis, compatible with time constraints during bioprocess development and it is suitable to be adapted to other viral particle-based drug products.

Discovery of functionally distinct anti-C7 monoclonal antibodies and stratification of anti-nicotinic AChR positive Myasthenia Gravis patients.

Myasthenia Gravis (MG) is mediated by autoantibodies against acetylcholine receptors that cause loss of the receptors in the neuromuscular junction. Eculizumab, a C5-inhibitor, is the only approved treatment for MG that mechanistically addresses complement-mediated loss of nicotinic acetylcholine receptors. It is an expensive drug and was approved despite missing the primary efficacy endpoint in the Phase 3 REGAIN study. There are two observations to highlight. Firstly, further C5 inhibitors are in clinical development, but other terminal pathway proteins, such as C7, have been relatively understudied as therapeutic targets, despite the potential for lower and less frequent dosing. Secondly, given the known heterogenous mechanisms of action of autoantibodies in MG, effective patient stratification in the REGAIN trial may have provided more favorable efficacy readouts. We investigated C7 as a target and assessed the in vitro function, binding epitopes and mechanism of action of three mAbs against C7. We found the mAbs were human, cynomolgus monkey and/or rat cross-reactive and each had a distinct, novel mechanism of C7 inhibition. TPP1820 was effective in preventing experimental MG in rats in both prophylactic and therapeutic dosing regimens. To enable identification of MG patients that are likely to respond to C7 inhibition, we developed a patient stratification assay and showed in a small cohort of MG patients (n=19) that 63% had significant complement activation and C7-dependent loss of AChRs in this in vitro set up. This study provides validation of C7 as a target for treatment of MG and provides a means of identifying patients likely to respond to anti-C7 therapy based on complement-activating properties of patient autoantibodies.

Neutralizing Monoclonal Antibodies against the Gn and the Gc of the Andes Virus Glycoprotein Spike Complex Protect from Virus Challenge in a Preclinical Hamster Model.

Hantaviruses are the etiological agent of hemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). The latter is associated with case fatality rates ranging from 30% to 50%. HCPS cases are rare, with approximately 300 recorded annually in the Americas. Recently, an HCPS outbreak of unprecedented size has been occurring in and around Epuyén, in the southwestern Argentinian state of Chubut. Since November of 2018, at least 29 cases have been laboratory confirmed, and human-to-human transmission is suspected. Despite posing a significant threat to public health, no treatment or vaccine is available for hantaviral disease. Here, we describe an effort to identify, characterize, and develop neutralizing and protective antibodies against the glycoprotein complex (Gn and Gc) of Andes virus (ANDV), the causative agent of the Epuyén outbreak. Using murine hybridoma technology, we generated 19 distinct monoclonal antibodies (MAbs) against ANDV GnGc. When tested for neutralization against a recombinant vesicular stomatitis virus expressing the Andes glycoprotein (GP) (VSV-ANDV), 12 MAbs showed potent neutralization and 8 showed activity in an antibody-dependent cellular cytotoxicity reporter assay. Escape mutant analysis revealed that neutralizing MAbs targeted both the Gn and the Gc. Four MAbs that bound different epitopes were selected for preclinical studies and were found to be 100% protective against lethality in a Syrian hamster model of ANDV infection. These data suggest the existence of a wide array of neutralizing antibody epitopes on hantavirus GnGc with unique properties and mechanisms of action.IMPORTANCE Infections with New World hantaviruses are associated with high case fatality rates, and no specific vaccine or treatment options exist. Furthermore, the biology of the hantaviral GnGc complex, its antigenicity, and its fusion machinery are poorly understood. Protective monoclonal antibodies against GnGc have the potential to be developed into therapeutics against hantaviral disease and are also great tools to elucidate the biology of the glycoprotein complex.

A kinetic ELISA to determine the immunoreactive fraction of monoclonal antibodies

We developed a two-step ELISA to determine the immunoreactive fraction of monoclonal antibodies in conditions of antigen excess. An antibody aliquot at limiting dilution was incubated in wells coated with increasing amounts of antigen up to concentrations that bind 100% of antibody. At equilibrium, a supernatant aliquot was transferred to a second plate coated with excess of antiglobulin, and the captured antibody was incubated with peroxidase-conjugated anti-IgG. Antibody was quantitated from the enzyme velocity gradient in a kinetic ELISA, and the immunoreactive fraction calculated as (1 - gradienti/gradientT) x 100, where i and T are the gradients for the free and total antibody fractions. For four distinct monoclonal antibodies (anti-diphtheria toxoid, −cholera toxin, −bovine serum albumin (BSA), and -trinitrophenyl-BSA), measurement of inter-assay variability yielded values ranging from 3.1 to 7.4 (% coefficient of variation), which supports method repeatability. This ELISA is simple, precise, and applicable to mono- and polyclonal antibodies.

Distinguishing Features of Cetuximab and Panitumumab in Colorectal Cancer and Other Solid Tumors.

Cetuximab and panitumumab are two distinct monoclonal antibodies (mAbs) targeting the epidermal growth factor receptor (EGFR), and both are widely used in combination with chemotherapy or as monotherapy to treat patients with RAS wild-type metastatic colorectal cancer. Although often considered interchangeable, the two antibodies have different molecular structures and can behave differently in clinically relevant ways. More specifically, as an immunoglobulin (Ig) G1 isotype mAb, cetuximab can elicit immune functions such as antibody-dependent cell-mediated cytotoxicity involving natural killer cells, T-cell recruitment to the tumor, and T-cell priming via dendritic cell maturation. Panitumumab, an IgG2 isotype mAb, does not possess these immune functions. Furthermore, the two antibodies have different binding sites on the EGFR, as evidenced by mutations on the extracellular domain that can confer resistance to one of the two therapeutics or to both. We consider a comparison of the properties of these two antibodies to represent a gap in the literature. We therefore compiled a detailed, evidence-based educational review of the known molecular, clinical, and functional differences between the two antibodies and concluded that they are distinct therapeutic agents that should be considered individually during treatment planning. Available data for one agent can only partly be extrapolated to the other. Looking to the future, the known immune activity of cetuximab may provide a rationale for this antibody as a combination partner with investigational chemotherapy plus immunotherapy regimens for colorectal cancer.

Rapid and accurate in silico solubility screening of a monoclonal antibody library

Antibodies represent essential tools in research and diagnostics and are rapidly growing in importance as therapeutics. Commonly used methods to obtain novel antibodies typically yield several candidates capable of engaging a given target. The development steps that follow, however, are usually performed with only one or few candidates since they can be resource demanding, thereby increasing the risk of failure of the overall antibody discovery program. In particular, insufficient solubility, which may lead to aggregation under typical storage conditions, often hinders the ability of a candidate antibody to be developed and manufactured. Here we show that the selection of soluble lead antibodies from an initial library screening can be greatly facilitated by a fast computational prediction of solubility that requires only the amino acid sequence as input. We quantitatively validate this approach on a panel of nine distinct monoclonal antibodies targeting nerve growth factor (NGF), for which we compare the predicted and measured solubilities finding a very close match, and we further benchmark our predictions with published experimental data on aggregation hotspots and solubility of mutational variants of one of these antibodies.

Construction and Testing of Two Distinct Humanized CD19-Specific Chimeric Antigen Receptors (CARs) for the Treatment of B-Cell Malignancies

Introduction: Modificiation of T cells using CD19-specific chimeric antigen receptor (CAR) therapy has produced dramatic responses against a number of hematologic malignancies in multiple clinical trials. To date, most of the CARs studied in clinical trials are derived from mouse single chain fragment variable (scFv), which can elicit an immune response when infused into human patients and thereby can limit the persistency of CAR-T cells. Indeed, a subset of patients with limited persistency of infused CAR-Ts has been observed in clinical trials. However, this can be overcome by utilizing the humanized scFv in CAR design. Here, we constructed two new CD19-specific CARs, which are derived from the scFv of two distinct humanized CD19 antibody clones and compared them with the widely used CD19-CAR derived from a mouse scFv (FMC63).Methods: Lentiviral constructs encoding FMC63-BBZ CAR was generated based on the published sequence of FMC63 scFV and cloned in to a lentiviral vector driven by an EF1α promoter. The FMC63-BBZ CAR sequence was fused in frame with T2A ribosomal skip sequence followed by a puromycin resistance gene (PAC). Humanized CD19-Specific CARs were generated by replacing the FMC63 sequence with two humanized CD19-specific scFv sequences that were derived from two distinct humanized monoclonal antibodies. 293FT cells were used to make lentiviruses and the concentrated viruses were used to infect T-cells from healthy donors, NK92MI and Jurkat-NFAT-GFP (JNG) cells. Surface expressions of CARs were detected by protein-L staining using flow cytometry. Cytolytic activity of CAR-engineered T and NK cells was measured using a 4 hour co-culture assay. Cytokines (IL-2, IFN-γ and TNF-α) were measured from the co-cultured supernatants by ELISA.Results: We were able to infect primary-T cells, NK92MI and JNG cells using the FMC63 and humanized CAR constructs, and the surface expression of CARs was comparable between them. Co-culture of JNG cells stably expressing the FMC63 or humanized CARs with CD19+ve Raji (Burkitt Lymphoma), Nalm6 (Pre- B-cell acute lymphoblastic leukemia) and BV173 (Chronic Myeloid Leukemia) cancer cells lead to robust expression of GFP (indicative of activated NFAT signaling), CD69 (an activation marker for cytotoxic cells), and a rapid increase in the secretion of IL-2. None of these effects were observed in unmodified JNG cells or with the co-culture of JNG cells stably expressing FMC63 or humanized CARs with CD19-ve HL60 (Acute Promyelocytic Leukemia) and U937 (Histiocytic Lymphoma) cancer cells. Next, we made stable NK92MI cells expressing FMC63, humanized CD19-specific CARs, and a control CAR, followed by cellular cytotoxicity assay. Both FMC63-CAR and humanized CD19-CARs expressing NK92MI cells readily eliminated CD19+ve cancer cells, whereas they had no discernible effect on CD19-ve cancer cells. Furthermore, parental or a control CAR expressing NK92MI cells are without any effect, either with CD19+ve or CD19-ve cancer cells, thereby strictly highlighting the comparable specificity of our humanized CD19-CARs with FMC63-CAR against CD19+ve cells. More importantly, co-culture of NK92MI cells stably expressing FMC63-CAR and humanized CD19-CARs with direct patient samples [CD19+ve B-ALLs and CD19-ve Acute Myelogenous Leukemia’s (AMLs)] eliminated only the patient B-ALLs, but without any effect on patient AMLs. Also, increased surface expression of CD69 and robust secretion of cytokines (IFN-γ and TNF-α) were observed only when FMC63 or humanized CD19-CARs expressing NK92MI cells were incubated with CD19+ve patient B-ALLs. Finally, expression of FMC63and humanized CD19-CARs in primary donor T-cells also resulted in the elimination CD19+ve cancer cells along with a significant increase in the secretion of cytokines. Most importantly, both humanized CD19-specific CARs significantly increased the survival of CD19+ve cancer cells bearing NSG mice, whereas the unmodified T-cells or the T-cells expressing a non-specific CAR were without any effect.Conclusion: Our extensive pre-clinical study clearly shows that humanized CD19-specific CAR-T or NK cells exhibit comparable potency with the widely used FMC63-CAR, which provides the basis for the clinical testing of these humanized CARs in CD19+ve malignancies, thereby allaying the possible concern on immune mediated rejection of mouse scFv based CD19-CAR therapy. DisclosuresNo relevant conflicts of interest to declare.

Development of a lateral flow immunochromatographic assay for the rapid diagnosis of Orf virus infections

A rapid and simple lateral-flow immunochromatographic assay (LFIA) was developed for the specific detection of Orf virus (ORFV) using two distinct monoclonal antibodies (MAbs: 5A5 and 6F2) against the ORFV ORF011 protein. The MAb 5A5 was conjugated with colloidal gold, and the MAb 6F2 and goat anti-mouse IgG were sprayed onto a nitrocellulose membrane in strips at positions designated test (T) and control (C), respectively. The results showed that samples of ORFV complexed with colloidal gold-conjugated MAb 5A5, were captured by MAb 6F2 at the T line resulting in the appearance of a purple band. When samples did not contain ORFV or when they contained a quantity of ORFV below the detection limit of the test, only the C line was visible. The analysis of sensitivity of the test demonstrated that the lowest detected quantity of ORFV was 2.03×103.0 TCID50/ml. Storage at room temperature for 6 months did not result in the loss of performance of the LFIA test. Using loop-mediated isothermal amplification (LAMP) as a reference test, the relative specificity and sensitivity of the LFIA test were determined to be 100% and 92.1%, respectively. Based on these results, the LFIA test developed may be a suitable tool for rapid on-site testing for ORFV infection.

Rapid detection and quantification of the marine toxic algae, Alexandrium minutum, using a super-paramagnetic immunochromatographic strip test

The dinoflagellates of Alexandrium genus are known to be producers of paralytic shellfish toxins that regularly impact the shellfish aquaculture industry and fisheries. Accurate detection of Alexandrium including Alexandrium minutum is crucial for environmental monitoring and sanitary issues. In this study, we firstly developed a quantitative lateral flow immunoassay (LFIA) using super-paramagnetic nanobeads for A. minutum whole cells. This dipstick assay relies on two distinct monoclonal antibodies used in a sandwich format and directed against surface antigens of this organism. No sample preparation is required. Either frozen or live cells can be detected and quantified. The specificity and sensitivity are assessed by using phytoplankton culture and field samples spiked with a known amount of cultured A. minutum cells. This LFIA is shown to be highly specific for A. minutum and able to detect reproducibly 105cells/L within 30min. The test is applied to environmental samples already characterized by light microscopy counting. No significant difference is observed between the cell densities obtained by these two methods. This handy super-paramagnetic lateral flow immnunoassay biosensor can greatly assist water quality monitoring programs as well as ecological research.

Membrane Glucocorticoid Receptor Activation Induces Proteomic Changes Aligning with Classical Glucocorticoid Effects

Glucocorticoids exert rapid nongenomic effects by several mechanisms including the activation of a membrane-bound glucocorticoid receptor (mGR). Here, we report the first proteomic study on the effects of mGR activation by BSA-conjugated cortisol (Cort-BSA). A subset of target proteins in the proteomic data set was validated by Western blot and we found them responding to mGR activation by BSA-conjugated cortisol in three additional cell lines, indicating a conserved effect in cells originating from different tissues. Changes in the proteome of BSA-conjugated cortisol treated CCRF-CEM leukemia cells were associated with early and rapid pro-apoptotic, immune-modulatory and metabolic effects aligning with and possibly "priming" classical activities of the cytosolic glucocorticoid receptor (cGR). PCR arrays investigating target genes of the major signaling pathways indicated that the mGR does not exert its effects through the transcriptional activity of any of the most common kinases in these leukemic cells, but RhoA signaling emerged from our pathway analysis. All cell lines tested displayed very low levels of mGR on their surface. Highly sensitive and specific in situ proximity ligation assay visualized low numbers of mGR even in cells previously thought to be mGR negative. We obtained similar results when using three distinct anti-GR monoclonal antibodies directed against the N-terminal half of the cGR. This strongly suggests that the mGR and the cGR have a high sequence homology and most probably originate from the same gene. Furthermore, the mGR appears to reside in caveolae and its association with caveolin-1 (Cav-1) was clearly detected in two of the four cell lines investigated using double recognition proximity ligation assay. Our results indicate however that Cav-1 is not necessary for membrane localization of the GR since CCRF-CEM and Jurkat cells have a functional mGR, but did not express this caveolar protein. However, if expressed, this membrane protein dimerizes with the mGR modulating its function.

Development of a convenient immunochromatographic strip for the diagnosis of vesicular stomatitis virus serotype Indiana infections

A rapid and simple immunochromatography strip (ICS) test for the specific detection of vesicular stomatitis virus serotype Indiana (VSV-IND) using two distinct monoclonal antibodies MAbs (1A2 and 4C3) against the G protein of VSV-IND was developed. The MAb 1A2 was conjugated with colloidal gold, and the MAb 4C3 and goat anti-mouse IgG were sprayed onto a nitrocellulose membrane in strips at positions designated T and C, respectively. The results showed that samples of VSV-IND combined with CG-MAb 1A2, and that these complexes were captured by MAb 4C3 at the test line (T), resulting in the appearance of a purple band. When samples did not contain VSV-IND or when they contained a quantity of VSV-IND below the detection limit of the test, only the control line (C) was visible. The analysis of the sensitivity of the test demonstrated that the lowest detected quantity of VSV-IND was 1.85×10(3.0)TCID50/ml. Storage of the ICS test at room temperature for 6 months or at 4°C for 12 months did not change their sensitivity and specificity. In clinical trials using RT-PCR as a reference test, the relative specificity and sensitivity of the ICS were determined to be 98.9% and 91.4%, respectively. Based on these results, the ICS test developed may be a suitable tool for rapid on-site testing for VSV-IND infection.

High Throughput Formulation Screening for Global Aggregation Behaviors of Three Monoclonal Antibodies

Global aggregation behaviors of three distinct monoclonal antibodies were characterized by high throughput, multiassay analysis. First, extensive screening of formulations was performed using both incubation at elevated temperature and differential thermal scanning. In incubation studies, formulation conditions representing native favored, native favored but with particulate formation, unfolding with slow aggregation, and fast aggregation with or without phase separation were mapped across a wide range of pH and ionic strength. The sample types or aggregation kinetic scenarios were classified based on fluorescence spectroscopy, light scattering, and micron particle count. Furthermore, apparent melting point was determined for each formulation condition by differential thermal scanning. The global aggregation behaviors and their apparent melting points together highlight the common underlying aggregation pathways and kinetics for the three antibodies. Overall, incorporating multistage aggregation mechanisms in multivariate data analysis provides valuable insights to what and how high throughput techniques can be implemented. Understanding global aggregation behaviors is a key element toward development of rational screening approach.

Loss of Nuclear Localized and Tyrosine Phosphorylated Stat5 in Breast Cancer Predicts Poor Clinical Outcome and Increased Risk of Antiestrogen Therapy Failure

To investigate nuclear localized and tyrosine phosphorylated Stat5 (Nuc-pYStat5) as a marker of prognosis in node-negative breast cancer and as a predictor of response to antiestrogen therapy. Levels of Nuc-pYStat5 were analyzed in five archival cohorts of breast cancer by traditional diaminobenzidine-chromogen immunostaining and pathologist scoring of whole tissue sections or by immunofluorescence and automated quantitative analysis (AQUA) of tissue microarrays. Nuc-pYStat5 was an independent prognostic marker as measured by cancer-specific survival (CSS) in patients with node-negative breast cancer who did not receive systemic adjuvant therapy, when adjusted for common pathology parameters in multivariate analyses both by standard chromogen detection with pathologist scoring of whole tissue sections (cohort I; n = 233) and quantitative immunofluorescence of a tissue microarray (cohort II; n = 291). Two distinct monoclonal antibodies gave concordant results. A progression array (cohort III; n = 180) revealed frequent loss of Nuc-pYStat5 in invasive carcinoma compared to normal breast epithelia or ductal carcinoma in situ, and general loss of Nuc-pYStat5 in lymph node metastases. In cohort IV (n = 221), loss of Nuc-pYStat5 was associated with increased risk of antiestrogen therapy failure as measured by univariate CSS and time to recurrence (TTR). More sensitive AQUA quantification of Nuc-pYStat5 in antiestrogen-treated patients (cohort V; n = 97) identified by multivariate analysis patients with low Nuc-pYStat5 at elevated risk for therapy failure (CSS hazard ratio [HR], 21.55; 95% CI, 5.61 to 82.77; P < .001; TTR HR, 7.30; 95% CI, 2.34 to 22.78; P = .001). CONCLUSION Nuc-pYStat5 is an independent prognostic marker in node-negative breast cancer. If confirmed in prospective studies, Nuc-pYStat5 may become a useful predictive marker of response to adjuvant hormone therapy.

Abstract 2277: Loss of nuclear localized and tyrosine phosphorylated Stat5: A predictor of poor clinical outcome and increased risk of antiestrogen therapy failure in breast cancer

Abstract Stat5 transcription factor is activated by prolactin in the mammary gland and is necessary for mammary gland development, differentiation and lactation. Previous work based on tissue microarrays has suggested that nuclear localized and tyrosine phosphorylated Stat5 (Nuc-pYStat5) is a marker of prognosis in node-negative breast cancer. The purpose of this study was to validate the prognostic value of Nuc-pYStat5 in whole tissue sections and expand the analyses to a quantitative immunofluoresence-based assay. In addition, we explored Nuc-pYStat5 as a predictor of response to antiestrogen therapy. Levels of Nuc-pYStat5 were analyzed in five archival materials of breast cancer by traditional diaminobenzidine-chromogen immunohistochemistry (DAB-IHC) and pathologist scoring of whole tissue sections or by immunofluorescence and automated quantitative analysis (AQUA) of tissue microarrays. In two prognostic cohorts of node-negative breast cancer patients not receiving systemic adjuvant therapy, Nuc-pYStat5 was an independent marker of cancer-specific survival (CSS) when adjusted for common pathology parameters in multivariate analyses. Corresponding results were obtained both by standard DAB-IHC with pathologist scoring of whole tissue sections (Material I; n=233) and by quantitative immunofluorescence of a tissue microarray (Material II; n=291) and using two distinct monoclonal antibodies. A breast tissue progression array (Material III; n=130) revealed loss of Nuc-pYStat5 in invasive ductal carcinoma (IDC) compared to normal breast epithelia or ductal carcinoma in situ (DCIS), with greatest loss of Nuc-pYStat5 in lymph node metastases. Importantly, loss of Nuc-pYStat5, detected by DAB-IHC (Material IV; n=221), was associated with increased risk of antiestrogen therapy failure as measured by CSS and time to recurrence (TTR). More sensitive AQUA quantification of Nuc-pYStat5 in patients treated with antiestrogen monotherapy (Material V; n=97) identified a subset of patients with low Nuc-pYStat5 at a 7.4-fold elevated risk of dying from breast cancer (CSS univariate Cox regression HR=7.36 (2.94-18.42), p&amp;lt;0.001, n=53). Importantly, low levels of Nuc-pYStat5 also predicted therapy failure in multivariate analyses (multivariate Cox regression, CSS HR=21.55 (5.61-82.77), p&amp;lt;0.001; TTR HR=7.30 (2.34-22.78), p=0.001; n=53) independent of ER/PR status and lymph node status. We conclude that Nuc-pYStat5 is an independent prognostic marker in node-negative breast cancer. Furthermore, this study suggests that Nuc-pYStat5 may become useful as a predictive marker of response to systemic adjuvant hormone therapy if confirmed by prospective studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2277. doi:10.1158/1538-7445.AM2011-2277

Detection of granulocyte antibodies using simultaneous analysis of specific granulocyte antibodies assay (SASGA)

Granulocyte-associated antibodies can cause several clinical granulocytopenic disorders. The monoclonal-antibody-specific immobilization of granulocyte antigens (MAIGA) is currently used as the standard assay to specify these antibodies. Here we describe an assay for specific analysis of granulocyte antibodies (SASGA) which is able to simultaneously detect and specify granulocyte IgG- and IgM-antibodies using flow cytometry. Bead populations with distinct fluorescence intensities were used as solid phase for immobilization of mAb. Typed granulocytes were incubated with human sera and a mix of three distinct mouse monoclonal antibodies against specific granulocyte antigens (for example CD16, CD11a, HLA class I). After cell lysis and incubation of lysate with beads, goat antibodies against human IgG and IgM antibodies were added. Seventy-one frozen sera of donors and patients previously implicated in transfusion reactions and various underlying disorders were analysed for specific granulocyte-binding antibodies using MAIGA and SASGA. The SASGA assay was able to simultaneously detect granulocyte-specific antibodies for different glycoproteins. Overall, the results of MAIGA and SASGA were concordant in 92·9%. 5 sera containing anti-HNA-1b (n=2) and -HLA class I (n=3) were not detected by MAIGA, but were recognized by the SASGA. In serial dilution tests with sera containing anti-HNA-1a, -1b, -2a and HLA class I, the SASGA assay detected the antibodies at higher dilutions than MAIGA. The SASGA assay permits reliable detection of specific granulocyte antibodies. Six distinct antibodies can be simultaneously determined. This method will potentially open the way to investigations on additional specific antibodies as it facilitates laboratory diagnosis.

Membrane-binding properties of the Factor VIII C2 domain

Factor VIII functions as a cofactor for Factor IXa in a membrane-bound enzyme complex. Membrane binding accelerates the activity of the Factor VIIIa-Factor IXa complex approx. 100000-fold, and the major phospholipid-binding motif of Factor VIII is thought to be on the C2 domain. In the present study, we prepared an fVIII-C2 (Factor VIII C2 domain) construct from Escherichia coli, and confirmed its structural integrity through binding of three distinct monoclonal antibodies. Solution-phase assays, performed with flow cytometry and FRET (fluorescence resonance energy transfer), revealed that fVIII-C2 membrane affinity was approx. 40-fold lower than intact Factor VIII. In contrast with the similarly structured C2 domain of lactadherin, fVIII-C2 membrane binding was inhibited by physiological NaCl. fVIII-C2 binding was also not specific for phosphatidylserine over other negatively charged phospholipids, whereas a Factor VIII construct lacking the C2 domain retained phosphatidyl-L-serine specificity. fVIII-C2 slightly enhanced the cleavage of Factor X by Factor IXa, but did not compete with Factor VIII for membrane-binding sites or inhibit the Factor Xase complex. Our results indicate that the C2 domain in isolation does not recapitulate the characteristic membrane binding of Factor VIII, emphasizing that its role is co-operative with other domains of the intact Factor VIII molecule.

Monoclonal antibodies against diverse xyloglucan structures as probes for plant cell wall chemistry and ultrastructure

The plant cell wall is a complex extracytoplasmic organelle whose structure and dynamics are poorly understood at the molecular scale. Traditional biochemical methods have documented plasticity in the cell wall properties during development and in response to stress, but are limited to characterizing bulk features. Alternatively, the structural discriminating power of monoclonal antibodies can be utilized to simultaneously probe the abundances and locations of molecular structures in muro at sub‐organellar resolution, and to examine cell wall components in vitro. We have generated more than 30 distinct monoclonal antibodies with a diverse range of specificities against xyloglucan, an abundant and structurally heterogenous class of carbohydrate polymer found in the plant cell walls. The binding specificities of these antibodies have been exhaustively characterized by ELISA‐based methods. The knowledge of the binding specificities allows structural interpretation of the immunolocalization patterns generated using these antibodies. Moreover, we have demonstrated the utility of these antibodies in structural classification of xyloglucans as well as in probing the biophysical properties of partially reconstituted plant cell walls, thus sheding light on the structure‐function relationships of this polysaccharide. This work is funded by NSF (DBI‐0421683) and DOE (DE‐FG02‐96ER20220).

Multisite Phosphorylation of Voltage-Gated Sodium Channel α Subunits from Rat Brain

Reversible phosphorylation of ion channels underlies cellular plasticity in mammalian neurons. Voltage-gated sodium or Nav channels underlie action potential initiation and propagation, dendritic excitability, and many other aspects of neuronal excitability. Various protein kinases have been suggested to phosphorylate the primary or alpha subunit of Nav channels, affecting diverse aspects of channel function. Previous studies of Nav alpha subunit phosphorylation have led to the identification of a small set of phosphorylation sites important in mediating diverse aspects of Nav channel function. Here we use nanoflow liquid chromatography tandem mass spectrometry (nano-LC MS/MS) on Nav alpha subunits affinity-purified from rat brain with two distinct monoclonal antibodies to identify 15 phosphorylation sites on Nav1.2, 12 of which have not been previously reported. We also found 3 novel phosphorylation sites on Nav1.1. In general, commonly used phosphorylation site prediction algorithms did not accurately predict these novel in vivo phosphorylation sites. Our results demonstrate that specific Nav alpha subunits isolated from rat brain are highly phosphorylated, and suggest extensive modulation of Nav channel activity in mammalian brain. Identification of phosphorylation sites using monoclonal antibody-based immunopurification and mass spectrometry is an effective approach to define the phosphorylation status of Nav channels and other important membrane proteins in mammalian brain.