Panel Of Antibodies Research Articles

Macaque antibodies targeting Marburg virus glycoprotein induced by multivalent immunization.

Marburg viruses were the first filoviruses characterized to emerge in humans in 1967 and cause severe hemorrhagic fever with average case fatality rates of ~50%. Although mAb countermeasures have been approved for clinical use against the related Ebola viruses, there are currently no approved countermeasures against Marburg viruses. We successfully isolated a panel of orthomarburgvirus GP-specific mAbs from a macaque immunized with a multivalent combination of filovirus antigens. Our analyses revealed that roughly half of the antibodies in the panel mapped to regions on the glycoprotein shown to protect from infection, including the host cell receptor binding domain and a protective region on the membrane-anchoring subunit. Other antibodies in the panel exhibited broad filovirus GP recognition. Our study describes the discovery of a diverse panel of cross-reactive macaque antibodies targeting orthomarburgvirus and other filovirus GPs and provides candidate immunotherapeutics for further study and development.

Simple and rapid flow cytometry assay for the detection of malignant epithelial cells in body fluids.

Morphology is routinely used for detecting malignant cells in body fluids, but it has limitations. Recently, flow cytometry (FCM) is used as an effective tool for studying non-haematological malignancies. The main objective of this study is to standardize a simple and rapid FCM test for the detection of malignant epithelial cells in body fluids. Body fluids that had been processed for cytology/cytology and FCM were enrolled in this prospective study. We developed a fluorescent-labelled, monoclonal antibody panel composed of cell surface markers for this FCM assay. We compared the results of cytology/cell block and FCM. A total of 121 fluid samples were studied. Comparing the diagnostic performance of cytology/cell block and FCM, 52 (43%) cases were positive and 60 (49.5%) cases were negative for carcinoma cells by both techniques. Nine cases showed discordant results between the two techniques. Six cases were cytology+ but FCM- and three cases were FCM+ cytology-. Clustered Epithelial Cell Adhesion Molecule (EpCAM)-positive events with high scatter properties were definitive for positive diagnosis by FCM. We studied PD-L1 expression in 13 cases by FCM. Six cases were reported as false negative by this FCM assay due to hypocellularity and lack of EpCAM expression in malignant cells. This FCM assay is simple, easier and cost-effective yielding sensitive results with no inter-observer variability. FCM would become a valuable tool to complement routine diagnostic cytology and reduces misdiagnosis.

Bispecific antibodies targeting two glycoproteins on SFTSV exhibit synergistic neutralization and protection in a mouse model

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with a high fatality rate of up to 30% caused by SFTS virus (SFTSV). However, no specific vaccine or antiviral therapy has been approved for clinical use. To develop an effective treatment, we isolated a panel of human monoclonal antibodies (mAbs). SF5 and SF83 are two neutralizing mAbs that recognize two viral glycoproteins (Gn and Gc), respectively. We found that their epitopes are closely located, and we then engineered them as several bispecific antibodies (bsAbs). Neutralization and animal experiments indicated that bsAbs display more potent protective effects than the parental mAbs, and the cryoelectron microscopy structure of a bsAb3 Fab-Gn-Gc complex elucidated the mechanism of protection. In vivo virus passage in the presence of antibodies indicated that two bsAbs resulted in less selective pressure and could efficiently bind to all single parental mAb-escape mutants. Furthermore, epitope analysis of the protective mAbs against SFTSV and RVFV indicated that they are all located on the Gn subdomain I, where may be the hot spots in the phleboviruses. Collectively, these data provide potential therapeutic agents and molecular basis for the rational design of vaccines against SFTSV infection.

The Development of Robust Antibodies to Sarcospan, a Dystrophin- and Integrin-Associated Protein, for Basic and Translational Research.

Sarcospan (SSPN) is a 25-kDa transmembrane protein that is broadly expressed at the cell surface of many tissues, including, but not limited to, the myofibers from skeletal and smooth muscles, cardiomyocytes, adipocytes, kidney epithelial cells, and neurons. SSPN is a core component of the dystrophin-glycoprotein complex (DGC) that links the intracellular actin cytoskeleton with the extracellular matrix. It is also associated with integrin α7β1, the predominant integrin expressed in skeletal muscle. As a tetraspanin-like protein with four transmembrane spanning domains, SSPN functions as a scaffold to facilitate protein-protein interactions at the cell membrane. Duchenne muscular dystrophy, Becker muscular dystrophy, and X-linked dilated cardiomyopathy are caused by the loss of dystrophin at the muscle cell surface and a concomitant loss of the entire DGC, including SSPN. SSPN overexpression ameliorates Duchenne muscular dystrophy in the mdx murine model, which supports SSPN being a viable therapeutic target. Other rescue studies support SSPN as a biomarker for the proper assembly and membrane expression of the DGC. Highly specific and robust antibodies to SSPN are needed for basic research on the molecular mechanisms of SSPN rescue, pre-clinical studies, and biomarker evaluations in human samples. The development of SSPN antibodies is challenged by the presence of its four transmembrane domains and limited antigenic epitopes. To address the significant barrier presented by limited commercially available antibodies, we aimed to generate a panel of robust SSPN-specific antibodies that can serve as a resource for the research community. We created antibodies to three SSPN protein epitopes, including the intracellular N- and C-termini as well as the large extracellular loop (LEL) between transmembrane domains 3 and 4. We developed a panel of rabbit antibodies (poly- and monoclonal) against an N-terminal peptide fragment of SSPN. We used several assays to show that the rabbit antibodies recognize mouse SSPN with a high functional affinity and specificity. We developed mouse monoclonal antibodies against the C-terminal peptide and the large extracellular loop of human SSPN. These antibodies are superior to commercially available antibodies and outperform them in various applications, including immunoblotting, indirect immunofluorescence analysis, immunoprecipitation, and an ELISA. These newly developed antibodies will significantly improve the quality and ease of SSPN detection for basic and translational research.

Interrogating the tumor microenvironment (TME) in patients (pts) with head and neck mucosal squamous cell carcinoma (HNmSCC) treated with programmed death-1 (PD-1) inhibitors.

6048 Background: Survival in recurrent/metastatic HNmSCC remain poor. PD-1 inhibitors have become standard of care, demonstrating improved overall survival and toxicity when compared to chemotherapy and targeted therapy. Biomarkers such as PD-Ligand(L)1 combined proportion score (CPS) remain rudimentary, with CPS >20 showing a response rate of only 23% to pembrolizumab (KEYNOTE-048). We used high-dimensional imaging mass cytometry (IMC) to explore predictive biomarkers in HNmSCC pts receiving PD-1 inhibitor-based therapy. Methods: We retrospectively analysed 27 formalin-fixed paraffin embedded tissue samples from 24 pts prior to receiving PD-1 inhibitor-based therapy between May 2016 – April 2021. Clinicopathological characteristics including PD-L1, p16 status, prior treatment and survival data were collected. Pts were classified into responders (RES, Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 complete response (CR) or partial response (PR), stable disease (SD) >6 months (mths)) and non-responders (non-RES, RECIST SD <6 mths or disease progression (PD)). An antibody panel (n = 40) was created to interrogate specific components of interest within the TME and was analysed by IMC using the HyperionTM Imaging System. Results: Of the 24 patients, 16/24 were male and median age 57.6 year. 8 pts were RES (RECIST CR, n = 1; PR, n = 3; SD > 6 mths, n = 4) and 14 pts were non-RES (RECIST SD < 6 mths, n = 1; PD, n = 11; clinical PD, n = 4). Four patients underwent rapid clinical disease progression prior to progress imaging and were categorised as non-RES. At time of data cut off on January 2024, and 23/24 pts had progressed on treatment. The cellular landscape within the TME was similar, irrespective of the location of the primary and p16 status. However, distinct immune profiles were observed between RES vs non-RES: RES showed higher infiltrates of CD4+ T cells, B cells, PD-1+ CD8+ T cells (P < 0.05) and both central memory and effector memory T cell subsets (p < 0.01). In contrast, non-RES showed high frequencies of CD44+ NK cells. Key cell interactions within the TME identified proliferating malignant squamous cells closely interacting with CD8+ T cells, CD4+ Tregs and endothelial cell in RES but not interacting in non-RES. Further spatial regional analysis identified a distinct tissue architecture with hallmarks of Tertiary Lymphoid-like Structures (TLS), present in higher proportions in RES. RES pts with TLS proportions >20% (n = 3) had a progression free survival of 80.3 mths, 26.8 mths and NE (unrelated death at 15.6 mths). Conclusions: The findings of this study identify mechanisms of PD-1 inhibitor response and resistance in HNmSCC pts, providing a unique opportunity to guide combination strategies and improve outcome.

TIM-3 Expression in Endometriosis.

Endometriosis is a prevalent chronic gynecological disease linked to immune dysfunction. The protein T-cell immunoglobulin and mucin domain-containing protein 3 (TIM-3) plays a crucial role in immune system balance. Malfunction of TIM-3 may result in excessive immune activation and inflammatory tissue damage. Given TIM-3's established role in the development of cancer and autoimmune diseases, we decided to study its role in women suffering from endometriosis. We included a total of 62 female patients, all of whom had undergone laparoscopic surgery. Of these, 47 had endometriosis and 15 did not. During surgery, we collected peritoneal fluid (PF) and peripheral blood (PB) samples from every patient for analysis using flow cytometry. To mark the samples, we used a panel of monoclonal antibodies and examined TIM-3 expression in their immune cells. Endometriosis patients in PB demonstrated a significantly lower percentage of CD56+ T cells with TIM-3 expression. As endometriosis progressed through its stages, this expression lessened. This decrease was particularly notable in women with stage III/IV endometriosis. Additionally, both women diagnosed with intestinal endometriosis and those with recent endometriosis diagnoses showed a significantly reduced percentage of CD56+ T cells expressing TIM-3. Patients with endometriosis exhibit diminished TIM-3 expression within circulating T cells. This warrants further investigation to discern whether it contributes to the progression of endometriosis, potentially through the amplification of autoreactive T cells and inflammation.

Comparison of T cell maturation profiles in the 1st and 5th wave of COVID-19 in the Polish population.

The coronavirus pandemic has become the most critical global health threat of this century and the greatest challenge to the human population. The search for simple and quick diagnostic methods enabling the identification of patients infected with the SARS-CoV-2 virus may be a valuable method to track infection. The aim of the study was the clinical and immunological characterization of patients by assessing the degrees of maturity of T lymphocytes from the 1st and 5th waves of coronavirus disease 2019 (COVID-19) in comparison to a healthy control group (HC). We determined leukocyte and T lymphocyte subpopulations (recent thymic emigrant (RTE), naïve, effector, central memory and effector memory) in patients from the 1st COVID-19 wave (n = 23), the 5th COVID-19 wave (n = 38) and HC (n=20) using a panel of monoclonal antibodies using multiparameter flow cytometry. We observed a lower median proportion of lymphocytes and NK cells, and elevated percentage and number of neutrophils in patients from the 5th wave compared to the 1st. We found a reduced percentage of CD4+ effector memory cells in the 1st wave group compared to the 5th wave (14.1 vs 23.2, p < 0.05), and a higher percentage of RTE and naïve CD8+ cells in the 1st wave compared to the 5th wave (p < 0.05). The effector memory CD8+ cells were highest in the 5th wave compared to both 1st wave and HC patients (respectively, 35.1 vs 18.1 vs 19.3%, p < 0.05). The 5th wave group showed significantly more differences compared to HC. Our results showed a clear increase of effector cells with a simultaneous decrease in virgin T cells in the 5th COVID-19 infection. Monitoring lymphocyte subsets during infection allows assessment of the patient's immune status and of readiness of lymphocytes to respond to the immune response, and may be necessary to improve clinical outcomes.

Neurosarcoidosis-Induced Winging Scapula: Efficacy of Infliximab Treatment in Addressing Multifaceted Challenges.

Sarcoidosis, a systemic granulomatous disease primarily affecting the respiratory and lymphatic systems, can rarely manifest as neurosarcoidosis either in isolation or alongside other systemic symptoms. Here, we describe the case of a 45-year-old male with a history of recurrent sinusitis refractory to antibiotics, who presented to the emergency department with sinus congestion and dysphagia. Clinical examination revealed left lower motor neuron facial palsy and enlarged submandibular salivary glands. Despite obtaining negative results from various antibody panels, the patient exhibited elevated Angiotensin Converting Enzyme levels of 83 nmol/kg/min. Additionally, computed tomography chest scans revealed bilateral hilar and mediastinal lymph node enlargement, findings consistent with sarcoidosis. Otorhinolaryngology evaluation for dysphagia confirmed left vocal cord palsy. Following a negative infectious disease workup, submandibular salivary gland biopsy confirmed sarcoidosis. Treatment with mycophenolate mofetil and oral steroids led to gradual improvement in salivary gland swelling, dysphagia, and facial palsy. However, worsening left shoulder pain prompted further investigation, revealing winging of the left scapula on repeat examination. Magnetic resonance imaging (MRI) of the cervical spine revealed a six mm hyperintensity in the left dorsal cord at the C5 level, suggesting possible neurosarcoidosis vs. demyelinating disease. Subsequently, the patient was prescribed anti-tumor necrosis factor alpha inhibitor infliximab. Subsequent MRI of the cervical spine, conducted six months after initiating Infliximab therapy, indicated resolution of the lesions. This positive outcome was supported by the patient's report of symptom improvement, notably reduced shoulder pain and improvement in left scapular winging. This case underscores the unusual co-occurrence of Bell's palsy and vocal cord palsy in the same patient, along with the potential contribution of neurosarcoidosis to the winged scapula. Additionally, it sheds light on the positive response of neurosarcoidosis to Infliximab therapy.

#1167 Examination of subsets of CD4+ lymphocyte subpopulations in long-surviving renal transplant patients

Abstract Background and Aims Subpopulations of CD4+ cells, play a major role in mediation of rejection and tolerance to a renal transplant. This study examined subsets of CD4+ T cells and CD4+CD25+CD127lo Treg in blood of renal graft recipients with grafts surviving &amp;gt;10 years for changes in lymphocyte subpopulations that may indicate transplant tolerance and potentially identify patients who could reduce immunosuppression. Based on CD45RA and CD25/Foxp3 expression, Miyara et al identified five populations (Pop) within CD4+ cells. Pop I, II and III are T regulatory cells (Treg); Pop I as naïve (CD45RA+Foxp3+) Treg, Pop II as activated (CD45RA-Foxp3hi) Treg, and Pop III as cytokine secreting (CD45RA-Foxp3+) cells which also includes activated effector cells. Pop IV are activated T cells (CD45RA-Foxp3−), and Pop V are naïve T cells (CD45RA+Foxp3−). Here, we examined three Treg populations (Pop I-III) within CD4+CD25+CD127lo Treg, and Pop IV and V within CD4+ T cells. To further characterise these subpopulations, we examined chemokine receptor expression (CXCR3, CCR4, CCR6, and CCR7) to identify T helper phenotype (Th-like) of Treg populations. Th1-like Treg were identified as CCR4+CXCR3+CCR6−, Th2-like as CCR4+CXCR3-CCR6−, Th17-like as CCR4+CXCR3-CCR6+, and Th1/Th17-like as CCR4+CXCR3+CCR6+. We also examined expression of activated Treg effector molecules CD39, Class II MHC, and PD-1. Method Peripheral blood mononuclear cells (PBMC) were isolated from fresh blood collected from healthy volunteers (HV) (n = 44) and long-term stable renal transplant patients with grafts surviving &amp;gt;10 yrs (RT) (n = 25). Panels of monoclonal antibodies for Treg (CD4/CD25/CD127/CD45RA/Foxp3), chemokine receptors (CXCR3, CCR4, CCR6, CCR7), and Treg activation and suppression-related molecules (CD39/HLA-DR/PD-1) were also used. Data was acquired on BD FACSCanto II using BD FACSDiva software (v8.0) and analysed using FlowJo. Lymphocyte populations were examined after FSC vs SSC gating and doublets exclusion. T cell and Treg populations were analysed within CD4+ and CD4+CD25+CD127lo T cells. Results RT had lower lymphocyte counts than HV (p = 0.0156) but had a similar percentage of CD4+ T cells. Treg were significantly lower in RT compared to HV (p = 0.0012). RT patients had less naïve Treg (Pop I, p = 0.0083) and naïve effector T cells (Pop V, p = 0.0003), but had higher activated effector T cells (Pop IV, p = 0.0002) than HV. There were no differences in activated Treg Pop II or III between the two groups. There were significantly less cells expressing CXCR3 in RT than HV in Pop I (p = 0.0120), Pop II (p &amp;lt; 0.0001), Pop III (p &amp;lt; 0.0001) and Pop IV (p = 0.0047). Similarly, RT had fewer cells expressing CCR6 compared to HV in Pop II (p = 0.0019), Pop III (p = 0.0015), and Pop V (p = 0.0017). RT had lower proportions of CCR7 expressing cells in Pop I (p = 0.0035), Pop IV (p = 0.0097), and Pop V (p = 0.0002), but higher in Pop II (p = 0.0041) compared to HV. There were similar percentages of cells with Th1 and Th17-like phenotypes in both groups. However, RT had significantly more Th2-like Treg in Pop II (p = 0.0033) and Pop III (p = 0.0100), and significantly less Th1/Th17-like Treg in Pop II (p = 0.0005) and Pop III (p = 0.0017) compared to HV. There were little to no differences in the Treg activation and suppression-related molecules within subpopulations of Treg. Conclusion Long-surviving RT patients had less naïve Treg and naïve effector cells, but increased proportions of activated effector cells. There were little to no differences in the expression of Treg activation or suppression-related molecules in Treg subpopulations. Unexpectedly, activated Treg in RT had significantly higher proportions with a Th2 phenotype and significantly less Treg with a Th1/Th17 phenotype. Whether this is a consequence of immunosuppression, or a biological shift associated with tolerance, remains to be resolved. Further studies are required to investigate the relevance of these changes in identifying induction of transplant tolerance.

#1896 Monitoring of peripheral blood B cell subsets in long-surviving renal transplant patients

Abstract Background and Aims Studies of peripheral blood B cells subsets in renal transplant patients with operational tolerance off immunosuppressive therapy have identified several differences in B cell subsets. Here we studied B cells in blood lymphocytes from long-surviving renal transplant patients on immunosuppression. Populations of CD4+ T cells, CD8+ T cells, NK cells and B cells, along with subpopulations of B cells, in long-surviving renal transplant recipients were compared to healthy volunteers. We were looking for changes in B cell subsets, which may indicate transplant tolerance and potentially identify patients who could reduce immunosuppression. Method Fresh blood was taken from healthy volunteers (HV) (n = 44) and stable renal transplant patients with grafts surviving &amp;gt;10yrs (RT) (n = 25). T, B, and NK cells were examined using a 6-color TBNK reagent (BD) (CD3/CD4/CD8/CD45/CD19/CD16&amp;CD56). Peripheral blood mononuclear cells were isolated from the remaining fresh blood and were stained with a panel of monoclonal antibodies (CD19/CD21/CD24/CD27/CD38/CD45/IgD/IgM) to identify subpopulations of B cells. Data was acquired on BD FACSCanto II using BD FACSDiva software (v8.0) and analysed using FlowJo. Lymphocyte populations were examined after FSC vs SSC gating and doublets exclusion. Results RT had significantly less lymphocyte counts in comparison to HV (p = 0.0156). There were no significant differences between the CD4+ T cell, CD8+ T cell, or NK cell percentages between RT and HV. B cells were markedly reduced in RT (p = 0.0001) vs HV when examined by TBNK staining. Peripheral blood mononuclear cells of HV (n = 13) and RT (n = 23) stained with a panel of B cell-related antibodies showed CD19+ cells were also significantly reduced in RT (p = 0.0006). There were less CD21hi cells (p = 0.0014) and more CD21lo (p = 0.0014) cells in RT than HV. No differences were seen between the two groups in their proportion of naïve B cells, marginal zone B cells, memory B cells, or class unswitched B cells. However, switched memory B cells were higher in RT than HV (p = 0.0181). Plasmablasts were also higher in RT compared to HV (p = 0.0491). Transitional B cells in RT appeared lower than HV on average, but this did not reach statistical significance (p = 0.1265). The ratio of Treg to B cells, RT (n = 25) showed significantly higher (p = 0.0256) proportions of activated Treg (CD4+CD25+CD127loCD45RA−Foxp3+/hi) to B cells, in comparison to HV (n = 44). There were no significant differences between the two groups in the ratio of naïve Treg (CD4+CD25+CD127loCD45RA+Foxp3+) to naïve T cells (CD4+CD45RA+Foxp3−), or highly activated Treg (CD4+CD25+CD127loCD45RA−Foxp3hi) to activated effector T cells (CD4+CD45RA−Foxp3−). Conclusion B cells were significantly lower in RT compared to HV. There were more plasmablasts and switched memory B cells in RT than HV. The ratio of activated Treg to B cells was higher in RT. This higher proportion of Treg to B cells may be clinically relevant and potentially demonstrate increased immunological suppression in long-surviving renal transplant recipients.

#2182 An unexpected life-threatening cause of kidney failure

Abstract Background and Aims Kidney failure can appear in acute clinical conditions and the cause cannot always be determined, as in approximately 40% of cases that require renal replacement therapy (RRT). In addition, there are other cases in which a patient with persistently low estimated glomerular filtration rate (eGFR) for 3 months is treated with RRT without a primary renal diagnosis. Systemic sclerosis (SSc) is a rare condition that can lead to RRT due to renal ”crisis”. Autopsy studies reveal kidney pathology in approximately 60 percent of patients with SSc. In addition, as many as 50 percent of patients with SSc have markers of kidney disease, as manifested by mild proteinuria, elevated serum creatinine concentration, and/or hypertension. The aim of our paper is to describe a case in which hemodialysis was initiated in emergency setting and the diagnosis was established after that. However clinical course was fatal and the final diagnosis was SSc. Method A 65-year-old male patient was admitted to the Nephrology department with a weight loss of 20 kg in 2 years, depression, low appetite and progressive decline of physical strength. He was previously diagnosed with diabetes mellitus (DM) and high blood pressure (HBP), the ponderal loss being attributed to DM. Insulin treatment was initiated together with antihypertensive medication. In the following 3 months, the kidney function deteriorated progressively and hemodialysis was started. Gray scale and CEUS US were performed to assess a possible cause of kidney failure. However, after the commencement of hemodialysis, the clinical condition did not improve and patient died in respiratory failure complicated by continuous pleural effusion. A skin biopsy from the right thigh was performed for the positive diagnosis. Results At clinical evaluation the patient was cachectic, with striking generalized parchment-like skin lesions which were suggestive both for ichthyosis or SSc. Laboratory tests revealed hyperglycemia, anemia, hypoalbuminemia, increased lactate dehydrogenase and creatine kinase (CK), mild proteinuria and glomerular hematuria. On the other side, myositis antibodies (AB) panel, antinuclear AB, tumor markers for pancreas and gastro-intestinal carcinoma, AB for vasculitis and lupus were negative. Ultrasound (US) (grey scale and CEUS) described dilated bile ducts and gallbladder with massive sludge, without evidence of tumoral neovascularization, and shrunk kidneys with hypoechoic medulla. CT scan confirmed the US findings. Dialysis parameters indicated kt/V 1.4 and urea reduction ratio of 79%. Therefore, no metabolic disturbances could explain the severely altered medical status. The clinical condition of the patient made the kidney biopsy unfeasible. Nevertheless, we decided to perform a skin biopsy, which revealed gross collagen bands, absence of sebaceous glands or hair follicles, as well as rare capillaries with lymphocyte inflammatory infiltrate and absence of hypoderma, thus confirming the diagnosis of SSc. Conclusion SSc can present with obscure clinical signs, leading to multiple organ dysfunction and initially unapparent cause of kidney failure. However, clinicians must be aware of potentially suggestive etiological signs such as parchment-like skin lesions and high blood pressure in a patient with multiple comorbidities. One must differentiate a dehydrated skin from a pathognomonic skin lesion as it is in SSc.

Delineation of chicken immune markers in the era of omics and multicolor flow cytometry

Multiparameter flow cytometry is a routine method in immunological studies incorporated in biomedical, veterinary, agricultural, and wildlife research and routinely used in veterinary clinical laboratories. Its use in the diagnostics of poultry diseases is still limited, but due to the continuous expansion of reagents and cost reductions, this may change in the near future. Although the structure and function of the avian immune system show commonalities with mammals, at the molecular level, there is often low homology across species. The cross-reactivity of mammalian immunological reagents is therefore low, but nevertheless, the list of reagents to study chicken immune cells is increasing. Recent improvement in multicolor antibody panels for chicken cells has resulted in more detailed analysis by flow cytometry and has allowed the discovery of novel leukocyte cell subpopulations. In this article, we present an overview of the reagents and guidance needed to perform multicolor flow cytometry using chicken samples and common pitfalls to avoid.

A novel LAG3 neutralizing antibody improves cancer immunotherapy by dual inhibition of MHC-II and FGL1 ligand binding

LAG3 is an inhibitory immune checkpoint expressed on activated T and NK cells. Blocking the interaction of LAG3 with its ligands MHC-II and FGL1 renders T cells improved cytotoxicity to cancer cells. Current study generated a panel of LAG3 monoclonal antibodies (mAbs) through immunization of mice followed by phage display. Some of them bound to the D1-D2 domain of LAG3, which is known for the engagement of its ligands FGL1 and MHC-II. Three outperformers, M208, M226, and M234, showed stronger blocking activity than Relatlimab in the FGL1 binding. Furthermore, M234 showed dual inhibition of FGL1 (IC50 of 20.6 nM) and MHC-II binding (IC50 of 6.2 nM) to LAG3. In vitro functional tests showed that M234 significantly stimulated IFN-γ secretion from activated PBMC cells. In vivo studies in a mouse model of hepatocellular carcinoma xenografts demonstrated that combining M234 IgG with GPC3-targeted bispecific antibodies significantly improved efficacy. In addition, GPC3-targeted CAR-T cells secreting IL-21-M234 scFv fusion protein exhibited enhanced activity in inhibiting tumor growth and greatly increased the survival rate of mice. Taken together, M234 has potential in cancer immunotherapy and warrants further clinical trial.

A potent Henipavirus cross-neutralizing antibody reveals a dynamic fusion-triggering pattern of the G-tetramer

The Hendra and Nipah viruses (HNVs) are highly pathogenic pathogens without approved interventions for human use. In addition, the interaction pattern between the attachment (G) and fusion (F) glycoproteins required for virus entry remains unclear. Here, we isolate a panel of Macaca-derived G-specific antibodies that cross-neutralize HNVs via multiple mechanisms. The most potent antibody, 1E5, confers adequate protection against the Nipah virus challenge in female hamsters. Crystallography demonstrates that 1E5 has a highly similar binding pattern to the receptor. In cryo-electron microscopy studies, the tendency of 1E5 to bind to the upper or lower heads results in two distinct quaternary structures of G. Furthermore, we identify the extended outer loop β1S2-β1S3 of G and two pockets on the apical region of fusion (F) glycoprotein as the essential sites for G-F interactions. This work highlights promising drug candidates against HNVs and contributes deeper insights into the viruses.

Identification of high-performing antibodies for the reliable detection of Tau proteoforms by Western blotting and immunohistochemistry

Antibodies are essential research tools whose performance directly impacts research conclusions and reproducibility. Owing to its central role in Alzheimer’s disease and other dementias, hundreds of distinct antibody clones have been developed against the microtubule-associated protein Tau and its multiple proteoforms. Despite this breadth of offer, limited understanding of their performance and poor antibody selectivity have hindered research progress. Here, we validate a large panel of Tau antibodies by Western blot (79 reagents) and immunohistochemistry (35 reagents). We address the reagents’ ability to detect the target proteoform, selectivity, the impact of protein phosphorylation on antibody binding and performance in human brain samples. While most antibodies detected Tau at high levels, many failed to detect it at lower, endogenous levels. By WB, non-selective binding to other proteins affected over half of the antibodies tested, with several cross-reacting with the related MAP2 protein, whereas the “oligomeric Tau” T22 antibody reacted with monomeric Tau by WB, thus calling into question its specificity to Tau oligomers. Despite the presumption that “total” Tau antibodies are agnostic to post-translational modifications, we found that phosphorylation partially inhibits binding for many such antibodies, including the popular Tau-5 clone. We further combine high-sensitivity reagents, mass-spectrometry proteomics and cDNA sequencing to demonstrate that presumptive Tau “knockout” human cells continue to express residual protein arising through exon skipping, providing evidence of previously unappreciated gene plasticity. Finally, probing of human brain samples with a large panel of antibodies revealed the presence of C-term-truncated versions of all main Tau brain isoforms in both control and tauopathy donors. Ultimately, we identify a validated panel of Tau antibodies that can be employed in Western blotting and/or immunohistochemistry to reliably detect even low levels of Tau expression with high selectivity. This work represents an extensive resource that will enable the re-interpretation of published data, improve reproducibility in Tau research, and overall accelerate scientific progress.

Abstract A023: Stratification of bladder cancer patients with the use of flow cytometry is increasing the diagnostic potential of molecular classifiers

Abstract Recent research suggests the potential categorization of bladder cancer (BLCa) patients into molecular subtypes to aid in the selection of appropriate treatment strategies, be it conventional, targeted, or a combination thereof. However, the practical implementation of molecular classifiers has faced obstacles due to the intricate nature of gene regulation, tumor heterogeneity, and challenges related to tumor sampling caused by substantial stromal infiltration and tumor multifocality. Hence, there is a pressing need for more straightforward marker-based methodologies to assist in genomic and transcriptomic subtyping efforts. Our study addressed this gap by establishing and validating a panel of antibodies for application in flow cytometry (FCM) to enhance the stratification of BLCa patients. We curated a set of 17 FCM markers capable of delineating four cell clusters (epithelial, immune, endothelial, and stromal) and defining tumor classification (basal and luminal), immune infiltration, and hot-target expression on BLCa tissue samples. This FCM panel was deployed on ex vivo tissue samples treated with chemotherapy and targeted therapy agents. Initially tested on a cohort of 10 BLCa tissue samples, our validation of the FCM panel revealed correlations between marker expression and clinical-pathological features, such as the presence of metastasis and heightened immune and stromal infiltration. Notably, samples exhibiting lower claudin-4 levels displayed increased immune infiltration, while those with metastases at diagnosis showcased elevated basal marker expression. The translational potential of the FCM panel was demonstrated in ex vivo experiments where tissue slices from six patients were subjected to chemotherapy and targeted therapy agents, leading to observable shifts in marker expression post-treatment, particularly pronounced with chemotherapy. Noteworthy effects included reductions in epithelial cells expressing FGFR3 and EGFR following targeted therapy with erdafitinib or lapatinib, alongside alterations in the basal/luminal cell ratio indicated by increased CD44, CD90, and CD239 marker expressions. Our findings underscore the value of FCM in categorizing BLCa patients based on specific marker expression, supplementing conventional histological analyses to enhance cancer diagnosis, guide personalized therapeutic approaches, and monitor treatment efficacy. Citation Format: Martina Radic, Federico La Manna, Martina Minoli, Panagiotis Chouvardas, George N. Thalmann, Roland Seiler-Blarer, Marianna Kruithof-de Julio, Bernhard Kiss. Stratification of bladder cancer patients with the use of flow cytometry is increasing the diagnostic potential of molecular classifiers [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr A023.

CARDIAC AMYLOIDOSIS IN ELDERLY WITH POSITIVE SCINTIGRAPHY AND MONOCLONALITY: A DIAGNOSTIC DILEMMA

Abstract Background and Aims Clinical identification of elderly patients with both wild–type transthyretin amyloidosis (ATTR) and monoclonal gammopathy of unknown significance (MGUS) is increasing. For this reason, accurate amyloid histologic subtyping is crucial in case of concomitant positivity of bisphosphonate scintigraphy and monoclonal protein testing. We report the diagnostic work–up of cardiac amyloidosis in this specific patient subtype in our tertiary referral center. Methods Among 133 patients who received the diagnosis of cardiac amyloidosis from March 2021 to March 2023, 21 (16%) presented with an abnormality of both bisphosphonate scintigraphy and at least one of the serum monoclonal protein tests. Patients underwent abdominal fat biopsy/needle aspiration as the first diagnostic procedure. In case of negative results, an endomyocardial biopsy (EMB) was planned. Amyloid was identified at histology by Congo Red staining. Amyloid typing was obtained by immunohistochemistry using a recently developed amyloid antibody panel AmYkit (Amimed) applicable on fixed paraffin–embedded tissues in an automated platform. The results were compared with those obtained with standard immunohistochemistry. Results Sixteen of the 21 patients were older than 75 years (76%, 81±10 ys) with a grade 3 (62%) or 2 (33%) scintigraphy. A grade 1 positive scintigraphy was detected in one patient. Serum immunofixation revealed a previously unknown monoclonal protein peak in 78%, while 22% had a history of MGUS. None of the patients had hematologic disorders. TTR pathogenic mutation was detected in one patient. On pathologic examination, abdominal fat was negative for amyloid in all cases, while Congo Red staining was positive in all examined EMBs. Immunohistochemistry performed with standard antibodies was not able to discriminate between AL and ATTR, due to signal overlapping of variable intensity. Conversely, our preliminary results with AmYkit panel of antibodies demonstrate absence of signal overlapping in over 90% of cases, allowing accurate histologic discrimination between AL and TTR. Conclusion Based on our clinical and histologic observations, in elderly patients with concomitant positivity of both bisphosphonate scintigraphy and monoclonal protein testing, TTR is the most frequent type of cardiac amyloid. EMB is a useful diagnostic tool to confirm the clinical suspicion of amyloidosis. Accurate amyloid subtyping is granted by a more sensitive panel of antibodies.

Interaction of heparin with human cardiac troponin complex and its influence on the immunodetection of troponins in human blood samples.

Heparin is a highly charged polysaccharide used as an anticoagulant to prevent blood coagulation in patients with presumed myocardial infarction and to prepare heparin plasma samples for laboratory tests. There are conflicting data regarding the effects of heparin on the measurement of cardiac isoforms of troponin I (cTnI) and troponin T (cTnT), which are used for the immunodiagnosis of acute myocardial infarction. In this study, we investigated the influence of heparin on the immunodetection of human cardiac troponins. Gel filtration (GF) techniques and sandwich fluoroimmunoassay were performed. The regions of сTnI and cTnT that are affected by heparin were investigated with a panel of anti-cTnI and anti-cTnT monoclonal antibodies, specific to different epitopes. Heparin was shown to bind to the human cardiac full-size ternary troponin complex (ITC-complex) and free cTnT, which increased their apparent molecular weights in GF studies. Heparin did not bind to the low molecular weight ITC-complex and to binary cTnI-troponin С complex. We did not detect any sites on cTnI in the ITC-complex that were specifically affected by heparin. In contrast, cTnT regions limited to approximately 69-99, 119-138 and 145-164 amino acid residues (aar) in the ITC-complex and a region that lies approximately between 236 and 255 aar of free cTnT were prone to heparin influence. Heparin binds to the ITC-complex via cTnT, interacting with several sites on the N-terminal and/or central parts of the cTnT molecule, which might influence the immunodetection of analytes in human blood.

Validation of an organ mapping antibody panel for cyclical immunofluorescence microscopy on normal human kidneys.

The lack of standardization in antibody validation remains a major contributor to irreproducibility of human research. To address this, we have applied a standardized approach to validate a panel of antibodies to identify 18 major cell types and 5 extracellular matrix compartments in the human kidney by immunofluorescence (IF) microscopy. We have used these to generate an organ mapping antibody panel for two-dimensional (2-D) and three-dimensional (3-D) cyclical IF (CyCIF) to provide a more detailed method for evaluating tissue segmentation and volumes using a larger panel of markers than would normally be possible using standard fluorescence microscopy. CyCIF also makes it possible to perform multiplexed IF microscopy of whole slide images, which is a distinct advantage over other multiplexed imaging technologies that are applicable to limited fields of view. This enables a broader view of cell distributions across larger anatomical regions, allowing a better chance to capture localized regions of dysfunction in diseased tissues. These methods are broadly accessible to any laboratory with a fluorescence microscope, enabling spatial cellular phenotyping in normal and disease states. We also provide a detailed solution for image alignment between CyCIF cycles that can be used by investigators to perform these studies without programming experience using open-sourced software. This ability to perform multiplexed imaging without specialized instrumentation or computational skills opens the door to integration with more highly dimensional molecular imaging modalities such as spatial transcriptomics and imaging mass spectrometry, enabling the discovery of molecular markers of specific cell types, and how these are altered in disease.NEW & NOTEWORTHY We describe here validation criteria used to define on organ mapping panel of antibodies that can be used to define 18 cell types and five extracellular matrix compartments using cyclical immunofluorescence (CyCIF) microscopy. As CyCIF does not require specialized instrumentation, and image registration required to assemble CyCIF images can be performed by any laboratory without specialized computational skills, this technology is accessible to any laboratory with access to a fluorescence microscope and digital scanner.

Abstract PO4-09-09: Deep Immunoprofiling Demonstrates Racial Differences in the Peripheral Immune System in Women at Risk for Breast Cancer

Abstract Background: Disparities in breast cancer outcomes between Non-Hispanic Black (NHB) and Non-Hispanic White (NHW) women have been attributed to NHB women presenting with more aggressive subtypes and later stage disease, differences in treatment receipt and adherence, access to care and tumor biology. However, previous work has shown that these known factors do not fully account for the observed disparities in outcomes. Systemic immune fitness is a factor not previously studied that may play a role in dictating disease progression and therapeutic responses. Numerous factors, including age and race, impact immune system function and understanding these changes is critical to address disparities in breast cancer outcomes. Here, we developed a pipeline for deep immunoprofiling of peripheral blood mononuclear cells (PBMC) at single cell resolution by full-spectrum flow cytometry. Using this pipeline, we sought to investigate whether there are differences in immune fitness between NHB and NHW women at high risk for developing breast cancer. Methods: PBMC were collected and processed from age-matched NHB and NHW women (n=20/cohort) identified as being at high risk for developing breast cancer through our institution’s B-PREP (Breast Cancer Personalized Risk Assessment Education and Prevention) clinic. Two custom antibody panels and protocols for comprehensive immunoprofiling of T and B cell subsets (T/B Panel), as well as monocytic, NK, and dendritic cell subsets (M/N/D Panel), along with functional and exhaustion markers were designed, optimized, and implemented. Traditional gating strategies were used to quantify proportions of canonical cell populations, and unbiased high dimensionality reduction analysis was performed using the OMIQ analysis platform to assess phenotypes and functional status of various immune cell subsets. Results: Significant differences between cohorts in abundance as well as phenotype of various cell populations were observed. Specifically, CD4+ follicular helper T cells, TEMRA CD8, and CD45RA Terminal Effector CD8+ cells were enriched in NHB women while PD-1+/CD3+ cells and PD-1+/CD8+ cells were enriched in the NHW women (Table). Additionally, several immunosuppressive and systemic inflammatory immune cell types were enriched in NHB women (Table). Conclusions: Deep immunoprofiling using single-cell spectral flow cytometry revealed differences in peripheral immune cells between NHB and NHW women at high risk for breast cancer. The significant enrichment of immunosuppressive monocytes and several activated NK cell populations in PBMC samples from NHB women relative to those from NHW women indicate an altered immune environment that may influence breast cancer development. Additional analysis, including a larger sample size and patients with invasive cancer, are ongoing to further understand if differences in immune fitness between NHB and NHW women are associated with disparities in breast cancer outcomes. Table: PBMC populations (% of CD45+) that are significantly enriched in NHB relative to NHW patients Citation Format: Esther Ogayo, Milos Spasic, Tasnim Rahman, Olga Kantor, Tari King, Peter van Galen, Sandra McAllister, Elizabeth Mittendorf. Deep Immunoprofiling Demonstrates Racial Differences in the Peripheral Immune System in Women at Risk for Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-09-09.