Recombinant Humanized Antibody Research Articles

Optimizing the method for expressing human monoclonal antibodies from a single peripheral blood cell from vaccinated donors

Human monoclonal antibodies are essential diagnostic and research tools and one of the most promising therapeutics. In the past years, single B cell technologies have evolved and over-come conventional methods' limitations, enabling the isolation of scarce B cell populations with desirable characteristics. In this study, we describe a simple and efficient method to isolate anti-gen-specific plasmablasts and memory B cells from hepatitis B virus vaccinated donors' peripheral blood and consequently amplification of immunoglobulin variable region genes. Amplified immunoglobulin variable region genes were cloned into expression vectors and transfected into a human cell line to produce human recombinant monoclonal antibodies. Major challenges in this protocol were isolation of antigen-specific B cells based on surface markers, recovering mRNA from a single cell for efficient amplification, and cloning the correct insert into a desired expression vector. The essential feature of our protocol was the separation of B cells from peripheral blood mononuclear cells before sorting. We identified antigen-specific binding B cells based on the expression of surface markers CD19, CD27, IgG, and binding to hepatitis B surface antigen. Efficient single-cell reverse transcription and polymerase chain reaction (RT-PCR) were achieved using a random primer mix and Kapa Hifi Hot Start Polymerase. Amplification efficiency differed among heavy and light chain variable regions (highest at heavy chain (68 %) and lowest at lambda light chain (22 %)). After co-transfection of HEK293T/17 with successfully cloned heavy and light chain vectors, 70 % of transfected cells produced recombinant monoclonal antibodies at a concentration ∼ 4 μg/ml and 7 % of them showed binding to HBsAg. Human monoclonal antibodies from peripheral blood have advantages over antibodies of mouse origin or phage display libraries, because of their high specificity and self-tolerance. Using the described protocol, we can generate fully human monoclonal antibodies to any other antigen for application in immunotherapy or basic research.

The effectiveness of nirsevimab in reducing the burden of disease due to respiratory syncytial virus (RSV) infection over time in the Madrid region (Spain): a prospective population-based cohort study.

Respiratory syncytial virus (RSV) infection is one of the main causes of morbidity and mortality from lower respiratory tract infections in children under 5 years of age worldwide. Given that, the objective of this study was estimate the effectiveness of nirsevimab (a single-dose, long-acting, human recombinant monoclonal antibody against RSV) over time for the prevention of respiratory episodes treated at different levels of care. A prospective and dynamic population-based cohort study was performed including infants born between April 1 and December 31, 2023, in the Madrid region who resided there during the follow-up period from October 1, 2023, to February 29, 2024. Infants were considered immunized from the day after receiving one dose (50 or 100 mg) of nirsevimab or nonimmunized individuals if they did not receive any dose. There were 4,100 episodes of primary care, 1,954 hospital emergencies, and 509 admissions, 82 of which required intensive care in the 33,859 participants analyzed. The adjusted effectiveness of nirsevimab in preventing hospitalization due to RSV infection was 93.6% (95% CI: 89.7 to 96.1) at 30 days and 87.6% (95% CI: 67.7 to 95.3) at 150 days. The number needed to treat to prevent one hospitalization were 314.19 (95% CI: 306.22 to 327.99) at 30 days and 24.30 (95% CI: 22.31 to 31.61) at 150 days. The adjusted effectiveness of nirsevimab in avoiding admission to an intensive care unit was 94.4% (95% CI: 87.3 to 97.5) at 30 days and 92.1% (95% CI: 64.0 to 98.3) at 90 days. The adjusted effectiveness of nirsevimab for avoiding primary care consultations and hospital emergency visits was lower. Immunization with nirsevimab is an effective measure for reducing the burden of care related to RSV at all levels of care albeit it decreases throughout follow-up. At 150 days it remained high for preventing hospital admissions. Other articles already published have also demonstrated high effectiveness although with preliminary results, short follow-up periods and wide confidence intervals. None have detected a decrease in effectiveness over time. These results can be quite useful in individual infant prevention and in the design of immunization campaigns.

Astrocytic stress response is induced by exposure to astrocyte-binding antibodies expressed by plasmablasts from pediatric patients with acute transverse myelitis

BackgroundPediatric acute transverse myelitis (ATM) accounts for 20–30% of children presenting with a first acquired demyelinating syndrome (ADS) and may be the first clinical presentation of a relapsing ADS such as multiple sclerosis (MS). B cells have been strongly implicated in the pathogenesis of adult MS. However, little is known about B cells in pediatric MS, and even less so in pediatric ATM. Our lab previously showed that plasmablasts (PB), the earliest B cell subtype producing antibody, are expanded in adult ATM, and that these PBs produce self-reactive antibodies that target neurons. The goal of this study was to examine PB frequency and phenotype, immunoglobulin selection, and B cell receptor reactivity in pediatric patients presenting with ATM to gain insight to B cell involvement in disease.MethodsWe compared the PB frequency and phenotype of 5 pediatric ATM patients and 10 pediatric healthy controls (HC) and compared them to previously reported adult ATM patients using cytometric data. We purified bulk IgG from the plasma samples and cloned 20 recombinant human antibodies (rhAbs) from individual PBs isolated from the blood. Plasma-derived IgG and rhAb autoreactivity was measured by mean fluorescence intensity (MFI) in neurons and astrocytes of murine brain or spinal cord and primary human astrocytes. We determined the potential impact of these rhAbs on astrocyte health by measuring stress and apoptotic response.ResultsWe found that pediatric ATM patients had a reduced frequency of peripheral blood PB. Serum IgG autoreactivity to neurons in EAE spinal cord was similar in the pediatric ATM patients and HC. However, serum IgG autoreactivity to astrocytes in EAE spinal cord was reduced in pediatric ATM patients compared to pediatric HC. Astrocyte-binding strength of rhAbs cloned from PBs was dependent on somatic hypermutation accumulation in the pediatric ATM cohort, but not HC. A similar observation in predilection for astrocyte binding over neuron binding of individual antibodies cloned from PBs was made in EAE brain tissue. Finally, exposure of human primary astrocytes to these astrocyte-binding antibodies increased astrocytic stress but did not lead to apoptosis.ConclusionsDiscordance in humoral immune responses to astrocytes may distinguish pediatric ATM from HC.

Human antibodies neutralizing the alpha-latrotoxin of the European black widow.

Poisoning by widow-spider (genus Latrodectus) bites occurs worldwide. The illness, termed latrodectism, can cause severe and persistent pain and can lead to muscle rigidity, respiratory complications, and cardiac problems. It is a global health challenge especially in developing countries. Equine serum-derived polyclonal anti-sera are commercially available as a medication for patients with latrodectism, but the use of sera imposes potential inherent risks related to its animal origin. The treatment may cause allergic reactions in humans (serum sickness), including anaphylactic shock. Furthermore, equine-derived antivenom is observed to have batch-to-batch variability and poor specificity, as it is always an undefined mix of antibodies. Because latrodectism can be extremely painful but is rarely fatal, the use of antivenom is controversial and only a small fraction of patients is treated. In this work, recombinant human antibodies were selected against alpha-latrotoxin of the European black widow (Latrodectus tredecimguttatus) by phage display from a naïve antibody gene library. Alpha-Latrotoxin (α-LTX) binding scFv were recloned and produced as fully human IgG. A novel alamarBlue assay for venom neutralization was developed and used to select neutralizing IgGs. The human antibodies showed in vitro neutralization efficacy both as single antibodies and antibody combinations. This was also confirmed by electrophysiological measurements of neuronal activity in cell culture. The best neutralizing antibodies showed nanomolar affinities. Antibody MRU44-4-A1 showed outstanding neutralization efficacy and affinity to L. tredecimguttatus α-LTX. Interestingly, only two of the neutralizing antibodies showed cross-neutralization of the venom of the Southern black widow (Latrodectus mactans). This was unexpected, because in the current literature the alpha-latrotoxins are described as highly conserved. The here-engineered antibodies are candidates for future development as potential therapeutics and diagnostic tools, as they for the first time would provide unlimited supply of a chemically completely defined drug of constant quality and efficacy, which is also made without the use of animals.

A phase II study of cadonilimab plus mFOLFIRINOX as induction therapy for locally advanced pancreatic adenocarcinoma (LAPC).

TPS4213 Background: Locally advanced pancreatic adenocarcinoma (LAPC) constitutes a significant proportion of pancreatic cancer, which ranks among the most lethal malignancies globally. Treatment options specifically tailored for LAPC patients (pts) are scarce, and chemotherapy alone yields limited efficacy. Various studies have provided supportive evidence for the synergistic effects of combining immunotherapy with chemotherapy in the context of pancreatic cancer. Cadonilimab, a novel recombinant humanized bispecific antibody, holds the capability to concurrently inhibit PD-1 and CTLA-4 pathways, thereby restoring T-cell immune response to the tumor. This study aims to assess the efficacy and safety of combining cadonilimab with modified FOLFIRINOX for the treatment of LAPC. Methods: This ongoing phase II trial is enrolling pts with histologically or cytologically confirmed unresectable LAPC who have an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0-1 and have not previously received systemic anti-tumor therapy. Eligible pts will be administered cadonilimab (6mg/kg, intravenous drip, Day 1, every 2 weeks) plus mFOLFIRINOX (oxaliplatin 85mg/m2, Day 2 + leucovorin 400mg/ m2, Day 2 + irinotecan 150mg/ m2, Day 2 + 5-fluorouracil 2,400mg/ m2, continuous infusion for 46 hours) for a total of 4 cycles (8 weeks). After the completion of every 4 treatment cycles, pts will undergo imaging examinations of tumor lesions. Pts will receive treatment continuously until surgical resection, disease progression, intolerable toxic reactions, initiation of new anticancer drug treatments, withdrawal from the study, death, or loss of follow-up. Following the 12th cycle of treatment, maintenance treatment will consist of capecitabine or S-1 in combination with cadonilimab. The primary endpoint of this study was the R0/R1 resection rate. The main secondary endpoints include the objective response rate (ORR) per RECIST 1.1, progression-free survival (PFS), overall survival (OS), and safety assessments. Additionally, pts will undergo peripheral blood next-generation sequencing (NGS) panel analysis before and after treatment to investigate the correlation between circulating tumor DNA (ctDNA) changes, surgical decisions, and prognosis. Enrollment is ongoing. Clinical trial information: NCT06153368 .

First-in-human study of ZGGS15, a dual specific antibody targeting LAG-3 and TIGIT, as monotherapy in patients with advanced solid tumors.

e14678 Background: ZGGS15 is a recombinant humanized bispecific antibody composed of a monoclonal antibody against LAG-3 and TIGIT. It can specifically bind LAG-3 and TIGIT. It reverses LAG-3 and TIGIT immune suppression to T and NK cells, relieves suppression of Treg to T and NK cells, promotes the activation and proliferation of T and NK cells, and cytokines release. ZGGS15 restores T and NK cell functions to kill tumor cells. In non-clinical studies, we found that ZGGS15 had significant anti-tumor effects and synergistic anti-tumor effects with Anti-PD-1 antibody. Therefore, we conducted a Phase 1 clinical study to assess the tolerability, safety, and preliminary efficacy of this drug as monotherapy in patients with advanced solid tumors. Methods: During the dose escalation stage, an accelerated titration design (ATD) in the first dose (1 subject if ≤Grade 2 treatment-related adverse event occurred) and the standard "3+3" design in the rest doses were used. Subjects were patients with advanced solid tumors who failed to the available standard treatments. The dose groups were set from 0.3 to 30 (0.3, 1, 3, 10, 20, 30) mg/kg, intravenous infusion, once every 3 weeks. The first 21-day period was defined as the dose-limiting toxicity (DLT) observation period. Subjects could continue to receive ZGGS15 until treatment discontinuation criteria were met. Tumor response was assessed by RECIST1.1 and iRECIST. Pharmacokinetics (PK) and receptor occupancy (RO) profiles were also assessed in this study. Results: A total of 12 patients (4 males and 8 females) completed the DLT observation in the first four dose groups (0.3 to 10 mg), with a median age of 57 years. Eight (66.7%) of them received at least 3 lines of antineoplastic therapies, and five (41.7%) have been exposed to PD-1 or PD-L1 inhibitors. There was no DLT event observed. Thirty-eight treatment-related adverse events (TRAEs) occurred. Up to now, TRAEs were all grade 1 ~ 2. The most frequent TRAEs were proteinuria (33.3%, 4/12), hypokalemia (25%, 3/12), hypoalbuminemia (25%, 3/12), and hypertriglyceridemia (25%, 3/12). The Cmax and AUC increased from 0.3-1 mg/kg approximately in dose proportion. Nearly complete and sustained RO of T and NK cells in PBMCs was observed at 1 mg/kg dose of ZGGS15 for at least 3 weeks. Conclusions: The first four dose levels of ZGGS15 were very well tolerated. A good PK profile, and a long-lasting RO were observed in this escalation study. It is anticipated that this product could provide an additional benefit only when use in combination with an anti-PD-1 antibody. Clinical trial information: NCT05864573 .

Isolation and characterization of rabies monoclonal antibody charge variants.

Current postexposure prophylaxis of rabies includes vaccines, human rabies immunoglobulin (RIG), equine RIG, and recombinant monoclonal antibodies (mAb). In the manufacturing of rabies recombinant mAb, charge variants are the most common source of heterogeneity. Charge variants of rabies mAb were isolated by salt gradient cation exchange chromatography (CEX) to separate acidic and basic and main charge variants. Separated variants were further extensively characterized using orthogonal analytical techniques, which include secondary and tertiary structure determination by far and near ultraviolet circular dichroism spectroscopy. Charge and size heterogeneity were evaluated using CEX, isoelectric focusing (IEF), capillary-IEF, size exclusion chromatography, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and western blotting. Antigen binding affinity was assessed by enzyme linked immuno-sorbent assay and rapid florescence foci inhibition test. Results from structural and physicochemical characterizations concluded that charge variants are formed due to posttranslational modification demonstrating that the charge heterogeneity, these charge variants did neither show any considerable physicochemical change nor affect its biological function. This study shows that charge variants are effective components of mAb and there is no need of deliberate removal, until biological functions of rabies mAb will get affected.

Validation of an enzyme-linked immunosorbent assay test-system for bevacizumab concentration determing in biological fluids

Introduction. One of the reasons for the development of many diseases primarily malignant is the increased expression of Vascular Endothelial Growth Factor (VEGF). Bevacizumab is a drug that neutralizes the biological activity of VEGF. The molecular structure of bevacizumab is a recombinant humanized antibody. Its use reduces vascularization in the foci of increased VEGF expression which slows down tumor growth and also helps restore vision in a number of ophthalmic diseases. To determine the concentration of bevacizumab in human biological fluids a test system based on Enzyme-linked Immunosorbent Assay (ELISA) is presented.Aim. Aim of this study is the validation of this test system.Materials and methods. Blank sera of volunteers, bevacizumab solution, enzyme-linked immunosorbent assay, solid-phase sandwich ELISA kit, microplate photometer.Results and discussion. The following characteristics of the test system were determined: the lower limit of quantification is 2.0 mcg/ml, the upper calibration range is up to 200 mcg/ml, the accuracy and precision within one series and between series does not exceed 20 %, and the total error of the method – 30 %, short-term stability for samples at room temperature – 6 hours, long-term stability – 14 days at –20 °C, the ability to freeze/thaw of samples is up to three times, the ability to determine samples with a concentration above the upper calibrator after diluting in 2 times.Conclusion. The results obtained fully comply with international acceptance criteria and allow the use of the ELISA test system manufactured by LLC "Probiotek" for use in the field of clinical laboratory diagnostics.

Neutralizing anti-diphtheria toxin scFv produced by phage display.

Diphtheria can be prevented by vaccination, but some epidemics occur in several places, and diphtheria's threat is considerable. Administration of diphtheria antitoxin (DAT) produced from hyperimmunized animals is the most common treatment. Recombinant human antibody fragments such as single-chain variable fragments (scFv) produced by phage display library may introduce an interesting approach to overcome the limitations of the traditional antibody therapy. In the present study, B cells of immunized volunteers were used to construct a human single-chain fragment (HuscFv) library. The library was constructed with the maximum combination of heavy and light chains. As an antigen, Diphtheria toxoid (DTd) was used in four-round phage bio-panning to select phage clones that display DTd bound HuscFv from the library. After panning, individual scFv clones were selected. Clones that were able to detect DTd in an initial screening assay were transferred to Escherichia coli HB2151 to express the scFvs and purification was followed by Ni metal ion affinity chromatography. Toxin neutralization test was performed on Vero cells. The reactivity of the soluble scFv with diphtheria toxin were done and affinity calculation based on Beatty method was calculated. The size of the constructed scFv library was calculated to be 1.3×106 members. Following four rounds of selection, 40 antibody clones were isolated which showed positive reactivity with DTd in an ELISA assay. Five clones were able to neutralize DTd in Vero cell assay. These neutralizing clones were used for soluble expression and purification of scFv fragments. Some of these soluble scFv fragments show neutralizing activity ranging from 0.6 to 1.2µg against twofold cytotoxic dose of diphtheria toxin. The affinity constant of the selected scFv antibody was determined almost 107M-1. This study describes the prosperous construction and isolation of scFv from the immune library, which specifically neutralizes diphtheria toxin. The HuscFv produced in this study can be a potential candidate to substitute the animal antibody for treating diphtheria and detecting toxins.

Real-Life Study of Patient Preference for Dupilumab or Revision Surgery for Recurrent Chronic Rhinosinusitis with Nasal Polyps.

(1) Background: Chronic rhinosinusitis with nasal polyps (CRSwNP) has a high rate of recurrence in patients, despite therapy with local corticosteroids and functional endoscopic sinus surgery. Dupilumab, a recombinant monoclonal human IgG4 antibody directed against the IL-4 receptor α that inhibits both IL-4 and IL-13 signal transduction, is available for symptomatic therapy. Patient preference between repeated surgery and injection therapy with Dupilumab is not known. (2) Methods: Patients who had experienced at least one surgical intervention for nasal polyps and were treated with Dupilumab for at least 3 months completed a retrospective patient questionnaire. (3) Results: In a cohort of 75 previously operated CRSwNP patients, 91.5% preferred therapy with Dupilumab to repeated surgery for nasal polyps. Preference for Dupilumab in the subgroups of patients with concomitant Non-steroidal Anti-inflammatory Drugs Exacerbated Respiratory Disease (N-ERD) (n = 32), patients with concomitant asthma (n = 25), and patients without concomitant disease (n = 18) was 100%, 96%, and 72%, respectively. (4) Conclusions: Patient preference for Dupilumab over repeat surgery is strongest in previously operated CRSwNP patients with concomitant asthma or N-ERD, but remains very high in patients without concomitant disease.

Abstract 1364: Characterization of CHS-1000, an Fc-modified anti-ILT4 monoclonal antibody for reprogramming suppressive myeloid cells in solid tumors

Abstract Tumor resident immunosuppressive myeloid cells play a significant role in inducing resistance to cancer immunotherapy and are associated with poor prognosis in several solid tumors. The leukocyte immunoglobulin-like receptor B2 (LILRB2), also known as ILT4, is primarily expressed on myeloid cells and is a negative regulator of myeloid cell activation. ILT4 and its primary ligands (HLA-G, HLA-A) are widely expressed in various solid tumors and are associated with disease progression, tumor metastasis and poor clinical outcome. Abrogating inhibitory signals mediated through ILT4 and its ligands is a promising strategy to reprogram suppressive myeloid cells and enhance efficacy of immune checkpoint therapies. Here we report IND-enabling preclinical characterization of CHS-1000, a novel recombinant humanized Fc-modified IgG1 antibody with attenuated Fc-gamma receptor (FcγR) binding, that specifically targets immunoglobulin-like transcript 4 (ILT4). CHS-1000 selectively binds to human ILT4 with high affinity and potently blocks ILT4 interactions with its primary ligands (HLA-A, HLA-G). Functionally, CHS-1000 promotes re-polarization of suppressive myeloid cells to a pro-inflammatory phenotype and enhances activation of dendritic cells and T cells. Combinations of CHS-1000 with PD-1 inhibitors or other immunotherapy agents hold particular promise for enhanced anti-tumor activity. These preclinical characterization data support clinical development of CHS-1000 in combination with toripalimab (a commercial stage anti-PD-1 antibody) as an immunotherapy treatment for patients with solid tumors. Citation Format: Narendiran Rajasekaran, Xiaoguang Wang, Scott Klakamp, Sruthi Ravindranathan, Suzanna Tatarewicz, Julia Du, Brian Nguyen, Kate Widmann, Nessa Hawkins, Daniel J. Chin, Theresa LaVallee, Varun Kapoor. Characterization of CHS-1000, an Fc-modified anti-ILT4 monoclonal antibody for reprogramming suppressive myeloid cells in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1364.

Rapid generation of human recombinant monoclonal antibodies from antibody-secreting cells using ferrofluid-based technology.

Monoclonal antibodies (mAbs) are one of the most important classes of biologics with high therapeutic and diagnostic value, but traditional methods for mAbs generation, such as hybridoma screening and phage display, have limitations, including low efficiency and loss of natural chain pairing. To overcome these challenges, novel single B cell antibody technologies have emerged, but they also have limitations such as in vitro differentiation of memory B cells and expensive cell sorters. In this study, we present a rapid and efficient workflow for obtaining human recombinant monoclonal antibodies directly from single antigen-specific antibody secreting cells (ASCs) in the peripheral blood of convalescent COVID-19 patients using ferrofluid technology. This process allows the identification and expression of recombinant antigen-specific mAbs in less than 10 days, using RT-PCR to generate linear Ig heavy and light chain gene expression cassettes, called "minigenes", for rapid expression of recombinant antibodies without cloning procedures. This approach has several advantages. First, it saves time and resources by eliminating the need for in vitro differentiation. It also allows individual antigen-specific ASCs to be screened for effector function prior to recombinant antibody cloning, enabling the selection of mAbs with desired characteristics and functional activity. In addition, the method allows comprehensive analysis of variable region repertoires in combination with functional assays to evaluate the specificity and function of the generated antigen-specific antibodies. Our approach, which rapidly generates recombinant monoclonal antibodies from single antigen-specific ASCs, could help to identify functional antibodies and deepen our understanding of antibody dynamics in the immune response through combined antibody repertoire sequence analysis and functional reactivity testing.

Recombinant human scFv antibody fragments against phospholipase A2 from Naja naja and Echis carinatus snake venoms: In vivo neutralization and mechanistic insights

Snake envenomation results in a range of clinical sequelae, and widely used animal-based conventional antivenoms exhibit several limitations including the adverse immunological effects in human snake bite victims. Therefore, human monoclonal anti-snake venom antibodies or fragments can be an alternate therapy for overcoming the existing limitations. We developed venom-neutralizing humanized scFv antibodies and analyzed biochemical mechanisms associated with the inhibition of toxicity. Tomlinson I and J human scFv antibody libraries were screened against Naja naja and Echis carinatus venoms, and seven unique scFv antibodies were obtained. Further, specific toxins of snake venom interacting with each of these scFvs were identified, and phospholipase A2 (PLA2) was found to be prominently captured by the phage-anchored scFv antibodies. Our study indicated PLA2 to be one of the abundant toxins in Naja naja and Echis carinatus venom samples. The scFvs binding to PLA2 were used to perform in vivo survival assay using the mouse model and in vitro toxin inhibition assays. scFv N194, which binds to acidic PLA2, protected 50% of mice treated with Naja naja venom. Significant prolongation of survival time and 16% survival were observed in Echis carinatus venom-challenged mice treated with scFv E113 and scFv E10, respectively. However, a combination comprised of an equal amount of two scFvs, E113 and E10, both interacting with basic PLA2, exhibited synergistically enhanced survival of 33% in Echis carinatus venom-challenged mice. No such synergistically enhanced survival was observed in the case of combinatorial treatment with anti-Naja naja scFvs, N194, and N248. These scFvs demonstrated partial inhibition of venom-induced myotoxicity, and E113 also inhibited hemolysis by 50%, which corroborates the enhanced survival during combinatorial treatment in Echis carinatus venom-challenged mice.

295. Humanized Mice and Convalescent Humans Yield an Antibody Panel against the Highly Immunogenic Decorin Binding Protein A (DbpA) of the Lyme Disease Spirochete, Borrelia Burgdorferi

Abstract Background Lyme disease is the most commonly diagnosed tick-borne infection, affecting more than 300000 people in the United States annually. The disease is principally caused by the transmission of the spirochete bacteria, by the black-legged (deer) ticks. With a renewed call for interest in a Lyme disease vaccine, antibodies relevance continues due to their efficacy, safety and versatile nature. Humanized mice and humans recovering from the disease have successfully been used to generate therapeutic antibodies against Ebola and SARS-CoV-2 diseases. Methods Our study used humanized mice and convalescent patients to generate recombinant human antibodies that recognize decorin-binding protein A (DbpA), a lipoprotein that is proposed to function as spirochete adhesin. The mAbs expressed as human IgG-Fc fragments were characterized for reactivity with recombinant DbpA, native DbpA on the surface of live Borrelia burgdorferi, borreliacidal activity in the presence of human complement and, finally subject to epitope mapping using an array of methodologies. Results The predominant lineage of humanized mice antibodies utilized VH5-51, VH3-20, VH3-23 and VH3-53 all paired with VK1-33 families. Other common families included VH4-31 paired with VK1-39, VH4-4 and VH4-8 paired with VK-9. The human derived antibody utilized VH3-30 paired with VK1-33. We observed an overlap in the repertoire of kappa chains between humanized mice and human-derived mAbs. Conclusion Combining the humanized mice and human platforms enabled the identification of antibodies with a high binding and specificity to DbpA, which have potential prophylactic and therapeutic properties. Disclosures All Authors: No reported disclosures

Neutralization of Centruroides tecomanus scorpion venom by the use of two human recombinant antibody fragments

The first toxic component identified against mammals in the venom from Centruroides tecomanus scorpion from Colima, Mexico was Ct1a toxin, which was neutralized by human single chain variable fragment (scFv) RAS27. Venom characterization from these scorpions collected on the Pacific coast of Colima, enabled the identification of a second component of medical importance named Ct71 toxin. Amino acid sequence of Ct71 shares a high identity with Chui5 toxin from C. huichol scorpion, which was neutralized by scFv HV. For this reason, the kinetic parameters of interaction between Ct71 toxin and scFv HV were determined by surface plasmon resonance. Results showed a significantly higher affinity for Ct71 as compared to Chui5. As expected, this toxin was neutralized by scFv HV. The injection of a mixture of scFvs HV and RAS27, resulted in the neutralization of C. tecomanus venom, corroborating that human recombinant antibody fragments can efficiently contribute to the neutralization of medically important toxins and their respective venoms from Mexican scorpions.

Expanding the Anti-Phl p 7 Antibody Toolkit: An Anti-Idiotype Nanobody Inhibitor.

We have previously produced a toolkit of antibodies, comprising recombinant human antibodies of all but one of the human isotypes, directed against the polcalcin family antigen Phl p 7. In this work, we complete the toolkit of human antibody isotypes with the IgD version of the anti-Phl p 7 monoclonal antibody. We also raised a set of nanobodies against the IgD anti-Phl p 7 antibody and identify and characterize one paratope-specific nanobody. This nanobody also binds to the IgE isotype of this antibody, which shares the same idiotype, and orthosterically inhibits the interaction with Phl p 7. The 2.1 Å resolution X-ray crystal structure of the nanobody in complex with the IgD Fab is described.

Production of recombinant humanized monoclonal anti-human neutrophil antigen (HNA) antibodies with potential applicability as standard antibodies.

Antibodies against human neutrophil antigen (HNA) are involved in the pathogenesis of neonatal alloimmune neutropenia, autoimmune neutropenia, and transfusion-related acute lung injury. The present methods for anti-HNA antibody identification strongly depend on the presence of standard antisera with known allo/isospecificities. Here, we aimed to produce recombinant humanized antibodies to HNA from available mouse monoclonal antibodies (MoAbs). RNAs were extracted from available hybridoma cells producing mouse anti-HNA antibodies recognizing HNA-1a (TAG-1), -1b (TAG-2), -2 (TAG-4), and FcγRIIIb, and the cDNA was synthesized. Recombinant fragments consisting of the variable regions of the H and L chains of the mouse MoAb ligated to the constant region of human IgG were incorporated into an expression vector and transfected into CHO cells. Antibody specificity of the selected humanized monoclonal antibodies was confirmed, and tested by the participants of the ISBT Granulocyte Immunobiology Working Party (GIWP) workshop 2020. GIFT results confirmed the specific reactivity of TAGH-1 to -4, except for a cross-reactivity of TAGH-2 with HNA-1a/a neutrophils, only in flow-cytometry. MAIGA results showed clear specificity of all humanized antibodies, but the selection of the appropriate capture monoclonal antibody was essential for the test. The results of the ISBT GIWP showed high concordance among the labs. These are the first humanized monoclonal antibodies to HNA-1 and HNA-2 antigens produced and they will be important standard reagents for laboratories testing for neutrophil antibodies. We plan to have these humanized MoAbs available through WHO.

Successful treatment of pulmonary hypertension and right heart failure by antibody-based functional blocking of the extra-domain A of fibronectin in a preclinical animal model

Abstract Background Pulmonary Hypertension (PH) as heterogeneous disease group is pathogenetically accompanied by pulmonary vascular and right ventricular tissue remodelling showing similarities between the clinical groups 1 (Pulmonary Arterial Hypertension), 2 (PH associated with left heart disease) and 3 (PH associated with lung disease). Since the remodelling process entails the abundant re-expression of extra-domain A containing fibronectin (ED-A+ Fn), which is virtually absent in healthy adult organs, a potential functional role in PH development and progression has been suggested and recently proven by our group. The human recombinant antibody F8 (IgG) specifically recognises ED-A+ Fn and is capable to block its function at least in vitro. Thus, F8 might serve as a novel therapeutic agent for the treatment or even prevention of PH. Purpose Against that background, the current study was aimed to test the therapeutic efficacy of F8 after systemic administration in a well-established preclinical model of PH in comparison to a non-specific control antibody and a dual endothelin receptor antagonist as standard of care. Methods Induction of PH was realized by subcutaneous injection of Monocrotaline (MCT) in mice. In total, 41 animals were included in the study approach and were divided into the following experimental groups: sham-treated controls (controls; n=7), PH mice without a specific treatment (PH_untreated; n=12), PH mice treated with the dual endothelin receptor antagonist Macitentan (PH_MAC; n=6), PH mice treated with the F8 antibody (PH_F8; n=8) and PH mice treated with an antibody of irrelevant antigen specificity in the murine system (PH_KSF; n=8). Treatment effects were evaluated on the haemodynamic, echocardiographic and microscopic level. Results In comparison to controls, untreated PH mice showed significantly higher right ventricular systolic pressure values (RVPsys, p<0.05) as well as impaired echocardiographic parameters of right ventricular morphology and function, i.e., enlarged basal right ventricular (RVbasal, p=0.016) diameters and reduced tricuspid annular plane systolic excursion values (TAPSE, p=0.008). In the PH_F8 group, haemodynamic and echocardiographic parameters were significantly improved compared to the PH_untreated or the PH_KSF group (p<0.05 for the majority of parameters). Histological evaluation revealed significant lung tissue damage after in the PH_untreated group compared to controls (p=0.008), which were significantly attenuated in the PH_F8 (p=0.04) but not the PH_KSF group (p=n.s.). Conclusion The therapeutic efficacy of the human recombinant F8 antibody specific to ED-A+ Fn has been proven for the first time in vivo in a well-established preclinical model of PH. F8 acts as a disease-modifier by attenuating PH associated lung tissue remodelling resulting in remarkable improvements of pulmonary hemodynamics and echocardiographic parameters of right ventricular load.

Impaired functional connectivity of the hippocampus in translational murine models of NMDA-receptor antibody associated neuropsychiatric pathology

Decreased hippocampal connectivity and disruption of functional networks are established resting-state functional MRI (rs-fMRI) features that are associated with neuropsychiatric symptom severity in human anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. However, the underlying pathophysiology of NMDAR encephalitis remains poorly understood. Application of patient-derived monoclonal antibodies against the NR1 (GluN1) subunit of the NMDAR now allows for the translational investigation of functional connectivity in experimental murine NMDAR antibody disease models with neurodevelopmental disorders. Using rs-fMRI, we studied functional connectivity alterations in (1) adult C57BL/6 J mice that were intrathecally injected with a recombinant human NR1 antibody over 14 days (n = 10) and in (2) a newly established mouse model with in utero exposure to a human recombinant NR1 antibody (NR1-offspring) at the age of (2a) 8 weeks (n = 15) and (2b) 10 months (n = 14). Adult NR1-antibody injected mice showed impaired functional connectivity within the left hippocampus compared to controls, resembling impaired connectivity patterns observed in human NMDAR encephalitis patients. Similarly, NR1-offspring showed significantly reduced functional connectivity in the hippocampus after 8 weeks, and impaired connectivity in the hippocampus was likewise observed in NR1-offspring at the age of 10 months. We successfully reproduced functional connectivity changes within the hippocampus in different experimental murine systems that were previously observed in human NMDAR encephalitis patients. Translational application of this method within a combined imaging and histopathological framework will allow future experimental studies to identify the underlying biological mechanisms and may eventually facilitate non-invasive monitoring of disease activity and treatment responses in autoimmune encephalitis.

A novel bispecific antibody dual-targeting approach for enhanced neutralization against fast-evolving SARS-CoV-2 variants.

The emergence of new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has caused unprecedented health and socioeconomic crises, necessitating the immediate development of highly effective neutralizing antibodies. Despite recent advancements in anti-SARS-CoV-2 receptor-binding domain (RBD)-specific monoclonal antibodies (mAbs) derived from convalescent patient samples, their efficacy against emerging variants has been limited. In this study, we present a novel dual-targeting strategy using bispecific antibodies (bsAbs) that specifically recognize both the SARS-CoV-2 RBD and fusion peptide (FP), crucial domains for viral attachment to the host cell membrane and fusion in SARS-CoV-2 infection. Using phage display technology, we rapidly isolated FP-specific mAbs from an established human recombinant antibody library, identifying K107.1 with a nanomolar affinity for SARS-CoV-2 FP. Furthermore, we generated K203.A, a new bsAb built in immunoglobulin G4-(single-chain variable fragment)2 forms and demonstrating a high manufacturing yield and nanomolar affinity to both the RBD and FP, by fusing K102.1, our previously reported RBD-specific mAb, with K107.1. Our comprehensive in vitro functional analyses revealed that the K203.A bsAb significantly outperformed the parental RBD-specific mAb in terms of neutralization efficacy against SARS-CoV-2 variants. Furthermore, intravenous monotherapy with K203.A demonstrated potent in vivo neutralizing activity without significant in vivo toxicity in a mouse model infected with a SARS-CoV-2 variant. These findings present a novel bsAb dual-targeting strategy, directed at SARS-CoV-2 RBD and FP, as an effective approach for rapid development and management against continuously evolving SARS-CoV-2 variants.