Rabbit Antibodies Research Articles

Experimental Induction of Anti-Muscarinic Type-3-Receptor Extracellular Loop Antibodies by Immunization with 4-Hydroxy-2-nonenal Modified Ro60 and Unmodified Ro60.

Sjögren's Disease (SjD) subjects have decreased lacrimal/salivary gland function. Studies have proposed that autoantibodies targeting G-protein-coupled muscarinic acetylcholine-type-3-receptor (M3R) are potential clinical markers for SjD. We hypothesized that rabbits/mice immunized with 4-hydroxy-2-nonenal (HNE)-modified/unmodified Ro60 will develop an autoimmunity, specifically a SjD phenotype, thus expressing increased levels of anti-M3R antibodies. We immunized two rabbits each with 10mM HNE-modified Ro60/unmodified Ro60 antigen or Ro274-290/Ro413-428/Ro500-517 Ro60 peptides. Two rabbits each were immunized with either M3R second extracellular loop (ECL2) or M3R ECL3 peptide. Finally, five groups of BALB/c mice were immunized as follows-Group-I immunized with Ro60, Groups-II-IV immunized with Ro60 modified with 0.4mM (low), 2mM (medium) and 10mM (high) HNE respectively and Group-V-Freund's adjuvant. Serum antibodies to M3R ECL2/ECL3/Ro60/La or Sm were detected by ELISA. Functional assays were also performed. Immunization with HNE-modified Ro60/unmodified Ro60 antigen or Ro274/Ro 413/Ro500 peptides induced a rapid intermolecular epitope spreading to M3R ECL2/ECL3, especially to M3R ECL3 in HNE-Ro immunized rabbits. These animals did not bind to scrambled M3R peptides. Ro60-immunized rabbit IgG inhibited M3R activity in a functional assay. Rabbits immunized with ECL2/ECL3 developed high reactivity to Ro60 but not against Sm/RNP. We found a differential antibody-induction against M3R ECL2 with Group-3 mice developing significant reactivity. Our data show induction of increasing anti-M3R antibodies in rabbits immunized with Ro60/HNE-Ro60 or Ro60 peptides and differential induction of these antibodies in mice immunized with Ro60 modified with increasing HNE. These findings suggest that M3R ECL2/ECL3 are involved in SjD autoimmunity progression.

Development and application of an uncapped mRNA platform

Background A novel uncapped mRNA platform was developed. Methods Five lipid nanoparticle (LNP)-encapsulated mRNA constructs were made to evaluate several aspects of our platform, including transfection efficiency and durability in vitro and in vivo and the activation of humoral and cellular immunity in several animal models. The constructs were eGFP-mRNA-LNP (for enhanced green fluorescence mRNA), Fluc-mRNA-LNP (for firefly luciferase mRNA), SδT-mRNA-LNP (for Delta strain SARS-CoV-2 spike protein trimer mRNA), gDED-mRNA-LNP (for truncated glycoprotein D mRNA coding ectodomain from herpes simplex virus type 2 (HSV2)) and gDFR-mRNA-LNP (for truncated HSV2 glycoprotein D mRNA coding amino acids 1–400). Results Quantifiable target protein expression was achieved in vitro and in vivo with eGFP- and Fluc-mRNA-LNP. SδT-mRNA-LNP, gDED-mRNA-LNP and gDFR-mRNA-LNP induced both humoral and cellular immune responses comparable to those obtained by previously reported capped mRNA-LNP constructs. Notably, SδT-mRNA-LNP elicited neutralizing antibodies in hamsters against the Omicron and Delta strains. Additionally, gDED-mRNA-LNP and gDFR-mRNA-LNP induced potent neutralizing antibodies in rabbits and mice. The mRNA constructs with uridine triphosphate (UTP) outperformed those with N1-methylpseudouridine triphosphate (N1mψTP) in the induction of antibodies via SδT-mRNA-LNP. Conclusions Our uncapped, process-simplified and economical mRNA platform may have broad utility in vaccines and protein replacement drugs. KEY MESSAGES The mRNA platform described in our paper uses internal ribosome entry site (IRES) (Rapid, Amplified, Capless and Economical, RACE; Register as BH-RACE platform) instead of caps and uridine triphosphate (UTP) instead of N1-methylpseudouridine triphosphate (N1mψTP) to synthesize mRNA. Through the self-developed packaging instrument and lipid nanoparticle (LNP) delivery system, mRNA can be expressed in cells more efficiently, quickly and economically. Particularly exciting is that potent neutralizing antibodies against Delta and Omicron real viruses were induced with the new coronavirus S protein mRNA vaccine from the BH-RACE platform.

In vivo Study of Nano Chitosan Beads-Based ELISA versus Traditional Sandwich ELISA for the Early Diagnosis of Trichinosis

Human trichinosis is a serious foodborne parasitic zoonosis. Diagnosing human trichinosis is usually difficult due to the nonspecific clinical picture and the limited effectiveness of serological tests in acute infections. While ELISA can detect circulating Trichinella antigens, aiding in early diagnosis, its sensitivity may be low. The application of nanoparticles can improve the sensitivity of ELISA and allow a specific early diagnosis of the disease. This work compares the nano chitosan beads-based ELISA (NCSB-ELISA) and traditional sandwich ELISA for the detection of circulating Trichinella spiralis (T. spiralis) crude extract-antigen (CEA) in serum samples of experimentally infected mice.Fifty-seven mice included in this study were classified into 3 groups: T. spiralis infected group (Group I) (36 mice), which was equally subdivided into six subgroups according to the time of sacrifice (6, 8, 10, 12, 14 and 16) day post-infection (dpi), cross-reactivity group (Group II) (9 mice) and negative control group (Group III) (12 mice). T. spiralis AW-CEA prepared from the adult worms were used to produce anti- T. spiralis IgG-polyclonal antibodies in rabbits; these antibodies were utilized to detect AW-CEA in serum samples by traditional sandwich ELISA and NCSB-ELISA. Using NCSB-ELISA, T. spiralis AW-CEA was detected in sera collected at 8 dpi, with a sensitivity of 50% and a specificity of 100%. Meanwhile, traditional sandwich ELISA could not detect the antigen at the same time interval. Both ELISA techniques were able to detect the antigen in samples collected at 10, 12, 14 and 16 dpi with a sensitivity of 16.67%, 50%, 67.67% and 83.67%, respectively, for traditional sandwich-ELISA and a specificity of 100% at 10, 12 and 14 dpi while at 16 dpi specificity was decreased to 90.91%. In contrast, the sensitivity of NCSB-sandwich ELISA on the same days was 66.67%, 83.34%, 100% and 100%, respectively, with a specificity of 100% at all days. False positive detection of T. spiralis AW-CEA in the serum of mice in GII was recorded on day 16 pi by only traditional sandwich ELISA.This study concluded that NCSB-ELISA is a promising and sensitive technique for the early and specific diagnosis of acute trichinosis in an animal model.

Unveiling the structural mechanisms behind high affinity and selectivity in phosphorylated epitope-specific rabbit antibodies

Protein phosphorylation is a crucial process in various cellular functions, and its irregularities have been implicated in several diseases, including cancer. Antibodies are commonly employed to detect protein phosphorylation in research. However, unlike the extensive studies on recognition mechanisms of the phosphate group by proteins such as kinases and phosphatases, only a few studies have explored antibody mechanisms. In this study, we produced and characterized two rabbit monoclonal antibodies that recognize a mono-phosphorylated Akt peptide. Through crystallography, thermodynamic mutational analyses, and molecular dynamics simulations, we investigated the unique recognition mechanism that enables higher binding affinity and selectivity of the antibodies compared to other generic proteins with lower binding affinity to phosphorylated epitopes. Our results demonstrate that molecular dynamics simulations provide novel insights into the dynamic aspects of molecular recognition of post-translational modifications by proteins beyond static crystal structures, highlighting how specific atomic level interactions drive the exceptional affinity and selectivity of antibodies.

Identification of new targets for the diagnosis of cysts (four) and trophozoites (one) of the eye pathogen Acanthamoeba.

Free-living amoeba in the soil or water cause Acanthamoeba keratitis, which is diagnosed by identification of cysts by microscopy of the eye or of corneal scrapings, using calcofluor-white that unfortunately cross-reacts with fungi and plants. Alternatively, Acanthamoeba infections are diagnosed by identification of trophozoites in cultures of scrapings. Here we showed that rabbit antibodies to four abundant cyst wall proteins (Jonah, Luke, Leo, and laccase) each efficiently detect calcofluor-white-labeled cysts of 10 of 11 Acanthamoeba isolates obtained from the ATCC. Further, laccase released into the medium by encysting Acanthamoebae was detected by an enzyme-linked immunoassay. We also showed that rabbit antibodies to the mannose-binding domain of the Acanthamoeba mannose-binding protein, which mediates adherence of trophozoites to keratinocytes, efficiently identifies trophozoites of all 11 ATCC isolates. In summary, four wall proteins and the ManBD appear to be excellent targets for diagnosis of Acanthamoeba cysts and trophozoites, respectively.

Generation of Antibody Libraries for Phage Display: Chimeric Rabbit/Human Fab Format.

Rabbit monoclonal antibodies are attractive reagents for research, and have also found use in diagnostic and therapeutic applications. This is owed to their high affinity and specificity, along with their ability to recognize epitopes conserved between mouse and human antigens. Phage display is a powerful method for the de novo generation, affinity maturation, and humanization of rabbit monoclonal antibodies from naive, immune, and synthetic antibody repertoires. Using phagemid family pComb3, a preferred phage display format is chimeric rabbit/human Fab, which consists of rabbit variable domains (VH, Vκ, and Vλ) fused to human constant domains. The human constant domains, CH1 of IgG1 and CL (Cκ or Cλ), not only provide established purification and detection handles but also facilitate higher expression in Escherichia coli compared to the corresponding rabbit constant domains. Here, we describe the use of a pComb3 derivative, phagemid pC3C, for the generation of chimeric rabbit/human Fab libraries with randomly combined rabbit variable domains of high sequence diversity, starting from the preparation of total RNA from rabbit spleen and bone marrow. Depending on the complexity of the parental antibody repertoire, the protocol can be scaled for yielding a library size of 108-1011 independent chimeric rabbit/human Fab clones. As such, it can be used, for instance, for the generation of either specialized immune or large naive rabbit antibody libraries.

Optimizing antigen preparation for oxalyl-CoA decarboxylase enzyme diagnostic kit and ELISA system cutoff determination.

The prevalence of kidney stone disease is increasing globally, with calcium oxalate stones being the most common type. Oxalyl-CoA decarboxylase (OXC), an enzyme produced by the gut bacterium Oxalobacter formigenes, plays a crucial role in oxalate metabolism. Deficiencies in OXC activity can lead to the accumulation of oxalate, contributing to kidney stone formation. This study aimed to develop a reliable diagnostic assay for OXC by optimizing antigen production and establishing a cutoff value for an enzyme-linked immunosorbent assay (ELISA). We cloned, expressed, and purified recombinant OXC protein in Escherichia coli BL21(DE3), and generated specific polyclonal antibodies in rabbits. The ELISA system was optimized and validated using serum samples from 40 healthy individuals and 6 patients with oxalate-related disorders. The cutoff value was determined using the formula (M + 2SD), where (M) is the mean and (SD) is the standard deviation of the healthy sample results. The calculated cutoff value of 0.656750 effectively distinguished between healthy and affected individuals, with a sensitivity of 97.5% and a specificity of 83.3%. These findings provide a valuable tool for the early detection and management of oxalate-related disorders, with significant implications for clinical practice.

Serotype 15C Streptococcus pneumoniae resistant to classical complement deposition and agglutination by polyclonal rabbit anti-capsular 15B sera

BackgroundS. pneumoniae (SP) serotypes 15B and 15C are frequent causative agents of invasive pneumococcal disease (IPD), otitis media, and nasopharyngeal colonization in the post PCV13 era. The principal difference between serotypes 15B and 15C is the presence of an O-acetyl group on the pentasaccharide repeating unit of 15B polysaccharide. It remains unclear if antibodies against SP15B polysaccharide demonstrate functional cross reaction with SP15C strains. We compared functional activity of polyclonal rabbit anti-capsular 15B sera against SP15B and SP15C isolates. MethodsUsing flow cytometry we measured complement factors C3c and C4d deposition on SP15B and 15C in the presence of polyclonal rabbit anti capsular 15B sera. We measured the binding of C3c, common to all complement pathways, and C4d, specific to classical pathway, on SP serotypes 15B and 15C when co-incubated with polyclonal rabbit anti capsular 15B sera and antibody depleted complement. Both the proportion of bacteria with complement deposition and the fluorescence intensity were measured. We also measured agglutination as the increase in forward and side scatter. ResultsPolyclonal rabbit anti-capsular 15B sera activated classical pathway resulting in deposition of C4d and C3c at high intensity on all SP15B cells but only achieved limited deposition and intensity of C4 with SP15C. Similarly, polyclonal rabbit anti-capsular 15B sera induced agglutination of SP15B strains in a dose dependent manner and limited agglutination of SP15C. ConclusionsAnti-capsular 15B sera induce limited C4d and C3c deposition, and minimal agglutination with SP15C strains, reflecting lower classical pathway activation in contrast to high C4d and C3c deposition and agglutination of SP15B. These observations support limited functional cross reactivity of anti-15B to SP15C strains and are consistent with the reduction in opsonophagocytic killing of SP15C reported following immunization with vaccines containing 15B polysaccharide.

B-245 Novel monoclonal antibodies validated specifically for immunohistochemistry by performance assessment on tissue microarrays

Abstract Background Immunohistochemistry (IHC) is a laboratory immunoassay that is a pillar of diagnostic pathology, particularly in the identification and characterization of neoplasms and other diseases/disorders. Though performed routinely, rigorous SOP protocols must be determined empirically for each molecular target, beginning with antibody selection. Both traditional polyclonal and hybridoma-based monoclonal antibodies have been employed in the past, though monoclonal, and particularly recombinant monoclonal, antibodies are preferred. However, any reagent used for diagnostic purposes must be meticulously validated to minimize, if not eliminate, erroneous interpretations of IHC assays. Thus, the extent of validation is the pivotal aspect for establishing an antibody as a reliable diagnostic tool for IHC applications. Methods GeneTex has assembled an extensive catalog of rabbit and mouse monoclonal antibodies validated specifically for IHC. These antibodies are tested on both human normal tissue and cancer tissue microarrays, with upwards of 76 normal and numerous tumor tissues included. Images of the staining are available for all the tested tissues. This broad spectrum of tissues allows a researcher to assess the performance of the antibody on known positive and negative samples, thereby minimizing the risk of false positive or false negative readouts (Gown, 2016). In addition, the data images are of sufficient resolution to determine proper cellular localization of the signal. This special catalog of IHC-optimized reagents are listed under the “HistoMAX” designation. New antibodies will be added continuously, many of them being fully recombinant rabbit monoclonals manufactured using a multi-parameter FACS-based methodology to select antigen-specific IgG+ memory B cells from an immunized rabbit with subsequent cloning of the matched IgG heavy and light chains (Starkie et al., 2016). These recombinant antibodies will be validated following the same approach described above. Results Presently more than 130 mouse or rabbit monoclonal antibodies are available in the HistoMAX line of IHC-validated products and are directed against a spectrum of important targets. This includes antibodies for the commonly analyzed cytokeratins 5, 6, 7, 18, 19, and 20, among many others. Antibodies for CTLA4 and PD-L1 headline products for immunology and immunotherapy research, while other reagents are directed against various cadherins. Hormone receptor antibodies are also represented, with antibodies against estrogen receptor alpha, progesterone receptor, Her2/ErbB2, and the androgen receptor. There are also antibodies against various key “Cluster of Differentiation” (CD) proteins as well as other membrane proteins such as ACE2. Many antibodies are relevant to the study of human malignancies, such as CD66e/CEACAM5/CEA, MSH6, p63, MUC1, Collagen IV, EpCAM, PAX6, PAX8, GP2, TRIM29, S100, and GAD65. All antibodies were evaluated as described above. Conclusions Antibodies are application-specific reagents, and the best antibodies for IHC are validated through systematic staining of a multitude of normal and abnormal tissues. This is the only way that an antibody’s performance for IHC can be critically assessed. The HistoMAX reagents consist only of those monoclonal antibodies that have generated expected signals, or the lack of a signal, in a wide range of tissues in a manner consistent with the literature.

Development of a novel humanized anti-TSLP monoclonal antibody, QX008N, and exploration of combination therapy of anti-TSLP antibody and anti-IL-4R antibody

BackgroundSevere asthma is a complex and chronic respiratory disease, and current conventional treatments are not effective in controlling the patients’ condition. Thymic stromal lymphopoietin (TSLP) is a key regulatory factor in the initiation and maintenance of asthma. Thus, blocking TSLP during allergic inflammation emerges as a promising therapeutic approach; however, novel anti-TSLP therapies remain to be developed. Furthermore, the importance of other signaling molecules, such as IL-4 and IL-13, should be considered. Moreover, to the best of our knowledge, the inhibitory effect of binding upstream and downstream signaling molecules has not been assessed. PurposeThis study aimed to develop a novel, humanized anti-TSLP antibody and explore the enhancement in its efficacy when combined with anti-IL-4R antibodies to treat asthma. ResultsQX008N, derived from a rabbit antibody platform, exhibits a high affinity for TSLP and superior efficacy in blocking TSLP-induced signaling pathways and inflammation in vitro compared with Tezepelumab. In a cynomolgus monkey asthma model, QX008N ameliorated lung function and reduced the levels of eosinophils and IgE. Moreover, the coadministration of QX008N with anti-IL-4R antibodies enhanced the inhibition of inflammatory mediator production triggered via costimulation in vitro. In mouse asthma models, the simultaneous blockade of TSLP and IL-4R using anti-TL4R and anti-TSLP surrogates surpassed the efficacy of monotherapy. To the best of our knowledge, the therapeutic effect of a combination of anti-TSLP and IL-4R antibodies in an asthma model has not yet been reported. ConclusionThese results furnish comprehensive preclinical evidence for QX008N as an innovative anti-TSLP therapeutic agent and provide a preliminary rationale for the development of combination therapies that simultaneously target the TSLP and IL-4R signaling pathways.

Production of highly soluble and immuno-reactive recombinant flagellin protein of Clostridium chauvoei

ObjectiveFlagellin protein, an integral component of flagella, provides motility to several bacterial species and also acts as a candidate antigen in diagnostics and subunit vaccines. The bulk production of flagellin with retention of all conformational epitopes using recombinant protein technology is of paramount importance in the development of pathogen-specific immuno-assays and vaccines. We describe the production of highly soluble and immuno-reactive rFliA(C) protein of Clostridium chauvoei, a causative agent of blackleg or black quarter (BQ) affecting cattle and small ruminants worldwide. The bacterium is known to possess peritrichous flagella that provide motility and also act as a virulence factor with high protective antigenicity. MethodsUpon sequence and structural analysis, a partial fliA(C) gene from Clostridium chauvoei was cloned and the recombinant mature protein with N- and C- terminal truncation was over-expressed as a His-tagged fusion protein (∼25 kDa) in Escherichia coli. Subsequently, rFliA(C) protein was purified by single-step affinity chromatography and characterized for its immuno-reactivity in laboratory animals, Western blot, and indirect-ELISA format. ResultsrFliA(C) was highly soluble and was purified in high quantity and quality. rFliA(C) elicited antigen-specific conformational polyclonal antibodies in rabbit and guinea pig models, as well as anti-Clostridium chauvoei-specific antibodies being specifically detected in BQ-vaccinated and convalescent sera of bovines in Western blot and in indirect-ELISA format. Further, no cross reactivity was noted with antibodies against major bovine diseases (e.g., foot-and-mouth disease, IBR, LSDV, hemorrhagic septicaemia, brucellosis, and leptospirosis). ConclusionThe study indicated the production of conformational recombinant flagellin—rFliA(C)—antigen and its potential utility in development of diagnostics for detection of Clostridium chauvoei-specific antibodies in BQ-recovered and/or vaccinated animals.

Synthesis of oligosaccharides from terminal B. pertussis LPS pentasaccharide and definition of the minimal epitope recognized by anti-pertussis antibodies.

Pertussis vaccines have been very effective in controlling whooping-cough epidemics but are ineffective in controlling circulation in older children and adults, thus facilitating the onset of future outbreaks. Antibodies against the lipopolysaccharide could reduce the carriage of the bacteria, its circulation, and transmission. The oligosaccharide fragments from the lipopolysaccharide may become a potential complement to existing vaccines in the form of protein glycoconjugates. An important step in the development of this type of vaccine is defining the minimal oligosaccharide epitope recognized by B. pertussis anti-lipopolysaccharide antibodies. This paper describes the complete synthesis of oligosaccharides containing two to five monosaccharide units corresponding to the pentasaccharide at the nonreducing end of the lipooligosaccharide and their recognition by mice and rabbit antibodies elicited against whole-cell B. pertussis. For the first time, we report that the terminal disaccharide, α-D-GlcNAcp-(1 → 4)-(2,3-di-NAc)-D-ManAp acid is the minimal structure recognized by antibodies induced by B. pertussis.

Evaluation of SARS-CoV-2-Specific IgY Antibodies: Production, Reactivity, and Neutralizing Capability against Virus Variants.

The emergence of SARS-CoV-2 in late 2019 initiated a global pandemic, which led to a need for effective therapeutics and diagnostic tools, including virus-specific antibodies. Here, we investigate different antigen preparations to produce SARS-CoV-2-specific and virus-neutralizing antibodies in chickens (n = 3/antigen) and rabbits (n = 2/antigen), exploring, in particular, egg yolk for large-scale production of immunoglobulin Y (IgY). Reactivity profiles of IgY preparations from chicken sera and yolk and rabbit sera were tested in parallel. We compared three types of antigens based on ancestral SARS-CoV-2: an inactivated whole-virus preparation, an S1 spike-protein subunit (S1 antigen) and a receptor-binding domain (RBD antigen, amino acids 319-519) coated on lumazine synthase (LS) particles using SpyCather/SpyTag technology. The RBD antigen proved to be the most efficient immunogen, and the resulting chicken IgY antibodies derived from serum or yolk, displayed strong reactivity with ELISA and indirect immunofluorescence and broad neutralizing activity against SARS-CoV-2 variants, including Omicron BA.1 and BA.5. Preliminary in vivo studies using RBD-lumazine synthase yolk preparations in a hamster model showed that local application was well tolerated and not harmful. However, despite the in vitro neutralizing capacity, this antibody preparation did not show protective effect. Further studies on galenic properties seem to be necessary. The RBD-lumazine antigen proved to be suitable for producing SARS-CoV-2 specific antibodies that can be applied to such therapeutic approaches and as reference reagents for SARS-CoV-2 diagnostics, including virus neutralization assays.

Optimization of DAC-ELISA and IC-RT-PCR using the developed polyclonal antibody and one-step RT-PCR assays for detection of Indian citrus ringspot virus in kinnow orange of Punjab, India

Indian citrus ringspot virus (ICRSV), a member of the Mandarivirus genus, causes citrus ringspot disease, impacting kinnow orange quality and yield. Early and accurate detection methods are crucial before visible symptoms manifest in plants. In this study, a 507 bp partial coat protein gene (pCPG) segment was amplified from infected kinnow leaf tissues, cloned into a pET28a vector, and transformed into E. coli BL21(DE3) cells. Induced with IPTG, the cells overexpressed a recombinant partial coat protein (rpCP) of approximately 23 kDa, purified using Ni-NTA resin via affinity chromatography. Validated in western blot with an anti-His antibody, rpCP was used to generate an ICRSV-specific polyclonal antibody (PAb) in rabbits. PAb, optimized at 1:1000 dilution, successfully detected ICRSV in infected kinnow orange leaf extracts via DAC-ELISA and IC-RT-PCR assays. ICRSV was detectable in sample dilutions up to 1:640 and 1:10240 (w/v, g mL−1) by DAC-ELISA and IC-RT-PCR, respectively. One-step RT-PCR assays were also optimized, confirming the presence of ICRSV by amplifying a 507 bp pCPG fragment from total RNA extracted from kinnow orange leaves, with dilution up to 1:5120 (w/v, g mL−1). The result demonstrated that IC-RT-PCR has a 16-fold and 2-fold higher sensitivity than DAC-ELISA and one-step RT-PCR assays.

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.

#2555 C4d—a novel predictor of the disease progression and treatment failure in primary focal segmental glomerulosclerosis?

Abstract Background and Aims Complement system seems to play a role in the pathogenesis of primary focal segmental glomerulosclerosis (pFSGS) where, due to unpredictable clinical course and outcome, novel prognostic factors are sought. The split product of C4 and tissue marker of complement activation, C4d, is a potential candidate whose prognostic significance was determined in this study. Method Patients >18 years with features consistent with pFSGS (full blown nephrotic syndrome, diffuse podocyte foot processes effacement and exclusion of known causes of FSGS), were recruited from our Hospital registry of kidney biopsies, from 2003 to 2021. Patients with end-stage renal disease (ESRD) defined as eGFR <15 ml/min/1.73 m2 were not included. Every renal biopsy specimen was analyzed by light, immunofluorescence and electron microscopy with additional immunochemistry for C4d performed on paraffin-embedded tissue using monoclonal rabbit antibody (detection system Ventana BenchMark Ultra). Samples with at least one non-globally sclerosed glomerulus (GSG) were examined by two renal pathologists who classified every non-GSG into C4d positive and negative. Based on ratio of C4d+ non-GGS/total N of non-GSG and C4d+ nonsclerotic glomeruli (NSG)/total N of NSG, patients were stratified into two groups: <50% and ≥50%. Primary outcome was defined as composite of ESRD and initial eGFR declining >50%. Failure to meet criteria for at least partial remission at the last follow-up visit according to KDIGO 2021 Guidelines was defined as treatment failure. Numeric variables are shown as median with interquartile range (IQR) and P value <0.05 was considered as significant. Results Relevant data of 58 included patients with renal outcomes are shown in Table. Median follow up was 90.7 (IQR 48-167) months. Patients with ≥50% of C4d+ non-GSG had higher proportion of treatment failure (Table) and worse renal survival (log-rank test, p = 0.006). In multivariate Cox regression analysis, after inclusion of age, sex, initial eGFR and 24-h proteinuria, IFTA, serum albumin and C4d category, only C4d ≥50% (HR = 4.077, 95% CI 1.101-15.09, p = 0.035) and IFTA (HR = 1.052, 95% CI 1.019-1.085, p = 0.002) remained independent predictors of progression to defined endpoint. Likewise, patients with ≥50% of C4d+ NSG/total N of NSG had higher proportion of treatment failure (chi-square, p = 0.03) and worse renal survival (log-rank, p = 0.037). Conclusion C4d deposition is an independent predictor of disease progression, treatment failure and renal survival in pFSGS. Significant influence of NSG-C4d deposition on disease progression may indicate pathophysiological role of the complement system activation in pFSGS independently of the presence of glomerular sclerosis.

Generation of targeted antibody conjugates using Sortase and the AbFlex technology platform.

Abstract The miniaturization of experiments to the single cell scale and a growing interest in multiplexing analyte detection is a major driver for the development of novel antibody conjugation technologies that are robust, and which also preserve antibody function. Relative to two step detection modalities, direct primary antibody conjugates provide enhanced specificity and selectivity. We have developed the AbFlex platform, a versatile epitope tagging system for the carboxyl terminus of recombinant mouse and rabbit immunoglobulin heavy chains. It consists of a tandem array of three tags: 1) The Sortase tag recognition sequence (LPXTG); 2) The motif recognized by the BirA biotin ligase, followed by 3) the 6XHis Tag, which can be used with nickel-based purification systems. Sortase A belongs to a family of transpeptidases found in Gram-positive bacteria that catalyze the attachment of poly-Glycine labels to the Sortase recognition sequence under physiological conditions and with reaction times of approximately one hour. We describe the use of the Staphylococcus aureus Sortase A5 pentamutant that is significantly more active than wild-type Sortase to provide a faster, more efficient labeling reaction. Performance of various recombinant mouse and rabbit antibody conjugates in a variety of applications will be presented.

IMMUNOHISTOCHEMICAL CHANGES IN RAT LYMPH NODES DURING INTRALYMPHATIC IMMUNOSTIMULATION WITH ACID PEPTIDOGLYCAN

The purpose of this research was to study the characteristics of the immunohistochemical reaction of lymph nodes after intralymphatic immunostimulation with acid peptidoglycan in a rat model. Material and Methods: Immunostimulation was modeled in groups by introducing APG with a molecular weight of 1000–40000 kDa at a dose of 0.3 U. The drug was administered intramuscularly in the comparison group (n=30) and intralymphatically in the main group (n=30), on days 1, 2, 3, 8, 9, 10 of the experiment. Hyaluronidase was used as a lymphotropic substance at a dose of 0.07 U. We used Bcl-2 rabbit antibodies, сlone: SP66 (Roche, Switzerland) and CD-3 antibodies (PrimeBioMed, Russia). The UltraVision Quanto Detection System HRP Polymer (ThermoFisher, USA) was used as a detection system. Results: Intralymphatic administration of APG gives an immunostimulating effect on the third day from the start of administration. Meanwhile, with intramuscular immunostimulation, the effect occurred only on the seventh day of the experiment (p≤0.05). Immunohistochemical studies using Bcl-2 and CD-3 showed the effectiveness of APG as an immunostimulator, which was confirmed by increased expression of CD-3+, while an increase in the pool of Bcl-2+ cells indicated strengthened barrier and anti-apoptotic properties of lymph nodes. The duration of the immunostimulating effect depended on the route of APG administration. With the lymphatic route of administration, the effect occurred on the third day, with the intramuscular route – on the seventh day from the start of administration of the immunostimulant (p≤0.05). Conclusion: An APG based drug stimulates the expression of genes for signaling receptors of immune effectors, which increases their sensitivity to pathogens of various natures and elicits an adequate immune response in the body.

Экспрессия ARID1a в эндометрии женщин репродуктивного возраста с аномальными маточными кровотечениями и ожирением

Objective. The aim of the study was to evaluate the expression of the proliferative marker ARID1a in endometrial biopsies of patients with abnormal uterine bleeding (AUB) and obesity and its role in the pathogenesis of endometrial dysfunction. Materials and methods. The study included 40 endometrial samples from patients of reproductive age with AUB-E: 20 from patients with AUB-E and obesity (group 1) and 20 from patients with normal body mass index (BMI) and AUB (group 2). 10 endometrial samples were obtained from healthy women of reproductive age, taken on the 2nd-3rd day of the menstrual cycle. All patients underwent histological examination according to the standard procedure. At the second stage, an immunohistochemical study of the ARID1a proliferation marker was performed using polyclonal rabbit antibodies to Anti-ARID1a (clone EPR13501-73) in standard dilution (1:500) according to the protocol of the manufacturer Abcam (Great Britain). The IBM SPSS Statistics v.26 program (IBM Corporation, USA) was used for statistical data analysis. To determine statistically significant differences between quantitative parameters with a normal distribution, one-factor analysis of variance (ANOVA) was used with the calculation of a 95% confidence interval followed by the post-hoc Games-Howell test for multiple comparisons. The differences were considered significant at p<0.05. Results. ARID1a expression was evaluated in the glandular and stromal compartments of the endometrium. In the endometrial glands, the expression of ARID1a was statistically significantly higher in the first group of obese patients compared with the normal and control groups. In the endometrial stroma, the expression of the proliferative marker was higher in the main group compared with the control group. However, when comparing between groups within the main group, statistical significance in the level of expression was not achieved. Conclusion. The results obtained demonstrate the possible pathological effect of obesity on the structural and functional properties of the endometrium, which leads to delayed regeneration of the endometrium due to the glandular component and, consequently, to AUB-E.

A conserved motif in the immune-subdominant RAP-1 related antigen of Babesia bovis contains a B-cell epitope recognized by antibodies from protected cattle.

Babesia bovis, a tick-borne apicomplexan parasite causing bovine babesiosis, remains a significant threat worldwide, and improved and practical vaccines are needed. Previous studies defined the members of the rhoptry associated protein-1 (RAP-1), and the neutralization-sensitive rhoptry associated protein-1 related antigen (RRA) superfamily in B. bovis, as strong candidates for the development of subunit vaccines. Both RAP-1 and RRA share conservation of a group of 4 cysteines and amino acids motifs at the amino terminal end (NT) of these proteins. Sequence comparisons among the RRA sequences of several B. bovis strains and other Babesia spp parasites indicate a high level of conservation of a 15-amino acid (15-mer) motif located at the NT of the protein. BlastP searches indicate that the 15-mer motif is also present in adenylate cyclase, dynein, and other ATP binding proteins. AlphaFold2 structure predictions suggest partial exposure of the 15-mer on the surface of RRA of three distinct Babesia species. Antibodies in protected cattle recognize a synthetic peptide representing the 15-mer motif sequence in iELISA, and rabbit antibodies against the 15-mer react with the surface of free merozoites in immunofluorescence. The presence of the 15-mer-like regions in dynein and ATP-binding proteins provides a rationale for investigating possible functional roles for RRA. The demonstrated presence of a surface exposed B-cell epitope in the 15-mer motif of the B. bovis RRA, which is recognized by sera from protected bovines, supports its inclusion in future subunit epitope-based vaccines against B. bovis.