Epitope Of mAb Research Articles

Generation of recombinant metapneumovirus nucleocapsid protein as nucleocapsid-like particles and development of virus-specific monoclonal antibodies

Human metapneumovirus (hMPV) is a member of the Pneumovirinea subfamily within the Paramyxoviridea family. Since its discovery in 2001, hMPV has been isolated in several continents, which suggests its prevalence worldwide. hMPV resembles human respiratory syncytial virus with regard to disease symptoms and its ability to infect and cause disease in young infants as well as individuals of all ages. The aim of the current study was to construct an efficient high-level yeast expression system for the generation of hMPV nucleocapsid (N) protein and to develop monoclonal antibodies (MAbs) suitable for hMPV detection. The genome of hMPV was isolated from oral fluid of an infected patient by using specific primers and reverse transcriptase polymerase chain reaction (RT-PCR). DNA sequence corresponding to the N protein gene was inserted into yeast expression vector under inducible GAL7 promoter. SDS-PAGE analysis of crude lysates of yeast Saccharomyces cerevisiae harbouring recombinant plasmid revealed the presence of a protein band of approximately 43 kDa corresponding to the molecular weight of hMPV N protein. Electron microscopy analysis of purified N protein revealed nucleocapsid-like structures with typical herring-bone morphology: rods of 20 nm diameter with repeated serration along the edges and central core of 5 nm. Recombinant hMPV N protein was reactive with human serum specimens collected from patients with confirmed hMPV infection. After immunization of mice with recombinant hMPV N protein, a panel of MAbs was generated. The specificity of newly generated MAbs was proven by immunofluorescence analysis of hMPV-infected cells. Epitope mapping using truncated variants of hMPV N revealed localization of linear MAb epitopes at the N-terminus of hMPV N protein, between amino acid residues 1 and 90. The MAbs directed against conformational epitopes did not recognize hMPV N protein variants containing either N- or C-terminal truncations. The reactivity of recombinant hMPV N protein with hMPV-positive serum specimens and the ability of MAbs to recognize virus-infected cells confirms the antigenic similarity between yeast-expressed hMPV N protein and native viral nucleocapsids. In conclusion, recombinant hMPV N protein and hMPV-specific MAbs provide new diagnostic reagents for hMPV infection.

A Conformation-Sensitive Monoclonal Antibody against the A2 Domain of von Willebrand Factor Reduces Its Proteolysis by ADAMTS13

The size of von Willebrand factor (VWF), controlled by ADAMTS13-dependent proteolysis, is associated with its hemostatic activity. Many factors regulate ADAMTS13-dependent VWF proteolysis through their interaction with VWF. These include coagulation factor VIII, platelet glycoprotein 1bα, and heparin sulfate, which accelerate the cleavage of VWF. Conversely, thrombospondin-1 decreases the rate of VWF proteolysis by ADAMTS13 by competing with ADAMTS13 for the A3 domain of VWF. To investigate whether murine monoclonal antibodies (mAbs) against human VWF affect the susceptibility of VWF to proteolysis by ADAMTS13 in vitro, eight mAbs to different domains of human VWF were used to evaluate the effects on VWF cleavage by ADAMTS13 under fluid shear stress and static/denaturing conditions. Additionally, the epitope of anti-VWF mAb (SZ34) was mapped using recombinant proteins in combination with enzyme-linked immunosorbent assay and Western blot analysis. The results indicate that mAb SZ34 inhibited proteolytic cleavage of VWF by ADAMTS13 in a concentration-dependent manner under fluid shear stress, but not under static/denaturing conditions. The binding epitope of SZ34 mAb is located between A1555 and G1595 in the central A2 domain of VWF. These data show that an anti-VWF mAb against the VWF-A2 domain (A1555-G1595) reduces the proteolytic cleavage of VWF by ADAMTS13 under shear stress, suggesting the role of this region in interaction with ADAMTS13.

Mimotopes of mutalysin-II from Lachesis muta snake venom induce hemorrhage inhibitory antibodies upon vaccination of rabbits

Mutalysin-II (mut-II) from Lachesis muta snake venom is an endopeptidase with hemorrhagic activity. A mAb against mutalysin-II that neutralized the hemorrhagic effect was produced previously. To identify the mAb epitopes, sets of 15-mer overlapping peptides covering the mut-II amino acid sequence were synthesized using the SPOT method and tested but failed to react with the mAb. Using a phage-display approach seventeen clones reactive with mAb were identified. Additional immunoassays with the peptides and mAb identified the QCTMDQGRLRCR, TCATDQGRLRCT, HCFHDQGRVRCA, HCTMDQGRLRCR and SCMLDQGRSRCR sequences as possible epitopes. Immunization of rabbits with these peptides induced antibodies that recognize mut-II and protected against the hemorrhagic effects of Lachesis venom.

Evaluation of epitopes specificity of antibodies to thyroid peroxidase in autoimmune thyroid disorders

The problem of the human antithyroid peroxidase autoantibodies epitopes heterogeneity diagnosed in case of Graves' disease and Hashimoto's thyroiditis has been researched using monoclonal antibodies to thyroid peroxidase. It was shown, that in the competition for the binding sites of thyroid peroxidase and autoantibodies taken from patients with Graves' disease and Hashimoto's thyroiditis sera participate 8 mAb to epitopes 1, 70, 82, 88, 2, 3, 77 and 79. The maxima of the binding inhibition has been marked for the conformation epitope mAb 3: in case of Graves' disease it amounts to 60.3 ± 12.7%, in case of Hashimoto's thyroiditis – 61.8 ± 32.2%. Moreover the level of the binding inhibition did not depend on the concentration of Ab to thyroid peroxidase in the sera of patient with Graves' as opposed to the serum of patients with Hashimoto's thyroiditis. Autoantibodies in the serum of the patientswith Hashimoto's thyroiditis inhibited the binding of mAb to epitope 77 much more effectively, than in the serum of the patients with: 36.3 ± 17.2 and 54.3 ± 9.6% (p ≤ 0.05).The obtained results represented the specific reaction of the autoantibodies to the certain thyroid peroxidase molecular patterns which corresponds to the literature data. It is possible to assume that the further research of the competitive interactions with other autoantibodies to monoclonal antibodies, not included in this trial, and widening of the different thyroid diseased patients' serum palette can expose new immunodominant thyroid peroxidase molecular patterns, forming antibodies for different diseases, and enable the development of diagnostics and control of the thyroid functions and applied therapy.

Monoclonal Antibodies against Accumulation-Associated Protein Affect EPS Biosynthesis and Enhance Bacterial Accumulation of Staphylococcus epidermidis

Because there is no effective antibiotic to eradicate Staphylococcus epidermidis biofilm infections that lead to the failure of medical device implantations, the development of anti-biofilm vaccines is necessary. Biofilm formation by S. epidermidis requires accumulation-associated protein (Aap) that contains sequence repeats known as G5 domains, which are responsible for the Zn2+-dependent dimerization of Aap to mediate intercellular adhesion. Antibodies against Aap have been reported to inhibit biofilm accumulation. In the present study, three monoclonal antibodies (MAbs) against the Aap C-terminal single B-repeat construct followed by the 79-aa half repeat (AapBrpt1.5) were generated. MAb18B6 inhibited biofilm formation by S. epidermidis RP62A to 60% of the maximum, while MAb25C11 and MAb20B9 enhanced biofilm accumulation. All three MAbs aggregated the planktonic bacteria to form visible cell clusters. Epitope mapping revealed that the epitope of MAb18B6, which recognizes an identical area within AapBrpt constructs from S. epidermidis RP62A, was not shared by MAb25C11 and MAb20B9. Furthermore, all three MAbs were found to affect both Aap expression and extracellular polymeric substance (EPS, including extracellular DNA and PIA) biosynthesis in S. epidermidis and enhance the cell accumulation. These findings contribute to a better understanding of staphylococcal biofilm formation and will help to develop epitope-peptide vaccines against staphylococcal infections.

Fine epitope mapping of monoclonal antibodies against hemagglutinin of a highly pathogenic H5N1 influenza virus using yeast surface display

Highly pathogenic H5N1 avian influenza viruses pose a debilitating pandemic threat. Thus, understanding mechanisms of antibody-mediated viral inhibition and neutralization escape is critical. Here, a robust yeast display system for fine epitope mapping of viral surface hemagglutinin (HA)-specific antibodies is demonstrated. The full-length H5 subtype HA (HA0) was expressed on the yeast surface in a correctly folded conformation, determined by binding of a panel of extensively characterized neutralizing human monoclonal antibodies (mAbs). These mAbs target conformationally-dependent epitopes of influenza A HA, which are highly conserved across H5 clades and group 1 serotypes. By separately displaying HA1 and HA2 subunits on yeast, domain mapping of two anti-H5 mAbs, NR2728 and H5-2A, localized their epitopes to HA1. These anti-H5 mAb epitopes were further fine mapped by using a library of yeast-displayed HA1 mutants and selecting for loss of binding without prior knowledge of potential contact residues. By overlaying key mutant residues that impacted binding onto a crystal structure of HA, the NR2728 mAb was found to interact with a fully surface-exposed contiguous patch of residues at the receptor binding site (RBS), giving insight into the mechanism underlying its potent inhibition of virus binding. The non-neutralizing H5-2A mAb was similarly mapped to a highly conserved H5 strain-specific but poorly accessible location on a loop at the trimer HA interface. These data further augment our toolchest for studying HA antigenicity, epitope diversity and accessibility in response to natural and experimental influenza infection and vaccines.

Neutralizing Monoclonal Antibodies against Hepatitis C Virus E2 Protein Bind Discontinuous Epitopes and Inhibit Infection at a Postattachment Step

The E2 glycoprotein of hepatitis C virus (HCV) mediates viral attachment and entry into target hepatocytes and elicits neutralizing antibodies in infected patients. To characterize the structural and functional basis of HCV neutralization, we generated a novel panel of 78 monoclonal antibodies (MAbs) against E2 proteins from genotype 1a and 2a HCV strains. Using high-throughput focus-forming reduction or luciferase-based neutralization assays with chimeric infectious HCV containing structural proteins from both genotypes, we defined eight MAbs that significantly inhibited infection of the homologous HCV strain in cell culture. Two of these bound E2 proteins from strains representative of HCV genotypes 1 to 6, and one of these MAbs, H77.39, neutralized infection of strains from five of these genotypes. The three most potent neutralizing MAbs in our panel, H77.16, H77.39, and J6.36, inhibited infection at an early postattachment step. Receptor binding studies demonstrated that H77.39 inhibited binding of soluble E2 protein to both CD81 and SR-B1, J6.36 blocked attachment to SR-B1 and modestly reduced binding to CD81, and H77.16 blocked attachment to SR-B1 only. Using yeast surface display, we localized epitopes for the neutralizing MAbs on the E2 protein. Two of the strongly inhibitory MAbs, H77.16 and J6.36, showed markedly reduced binding when amino acids within hypervariable region 1 (HVR1) and at sites ∼100 to 200 residues away were changed, suggesting binding to a discontinuous epitope. Collectively, these studies help to define the structural and functional complexity of antibodies against HCV E2 protein with neutralizing potential.

Endospanins Regulate a Postinternalization Step of the Leptin Receptor Endocytic Pathway

Endospanin-1 is a negative regulator of the cell surface expression of leptin receptor (OB-R), and endospanin-2 is a homologue of unknown function. We investigated the mechanism for endospanin-1 action in regulating OB-R cell surface expression. Here we show that endospanin-1 and -2 are small integral membrane proteins that localize in endosomes and the trans-Golgi network. Antibody uptake experiments showed that both endospanins are transported to the plasma membrane and then internalized into early endosomes but do not recycle back to the trans-Golgi network. Overexpression of endospanin-1 or endospanin-2 led to a decrease of OB-R cell surface expression, whereas shRNA-mediated depletion of each protein increased OB-R cell surface expression. This increased cell surface expression was not observed with OB-Ra mutants defective in endocytosis or with transferrin and EGF receptors. Endospanin-1 or endospanin-2 depletion did not change the internalization rate of OB-Ra but slowed down its lysosomal degradation. Thus, both endospanins are regulators of postinternalization membrane traffic of the endocytic pathway of OB-R.

214 Derivation and Characterization of Novel Anti-HIV Envelope Monoclonal Antibodies from Macaques Vaccinated With a Constrained HIV Gp120 Immunogen and Challenged with SHIV162p3

An approach to the development of an effective vaccine to HIV will be to generate antibodies that recognize conserved HIV envelope domains and thereby afford protection against heterologous infection. We have been exploring the approach of targeting epitopes located in the HIV-1 envelope glycoprotein (gp120) that are exposed on transition state structures formed after attachment to the CD4 receptor. These so-called CD4-induced (CD4i) epitopes comprise some of the most conserved and functionally important domains on the viral envelope including the co-receptor binding site; further, cognate antibodies appear in most HIV infected individuals and are cross-reactive for neutralizing and other antiviral activities against heterologous HIV strains in vitro. Towards this goal, rhesus macaques were vaccinated with a gp120 immunogen that is constrained into a transition state structure by covalent linkage to macaque CD4 (rhesus full-length signal-chain; rhFLSC) in order to favor the immunogenicity of CD4i epitopes. These animals developed conventional cross-reactive neutralizing activities and exhibited non-sterilizing control of heterologous mucosal challenge with SHIV162P3 that correlated with stronger responses to CD4i epitopes in the rhFLSC-vaccinated animals. Further, viremia associated with infection significantly boosted conventional neutralizing and CD4i responses. To census and characterize the antibody specificities in these animals, we employed a new algorithm to isolate monoclonal antibodies (Mabs) from rhesus macaques. So far, we have isolated several anti-CD4i epitope Mabs from vaccinated/challenged animals that showed the most broadly neutralizing responses following vaccination and/or challenge. Antibodies with other specificities for the HIV envelope have also been identified. The variable (V)-gene usage, CDR-H3 length, potency and breadth of neutralization exhibited by various Mabs will be presented.

Anti-HIV-1 antibodies 2F5 and 4E10 interact differently with lipids to bind their epitopes

2F5 and 4E10 are two broadly neutralizing monoclonal antibodies (mAbs) targeting the membrane proximal external region (MPER) of HIV-1 gp41 envelope protein. This region, which contacts the viral membrane, is highly conserved and has been regarded as a promising target for vaccine development. We aimed to clarify the basis of 2F5 and 4E10 molecular interactions with epitope cores in MPER and lipid bilayers. Microscopy-based approaches were used to infer and quantify the effects of both mAbs on membranes, in the presence and absence of the epitope cores. Supported lipid bilayers (SLBs), with and without phase separation, were used as membrane models. Fluorescent-labeled and nonlabeled MPER-derived peptides containing both 2F5 and 4E10 epitopes were used. mAbs 2F5 and 4E10 membrane interactions, in the presence or absence of MPER-derived peptides, were evaluated by combined atomic force and confocal microscopies. Both mAbs form lipid-segregated aggregates on SLBs and do not induce other significant membrane perturbations. Furthermore, the affinity of MPER toward membranes is differently affected by both mAbs and correlates with the mAbs-epitope core lipid interactions. 2F5 is able to dock the MPER peptide on the membrane, whereas 4E10 extracts the MPER from the lipid bilayer. The results reveal the molecular details underneath 2F5/4E10 membrane-epitope binding and a model is proposed to explain the differential mAbs neutralization efficacies, which relates to the exposure of the epitopes in the lipid bilayers and the role of the lipids in mAb-epitope binding.

Conformational analysis of human serum albumin and its non-enzymatic glycation products using monoclonal antibodies

Monoclonal antibodies (mAbs) were prepared to analyse the conformation of human serum albumin (HSA) and its non-enzymatic glycation (NEG) products. We first determined the epitopes of the mAbs using HSA subdomains expressed on the surface of yeast. Each mAb was classified as belonging to one of two groups; Type I mAbs which recognized a single subdomain structure and Type II mAbs which bound to plural subdomains. We analysed the pH-dependent conformational change in HSA. We found that one Type II mAb, HAy2, detected the normal to base form (N-B) transition while the other did not, suggesting that N-B transition occurred around Domain I accompanied by topological isomerization of subdomains without changing the subdomain structure itself. Next, we analysed the conformations of the NEG products. Since all mAbs reacted with the early NEG products, no structural change was thought to have occurred in the early NEG products. On the other hand, only a Type I mAb, HAy1, had full binding activity with the advanced glycation end products (AGE) while the other mAbs had lost or had diminished activity, suggesting that the over-all tertiary structure of HSA was altered except for a subdomain, sDOM Ia, in AGE.

Carbohydrates contribute to the interactions between cockroach allergen Bla g 2 and a monoclonal antibody.

The crystal structure of a murine mAb, 4C3, that binds to the C-terminal lobe of the cockroach allergen Bla g 2 has been solved at 1.8 Å resolution. Binding of 4C3 involves different types of molecular interactions with its epitope compared with those with the mAb 7C11, which binds to the N-terminal lobe of Bla g 2. We found that the 4C3 surface epitope on Bla g 2 includes a carbohydrate moiety attached to Asn(268) and that a large number of Ag-Ab contacts are mediated by water molecules and ions, most likely zinc. Ab binding experiments conducted with an enzymatically deglycosylated Bla g 2 and a N268Q mutant showed that the carbohydrate contributes, without being essential, to the Bla g 2-4C3 mAb interaction. Inhibition of IgE Ab binding by the mAb 4C3 shows a correlation of the structurally defined epitope with reactivity with human IgE. Site-directed mutagenesis of the 4C3 mAb epitope confirmed that the amino acids Lys(251), Glu(233), and Ile(199) are important for the recognition of Bla g 2 by the 4C3 mAb. The results show the relevance of x-ray crystallographic studies of allergen-Ab complexes to identify conformational epitopes that define the antigenic surface of Bla g 2.

An Engineered Cell Surface Polypeptide for Selection, Tracking and Ablation of Genetically Modified Hematopoietically Derived Cells Based on Human EGFR.

AbstractAbstract 1469Hematopoietic cell-based therapies, including genetically manipulated cell products derived from either hematopoietic stem cells or T cells, is an emerging area in applied biotechnology. In both of these venues, a variety of genetic engineering approaches are being studied to endow cells with novel attributes, to increase their therapeutic potency and/or safety. Common to the field of ex vivo cellular genetic engineering is the need to purify cells that express desired quantities of therapeutic transgene(s) and cull out non-expressing cells that either lack transgene endowed therapeutic activity or safety features. However, current drug selection strategies are associated with prolonged ex vivo culture that drives terminal differentiation of the T cells, which has in turn been found to be associated with impaired antitumor efficacy of adoptively transferred CD8+ T cells in vivo. Thus, we were interested in developing a single transgene encoded polypeptide that can serve both as an ex vivo selection epitope and in vivo tracking marker/target for mAb-mediated cell ablation, while fulfilling the criteria of being functionally inert, non immunogenic, and amenable to commercially available cGMP-grade selection systems appropriate for clinical use. Here we describe a truncated human EGFR polypeptide (huEGFRt) devoid of extracellular N-terminal ligand binding domains and intracellular receptor tyrosine kinase domains. Retained features of huEGFRt include type I transmembrane cell surface localization and a conformationally intact binding epitope for pharmaceutical-grade anti-EGFR mAb, cetuximab/Erbitux™. [Display omitted] Applying this system to cellular immunotherapy, we designed lentiviral vector prototypes housing multifunctional constructs combining huEGFRt with CD19-specific chimeric antigen receptors (CARs), and demonstrate that biotinylated-cetuximab immunomagnetic selection of transduced human T cells results in coordinate enrichment of CAR+ cells from 2% to over 90%. The huEGFRt-mediated selection did not affect the phenotype (i.e., TCR, CD3, CD4, CD8, CD28, and granzyme A expression), the in vitro expansion potential, nor the in vivo engraftment fitness (upon transfer into immunodeficient mice) of the T cells. Direct examination of EGF-binding and phospho-tyrosine analysis confirmed that this selection marker is functionally inert and has no negative effect on the T cell product. In addition, cytotoxicity against B cell malignancies and IFN-g/TNF-a production through the CD19-specific CAR was dramatically enhanced in the huEGFRt-selected population. The utility of huEGFRt in tracking the gene modified, transferred cells in vivo within easily obtained human tissues such as blood, bone marrow and tissue biopsies was then also proven via detection of huEGFRt using multiparameter flow cytometric analysis or FDA approved immunohistochemical techniques/reagents. In addition, we were able to demonstrate that Erbitux™ could mediate ADCC of huEGFRt+ T cells in vitro and inhibit the growth of huEGFRt+ CTLL2 cells in NOD/Scid mice, supporting the use of huEGFRt as a suicide gene via cetuximab-mediated ADCC after adoptive transfer. Together these data suggest that huEGFRt is a superior selection marker for any transduction system that can be applied to the generation of cell products for hematopoietic cell-based medical therapies. Disclosures:No relevant conflicts of interest to declare.

Analysis of the epitope and neutralizing capacity of human monoclonal antibodies induced by hepatitis B vaccine

Hepatitis B virus (HBV) is an infectious agent that is a significant worldwide public health issue. However, the mechanism by which vaccination-induced antibodies prevent HBV infection remains unclear. To investigate the mechanism by which antibodies induced by hepatitis B surface Ag (HBsAg)-vaccination prevent HBV infection in humans, we prepared human monoclonal antibodies (mAbs) against HBsAg using a novel cell-microarray system from peripheral blood B-lymphocytes from vaccinated individuals. We then characterized the IgG subclass, L-chain subtype, and V-gene repertoire of the H/L-chain, as well as affinities of each of these mAbs. We also determined the epitopes of the individual mAbs using synthesized peptides, and the HBV-neutralizing activities of mAbs using the hepatocyte cell line HepaRG. Consequently, IgG1 and kappa chain was mainly used as the mAbs for HBsAg. Seventy percent of the mAbs bound to the loop domain of the small-HBsAg and showed greater neutralizing activities. There were no relationships between their affinities and neutralization activities. A combination of mAbs recognizing the first loop domain showed a synergistic effect on HBV-neutralizing activity that surpassed conventional hepatitis B-Ig (HBIG) in the HepaRG cell line assay. These results may contribute to the development of effective mAb treatment against HBV infection replacing conventional HBIG administration.

Generation and Characterization of Four Novel Monoclonal Antibodies Against Human Programmed Death-1 Molecule

Programmed death-1 (PD-1, CD279), an inhibitory co-stimulatory molecule of the CD28 superfamily, plays a critical role in immune response. In this report, four novel mouse anti-human PD-1 monoclonal antibodies (MAbs) were prepared using hybridoma technology and immunological characteristics of the MAbs were determined. The results showed that all the MAbs (clones 9H1, 4B9, 8F5, and 1F8) were IgG1(kappa) and bound specifically to human PD-1. By mutual competition, we found that the antibodies recognized three different epitopes of PD-1 antigen and 9H1 MAb could block both PD-1/PD-L1 and PD-1/PD-L2 interaction. Cross-linking of PD-1 with MAb 9H1 markedly blocked PD-1 negative signal and promoted T cell proliferation. In addition, 4B9 and 9H1 MAbs were suitable for indirect ELISA detection. Thus, the MAbs against human PD-1 with high specificity and different activity would be useful for the further study of this molecule.

Prolonged exposure of the HIV-1 gp41 membrane proximal region with L669S substitution

The conserved membrane-proximal external region (MPER) of HIV-1 envelope is a target for the rare broadly neutralizing 2F5, Z13, and 4E10 monoclonal antibodies (mAbs). One strategy to elicit such antibodies is to design an immunogen with increased exposure of the 2F5 and 4E10 mAb epitopes. In this study we characterize a single leucine to serine substitution at position 669 (L669S) in the gp41 Env MPER that confers >250-fold more neutralization sensitivity to 2F5 and 4E10 mAbs than does the wild-type gp41 sequence. On synthetic liposomes, increased solvent exposure of MPER tryptophan residues and stable docking of 2F5 and 4E10 mAbs to mutant MPER peptide liposomes indicate more favorable membrane orientation of MPER neutralizing epitopes with L669S substitution. The time during which virus is sensitive to 2F5 mAb-mediated neutralization is approximately 3-fold longer when the mutation is present. These data suggest that a major contribution to the L669S mutant virus phenotype of enhanced susceptibility to MPER mAbs is prolonged exposure of the MPER neutralizing epitope during viral entry.

Gene optimization for expression of Crimean-Congo haemorrhagic fever viral nucleoprotein

experiments showed that mAb 2A10G6 protected sucking mice from lethal dengue 1-4 viruses challenge in a dosedependent manner. Thus, we have established a novel flavivirus cross-reactive neutralizing mAb 2A10G6. Phagedisplayed random peptide library mapped the epitope of mAb 2A10G6 to a common antigenic site within the highly conserved N-terminal fusion loop peptide of flavivirus envelope protein. Functional assays confirmed that mAb 2A10G6 bind with the fusion peptide and blocks infection primarily at a step after viral attachment. Conclusion: Together, these experiments define the characteristics of a novel flavivirus cross-reactive neutralizing MAb 2A10G6 and make it a suitable candidate for humanization into a therapeutic antibody to treat severe flavivirus infections in human.

An Essential Epitope of Anti-MUC1 Monoclonal Antibody KL-6 Revealed by Focused Glycopeptide Library

Human serum Krebs von den Lungen-6 (KL-6) antigen, a high-molecular-weight glycoprotein classified as a polymorphic epithelial mucin (MUC1), is a biomarker of diseases such as interstitial pneumonia, lung adenocarcinoma, breast cancer, colorectal adenocarcinoma, and hepatocellular carcinoma. Anti-KL-6 monoclonal antibody (anti-KL-6 MAb) is therefore a potential diagnostic and therapeutic reagent. Although glycosylation at Thr/Ser residues of the tandem-repeating MUC1 peptides appears to determine the disease-associated antigenic structures of KL-6, an essential epitope structure recognized by anti-KL-6 MAb remains unclear. In the present study, a novel compound library of synthetic MUC1 glycopeptides allowed the first rapid and precise evaluation of the specific epitope structure of anti-KL-6 MAb by combined use of a tailored glycopeptides library and common ELISA protocol. We demonstrated that the minimal antigenic structure, an essential epitope, recognized by anti-KL-6 MAb is a heptapeptide sequence Pro-Asp-Thr-Arg-Pro-Ala-Pro (PDTRPAP), in which the Thr residue is modified by Neu5Ac alpha2,3Gal beta1,3GalNAc alpha (2,3-sialyl T antigen, core 1-type O-glycan). Anti-KL-6 MAb did not bind with other tumor-relevant antigens, such as GalNAc alpha (Tn), Neu5Ac alpha2,6GalNAc alpha (STn), and Gal beta1,3GalNAc alpha (T), except for Neu5Ac alpha2,3Gal beta1,3(Neu5Ac alpha2,6)GalNAc alpha (2,3/2,6-disialyl T). However, anti-KL-6 MAb could not differentiate the above minimal antigenic glycopeptide from some core 2-based glycopeptides involving this crucial epitope structure and showed a similar binding affinity toward these compounds, indicating that branching at the O-6 position of GalNAc residue does not influence the interaction of anti-KL-6 MAb with some MUC1 glycoproteins involving an essential epitope. Actually, anti-KL-6 MAb reacts with 2,3/2,6-disialyl T having a 2,3-sialyl T component. This is why anti-KL-6 MAb often reacts with various kinds of tumor-derived MUC1 glycoproteins as well as a clinically important MUC1 glycoprotein biomarker of interstitial pneumonia, namely KL-6, originally discovered as a circulating pulmonary adenocarcinoma-associated antigen. In other words, combined use of anti-KL-6 MAb and some probes that can differentiate the sugars substituted at the O-6 position of the GalNAc residue in MUC1 glycopeptides including the PDTRPAP sequence might be a promising diagnostic protocol for individual disease-specific biomarkers. It was also revealed that glycosylation at neighboring Thr/Ser residues outside the immunodominant PDTRPAP motif strongly influences the interaction between anti-KL-6 MAb and MUC1 glycopeptides involving the identified epitope. Our novel strategy will greatly facilitate the processes for the identification of the tumor-specific and strong epitopes of various known anti-MUC1 MAbs and allow for their practical application in the generation of improved antibody immunotherapeutics, diagnostics, and MUC1-based cancer vaccines.

Novel monoclonal antibodies against Menangle virus nucleocapsid protein

Menangle virus (MenV) is a member of the family Paramyxoviridae isolated in Australia that causes a reproductive disease of pigs. There is a need for specific immunoassays for virus detection to facilitate the diagnosis of MenV infection. Three novel monoclonal antibodies (MAbs) of the IgG1 subtype were generated by immunizing mice with recombinant yeast-expressed MenV nucleocapsid (N) protein self-assembled to nucleocapsid-like structures. One MAb was cross-reactive with recombinant N protein of Tioman virus. The epitopes of MAbs were mapped using a series of truncated MenV N proteins lacking the 29-119 carboxy-terminal amino acid (aa) residues. The epitopes of two MAbs were mapped to aa 430-460 of the MenV N protein, whilst the epitope of one MAb was mapped to residues 460-490. All three MAbs specifically recognized MenV, as indicated by immunohistochemical staining of brain tissue isolated from a field case (a stillborn piglet) of MenV infection. The MAbs against MenV N protein may be a useful tool for immunohistological diagnosis of MenV infection.

OA021-04. HIV-1 gp41 envelope MPER mutation altered epitope conformation in lipid and increased sensitivity to 2F5 and 4E10 neutralizing antibodies

Background The conserved membrane-proximal external region (MPER) of HIV-1 envelope is a target for the rare broadly neutralizing 2F5, Z13 and 4E10 monoclonal antibodies (mAbs). However, MPER antibodies are rarely found in HIV-1 infected subjects nor arise following envelope immunization. A potential strategy to elicit such antibodies more frequently is to design an envelope protein with increased exposure of the 2F5 and 4E10 mAb epitopes.