Neutralizing Activity (neutralizing + activity)

Distribution by Scientific Domains

Selected Abstracts

A CD14 Domain with Lipopolysaccharide-Binding and -Neutralizing Activity,

CHEMBIOCHEM, Issue 2 2006
Söhnke Voss
Abstract The interaction of lipopolysaccharide with CD14 plays a key role in signaling that activates an early defense against pathogens but also contributes to the development of sepsis and septic shock. Here we have mapped the entire 356-amino-acid protein with synthetic 20-amino-acid peptides and have identified a new lipopolysaccharide-binding domain with a strong LPS-neutralizing activity. Moreover, analysis of the structure,activity relationship of this peptide, which corresponds to amino acids 81,100 of human CD14, revealed that leucines 87, 91, and 94 are essential for these activities. The functional relevance of these residues was confirmed by cellular expression of mutant CD14 proteins that are no longer able to bind LPS. Furthermore, the peptide provided a basis for the generation of highly soluble analogues with stronger lipopolysaccharide-neutralizing activity. [source]

Efficient generation of respiratory syncytial virus (RSV)-neutralizing human MoAbs via human peripheral blood lymphocyte (hu-PBL)-SCID mice and scFv phage display libraries

H. Nguyen
RSV is one of the major causes of pneumonia and bronchiolitis in infants and young children and is associated with high mortality. RSV neutralizing human antibody (hu-Ab) is known to mediate resistance to viral infection as well as to be an effective treatment for severe lower respiratory tract RSV infection. We have previously demonstrated that human primary and secondary immune responses can be established in severe combined immunodeficient mice engrafted with human peripheral blood lymphocytes (hu-PBL-SCID). By combining this animal model with the single-chain Fv antibody (scFv) phage display library technique, we were able to investigate further its clinical potential by generating a panel of human scFvs that exhibit both high F glycoprotein (RSV-F) binding affinities (,108 M,1) and strong neutralizing activities against RSV infection in vitro. Sequencing analysis of the randomly isolated anti-RSV-F scFv clones revealed that they were derived from different VH families with mutations in the complementarity-determining region 1 (CDR1). The results suggest that: (i) RSV-F-specific human immune responses and affinity maturation can be induced in hu-PBL-SCID mice; and (ii) this approach can be applied to generate large numbers of human scFvs with therapeutic potential. Despite the fact that hu-PBL-SCID mouse and human scFv phage display library have individually been established, our approach contributes a simple and significant step toward the generalization of antigen-specific human monoclonal antibody (hu-MoAb) production and their clinical applications. [source]

Longitudinal study of serum neutralization of HIV-1 in infected plasma donors

Arthur V. Abelian
Abstract Earlier studies provided suggestive evidence about the effectiveness of passive immunotherapy for AIDS patients using plasma donated by healthy HIV-1 infected individuals and revealed beneficial effects of plasmapheresis for the immune system of the donors. In this study, anti-HIV-1 neutralizing activity in 31 healthy HIV-1 infected donors of plasma participating in a passive immunotherapy study was investigated as a function of time. Average studied period was 33 months. Using the highly cytopathic HIV-1 NDK strain and MOLT4 cells, it was shown by means of syncytia formation inhibition assay and polyclonal HIV-1 antigen-capture assay that viral neutralizing titers tend either to remain unchanged or increase over time. These findings support the notion that the immune system is not affected adversely in HIV-1 infected plasma donors and lend further support to the feasibility of passive immunotherapy for AIDS patients. J. Med. Virol. 65:649,658, 2001. © 2001 Wiley-Liss, Inc. [source]

Functional reconstruction and synthetic mimicry of a conformational epitope using CLIPSÔ technology,

Peter Timmerman
Abstract This paper describes immunization studies with CLIPS-constrained peptides covering only the major part (,3-loop) of a structurally complex antigenic site on human Follicle Stimulating Hormone , -subunit (FSH- ,). In cases where linear and SS-constrained peptides fail, the CLIPS-constrained peptides generate polyclonal antibodies with high neutralizing activity for hFSH. The sera were shown to be specific for hFSH over human Luteinizing Hormone (hLH) and human Chorionic Gonadotropin (hCG). ELISA-competition studies and circular dichroism (CD)-measurements illustrate clearly that activity of the peptides in antibody binding and generation relates directly to precise and appropriate fixation of the peptide conformation. Design of the CLIPS-peptides was entirely based on epitope mapping studies with two neutralizing anti-hFSH mAbs. Both mAbs were shown to bind to a conformational epitope located at the top of the ,1,,3-loop covering the amino acid sequences Y58 -P77 (,3-loop). The results described in this paper show that CLIPS-constrained peptides covering the Y58 -P77 sequence provide the minimally required structural entity necessary to generate reproducibly sera with high hFSH-neutralizing activity. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Variable region heavy chain glycosylation determines the anticoagulant activity of a factor VIII antibody

Summary.,Background:,N -glycosylation occurs in the variable region of about 10% of antibodies but the role of carbohydrate at this location is still poorly understood. Objectives:,We investigated the function of N -glycosylation in the variable region of the heavy chain of a human monoclonal antibody, mAb-LE2E9, that partially inhibits factor VIII (FVIII) activity during coagulation. Methods and results:,Enzymatic deglycosylation indicated that the oligosaccharides do not determine the affinity of the antibody but enhance its FVIII neutralizing activity. A mutant antibody lacking the N -glycosylation site in the variable region of the heavy chain inhibited FVIII activity by up to 40%, while inhibition by the native antibody was 80%. To evaluate the physiological effect of such a FVIII inhibition, we investigated the ability of the mutant antibody devoid of N -glycosylation in the variable region to prevent thrombosis in mice with a strong prothombotic phenotype resulting from a type II deficiency mutation in the heparin binding site of antithrombin. Despite its moderate inhibition of FVIII activity, the mutant antibody significantly prevented thrombosis in treated animals. We also carried out glycan analysis of native and mutant antibodies. Conclusions:,Modification of glycosylation in the variable region of antibodies contributes to the diversity of FVIII type II inhibition possibly by steric hindrance of the active site of FVIII by glycans, and may provide a novel strategy to modulate the functional activity of therapeutic antibodies. [source]

Mouse × pig chimeric antibodies expressed in Baculovirus retain the same properties of their parent antibodies

Ana M. Jar
Abstract The development of hybridoma and recombinant DNA technologies has made it possible to use antibodies against cancer, autoimmune disorders, and infectious diseases in humans. These advances in therapy, as well as immunoprophylaxis, could also make it possible to use these technologies in agricultural species of economic importance such as pigs. Porcine reproductive and respiratory syndrome virus (PRRSV) is an arterivirus causing very important economic losses to the industry. Passive transfer of antibodies obtained by biotechnology could be used in the future to complement or replace vaccination against this and other pig pathogens. To this end, we constructed and studied the properties of chimeric mouse × pig anti-PRRSV antibodies. We cloned the constant regions of gamma-1 and gamma-2 heavy chains and the lambda light chain of pig antibodies in frame with the variable regions of heavy and light chains of mouse monoclonal antibody ISU25C1, which has neutralizing activity against PRRSV. The coding regions for chimeric IgG1 and IgG2 were expressed in a baculovirus expression system. Both chimeric antibodies recognized PRRSV in ELISA as well as in a Western-blot format and, more importantly, were able to neutralize PRRSV in the same fashion as the parent mouse monoclonal antibody ISU25C1. In addition, we show that both pig IgG1 and IgG2 antibodies could bind complement component C1q, with IgG2 being more efficient than IgG1 in binding C1q. Expressing chimeric pig antibodies with protective capabilities offers a new alternative strategy for infectious disease control in domestic pigs. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Cationic Liposome Conjugation to Recombinant Adenoviral Vector Reduces Viral Antigenicity

CANCER SCIENCE, Issue 4 2000
Atsushi Natsume
Adenoviral (Ad) vectors are commonly used in gene therapy trials because of their efficiency in gene transfer. However, their use is limited by immune responses that reduce transgene expression and decrease the efficacy of repeated vector administration. In this study, we demonstrated that conjugation of Ad vector with our novel cationic liposomes could reduce viral antigenicity in vivo. Mice subcutaneously injected with liposome-conjugated Ad vector showed a 6.5-fold reduction of anti-Ad antibodies with neutralizing activity, compared to those with unconjugated Ad vector. Interestingly, we also found that the conjugated vector is less susceptible to inactivation by neutralizing antibodies in vitro and in vivo. Our results suggest that liposome conjugation reduces viral antigenicity, shields vectors from neutralizing antibody, and may allow repeated Ad vector administration. [source]