Selection of recombinant, library-derived antibody fragments against p24 for human immunodeficiency virus type 1 diagnostics

A gp41 MPER-specific llama VHH requires a hydrophobic CDR3 for neutralization but not for antigen recognition

The membrane proximal external region (MPER) of the HIV-1 glycoprotein gp41 is targeted by the broadly neutralizing antibodies 2F5 and 4E10. To date, no immunization regimen in animals or humans has produced HIV-1 neutralizing MPER-specific antibodies. We immunized llamas with gp41-MPER proteoliposomes and selected a MPER-specific single chain antibody (VHH), 2H10, whose epitope overlaps with that of mAb 2F5. Bi-2H10, a bivalent form of 2H10, which displayed an approximately 20-fold increased affinity compared to the monovalent 2H10, neutralized various sensitive and resistant HIV-1 strains, as well as SHIV strains in TZM-bl cells. X-ray and NMR analyses combined with mutagenesis and modeling revealed that 2H10 recognizes its gp41 epitope in a helical conformation. Notably, tryptophan 100 at the tip of the long CDR3 is not required for gp41 interaction but essential for neutralization. Thus bi-2H10 is an anti-MPER antibody generated by immunization that requires hydrophobic CDR3 determinants in addition to epitope recognition for neutralization similar to the mode of neutralization employed by mAbs 2F5 and 4E10.

Chimeric peptide beacons: a direct polypeptide analog of DNA molecular beacons

We have developed a new biosensor architecture, which is comprised of a polypeptide-peptide nucleic acid tri-block copolymer and which we have termed chimeric peptide beacons (CPB), that generates an optical output via a mechanism analogous to that employed in DNA-based molecular beacons.

Demystified...recombinant antibodies

Recombinant antibodies are important tools for biomedical research and are increasingly being used as clinical diagnostic/therapeutic reagents. In this article, a background to humanized antibodies is given, together with details of the generation of antibody fragments--for example, single chain Fv fragments. Phage antibody fragments are fast becoming popular and can be generated by simple established methods of affinity enrichment from libraries derived from immune cells. Phage display methodology can also be used for the affinity enrichment of existing antibody fragments to provide a reagent with a higher affinity. Here, phage antibodies are demystified to provide a greater understanding of the potential of these reagents and to engage clinicians and biomedical scientists alike to think about potential applications in pathology and clinical settings.

Generation and characterization of single-chain antibody fragments specific against transmembrane envelope glycoprotein gp46 of maedi-visna virus

A single-chain antibody fragments (scFv) was developed directed against transmembrane envelope glycoprotein gp46 of the virus maedi-visna, by the application of the antibody phage display library. To get specific scFv binders, the library was panned against the biotinylated peptide of 20 amino acids corresponding to the principal immunodominant domain of gp46 protein. The number of positively binding scFvs was evaluated by scFv-phage ELISA, BstN1 fingerprinting and DNA sequencing. The scFvs were expressed in soluble form and purified by immobilized metal affinity chromatography (IMAC) with a yield of 2-2.5 mg/l. Two scFvs have shown to recognize gp46 and gp150 proteins in Western blot analysis. The scFvs also recognized the virus in infected cells as shown by immunofluorescence assay. The affinity of the obtained antibody fragments to gp46 peptide was measured by surface plasmon resonance, and the resulting K(A) was in the 10(6)-10(7)lmol(-1) range. The application of characterized scFvs for expression as intrabodies in intracellular immunization against virus maedi-visna infection and for the diagnosis of this virus is discussed.

Recombinant single-chain Fv antibodies that recognize the p25 protein of the Maedi-Visna virus

Single chain Fv (scFv) antibodies (generated by phage display technology, molecules representing new and efficient tools in the research and diagnostics of infectious diseases) against the capsid protein (p25) of Maedi-Visna virus were selected. Several clones of p25 specific scFv antibodies were identified; one of them was expressed as a soluble scFv molecule, purified by immobilized metal-affinity chromatography and further characterized by sequencing and determination of the kinetic equilibrium association constant. Sequence analysis showed that the rearranged VL and VH domains of the analyzed scFv clone used sequences from the VL3 family (germline DPL16/VL3.1) and VH1 family (germline VH20), respectively. The kinetic equilibrium association constant was determined as KA = 1.12 +/- 0.52 L/mumol.

The production and application of single-chain antibody fragments

This review discusses methods for the single-chain antibody fragment ($cFv) generation and scFv expression systems, and describes potential applications of scFv in the therapy of viral diseases and cancer, with emphasis on intracellularly expressed scFvs (intrabodies), application of scFvs in detection and diagnostics, and their use in proteomics.

A large non-immunized human Fab fragment phage library that permits rapid isolation and kinetic analysis of high affinity antibodies

We report the design, construction, and use of the first very large non-immunized phage antibody library in Fab format, which allows the rapid isolation and affinity analysis of antigen-specific human antibody fragments. Individually cloned heavy and light chain variable region libraries were combined in an efficient two-step cloning procedure, permitting the cloning of a total of 3.7 x 10(10) independent Fab clones. The performance of the library was determined by the successful selection of on average 14 different Fabs against 6 antigens tested. These include tetanus toxoid, the hapten phenyl-oxazolone, the breast cancer-associated MUC1 antigen, and three highly related glycoprotein hormones: human chorionic gonadotropin, human luteinizing hormone, and human follicle-stimulating hormone. In the latter category, a panel of either homone-specific or cross-reactive antibodies were identified. The design of the library permits the monitoring of selections with polyclonal phage preparations and to carry out large scale screening of antibody off-rates with unpurified Fab fragments on BIAcore. Antibodies with off-rates in the order of 10(-2) to 10(-4) s-1 and affinities up to 2.7 nM were recovered. The kinetics of these phage antibodies are of the same order of magnitude as antibodies associated with a secondary immune response. This new phage antibody library is set to become a valuable source of antibodies to many different targets, and to play a vital role in target discovery and validation in the area of functional genomics.