Human antibody derivatives against the fibroblast activation protein for tumor stroma targeting of carcinomas.

The fibroblast activation protein (FAP) is selectively expressed on activated fibroblasts of the tumor stroma on more than 90% of lung, breast and colon carcinomas. The high prevalence and abundance of FAP(+) stroma make it a promising target for in vivo diagnosis and therapy of a variety of carcinomas. We describe the humanization of the murine FAP-specific MAb, F19, which has already been clinically used for in vivo diagnostic purposes. Using phage display technology and human V-repertoires, VL and VH regions of F19 were replaced by analogous human V-regions while retaining the original HCDR3 sequence in order to maintain F19 epitope specificity. The resulting human single-chain fragments of immunoglobulin variable regions (scFv 34, scFv 18) showed affinities of 6 nM on cell membrane-bound FAP. scFv 34 was expressed as a bivalent minibody (Mb 34). The antigen-binding characteristics of Mb 34 were comparable to the parental and a complementarity-determining region (CDR)-grafted version of F19. This was revealed by binding competition studies, FACS analyses and immunohistochemistry on various tumor samples including breast, colon and lung carcinomas. Importantly, compared with the CDR-grafted humanized scFv version of F19, the V-regions of the selected human scFv 34 showed sequence identity with the parental antibody (Ab) only over the short, 15-amino acid long HCDR3. Thus, a largely reduced xenoantigenic potential is expected. These human Ab derivatives are suitable to develop novel therapeutic concepts with broad applicability for a wide variety of histological carcinomas based on tumor stroma targeting.

Generation of human high-affinity antibodies specific for the fibroblast activation protein by guided selection.

Four completely human antibody derivatives [single-chain-antibody fragments (scFvs)] with specificity for the general tumor stroma marker fibroblast activation protein (FAP) were isolated by guided selection. Highly diverse IgG, IgM and IgD isotypes comprising heavy-chain variable domain libraries were generated using cDNAs derived from diverse lymphoid organs of a multitude of donors. Three of the human scFvs were converted into bivalent minibodies and expressed in eukaryotic cells for further functional characterization. Binding-competition studies and analysis by fluorescence-activated cell sorting showed high-affinity binding (10--20 nM) for two clones and recognition of the same epitope as the murine guiding antibody. The minibodies were successfully used for immunohistology of a variety of human carcinoma biopsies, revealing specific staining of stromal fibroblasts. Therefore, they should be suitable for in vivo diagnostic and tumor-targeting studies and, because of their completely human origin, be superior to murine or humanized antibody derivatives.

[Treatment modalities in infected knee alloarthroplasties]. / Therapiemöglichkeiten und -ergebnisse bei der infizierten Kniealloarthroplastik.

PURPOSE: The purpose of this study was to present and to evaluate different treatment options in the infected knee alloarthroplasty. METHODS: We followed 47 infected knee alloarthroplasties with a mean follow-up of 62 months which were surgically treated by different techniques. There were 20 cases with early infection (< or = 12 months) and 27 cases with late infections (> 12 months). RESULTS: In 10 patients a two stage exchange of the implant were undertaken. In 6 of those 10 cases the infection could be successfully treated. 30 patients underwent an arthrodesis, two of those after an unsuccessful exchange procedure. In this group only in two patients the infection was not managed successfully. 28 of the patients with an arthrodesis showed a good result of the fusion side. One case was only debrided and in 8 cases bony and soft tissue damage lead to amputation. The HSS-score showed an excellent results in 5.3%, a good result in 21%, a fair result in 26.3% and a poor results in 47.4% of the cases. Comparable distribution was documented with the Hungerford-score. Patients with a stable and painless fusion showed a comparable functional outcome to those patients with a new replacement. CONCLUSION: Revision of an infected knee implant is best managed by a two stage procedure and can lead to a good functional result. Fusion is indicated in cases with bad bony and soft tissue situation. A solid arthrodesis gives a painfree and stable extremity.

Monitoring of scFv selected by phage display using detection of scFv-pIII fusion proteins in a microtiter scale assay.

We describe here a method for the efficient and rapid analysis of antigen binding characteristics of recombinant antibodies (ab) selected by phage display. This novel approach combines the bacterial production of soluble single chain ab (scFv)-pIII fusion proteins on a microtiter scale with the detection of these fusion proteins via a pIII-specific ab. It facilitates the parallel analysis of large numbers of clones and is more efficient than current analysis protocols. Applying this technique, we analysed phage display selection of tetanus toxoid (TTX) specific scFv with respect to: (i) the productive expression of fusion proteins; (ii) the enrichment of specific scFv in subsequent rounds of phage display selection on a polyclonal level; (iii) the antigen specificity of individual scFv clones; (iv) the antigen binding affinity of a selected scFv. A TTX-specific scFv (clone 4.3) was further examined in a mono- and bivalent form by surface plasmon resonance analysis. ScFv 4.3 possesses a subnanomolar affinity and a low off rate constant.