Development and characterization of human monoclonal antibodies that neutralize multiple TGFß isoforms.

Transforming growth factor (TGF)ß levels are elevated in, and drive the progression of, numerous disease states such as advanced metastatic cancer and systemic and ocular fibrosis. There are 3 main isoforms, TGFß1, 2, and 3. As multiple TGFß isoforms are involved in disease processes, maximal therapeutic efficacy may require neutralization of 2 or more of the TGFß isoforms. Fully human antibody phage display libraries were used to discover a number of antibodies that bind and neutralize various combinations of TGFß1, 2 or 3. The primary panning did not yield any uniformly potent pan-isoform neutralizing antibodies; therefore, an antibody that displayed potent TGFß 1, 2 inhibition, but more modest affinity versus TGFß3, was affinity matured by shuffling with a light chain sub-library and further screening. This process yielded a high affinity pan-isoform neutralizing clone. Antibodies were analyzed and compared by binding affinity, as well as receptor and epitope competition by surface plasmon resonance methods. The antibodies were also shown to neutralize TGFß effects in vitro in 3 assays: 1) interleukin (IL)-4 induced HT-2 cell proliferation; 2) TGFß-mediated IL-11 release by A549 cells; and 3) decreasing SMAD2 phosphorylation in Detroit 562 cells. The antibodies' potency in these in vitro assays correlated well with their isoform-specific affinities. Furthermore, the ability of the affinity-matured clone to decrease tumor burden in a Detroit 562 xenograft study was superior to that of the parent clone. This affinity-matured antibody acts as a very potent inhibitor of all 3 main isoforms of TGFß and may have utility for therapeutic intervention in human disease.

A case of phlegmonous gastritis with multiple liver and splenic abscesses.

A 63-year-old woman was admitted with high fever. Laboratory tests showed leukocytosis and elevated C-reactive protein (CRP) levels. Abdominal ultrasonography and computed tomography revealed multiple liver and splenic tumors. We diagnosed phlegmonous gastritis with multiple liver and splenic abscesses based on a discharge of pus from the gastric ulcer on biopsy obtained during esophagogastroduodenoscopy. She showed remission after spontaneous drainage and treatment with antibiotics. A search of the literature yielded no other cases of phlegmonous gastritis with multiple liver and splenic abscesses, and we therefore report this case.

Engineering ecotin for identifying proteins with a trypsin fold.

Ecotin is a bidentate, fold-specific inhibitor of mammalian serine-proteases produced by Escherichia coli. This molecule may be engineered to increase and/or change its affinity and specificity providing significant biotechnological potential. Since ecotin binds tightly to serine proteases of the trypsin fold, it may help to identify the role of these enzymes in different biological processes. In this work, we tested ecotin variants as an affinity purification reagent for identifying enzymes in samples of tumor progression and mammary gland involution. Initially, we used a commercial source of urokinase-type plasminogen activator (u-PA) that remained fully active after elution from an affinity column of the ecotin variant (M84R, M85R). We then successfully identified u-PA from more complex mixtures including lysates from a prostate cancer cell line and involuting mouse mammary glands. Interestingly, a membrane-type serine protease 1 was isolated from the Triton X-100-solubilized PC-3 cell lysates, and surprisingly, haptoglobin, a serine-protease homolog protein, was also identified in mammary gland lysates and in blood. Haptoglobin does not prevent ecotin inhibition of u-PA, but it may act as a carrier within blood when ecotin is used in vivo. Finally, this affinity purification matrix was also able to identify a thrombin-like enzyme from snake venom using an ecotin variant directed against thrombin. Overall, the ecotin variants acted as robust tools for the isolation and characterization of proteins with a trypsin fold. Thus, they may assist in the understanding of the role of these serine proteases and homologous proteins in different biological processes.

A general method for greatly improving the affinity of antibodies by using combinatorial libraries.

Look-through mutagenesis (LTM) is a multidimensional mutagenesis method that simultaneously assesses and optimizes combinatorial mutations of selected amino acids. The process focuses on a precise distribution within one or more complementarity determining region (CDR) domains and explores the synergistic contribution of amino acid side-chain chemistry. LTM was applied to an anti-TNF-alpha antibody, D2E7, which is a challenging test case, because D2E7 was highly optimized (K(d) = 1 nM) by others. We selected and incorporated nine amino acids, representative of the major chemical functionalities, individually at every position in each CDR and across all six CDRs (57 aa). Synthetic oligonucleotides, each introducing one amino acid mutation throughout the six CDRs, were pooled to generate segregated libraries containing single mutations in one, two, and/or three CDRs for each V(H) and V(L) domain. Corresponding antibody libraries were displayed on the cell surface of yeast. After positive binding selection, 38 substitutions in 21 CDR positions were identified that resulted in higher affinity binding to TNF-alpha. These beneficial mutations in both V(H) and V(L) were represented in two combinatorial beneficial mutagenesis libraries and selected by FACS to produce a convergence of variants that exhibit between 500- and 870-fold higher affinities. Importantly, these enhanced affinities translate to a 15- to 30-fold improvement in in vitro TNF-alpha neutralization in an L929 bioassay. Thus, this LTM/combinatorial beneficial mutagenesis strategy generates a comprehensive energetic map of the antibody-binding site in a facile and rapid manner and should be broadly applicable to the affinity maturation of antibodies and other proteins.