The availability of stable human antibody reagents would be of considerable advantage for research, diagnostic, and therapeutic applications. Unfortunately, antibody variable heavy and light domains (V H and V L ) that mediate the interaction with antigen have the propensity to aggregate. Increasing their aggregation resistance in a general manner has proven to be a difficult and persistent problem, due to the high level of sequence diversity observed in human variable domains and the requirement to maintain antigen binding. Here we outline such an approach. By using phage display we identified specific positions that clustered in the antigen binding site (28, 30-33, 35 in V H and 24, 49-53, 56 in V L ). Introduction of aspartate or glutamate at these positions endowed superior biophysical properties (non-aggregating, well-expressed, and heat-refoldable) onto domains derived from common human germline families (V H 3 and V κ 1). The effects of the mutations were highly positional and independent of sequence diversity at other positions. Moreover, crystal structures of mutant V H and V L domains revealed a surprising degree of structural conservation, indicating compatibility with V H ∕V L pairing and antigen binding. This allowed the retrofitting of existing binders, as highlighted by the development of robust high affinity antibody fragments derived from the breast cancer therapeutic Herceptin. Our results provide a general strategy for the generation of human antibody variable domains with increased aggregation resistance.biotechnology | monoclonal antibodies | protein aggregation | protein engineering | antibody therapeutics P rotein aggregation represents a key bottleneck in the generation of antibody-based reagents and hinders the development and production of human therapeutics (1). It is generally believed that the aggregation propensity of larger antibody reagents (such as immunoglobulin G and Fab) is mostly determined by their variable domain components (V H and V L ), although there is currently little understanding of the mechanisms involved (1, 2). Indeed, significant differences of aggregation rates have been reported for antibodies that differ exclusively in their variable domains (1, 2). Aggregation propensity is even more pronounced for smaller antibody reagents, which lack the interdomain stabilization of their larger counterparts (3, 4). This is a major problem in biotechnology due to an increasing trend toward smaller antibody formats for imaging and tumor targeting applications (4). Common formats include human single chain fragments (scFv) and human single domain antibodies, both of which frequently display poor biophysical properties (1, 3).The aggregation propensity of human variable domains is in marked contrast to the variable heavy domains of camels and llamas, which are generally nonaggregating and soluble ("V HH domains") (5-7). More favorable properties have also been described for "camelized" and other engineered human V H model domains (8-12) but not for human V L domains. Their p...

A high proportion of β-cells die within days of islet transplantation. Reports suggest that induction of hypoxia-inducible factor-1α (HIF-1α) predicts adverse transplant outcomes. We hypothesized that this was a compensatory response and that HIF-1α protects β-cells during transplantation. Transplants were performed using human islets or murine β-cell-specific HIF-1α-null (β-HIF-1α-null) islets with or without treatment with deferoxamine (DFO) to increase HIF-1α. β-HIF-1α-null transplants had poor outcomes, demonstrating that lack of HIF-1α impaired transplant efficiency. Increasing HIF-1α improved outcomes for mouse and human islets. No effect was seen in β-HIF-1α-null islets. The mechanism was decreased apoptosis, resulting in increased β-cell mass posttransplantation. These findings show that HIF-1α is a protective factor and is required for successful islet transplant outcomes. Iron chelation with DFO markedly improved transplant success in a HIF-1α-dependent manner, thus demonstrating the mechanism of action. DFO, approved for human use, may have a therapeutic role in the setting of human islet transplantation.

In transplantation, the contribution of B cells to the rejection or acceptance of the allograft is a topic of major interest. The presence of donor-specific antibodies in transplant recipients is often associated with decreased graft function and rejection, clearly indicating a pathogenetic role of B cells in transplantation. However, data from studies in humans and rodents suggest that under certain conditions, B cells have the capacity to control or regulate the immune response to a transplanted organ. Although a great deal of attention has been focused on B cells in human and murine models of autoimmunity, our understanding of the role of these cells in transplantation is limited at present. Indeed, results in this setting are controversial and seem to depend on the model system used or the clinical situation studied. Here, we review the current understanding of the various phenotypes and roles that have been associated with immune-regulating B cells. We also discuss the mechanisms employed by subsets of these regulatory B cells to control the immune response in transplant recipients and in animal models of transplantation.

Compared with lymphoid tissues, the immune cell compartment at mucosal sites is enriched with T cells bearing the γδ T-cell receptor (TCR). The female reproductive tract, along with the placenta and uterine decidua during pregnancy, are populated by γδ T cells predominantly expressing the invariant Vγ6 + Vδ1 + receptor. Surprisingly little is understood about the function of these cells. We found that the majority of γδ T cells in the non-pregnant uterus, pregnant uterus, decidua and placenta of mice express the transcription factor RORγt and produce interleukin-17 (IL-17). In contrast, IFNγ-producing γδ T cells were markedly reduced in gestational tissues compared with uterine-draining lymph nodes and spleen. Both uterine-resident invariant Vγ6 + and Vγ4 + γδ T cells which are more typically found in lymphoid tissues and circulating blood, were found to express IL-17. Vγ4 + γδ T cells were particularly enriched in the placenta, suggesting a pregnancy-specific recruitment or expansion of these cells. A small increase in IL-17-producing γδ T cells was observed in allogeneic compared with syngeneic pregnancy, suggesting a contribution to regulating the maternal response to paternally-derived alloantigens. However, their high proportions also in non-pregnant uteri and gestational tissues of syngeneic pregnancy imply a role in the prevention of intrauterine infection or quality control of fetal development. These data suggest the need for a more rigorous evaluation of the role of IL-17 in sustaining normal pregnancy, particularly as emerging data points to a pathogenic role for IL-17 in pre-eclampsia, pre-term birth, miscarriage and maternal immune activation-induced behavioral abnormalities in offspring.