Targeted and shielded adenovectors for cancer therapy

Conditionally replicative adenovirus (CRAd) vectors are novel vectors with utility as virotherapy agents for alternative cancer therapies. These vectors have already established a broad safety record in humans and overcome some of the limitations of non-replicative adenovirus (Ad) vectors. In addition, one potential problem with these vectors, attainment of tumor or tissue selectivity has widely been addressed. However, two confounding problems limiting efficacy of these drug candidates remains. The paucity of the native Ad receptor on tumor tissues, and host humoral response due to pre-existing titers of neutralizing antibodies against the vector itself in humans have been highlighted in the clinical context. The well-characterized CRAd, AdΔ24-RGD, is infectivity enhanced, thus overcoming the lack of coxsackievirus and adenovirus receptor (CAR), and this agent is already rapidly progressing towards clinical translation. However, the perceived host humoral response potentially will limit gains seen from the infectivity enhancement and therefore a strategy to blunt immunity against the vector is required. On the basis of this caveat a novel strategy, termed shielding, has been developed in which the genetic modification of a virion capsid protein would provide uniformly shielded Ad vectors. The identification of the pIX capsid protein as an ideal locale for genetic incorporation of shielding ligands to conceal the Ad vector from pre-existing neutralizing antibodies is a major progression in the development of shielded CRAds. Preliminary data utilizing an Ad vector with HSV-TK fused to the pIX protein indicates that a shield against neutralizing antibodies can be achieved. The utility of various proteins as shielding molecules is currently being addressed. The creation of AdΔ24S-RGD, an infectivity enhanced and shielded Ad vector will provide the next step in the development of clinically and commercially feasible CRAds that can be dosed multiple times for maximum effectiveness in the fight against cancers in humans.This article is a symposium paper from the Annual Meeting of the "International Society for Cell and Gene Therapy of Cancer", held in Shenzhen, China, on 9–11 December 2005.     

Exploiting diverse stereochemistry of β-amino acids: toward a rational design of sheet-forming β-peptide systems

Due to the two methylene groups in their backbone, β-amino acids can adopt numerous secondary structures, including helices, sheets and nanotubes. Chirality introduced by the additional side chains can significantly influence the folding preference of β-peptides composed of chiral β-amino acids. However, only conceptual suggestions are present in the literature about the effect of chirality on folding preferences. Summarizing both the experimental and computational results, Seebach (Chem Biodivers 1:1111-1240, 2004) has proposed the first selection rule on the effect of side chain chirality, on the folding preference of β-peptides. In order to extend and fine-tune the aforementioned predictions of Seebach, we have investigated its validity to the novel type of apolar sheet proposed recently (Pohl et al. in J Phys Chem B 114:9338-9348, 2010). In order to facilitate the rational design of sheet-like structures, a systematic study on the effect of chirality on "apolar" sheet stability is presented on disubstituted [HCO-β-Ala-β(2,3)-hAla-β-Ala-NH(2)](2) model peptides calculated at the M05-2X/6-311++G(d,p)//M05-2X/6-31G(d) and B3LYP/6-311++G(d,p)//B3LYP/6-31G(d) levels of theory both in vacuum and in polar and apolar solvents. In addition, both types of "apolar" sheets were investigated; the one with two strands of identical (AA) and enantiomeric (AB) backbone structure. Our results show that heterochirally disubstituted sheets have the greatest preference for sheet formation (ΔG ~ -11 kcal mol(-1)). However, in contrast to Seebach's predictions, "homochiral disubstitution" itself does not necessarily disrupt the sheet structure, rather it could result stable fold (ΔG ~ -5 kcal mol(-1)). Results indicate that both the methyl group orientation and the local conformational effect of substitution affects sheet stability, as point chirality was found to have influence only on the backbone torsional angles. These results enabled us to extend and generalize Seebach's predictions and to propose a more general and accurate "rule of thumb" describing the effect of chirality on sheet stability. This offers an easy-to-use summary on how to design β-peptide sheet structures. We conclude that heterochirally disubstituted models are the best candidates for sheet formation, if the two strands are substituted in a way to create identical torsional angle sets on the two backbones for ideal hydrogen-bonding pattern. With adequately selected side chains, homochirally disubtituted derivatives may also form sheet structures, and the position of methyl groups would prevent assembly of more than two strands making it ideal to create hairpins.     

Results of the treatment of pediatric osteosarcoma in the Hungarian population

The objective of this report was to estimate long-term outcome and prognostic factors in children and adolescents with osteosarcoma. To evaluate the efficacy of surgery and multiagent chemotherapy for treating osteosarcoma, we reviewed 122 cases (65 males, 57 females, mean age 13.8 ± 3.6 years) treated at the Second Department of Pediatrics in Budapest between 1988 and 2006. Demographic parameters, tumor-related and treatment-related variables, response, overall survival (OS) and event-free survival (EFS) were analyzed. The 5-year OS and EFS were 68% and 61.5%, respectively. OS of patients without metastasis was 79%, while OS with early metastasis was 17%. Survival of patients with amputation (n=30) was not significantly different from that of patients with limb-salvage surgery (n=82), but all patients without radical surgery died. Gender and histological classification had no prognostic significance. Patients with localized tumors in extremities had increased survival compared to those with axial skeleton tumors (p=0.013). Poor histological response to neoadjuvant chemotherapy (rate of survivor tumor cells >10%) was associated with decreased survival (p=0.018). Patients under 14 years had better EFS than patients over 14 years (p=0.008). Our results demonstrate that younger patients with localized osteosarcoma of the extremities who receive limb-salvage surgery and chemotherapy have an excellent survival.     

On the emerging role of rabbit as human disease model and the instrumental role of novel transgenic tools

The laboratory rabbit (Oryctolagus cuniculus) is widely used as a model for human diseases, because of its size, which permits non-lethal monitoring of physiological changes and similar disease characteristics. Novel transgenic tools such as, the zinc finger nuclease method and the sleeping beauty transposon mediated or BAC transgenesis were recently adapted to the laboratory rabbit and opened new opportunities in precise tissue and developmental stage specific gene expression/silencing, coupled with increased transgenic efficiencies. Many facets of human development and diseases cannot be investigated in rodents. This is especially true for early prenatal development, its long-lasting effects on health and complex disorders, and some economically important diseases such as atherosclerosis or cardiovascular diseases. The first transgenic rabbits models of arrhythmogenesis mimic human cardiac diseases much better than transgenic mice and hereby underline the importance of non-mouse models. Another emerging field is epigenetic reprogramming and pathogenic mechanisms in diabetic pregnancy, where rabbit models are indispensable. Beyond that rabbit is used for decades as major source of polyclonal antibodies and recently in monoclonal antibody production. Alteration of its genome to increase the efficiency and value of the antibodies by humanization of the immunoglobulin genes, or by increasing the expression of a special receptor (Fc receptor) that augments humoral immune response is a current demand.     

SweetBac: a new approach for the production of mammalianised glycoproteins in insect cells

Recombinant production of therapeutically active proteins has become a central focus of contemporary life science research. These proteins are often produced in mammalian cells, in order to obtain products with post-translational modifications similar to their natural counterparts. However, in cases where a fast and flexible system for recombinant production of proteins is needed, the use of mammalian cells is limited. The baculoviral insect cell system has proven to be a powerful alternative for the expression of a wide range of recombinant proteins in short time frames. The major drawback of baculoviral systems lies in the inability to perform mammalian-like glycosylation required for the production of therapeutic glycoproteins. In this study we integrated sequences encoding Caenorhabditis elegans N-acetylglucosaminyltransferase II and bovine β1,4-galactosyltransferase I into the backbone of a baculovirus genome. The thereby generated SweetBac virus was subsequently used for the production of the human HIV anti-gp41 antibody 3D6 by integrating heavy and light chain open reading frames into the SweetBac genome. The parallel expression of target genes and glycosyltransferases reduced the yield of secreted antibody. However, the overall expression rate, especially in the recently established Tnao38 cell line, was comparable to that of transient expression in mammalian cells. In order to evaluate the ability of SweetBac to generate mammalian-like N-glycan structures on 3D6 antibody, we performed SDS-PAGE and tested for the presence of terminal galactose using Riccinus communis agglutinin I. The mammalianised variants of 3D6 showed highly specific binding to the lectin, indicating proper functionality. To confirm these results, PNGase A released N-glycans were analyzed by MALDI-TOF-MS and shown to contain structures with mainly one or two terminal galactose residues. Since the presence of specific N-glycans has an impact on antibodies ability to exert different effector functions, we tested the binding to human Fc gamma receptor I present on U937 cells.     

FcRn overexpression in transgenic mice results in augmented APC activity and robust immune response with increased diversity of induced antibodies

Our previous studies have shown that overexpression of bovine FcRn (bFcRn) in transgenic (Tg) mice leads to an increase in the humoral immune response, characterized by larger numbers of Ag-specific B cells and other immune cells in secondary lymphoid organs and higher levels of circulating Ag-specific antibodies (Abs). To gain additional insights into the mechanisms underlying this increase in humoral immune response, we further characterized the bFcRn Tg mice. Our Western blot analysis showed strong expression of the bFcRn transgene in peritoneal macrophages and bone marrow derived dendritic cells; and a quantitative PCR analysis demonstrated that the expression ratios of the bFcRn to mFcRn were 2.6- and 10-fold in these cells, respectively. We also found that overexpression of bFcRn enhances the phagocytosis of Ag-IgG immune complexes (ICs) by both macrophages and dendritic cells and significantly improves Ag presentation by dendritic cells. Finally, we determined that immunized bFcRn mice produce a much greater diversity of Ag-specific IgM, whereas only the levels, but not the diversity, of IgG is increased by overexpression of bFcRn. We suggest that the increase in diversity of IgG in Tg mice is prevented by a selective bias towards immunodominant epitopes of ovalbumin, which was used in this study as a model antigen. These results are also in line with our previous reports describing a substantial increase in the levels of Ag-specific IgG in FcRn Tg mice immunized with Ags that are weakly immunogenic and, therefore, not affected by immunodominance.     

Drosophila Src regulates anisotropic apical surface growth to control epithelial tube size

Networks of epithelial and endothelial tubes are essential for the function of organs such as the lung, kidney and vascular system. The sizes and shapes of these tubes are highly regulated to match their individual functions. Defects in tube size can cause debilitating diseases such as polycystic kidney disease and ischaemia. It is therefore critical to understand how tube dimensions are regulated. Here we identify the tyrosine kinase Src as an instructive regulator of epithelial-tube length in the Drosophila tracheal system. Loss-of-function Src42 mutations shorten tracheal tubes, whereas Src42 overexpression elongates them. Surprisingly, Src42 acts distinctly from known tube-size pathways and regulates both the amount of apical surface growth and, with the conserved formin dDaam, the direction of growth. Quantitative three-dimensional image analysis reveals that Src42- and dDaam-mutant tracheal cells expand more in the circumferential than the axial dimension, resulting in tubes that are shorter in length-but larger in diameter-than wild-type tubes. Thus, Src42 and dDaam control tube dimensions by regulating the direction of anisotropic growth, a mechanism that has not previously been described.