In the assembly of DNA nanostructures, the specificity of Watson-Crick base pairing is used to control matter at the nanoscale. Using this technology for drug delivery is a promising route toward the magic bullet concept, as it would allow the realization of complex assemblies that co-localize drugs, targeting ligands and other functionalities in one nanostructure. Anthracyclines' mechanism of action in cancer therapy is to intercalate DNA, and since DNA nanotechnology allows for such a high degree of customization, we hypothesized that this would allow us to tune the DNA nanostructures for optimal delivery of the anthracycline doxorubicin (Dox) to human breast cancer cells. We have tested two DNA origami nanostructures on three different breast cancer cell lines (MDA-MB-231, MDA-MB-468, and MCF-7). The different nanostructures were designed to exhibit varying degrees of global twist, leading to different amounts of relaxation in the DNA double-helix structure. By tuning the nanostructure design we are able to (i) tune the encapsulation efficiency and the release rate of the drug and (ii) increase the cytotoxicity and lower the intracellular elimination rate when compared to free Dox. Enhanced apoptosis induced by the delivery system in breast cancer cells was investigated using flow cytometry. The findings indicate that DNA origami nanostructures represent an efficient delivery system for Dox, resulting in high degrees of internalization and increased induction of programmed cell death in breast cancer cells. In addition, by designing the structures to exhibit different degrees of twist, we are able to rationally control and tailor the drug release kinetics.

The spatial organization of membrane-bound ligands is thought to regulate receptor-mediated signaling. However, direct regulation of receptor function by nanoscale distribution of ligands has not yet been demonstrated, to our knowledge. We developed rationally designed DNA origami nanostructures modified with ligands at well-defined positions. Using these 'nanocalipers' to present ephrin ligands, we showed that the nanoscale spacing of ephrin-A5 directs the levels of EphA2 receptor activation in human breast cancer cells. Furthermore, we found that the nanoscale distribution of ephrin-A5 regulates the invasive properties of breast cancer cells. Our ligand nanocaliper approach has the potential to provide insight into the roles of ligand nanoscale spatial distribution in membrane receptor-mediated signaling.

The antiviral characteristics of monoclonal antibody IAM-41-2F5 (2F5) were determined in cell culture.

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The safety and immunogenecity of a booster dose of live attenuated varicella-zoster virus (VZV) vaccine was evaluated in 196 healthy subjects, >or=60 years old, who had already received a VZV vaccine >5 years before. This repeat booster dose was well tolerated. Cell-mediated immunity (CMI) to VZV was measured by an interferon-gamma (IFN-gamma) enzyme-linked immunosorbent spot-forming cell (ELISPOT) assay and a limiting dilution responder cell frequency (RCF) assay. Prevaccination responses decreased as a function of increasing age but were detectable in all subjects by use of the IFN-gamma ELISPOT assay. In most subjects, VZV-specific CMI was increased at 6 weeks postvaccination. The magnitude of the vaccine-induced IFN-gamma ELISPOT response was inversely related to prevaccination values. Although there was a significant correlation between the IFN-gamma ELISPOT and RCF assays, the ELISPOT assay had greater sensitivity and a wider dynamic range. A live attenuated VZV vaccine is safe and immunogenic in an elderly population, and the vaccine-induced immunity may be monitored by the IFN-gamma ELISPOT assay.

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Phytochromes are red and far-red photoreceptors that regulate plant growth and development in response to environmental light cues. Phytochromes exist in two photo-interconvertible conformational states: an inactive Pr form and an active Pfr form. The alteration of phytochromes' subcellular location functions as a major regulatory mechanism of their biological activities. Whereas phytochromes in the Pr form localize in the cytoplasm, phytochromes in the Pfr form accumulate in the nucleus, where they interact with transcription factors to regulate gene expression. The molecular details of the regulation of phytochrome translocation by light are poorly understood. Using Arabidopsis phyB as a model, we demonstrate that the C-terminal PAS-related domain (PRD) is both necessary and sufficient for phyB nuclear import and that the entire C terminus is required for nuclear-body (NB) localization. We also show that phyB's N-terminal bilin lyase domain (BLD) and PHY domain interact directly with the PRD in a light-dependent manner. In vivo localization studies indicate that BLD-PHY is sufficient to regulate phyB's nuclear accumulation. For phyB nuclear localization, our results suggest a molecular mechanism in which the nuclear-localization signal in the PRD is masked by interactions with phyB's chromophore-attachment domains and unmasked by light-dependent conformational changes.