Exploitation of Langerhans cells for in vivo DNA vaccine delivery into the lymph nodes.

There is no clinically available cancer immunotherapy that exploits Langerhans cells (LCs), the epidermal precursors of dendritic cells (DCs) that are the natural agent of antigen delivery. We developed a DNA formulation with a polymer and obtained synthetic 'pathogen-like' nanoparticles that preferentially targeted LCs in epidermal cultures. These nanoparticles applied topically under a patch-elicited robust immune responses in human subjects. To demonstrate the mechanism of action of this novel vaccination strategy in live animals, we assembled a high-resolution two-photon laser scanning-microscope. Nanoparticles applied on the native skin poorly penetrated and poorly induced LC motility. The combination of nanoparticle administration and skin treatment was essential both for efficient loading the vaccine into the epidermis and for potent activation of the LCs to migrate into the lymph nodes. LCs in the epidermis picked up nanoparticles and accumulated them in the nuclear region demonstrating an effective nuclear DNA delivery in vivo. Tissue distribution studies revealed that the majority of the DNA was targeted to the lymph nodes. Preclinical toxicity of the LC-targeting DNA vaccine was limited to mild and transient local erythema caused by the skin treatment. This novel, clinically proven LC-targeting DNA vaccine platform technology broadens the options on DC-targeting vaccines to generate therapeutic immunity against cancer.

Integrative plasmid vector for constructing single-copy reporter systems to study gene regulation in Rhizobium meliloti and related species.

The integrative system of phage 16-3 of Rhizobium meliloti 41 was shown to function in several bacterial species belonging to the Rhizobium, Bradyrhizobium, Azorhizobium, and Agrobacterium genera. It might also function in many other bacterial species provided that both the target site (attB) and the required host factor(s) are present. Here we report on the construction of a new integrative vector that can be utilized in gene regulation studies. It provides an opportunity to create a single-copy set-up for characterizing DNA-protein interactions in vivo, in a wide range of bacteria. To demonstrate the usefulness of the vector, transcription repression by binding of the C repressor protein of phage 16-3 to wild type operators was studied. The assay system provided highly reproducible quantitative data on repression.