Delivery of functional DNA and messenger RNA to mammalian phagocytic cells by recombinant yeast.

Among the different vaccination approaches, DNA/RNA vaccination represents a promising means in particular for the induction of effective cellular immune responses conferred by CD8-positive T lymphocytes. To achieve such immune responses, there is a need for novel delivery systems that allow the introduction of nucleic acids to the cytosol of immune cells. We show, for the first time, the delivery of functional DNA and messenger RNA (mRNA) to mammalian antigen-presenting cells, including murine macrophages and human dendritic cells, using the yeast Saccharomyces cerevisiae as the delivery vehicle. After transfer of the particular nucleic acid, subsequent antigen processing and presentation were demonstrated in a human system. Remarkably, release of DNA/mRNA does not require additional 'helper' proteins such as listeriolysin. In conclusion, the yeast-based system described here is superior to many bacterial and viral systems in terms of efficacy, safety and targeting suggesting 'mycofection' as a promising approach for the development of a novel type of live vaccines.

Experimental observation of the trapped particle pinch effect.

The trapped particle pinch effect (Ware's drift) has been observed in a non-neutral plasma of electrons in a modified Malmberg-Penning trap in which electrons are contained in the annular volume between concentric cylinders. A pulsed azimuthal electric field is applied by increasing the flux within a solenoid on the axis. Radial displacements of the electrons are observed which show that they remain on a surface enclosing constant axial flux. These displacements are independent of the azimuthal field and thus are consistent with Ware's drift and inconsistent with the guiding center drift alone.

Amino acid utilization and isotope discrimination of amino nitrogen in nitrogen metabolism of rat liver in vivo.

Urea and plasma protein differ in natural 15N abundance up to 10%. The origin of this difference is the branched nitrogen metabolism in the liver. One main branch is the protein synthesis pathway, the other the urea synthesis pathway. By this branching 15N of precursor amino acids is depleted in urea while it is enriched in protein. With the 15N abundance of precursor amino acids, which may be taken from jejunum tissue, utilization of amino acids in liver metabolism can be calculated from isotope discrimination in either pathway. This was investigated by feeding different proteins to rats. When feeding high quality protein (whey protein) utilization of amino acids in liver metabolism at requirement intake was better than at zero protein intake (> 85% vs. 70%). From this we conclude that the pattern of amino acids available from the metabolic pool at zero protein intake is characterized by an imbalance. This endogenous imbalance can be complemented by exogenous dietary amino acids so that nitrogen excretion may even be smaller than the so-called "obligatory" losses of intakes not exceeding requirement. Thus, the quality of dietary protein is reflected not only by N balance. It also may be quantified by analysis of isotope discrimination in nitrogen metabolism of the liver. In addition, the quality of amino acid pattern available from the metabolic pool is indicated by this method.