Development of optimized AAV3 serotype vectors: mechanism of high-efficiency transduction of human liver cancer cells

Our recent studies have revealed that among the 10 different commonly used adeno-associated virus (AAV) serotypes, AAV3 vectors transduce human liver cancer cells extremely efficiently because these cells express high levels of human hepatocyte growth factor receptor (hHGFR), and AAV3 utilizes hHGFR as a cellular co-receptor for viral entry. In this report, we provide further evidence that both extracellular as well as intracellular kinase domains of hHGFR are involved in AAV3 vector entry and AAV3-mediated transgene expression. We also document that AAV3 vectors are targeted for degradation by the host cell proteasome machinery, and that site-directed mutagenesis of surface-exposed tyrosine (Y) to phenylalanine (F) residues on AAV3 capsids significantly improves the transduction efficiency of Y701F, Y705F and Y731F mutant AAV3 vectors. The transduction efficiency of the Y705+731F double-mutant vector is significantly higher than each of the single mutants in liver cancer cells in vitro. In immunodeficient mouse xenograft models, direct intratumoral injection of AAV3 vectors also led to high-efficiency transduction of human liver tumor cells in vivo. We also document here that the optimized tyrosine-mutant AAV3 vectors lead to increased transduction efficiency following both intratumoral and tail-vein injections in vivo. The optimized tyrosine-mutant AAV3 serotype vectors containing proapoptotic genes should prove useful for the potential gene therapy of human liver cancers.

[Dynamics of bacterial population waves in relation to the function of chemotaxis response]

The time of formation and rate of bacterial population waves as a function of substrate concentration has been investigated. It was shown both theoretically and in experiment that the time of wave formation increases with substrate concentration. At the same time, the rate of wave propagation decreases at relatively high substrate concentrations. A comparative analysis of the dynamics of bacterial population waves in different chemotaxis responses was carried out in in silico experiments with the Keller-Segel model.

The mechanism of fractal-like structure formation by bacterial populations

Three types of population growth and development of chemotaxic motile bacteria Escherichia coli on semi-solid nutrient media are investigated: a) stable development - circular symmetrical waves; b) bursts; c) fractal-like self-organization. Experimental investigation of the burst formation is presented. The microscopic analysis of growing, fractal-like structures is carried out, and a mechanism for such structure formation is suggested. It is supposed that fractal-like bacterial structures growth is based on the principle of successively forming multiple micro-bursts. A mathematical model has been suggested to reproduce the experimental results. The structures obtained by numerical modeling of population growth in the parameter space 'substrate concentration - bacterial movement rate' reproduce the corresponding experimental structures in the space 'nutrient concentration in the media - the density of the media'.

A possible role of cold-induced ionic stress in cold-induced cell death

Analysis of experimental results and published data within the framework of the suggested mathematical model of ion-osmotic homeostasis revealed the dependence of a variety of cell parameters on temperature. It was shown that the cold-induced drastic increase in the basal concentration of cytoplasmic Ca was determined, on the one hand, by the suppression of transport processes responsible for Ca removal from the cytoplasm, and, on the other hand, by the increase of calcium fluxes, both from the outer medium and from cell organelles. The cold-induced variation in the ratio of permeabilities for Na and K ions was found, which can be due to the activation of different calcium- and potential-dependent channels or by formation of membrane defects. Besides the flow of calcium ions through appropriate selective channels, its delivery into the cytosol through membrane defects actively induced by cell cooling can not be excluded. Formation of nonselective transmembrane channels was promoted by lipid peroxidation and proteolysis induced by an increase in the basal concentration of calcium. The new approaches to protecting the cell from cold injury are discussed.