Heat treatment improves antigen-specific T cell activation after protein delivery by several but not all yeast genera.

A central prerequisite in using yeast as antigen carrier in vaccination is its efficient interaction with cellular components of the innate immune system, mainly mediated by cell surface structures. Here, we investigated the distribution of major yeast cell wall components such as mannan, β-glucan and chitin of four different and likewise biotechnologically relevant yeasts (Saccharomyces, Pichia, Kluyveromyces and Schizosaccharomyces) and analyzed the influence of heat-treatment on β-1,3-glucan exposure at the outer yeast cell surface as well as the amount of yeast induced reactive oxygen species (ROS) production by antigen presenting cells (APC) in human blood. We found that yeasts significantly differ in the distribution of their cell wall components and that heat-treatment affected both, cell wall composition and yeast-induced ROS production by human APCs.

mRNA delivery to human dendritic cells by recombinant yeast and activation of antigen-specific memory T cells.

The import of functional nucleic acids like messenger RNA into mammalian cells has proven to be a powerful tool in cell biology and several delivery systems have been described. However, as targeting of particular cell types is a major challenge and RNA vaccination represents a promising means for the induction of cellular immune responses, there is a need for novel delivery systems that permit the introduction of functional messenger RNA to the cytosol of immune cells. Here, we describe a delivery system based on the yeast Saccharomyces cerevisiae that allows the delivery of functional messenger RNA to mammalian antigen-presenting cells such as human dendritic cells.

Human yeast-specific CD8 T lymphocytes show a nonclassical effector molecule profile.

Pathogenic yeast and fungi represent a major group of human pathogens. The consequences of infections are diverse and range from local, clinically uncomplicated mycosis of the skin to systemic, life-threatening sepsis. Despite extensive MHC class I-restricted frequencies of yeast-specific CD8 T lymphocytes in healthy individuals and the essential role of the cell-mediated immunity in controlling infections, the characteristics and defense mechanisms of antifungal effector cells are still unclear.

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.

Uptake of various yeast genera by antigen-presenting cells and influence of subcellular antigen localization on the activation of ovalbumin-specific CD8 T lymphocytes.

Yeasts of the genus Saccharomyces expressing recombinant antigens are currently evaluated as candidate T cell vaccines. Here, we compared the interaction kinetics between four biotechnologically relevant yeast genera (Saccharomyces cerevisiae, Schizosaccharomyces pombe, Kluyveromyces lactis and Pichia pastoris) and human dendritic cells as well as the involvement of Dectin-1 and mannose receptor in phagocytosis. Further, we analyzed the activation capacity of recombinant yeasts expressing ovalbumin (OVA) either intracellular, extracellular or surface-displayed by OVA-specific CD8 T lymphocytes.