CELL ATTACHMENT AND INVASION BY TOXOPLASMA GONDII

Tachyzoites of Toxoplasma gondii attach to and enter all nucleated cells,
evading killing by oxidative and non-oxidative mechanisms both during and
after cell entry. This proposal outlines our plan for investigation of I.)
selected ligands and receptors involved in attachment of tachyzoites to
cells and II.) the mechanism by which tachyzoites enter macrophages without
triggering a respiratory burst and reside in a vacuole in all cells which
neither acidifies nor fuses with lyosomes. Specific plans for I include a.) definition of the role of complement
component Clq in cell binding of tachyzoites, b.) characterization of
receptors for the extracellular matrix protein laminin on tachyzoites and
the role of laminin and host cell receptors in the attachment process, and
c.) identification of apical components in the parasite involved in cell
binding. Specific plans for II include investigation of a.) the interaction of
parasitophorous vacuoles containing T. gondii with other intracellular
compartments, b.) the influence of phagocytosis of tachyzoiters via
different receptors on vacuole composition and of parasite fate, c.)
incorporation and functional activity of components of the phagocyte NADPH
oxidase system in the parasitophorous vacuole membrane, d.) functional
analysis of acidification of purified parasitophorous vacuoles, e.)
immunochemical characterization of the parasitophorous vacuole membrane,
and f.) functional analysis of cell components involved in fusion of
parasitophorous vacuoles with lysosomes. These studies, for which we have a substantial amount of preliminary data,
will investigate important issues in cell attachment and entry by T.
gondii, and will address critical issues in the cell biology of
intracellular fusion and acidification events. Such experiments should
define the molecular mechanisms involved in these events and may suggest
strategies for intervention.