Molecular cloning and immunoelectron microscopy have been used
to clone
the full-length gene encoding Cryptosporidium
parvum oocyst wall protein (COWP) and to analyse at the ultrastructural
level the expression and localization of COWP
during development in the gut. COWP is 1622 amino acids long, has a typical
leader peptide and consists of 2 amino acidic
domains each containing distinct repeated elements possibly originating
from
a common ancestral precursor. Electron
microscopy localized COWP in a large cytoplasmic inclusion and in the
wall-forming bodies of early and late macrogametes, respectively. Ultrastructural
analysis of double-walled sporulating and mature oocysts indicated that
COWP is
selectively localized in the inner layer of the oocyst wall. This study
provides the first localization at the ultrastructural
level of a cloned coccidian oocyst wall protein.