The fine structure of sexual stage development and sporogony ofCryptosporidium parvumin cell-free culture

Abstract

The sexual stages and new oocysts development of Cryptosporidium parvum were investigated in a cell-free culture system using transmission electron microscopy (TEM). Sexual development was extremely rapid after inoculation of oocysts into the medium. The process began within 1/2-12 h and was completed with new oocyst formation 120 h post-inoculation. The macrogamonts were bounded by two membranes and had amylopectin granules and two distinct types of wall-forming bodies. The microgamonts had a large nucleus showing lobe projections and condensation of chromatin, giving rise to peripherally budding microgametes. The microgametes contained a large area of granular substance containing groups of microtubules surrounding the electron-dense nucleus. In some instances, the dividing microgamy was observed in cell-free cultures with no preceding merogonic process. Fertilization was observed with the bullet-shaped microgamete penetrating an immature macrogamont at 24 and 216 h. The new thin- and thick-walled oocysts had a large residuum with polysaccharide granules and sporogony noted inside these oocysts. Novel immature four-layer walled thick oocysts with irregular knob-like protrusions on the outer layer resembling the immature Eimeria oocysts were also observed. The present study confirms the gametogony and sporogony of C. parvum in cell-free culture and describes their ultra-structure for the first time.

RNA-Seq analysis during the life cycle of Cryptosporidium parvum reveals significant differential gene expression between proliferating stages in the intestine and infectious sporozoites

“…Components of the oocyst walls in Cryptosporidium spp. are secreted from wall forming bodies (Spano et al, 1997;Aldeyarbi and Karanis, 2016) in the macrogametocyte that contain inter alia COWP proteins. As expression of COWP genes is specific to macrogametocytes, they are good indicators for sexual stage development (Smith et al, 2005).…”

Recent Breakthroughs and Ongoing Limitations in Cryptosporidium Research

“…However, these cell lines support C. parvum infection for only a few days, do not permit completion of the life cycle or continuous propagation 12 , and can display variation in gene expression depending on culture conditions 19 . Cell-free systems for C. parvum culture have been reported 20 , but although the parasite was observed to complete its life cycle by transmission electron microscopy 21 , these in vitro axenic systems do not permit investigations of the parasite interactions with the host epithelia.…”

An overview of parasitic infections of the gastro-intestinal tract in developed countries affecting immunocompromised individuals

“…Here the parasite undergoes asexual merogony followed by gamogony, which results in the formation of oocysts; the oocysts then form four naked sporozoites (Aldeyarbi and Karanis 2016). Once the oocytes mature in the gut and are excreted from the host, they are infective.…”

“…Once the oocytes mature in the gut and are excreted from the host, they are infective. Within the original host, autoinfection may occur at a stage in the life cycle of the parasite when a thin walled oocyst excysts (Aldeyarbi and Karanis 2016).…”