T Cells Involved In Adaptive Immunity

Much of the data on the role of T cells in immunity to cryptosporidial infection has been obtained from murine infection models. T cells are essential for parasite clearance as chronic C. parvum or C. muris infections are observed in T cell-deficient mice whereas infections in normal mice are self-limiting (reviewed by McDonald and Bancroft, 1998). Infections in immunocompromised mice can be cleared by injection of T cell-containing lymphoid cells from normal mice (reviewed by Theodos, 1998)....

References

Rangel. 1992. Structural organization of chromatin during the cell cycle of Entamoeba histolytica trophozoites. Archives of Medical Research 23 77-80. Bakatselou, C., C. Kidgell, and C. Graham Clark. 2000. A mitochondrial-type hsp70 gene of Entamoeba histolytica. Molecular and Biochemical Parasitology 110 177-182. Bhattacharya, S., A. Bhattacharya, L. S. Diamond, and A. T. Soldo. 1989. Circular DNA of Entamoeba histolytica encodes ribosomal RNA. Journal of...

Epidemiology Person Time And Place

In developing countries, infection is common in infants aged less than 1 year, while in developed countries infection is most common in children aged from 1 to 5 years, with a secondary peak in young, mainly urban, adults (Casemore 1990 Palmer & Biffin, 1990). A relative increase in incidence in adults is often seen in waterborne outbreaks (Meinhardt et al., 1996). Males and females are generally affected with equal frequency although there is evidence from some studies in developing...

Antigenic Variation In Vitro And In Vivo Clues To The Biological Role Of Antigenic Variation

Since surface antigen variation was initially identified as an in vitro phenomenon of Giardia, a subsequent determination of the biologic role of antigenic variation has been of special interest. Individual trophozoites studied during in vitro growth express only one VSP on their surface at any time except during switching when two VSPs can be transiently detected. Rates of switching are both VSP and isolate dependent. Selection of trophozoites following random expression of VSPs appears to be...

Cyclospora

Cyclospora cayetanensis is a protozoan parasite of humans causing diarrheal illness after colonizing the mucosal epithelium ofthe small intestine. C. cayetanensis is a parasite that has been described world-wide and identified in water and food. Cyclosporiasis causes flu-like symptoms including profound diarrhea lasting 1 to 3 weeks. Clinical signs include weight loss, nausea, anorexia, vomiting, and abdominal cramping (Herwalt, 2000). Among immunocompromised individuals (e.g. HIV-infected),...

Molecular Studies Strain Variation

Molecular methods have answered many of the questions raised by earlier field epidemiology since investigation of strain variation began in the late 1980s and early 1990s. This included the observations that different isolates have varying infective dose size and clinical responses (Fayer and Ungar, 1986). Phenotyping tools tell us something about the characteristics an organism expresses as a distinguishable trait. Those applied to C. parvum include protein analysis and antigenic diversity...