SOME OPPORTUNISTIC PARASITIC INFECTIONS IN AIDS - CANDIDIASIS, PNEUMOCYSTOSIS, CRYPTOSPORIDIOSIS, TOXOPLASMOSIS

Almost 80% of patients with AIDS die from infections other than human immunodeficiency virus (HIV). These infections usually occur late in t he course of disease when CD4(+) T-cell count has fallen below 200 per mm(3) cells per milliliter. Most of these infections are caused by or ganisms that do not normally afflict healthy individuals and are thus considered to be opportunistic. In this article, Lloyd Kasper and Domi nique Buzoni-Gatel review the host-parasite interaction for four impor tant pathogens: Candida albicans and Pneumocystis carinii (usually non -invasive pathogens), Cryptosporidium parvum (invades the cells but re mains localized in the gut) and Toxoplasma gondii (penetrates through the gut to cause systemic infection). These organisms, which generally cause limited or even insignificant clinical evidence of infection in the normal host, were chosen because of their high prevalence in AIDS patients and because they exhibit different invasive abilities. The r eason why individuals with AIDS are susceptible to this particular gro up of pathogens is uncertain.