Virulence of Giardia lamblia: an in vitro study on host-parasite interaction

Trophozoites of G. lamblia, a human parasite, were lysed by polymorphonuclear leukocytes (PMNL) of healthy individuals during in vitro interaction. However, the parasite damaged PMNL of giardiasis patients. A prior treatment of giardia trophozoites with anti-giardia serum, caused agglutination of pathogen and, thereby, the cytotoxic capacity of the parasite was reduced. Interaction of giardia-trophozoites with peritoneal macrophage, derived from infected mouse, reduced the phagocytic activity of the latter to 43% (against 100% in control). Macrophage activity was, however, stimulated to 131% when the mice were immunized with giardia antigen prior to experimental infection. Giardia extract proved cytotoxic at a dose of 0.7 mg, to HeLa cells in tissue culture. These in vitro studies offer experimental evidence of the cytotoxic and immuno-toxic behaviour of G. lamblia towards the host cells.