Cytotoxicity of monoclonal antibodies to a subset of Giardia isolates.

Previous studies showed that some Giardia lamblia isolates differ and can be categorized on the basis of their DNA banding patterns after digestion with endonuclease restriction enzymes, surface antigens, and excretory-secretory (E-S) products. In the present study, monoclonal antibodies (McAb) were produced that reacted with one specific group of Giardia isolates. These McAb recognized a 170,000 dalton antigen, which was present on the surface of these Giardia and released into the medium as an E-S antigen. This antigen was previously characterized and found to distinguish this subgroup of Giardia. In addition, these McAb were cytotoxic only for this subgroup of Giardia. Immobilization occurred immediately, and killing was documented by 7 min. The mechanism(s) of killing remains unknown but was shown to be complement independent and did not occur with Fab'. These McAb identifies certain isolates and can be used to type Giardia.