ANTIBODIES INHIBITING TRYPANOSOMA-CRUZI TRANS-SIALIDASE ACTIVITY IN SERA FROM HUMAN INFECTIONS

Trans-sialidase, an enzyme that transfers sialic acid among macromolec ules, has been implicated in invasion of host cells by Trypanosoma cru zi, the agent of Chagas' disease. Most antibodies produced in natural and experimental infections are directed to the highly antigenic C-ter minal domain (shed acute-phase antigen). These antibodies do not inhib it the trans-sialidase activity, which is present in the N-terminal do main of the molecule. Antibodies able to inhibit trans-sialidase in se ra from human infections have been found. TIA (trans-sialidase inhibit ion assay) was positive in sera from patients with acute and chronic i nfections. Healthy and congenitally infected infants born to mothers w ith Chagas' disease were also TIA-positive, but the antibody titers di minished within months after birth or after treatment. Thus, antibodie s neutralizing trans-sialidase are detectable in most forms of T. cruz i human infections, and TIA may be useful in the diagnosis of Chagas' disease.