Neuraminidase from Trypanosoma cruzi: analysis of enhanced expression of the enzyme in infectious forms

We purified the neuraminidase (sialidase, acylneuraminyl hydrolase, EC 3.2.1.18) from the protozoan parasite Trypanosoma cruzi, strain Y, and examined the developmental regulation of the enzyme. The detectable amount of enzyme activity increased 10- to 20-fold upon conversion of the parasite from the noninfectious epimastigote form to the infectious trypomastigote form. The enzyme was purified from membranes of trypomastigotes greater than 5000-fold to apparent homogeneity and migrated as an entity of Mr 60,000 under denaturing conditions. Antibodies produced in rabbits against the denatured protein recognized the neuraminidase in membrane extracts from the infectious stage but not from the noninfectious stage. Sera from a patient with acute chagasic disease also reacted strongly with the neuraminidase. Other T. cruzi strains exhibited similar neuraminidase activities and induction rates. The coincidence of infectivity and enhanced expression of neuraminidase in trypomastigotes suggests that this enzyme constitutes a virulence factor in T. cruzi.