COMBINED OCCURRENCE OF TRYPANOSOMAL SIALIDASE TRANS-SIALIDASE ACTIVITIES AND LEISHMANIAL METALLOPROTEINASE GENE HOMOLOGS IN ENDOTRYPANUM SP/

Endotrypanum (order Kinetoplastida: family Trypanosomatidae) is a para site of forest dwelling tree sloths (Edentata: genera Choleopus and Br adypus). Unique among the haemoflagellates. this protozoan has an intr aerythrocytic phase in the mammalian host. Nevertheless, many striking similarities exist between Endotrypanum and the human pathogen Leishm ania that make it a useful model for epidemiological and evolutionary aspects of the biology of trypanosomatids. Importantly, Endotrypanum s pecies share both the insect vector and host reservoir with certain sp ecies of Leishmania (subgenus Viannia). Because mixed infections with Endotrypanum and Leishmania are common in sloths and, therefore, likel y to occur in the sandfly vector, there is a need for adequate biochem ical markers to distinguish Endotrypanum from Leishmania infections. I n this paper we show that Endotrypanum promastigotes possess sialidase and trans-sialidase activities, which are absent from Leishmania, and which are not closely related to the previously described trypanosoma l sialidase/trans-sialidase enzyme. We also document the occurrence in Endotrypanum of homologues of the leishmanial surface metalloproteina se gp63 genes. The combined occurrence of sialidase/trans-sialidase ac tivities and gp63 gene homologues in a unique organism has important r amifications for both field and laboratory studies on the biology of t rypanosomatids, especially those related to host infection and evoluti on.