Characterisation of Trypanosoma cruzi populations by DNA polymorphism of the cruzipain gene detected by single-stranded DNA conformation polymorphism(SSCP) and direct sequencing

Fifty fresh isolates of Trypanosoma cruzi from Triatoma dimidiata Vectors a nd 31 from patients with Chagas' disease were analysed for DNA polymorphism s within the 432-bp core region of the cruzipain gene which encodes the act ive site of cathepsin L-like cystein proteinase. The cruzipain gene showed signs of polymorphism consisting of four different DNA sequences in Central and South American isolates of T. cruzi. The PCR fragments of Guatemalan i solates could be divided into three groups, Groups 1, 2 and 3, based on dif ferent patterns of single-stranded DNA conformation polymorphism. All of th e strains isolated from Brazil, Chile, and Paraguay, except for the CL stra in, showed a Group 4 pattern. Two to four isolates from each group were ana lysed by cloning and sequencing. A silent mutation occurred between Groups 1 and 2, and five nucleotides and two aa substitutions were detected betwee n Groups 1 and 3. The DNA sequence of Group 4 contained five nucleotides an d one aa substitution from Group 1. All of the DNA sequences corresponded w ell with the single-stranded DNA conformation polymorphism. The Group 1 isolates, the majority in the Guatemalan population (70/81, 86. 4%), were isolated from both triatomines and humans, but Group 3 were isola ted only from humans. Moreover, the Group 2 isolates were detected only in triatomine vectors (9/50; 18%), but never in humans (0/32, P < 0.05) sugges ting that this group has an independent lifecycle in sylvatic animals and i s maintained by reservoir hosts other than humans. (C) 1998 Australian Soci ety for Parasitology. Published by Elsevier Science Ltd. All rights reserve d.