Studies on the virulence and attenuation of Trypanosoma cruzi using immunodeficient animals

Tissue invasion and pathology by Trypanosoma cruzi result from an interacti on between parasite virulence and host immunity. Successive in vivo generat ions of the parasite select populations with increasing ability to invade t he host. Conversely, prolonged in vitro selection of the parasite produces attenuated sublines with low infectivity for mammals. One such subline (TCC clone) has been extensively used in our laboratory as experimental vaccine and tested in comparative experiments with its virulent ancestor (TUL). Th e experiments here reviewed aimed at the use of immunodeficient mice for te sting the infectivity of TCC parasites. It has not been possible to obtain virulent, revertant sublines by prolonged passaged in such mice.