The un-infectivity of the PF cultivated strain of trypanosoma cruzi to mice. An evaluation through a one year period by blood cultures and histopathology

Abstract

Trypanosoma cruzi of the cultivated PF strain w hen injecteã in mice per subcutaneous route, in aâequate doses, is able to induce an, efficient sterile im m unization in the animais (for at least one year) as determ ined by whole blood cultures and histopathology. IN T R O D U C T IO NIt is well known th a t each antigen presented to th e lymphoid system can react with a population of im munocompetent cells, variable with the antigen used (4).The quantity and th e route used for the antigen are also of im portance, giving place to an im mune response which may vary from optimal to no response a t ali (im m unotolerant condition).I h ad dem onstrated (14) th a t 3 x 102 live parasites of the PF strain injected by subcutaneous route, with about 30 trypomastigotes, were able to give an efficient protection to lOg body weight mice, against a virulent infection of Trypanosoma cruzi th a t killed 80% of th e control animais.This work aims to dem onstrate th a t the route and th e dose of the live PF parasi tes are very im portant in obtaining a safe immune response, as applicable to any live vaccine. MATERIAL AND METHODSAlbino mice from our Medicai School Animal Facilities were used. 130 of them, ali male, with an initial body weight of lOg were divided in groups of 10. 80 of these anim ais received by sub cutaneous route 6 x 103 parasites of the PF strain raised in W arren médium (22), dialyzated in accordance with the Nakam ura technique (20).The culture médium was put into cellophane bags immersed in 1.5 volumes of R inger-H artm ann solution (10) adjusted w ith NaOH sol. to pH 7.5.The culture used as vaccine was 8 days old and the percentage of mobile forms was about 80% with 0.8% trypomastigotes, as determ ined in 1,000 parasites counted a t rantíom in Giemsa stained smears.The Ringer solution with flagellates was centrifuged a t 1,500 rpm for 15 minutes and the sedim ent suspended in sterile so-* P r e s e n te d t o t h e X C o n g re ss o B ra s ile ir o d e P a to lo g ia . C iir itib a , 05/09/74. ** U S P . D e p a r ta m e n to d e G e n é ti c a e M a te m á tic a A p lic a d a à B io lo g ia d a F a c u ld a d e d e M e d ic in a d e R i b e ir ã o P r e to , S á o P a u lo , 14.100, B ra s il. S u b m i tte d to p u b lic a tio n o n 12-6-1974.