Avaliação de diferentes métodos de criopreservação de Trypanosoma congolense em nitrogênio líquido

Abstract

Members of the genus Trypanosoma are parasites of un^doy large groups of vertebrates. In general, trypanosomes are well adapted to their hosts and cause no appreciable damage, however, the group that parasitises mammals is poorly adapted, causing common diseases - the trypanosomoses. T. congolense is a species of trypanosome widely distributed in Africa and one of the most prevalent, infecting^ a large number of domestic animals. For this reason, it has been the subject of intense scientific research, which makes its constant availability in the laboratories of all countries dedicated to its study essential. Conventional methods for the propagation and preservation of parasitic micro-organisms in vivo, or in vitro, have some limitations which include the need for laboratories, initial isolation and strain loss, bacterial and fungal contamination and changes in the original biological and metabolic characteristics. These disadvantages can be overcome if the method of preservation is cryopreservation, which is a liquid nitrogen preservation technique. The purpose of the present work was to evaluate different methods of cryopreservation of T. congolense in liquid nitrogen by combining the following factors: freezing speeds (2 and 27.5°C/min), types of cryoprotectants (glycerol, dimethyl sulfoxide and polyvinylpyrrolidone) and concentrations of each cryoprotectant (8 and 10%). 2 kf z \ Z After freezing of trypanosomes and 25 days storage in (-196°C), the efficiency of each freezing speed, type and concentration of cryoprotector was determined in vivo in mice. The results showed that, although there was no significant difference between the two speeds tested, 2°C/min was quite effective for preservation and that, of the three cryoprotectants evaluated, glycerol/(in both concentrations) showed a high cryoprotection effect.