Characterization of cyclically transmitted Trypanosoma (T.) brucei isolates from man

Four different trypanosome isolates from human patients isolated in 1979 during the epidemic of sleeping sickness in Busoga, south-east Uganda, were characterized by the following methods: isoenzyme analyses of bloodstream forms by isoelectric focusing; in vitro tests of human serum resistance of bloodstream as well as metacyclic forms; tsetse fly transmission through Glossina morsitans centralis and Glossina morsitans morsitans to compare the above characteristics of parasite populations before and after the cyclical passage; the indirect immunofluorescent antibody test (IFAT) to analyse the antigenic relationship between metacyclic populations of the four different stocks. The results of the isoenzyme analyses and the in vitro tests of human serum resistance separated one stock (TH K 86) from the 3 other isolates which behaved similarly. The tsetse fly transmission did not influence the characteristics except that a temporary switch to human serum sensitivity occurred in the metacyclic population of isolate TH K 86. The indirect immunofluorescent antibody test (IFAT) revealed a close antigen relationship between the four metacyclic populations. Mice immunized against metacyclic forms of two isolates exhibited solid cross-protection against the infection with one different isolate.