Production of metacyclic forms by cyclical transmission of west African Trypanosoma (T.) brucei isolates from man and animals.

Fifteen West African Trypanosoma (T.) brucei isolates from man and animals were cyclically transmitted. Five stocks, belonging to the non-gambiense group, could easily be transmitted through Glossina morsitans morsitans or Glossina m. centralis infected on mice, whereas successful transmission of the 10 isolates, identified as Trypanosoma brucei gambiense, was performed using G. palpalis gambiensis as vector. Glossina p. gambiensis was infected with culture-derived procyclic trypanosomes by repeated membrane feeding. In both cases, metacyclic forms could normally be detected in saliva samples of positive flies 3 to 4 weeks after first infection. These forms of major interest were subsequently characterized relative to their resistance/sensitivity against normal human serum in vitro and their antigenic properties, using indirect immunofluorescence: Metacyclic forms of all the T. b. gambiense isolates were determined by a stable human serum resistance and a restricted metacyclic variable antigen type (mVAT) repertoire, whereas representatives of the non-gambiense group (including TH162/78E 021) were sensitive against the trypanolytic factors of normal human serum and expressed a heterogeneous metacyclic antigen profile.