Infectivity of Trypanosoma brucei Cultivated at 28 C with Tsetse Fly Salivary Glands*

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Abstract
When transformed procyclic noninfective [blood stream] trypanosomes of several unrelated stocks of T. brucei were cultivated in T-30 Falcon flasks at 28.degree. C in a liquid medium containing head-salivary gland explants of G. morsitans morsitans, some of the organisms developed into forms infective for mice. Infective trypanosomes were detected 7-14 days after the cultures were prepared and they persisted for varying periods of up to 88 days when the cultures were terminated. A few of the salivary glands became invaded with parasites about the time infective organisms appeared in the cultures. Using T. brucei TREU 929, it was shown that trypanosomes grown with 27-50 explants were capable of producing infections consistently for prolonged periods. Trypanosomes cultivated with 25 or fewer explants rarely infected mice. Infectivity titrations on trypanosome suspensions from cultures of stocks TREU 1275 and TREU 929 revealed that the maximum number of infective organisms was present 26-50 days after initiation of the cultures. Control cultures of trypanosomes grown in medium alone were generally not infective but 2 of the 6 stocks gave rise to a few sporadic infections. A few epimastigote-like and metacyclic-like trypanosomes were seen in stained preparations of infective inocula.