Quantitative studies on trypanosomes in tsetse tissue culture

Cultivation of procyclic trypomastigotes of Trypanosoma congolense in a semi-defined medium with direct adaptation from bloodstream forms

Bloodstream forms of Trypanosoma congolense added to the semi-defined medium 109-c (Minimum Essential Medium with Earle's salts, 60 mM HEPES, haemin, and heat-inactivated FBS) and incubated at 28 degrees C transformed into procyclic trypomastigotes. Established cultures of the procyclic forms yielded up to 4.5 X 10(7) parasites/ml. The cultivated populations consisted only of trypomastigotes and were not infective for mice. The amino acids consumed to the greatest extent were glutamine, proline, and threonine. Changes in glucose, pyruvate, and lactate concentrations during growth were determined. The procyclic organisms possessed a well-developed mitochondrion.

Cultivation of infective forms of Trypanosoma congolense from trypanosomes in the proboscis of Glossina morsitans

Two stocks of Trypanosoma congolense were established in culture at 28 degrees C using trypanosomes from the proboscides of infective Glossina morsitans. Successful primary cultures were initiated by placing an infected tsetse proboscis beside a bovine dermal collagen explant in Eagle's minimum essential medium supplemented with foetal calf serum. The trypanosomes multiplied rapidly in the medium and also gradually formed an adherent layer o the plastic surface of the culture vessel. Three primary cultures produced organisms infective for mice from 14, 20 and 35 days after initiation and thereafter continuously until days 76, 76 and 52 when they were discarded. Four attempts to initiate infective cultures using infected tsetse proboscides in medium without dermal explants were unsuccessful. When trypanosomes from primary cultures were placed in culture medium with proboscides from uninfected tsetse flies, the parasites multiplied, formed an adherent layer in the culture flasks and were seen in the proboscides within 24 h. A line of 1 stock was serially sub-passaged in this way 4 times during a period of 215 days. Infectivity titrations in mice indicated that primary and sub-passaged cultures each contained similar numbers of infective organisms. Another line of the same stock was also sub-passaged 4 times in medium alone over a period of 186 days. These sub-cultures again retained infectivity for mice, but titrations showed a decrease in infective organism production in the 4th sub-culture. Primary and sub-passaged cultures all included a variety of morphologically different developmental forms of T. congolense, closely resembling those described in the labrum and hypopharynx of Glossina by previous workers. Short metacyclic-like trypanosomes and organisms with proteinaceous surface coats were present in infective cultures. Cultures were successfully re-established after cryopreservation at -196 degrees C and retained the ability to produce infective organisms.

The separation and structure of infective trypanosomes from cultures of Trypanosomas brucei grown in association with tsetse fly salivary glands

Infective trypanosomes developed when Trypanosoma brucei was cultivated at 28 C in a liquid medium containing tsetse fly head-salivary gland explants. They were separated from the noninfective culture forms using DEAE-cellulose column chromatography. It was demonstrated by light and electron microscopy that the separated organisms were morphologically similar to metacyclic stages found in a tsetse fly and that they had a characteristic surface coat. Single metacyclic trypanosomes isolated from the cultures gave rise to infections in mice.

Growth and differentiation of Trypanosoma cruzi cultivated with a Triatoma infestans embryo cell line

Trypanosoma cruzi strain Peru was cultivated in the presence of an established cell line of Triatoma infestans embryo cells (TI- 32). Bloodstream trypomastigotes differentiated into amastigote-like cells (first differentiation phase) which multiplied to form large clusters of cells. Because of their clustering nature, a new term, "staphylomastigotes," has been proposed for this stage. After 10 days of cultivation, 90% of the staphylomastigotes underwent differentiation (2nd differentiation phase) to trypomastigotes (approximately 98%) or epimastigotes (approximately 2%). Bloodstream trypomastigotes cultivated without TI-32 cells underwent the first, but not the 2nd differentiation phase, although occasional epimastogotes were seen (less than 1%). The evidence presented suggests that TI-32 cells produce a labile factor(s) important not only for initiation of the 2nd differentiation phase but also for maintaining the parasites in the trypomastigote stage. The pH of the culture medium was not the initiating factor for the 2nd differentiation phase. Infectivity studies indicated that staphylomastigotes were as infective as blood stream trypomastigotes, but that metacyclic trypomastigotes isolated from culture after the 2nd differentiation phase were slightly more infective than bloodstream forms. Electromicrographs of styphylomastigotes do not provide any evidence of exchange of genetic material between cells.

Infectivity of Trypanosoma brucei cultivated at 28 C with tsetse fly salivary glands

When transformed procyclic noninfective trypanosomes of several unrelated stocks of Trypanosoma brucei were cultivated in T-30 Falcon flasks at 28 C in a liquid medium containing head-salivary gland explants of Glossina morsitans morsitans some of the organisms developed into forms infective for mice. Infective trypanosomes were detected 7 to 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 between 2m and 50 explants were capable of producing infections consistently for prolonged periods. On the other hand, 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 to 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.

Infectivity reacquisition by Trypanosoma brucei brucei cultivated with tsetse salivary glands

Reacquisition of infectivity four mice was observed in cultures of Trypanosoma brucei brucei grown in the presence of tests fly salivary gland explants in a medium based on the amino acid composition of Glossina hemolymph and containing fetal bovine serum. High infection rates were obtained in mice inoculated with about 1.5 X 10(8) organisms. Infectivity reacquisition was correlated with invasion of the salivary glands by the parasites. Few small trypanosomes with subterminal kinetoplasts (metacyclic-like forms) were found in the infective inoculums. The parasitemias in mice consisted of pleomorphic cultivable trypanosomes. Cultures initiated by these organisms and then placed with the head-salivary gland preparations became infective for mice.

African trypanosomes: cultivation of animal-infective Trypanosoma brucei in vitro

Trypanosoma brucei grew in the presence of bovine fibroblast-like cells in Hepes-buffered RPMI 1640 medium with 20 percent fetal bovine serum for more than 220 days at 37 degrees C. The organisms grown in this system were infective to mammalian hosts, retained the morphological and biochemical characteristics of long slender bloodstream forms, and displayed variant-antigen on their surfaces.