Study on Promastigote Transformation to Amastigotes in Different Leishmania spp. in vitro

Objective To investigate the different Leishmania spp. promastigote transformation to amastigotes in different cultivated conditions in vitro. Methods Six strains of Leishmania spp. promastigotes in the logarithm growth period were inoculated in 24 well plates containing M199 or RPMI 1640 medium. The protozoa were cultivated under different temperatures, pH values, newborn calf blood serum, and 5%CO2, quantified and the different protozoan shapes classified after 3 days and 6 days. Results When the promastigotes were cultivated at 26℃, whatever other conditions changed, the multiplication speed of the protozoa changed. Most promastigotes maintained a typical shape and were active. When the promastigotes were cultivated at 37℃, the protozoa deposited to the well bottom, stopped multiplying, their activity level decreased, and transformed to the intermediate or the amastigote form. The acidic pH value and 5% CO2 may promote promastigote transformation to amastigote form and the newborn calf serum may lengthen the amastigotes survival time. Under the same conditions, the Leishmania donovani transfer efficiency was lower than other Leishmania spp. Conclusion Temperature was the essential element to determine promastigote transformation to amastigotes, while the acidic pH value and CO2 may assist in promoting transfer efficiency. Different Leishmania spp. also affected the transfer efficiency.