Fast high yield of pure Leishmania (Leishmania) infantum axenic amastigotes and their infectivity to mouse macrophages

The first successful report of the in vitro life cycle of Chinese Leishmania: the in vitro conversion of Leishmania amastigotes has been raised to 94% by testing 216 culture medium compound

Chinese Leishmania isolate MHOM/CN/90/SC10H2 (L. H2), which was obtained from the spinal cords of patients from the Sichuan province of China, is an uncharacterized, pathogenic species closely related to Leishmania tarentolae. The in vitro transformation rate of L. H2 promastigotes into amastigotes has not been studied. This study is the first to successfully define the in vitro life cycle of L. H2 by investigating the percent conversion of L.H2 promastigotes to amastigotes in vitro under 216 different culture conditions. The highest proportion of L. H2 amastigotes observed (94%) was significantly higher than that previously reported. After conversion, the axenic amastigotes remained viable as verified by the levels of stage-specific genes (Gp46, A2 and β-tubulin) detected by RT-PCR. Meanwhile, morphological and protein characterizations of these axenic amastigotes were carried out in order to confirm the successful conversion. Specific antibodies were only able to detect 46 kDa, 52 kDa and 75 kDa proteins in samples isolated from axenic amastigotes. Afterward, these converted axenic amastigotes were transformed into the promastigote form by altering the culture condition. These converted axenic promastigotes still have the ability to infect macrophages, and their morphology changed back to the amastigote form following infection. These findings will assist further investigations into the biological characteristics of the host-parasite relationship and the process of pathogenesis.

Development of Leishmania (Leishmania) infantum chagasi in its natural sandfly vector Lutzomyia longipalpis

We analyzed the development of Leishmania (Leishmania) infantum chagasi in its natural sandfly vector Lutzomyia longipalpis. In addition, we compared sandfly infections initiated with axenic amastigotes or promastigotes. Our data showed no important difference between Lu. longipalpis infection rates resulting from either type of infections. Furthermore, development of infection was equivalent in both cases. All promastigote forms were found inside the sandfly and, after blood digestion, most of the population consisted of procyclics and nectomonads. A low percentage of metacyclic forms was coincident with a high number of nectomonads during late stages of infection, but which form gives rise to metacyclic forms in L. infantum chagasi is unknown. These results also show that the promastigote infection model, at least for this situation, is suitable for obtaining of infected sandflies because it is easier and less laborious.