LEISHMANIA-AMAZONENSIS - LONG-TERM CULTIVATION OF AXENIC AMASTIGOTES IS ASSOCIATED TO METACYCLOGENESIS OF PROMASTIGOTES

Axenic Leishmania amazonensis cultures were obtained (with 2 years of follow-up) in Schneider's medium at pH 5.5 and a temperature of 32 deg rees C. Differentiation of promastigotes into amastigotes is directly associated with the metacyclogenesis rate of the original promastigote s. Promastigote cultures containing different percentages of metacycli c forms, as evaluated by the complement lysis test, resulted in axenic amastigote cultures containing a variable amount of undifferentiated forms. We observed that a culture originally containing a large amount of metacyclic forms (73%) underwent a complete differentiation proces s, resulting in a 100% amastigote culture with no promastigote forms. All other cultures (with a decreasing amount of metacyclic forms: 50% and fewer) failed to differentiate completely, resulting in cultures w ith increasing percentages of promastigote contamination. The amastigo te/promastigote rate in these cultures has been maintained at the same level thus far. The axenic Leishmania amazonensis amastigotes were cr yopreserved, thawed as such, and successfully cultivated under appropr iately defined growth conditions. (C) 1998 Academic Press.