In vitro Assessment and Characterization of the Growth and Life Cycle of Leishmania tropica
In vitro Assessment and Characterization of the Growth and Life Cycle of Leishmania tropica
Qaisar Jamal*, Akram Shah, Syed Basit Rasheed and Muhammad Adnan
ABSTRACT
Present study aimed at determining the in vitro life cycle of Leishmania tropica. Temporal variability in the morphology and various morphotypes of the promastigotes were noted. Acquisition and propagation of axenic amastigotes was assessed. During promastigote culture, log, mid-log, and late-log phases were observed respectively on day 4, 5 and 6. The stationary phase was observed on day 7. The day following inoculation, most of the promastigotes were nectomonads having long and slender bodies with roughly uniform width from anterior to near posterior end, having as long flagella as one and a half to twice the body. The nectomonads changed to leptomonads with a ratio of 5% and 44% on day 2and 3 respectively. The body to flagellum ratio decreased in leptomonads giving a wider and shorter appearance than the nectomonads. On day 4, the log phase, the metacyclic promastigotes appeared in the culture. The metacyclic to leptomonad to nectomonad ratio was 27%, 43% and 29% respectively. The ratio of metacyclics steadily increased towards the mid-log (53%), late-log (67%), and stationary phase (83%). Metacyclics had long flagella and short stumpy cell bodies with anterior end much broader than the posterior as compared to that in leptomonads and nectomonads. The posterior end of the body was bearing a slender tail like extension . During logarithmic growth, 17 % of promastigotes were found dividing. During a 10 days transformation of axenic amastigotes, the day following inoculation to the day 3 different morphological forms were observed. The day 7 onward only rounded no flagellum (RNF=41-47%) and oval no flagellum (ONF= 53-59%) forms were present. Viability remained 96-98% during transformation. Bulk growth of the promastigotes for prolong (over a week) duration resulted in the acidification of medium and change to viable amastigotes that could be successfully retransformed to promastigotes. Use of orthophosphoric acid for acquiring acidic medium to transform promastigotes to amastigotes proved effective.
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April 2020
Vol. 52, Iss. 2, Pages 425-824
