Artemisinin‐induced dormancy in plasmodium falciparum: duration, recovery rates, and implications in treatment failure.
BACKGROUND
Despite the remarkable activity of artemisinin and its derivatives, monotherapy with these agents has been associated with high rates of recrudescence. The temporary arrest of the growth of ring-stage parasites (dormancy) after exposure to artemisinin drugs provides a plausible explanation for this phenomenon.


METHODS
Ring-stage parasites of several Plasmodium falciparum lines were exposed to different doses of dihydroartemisinin (DHA) alone or in combination with mefloquine. For each regime, the proportion of recovering parasites was determined daily for 20 days.


RESULTS
Parasite development was abruptly arrested after a single exposure to DHA, with some parasites being dormant for up to 20 days. Approximately 50% of dormant parasites recovered to resume growth within the first 9 days. The overall proportion of parasites recovering was dose dependent, with recovery rates ranging from 0.044% to 1.313%. Repeated treatment with DHA or with DHA in combination with mefloquine led to a delay in recovery and an approximately 10-fold reduction in total recovery. Strains with different genetic backgrounds appeared to vary in their capacity to recover.


CONCLUSIONS
These results imply that artemisinin-induced arrest of growth occurs readily in laboratory-treated parasites and may be a key factor in P. falciparum malaria treatment failure.
Teuscher
Franka
F
Malaria Drug Resistance and Chemotherapy Laboratory, Queensland Institute of Medical Research, Australian Army Malaria Institute, Brisbane, Australia.
Gatton
Michelle L
ML
Chen
Nanhua
N
Peters
Jennifer
J
Kyle
Dennis E
DE
Cheng
Qin
Q
D000962:Antimalarials / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology*; D015767:Mefloquine / Q000494:pharmacology; D050296:Microbial Viability / Q000187:drug effects*; D010963:Plasmodium falciparum / Q000187:drug effects*; D013997:Time Factors
D000962:Antimalarials; D037621:Artemisinins; C031327:artemisinin; D015767:Mefloquine