Assessment of artemisinin tolerance in Plasmodium falciparum clinical isolates in children with uncomplicated malaria in Ghana
Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
Malaria Journal
Abstract
Background Artemisinin-based combination therapy (ACT) is the first-line treatment for uncomplicated malaria in
Ghana. Artemisinin (ART) tolerance in Plasmodium falciparum has arisen in Southeast Asia and recently, in parts of
East Africa. This is ascribed to the survival of ring-stage parasites post treatment. The present study sought to assess
and characterize correlates of potential ART tolerance based on post-treatment parasite clearance, ex vivo and in vitro
drug sensitivity, and molecular markers of drug resistance in P. falciparum isolates from children with uncomplicated
malaria in Ghana.
Methods Six months to fourteen years old children presenting with acute uncomplicated malaria (n=115) were
enrolled in two hospitals and a Health Centre in Ghana’s Greater Accra region and treated with artemether-lume‑
fantrine (AL) according to body weight. Pre- and post-treatment parasitaemia (day 0 and day 3) was confirmed by
microscopy. The ex vivo ring-stage survival assay (RSA) was used to detect percent ring survival while the 72 h SYBR
Green I assay was used to measure the 50% inhibition concentration (IC50s) of ART and its derivatives and partner
drugs. Genetic markers of drug tolerance /resistance were evaluated using selective whole genome sequencing.
Results Of the total of 115 participants, 85 were successfully followed up on day 3 post-treatment and 2/85 (2.4%)
had parasitaemia. The IC50 values of ART, artesunate (AS), artemether (AM), dihydroartemisinin (DHA), amodiaquine
(AQ), and lumefantrine (LUM) were not indicative of drug tolerance. However, 7/90 (7.8%) pre-treatment isolates
had>10% ring survival rates against DHA. Of the four isolates (2 RSA positive and 2 RSA negative) with high genomic
coverage, P. falciparum (Pf ) kelch 13 K188* and Pfcoronin V424I mutations were only present in the two RSA positive
isolates with>10% ring survival rates.
Conclusions The observed low proportion of participants with day-3 post-treatment parasitaemia is consistent
with rapid ART clearance. However, the increased rates of survival observed in the ex vivo RSA against DHA, maybe a
pointer of an early start of ART tolerance. Furthermore, the role of two novel mutations in PfK13 and Pfcoronin genes,
harboured by the two RSA positive isolates that had high ring survival in the present study, remains to be elucidated.
Description
Research Article
Keywords
Artemisinin tolerance, Plasmodium falciparum, Uncomplicated Malaria