Confirmation of emergence of mutations associated with atovaquone-proguanil resistance in unexposed Plasmodium falciparum isolates from Africa

Christian T Happi¹^,2 , Grace O Gbotosho¹ , Onikepe A Folarin¹ , Danny Milner² , Ousmane Sarr³ , Akintunde Sowunmi¹ , Dennis E Kyle⁴ , Wilbur K Milhous⁴ , Dyann F Wirth² and Ayoade MJ Oduola⁵

¹Malaria Research Laboratories, Institute for Advanced Medical Research and Training, College of Medicine, University of Ibadan, Nigeria

²Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA, USA

³Laboratory of Bacteriology and Virology, Dantec Hospital, Dakar, Senegal

⁴Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Springs, MD, USA

⁵Special Programme for Research and Training in Tropical Diseases (WHO/TDR), Geneva, Switzerland

author email corresponding author email

Malaria Journal 2006, 5:82doi:10.1186/1475-2875-5-82


Published:	4 October 2006

Abstract

Background

In vitro and in vivo resistance of Plasmodium falciparum to atovaquone or atovaquone-proguanil hydrochloride combination has been associated to two point mutations in the parasite cytochrome b (cytb) gene (Tyr268Ser and Tyr268Asn). However, little is known about the prevalence of codon-268 mutations in natural populations of P. falciparum without previous exposure to the drug in Africa.

Methods

The prevalence of codon-268 mutations in the cytb gene of African P. falciparum isolates from Nigeria, Malawi and Senegal, where atovaquone-proguanil has not been introduced for treatment of malaria was assessed. Genotyping of the cytb gene in isolates of P. falciparum was performed by PCR-restriction fragment length polymorphism and confirmed by sequencing.

Results

295 samples from Nigeria (111), Malawi (91) and Senegal (93) were successfully analyzed for detection of either mutant Tyr268Ser or Tyr268Asn. No case of Ser268 or Asn268 was detected in cytb gene of parasites from Malawi or Senegal. However, Asn268 was detected in five out of 111 (4.5%) unexposed P. falciparum isolates from Nigeria. In addition, one out of these five mutant Asn268 isolates showed an additional cytb mutation leading to a Pro266Thr substitution inside the ubiquinone reduction site.

Conclusion

No Tyr268Ser mutation is found in cytb of P. falciparum isolates from Nigeria, Malawi or Senegal. This study reports for the first time cytb Tyr268Asn mutation in unexposed P. falciparum isolates from Nigeria. The emergence in Africa of P. falciparum isolates with cytb Tyr268Asn mutation is a matter of serious concern. Continuous monitoring of atovaquone-proguanil resistant P. falciparum in Africa is warranted for the rational use of this new antimalarial drug, especially in non-immune travelers.