Plasmodium falciparum isolates from Angola show the StctVMNT haplotype in the pfcrt gene

<p>Abstract</p> <p>Background</p> <p>Effective treatment remains a mainstay of malaria control, but it is unfortunately strongly compromised by drug resistance, particularly in <it>Plasmodium falciparum</it>, the most important human malaria parasite. Although <it>P. falciparum </it>chemoresistance is well recognized all over the world, limited data are available on the distribution and prevalence of <it>pfcrt </it>and <it>pfmdr1 </it>haplotypes that mediate resistance to commonly used drugs and that show distinct geographic differences.</p> <p>Methods</p> <p><it>Plasmodium falciparum</it>-infected blood samples collected in 2007 at four municipalities of Luanda, Angola, were genotyped using PCR and direct DNA sequencing. Single nucleotide polymorphisms in the <it>P. falciparum pfcrt </it>and <it>pfmdr1 </it>genes were assessed and haplotype prevalences were determined.</p> <p>Results and Discussion</p> <p>The most prevalent <it>pfcrt </it>haplotype was <b>S</b>_tctVMN<b>T </b>(representing amino acids at codons 72-76). This result was unexpected, since the <b>S</b>_tctVMN<b>T </b>haplotype has previously been seen mainly in parasites from South America and India. The CV<b>IET</b>, CVMN<b>T </b>and CV<b>I</b>N<b>T </b>drug-resistance haplotypes were also found, and one previously undescribed haplotype (CVM<b>DT</b>) was detected. Regarding <it>pfmdr1</it>, the most prevalent haplotype was <b>Y</b>EYSNVD (representing amino acids at codons 86, 130, 184, 1034, 1042, 1109 and 1246). Wild haplotypes for <it>pfcrt </it>and <it>pfmdr1 </it>were uncommon; 3% of field isolates harbored wild type <it>pfcrt </it>(CVMNK), whereas 21% had wild type <it>pfmdr1 </it>(NEYSNVD). The observed predominance of the <b>S</b>_tctVMN<b>T </b>haplotype in Angola could be a result of frequent travel between Brazil and Angola citizens in the context of selective pressure of heavy CQ use.</p> <p>Conclusions</p> <p>The high prevalence of the <it>pfcrt </it><b>S</b>VMN<b>T </b>haplotype and the <it>pfmdr1 </it>86<b>Y </b>mutation confirm high-level chloroquine resistance and might suggest reduced efficacy of amodiaquine in Angola. Further studies must be encouraged to examine the <it>in vitro </it>sensitivity of <it>pfcrt </it><b>S</b>VMN<b>T </b>parasites to artesunate and amodiaquine for better conclusive data.</p

Molecular markers of antifolate resistance in Plasmodium falciparum isolates from Luanda, Angola

Abstract Background Plasmodium falciparum malaria remains a leading health problem in Africa and its control is seriously challenged by drug resistance. Although resistance to the sulphadoxine-pyrimethamine (SP) is widespread, this combination remains an important component of malaria control programmes as intermittent preventive therapy (IPT) for pregnant women and children. In Angola, resistance patterns have been poorly characterized, and IPT has been employed for pregnant women since 2006. The aim of this study was to assess the prevalence of key antifolate resistance mediating polymorphisms in the pfdhfr and pfdhps genes in P. falciparum samples from Angola. Methods Plasmodium falciparum samples collected in Luanda, in 2007, were genotyped by amplification and DNA forward and reverse sequencing of the pfdhfr and pfdhps genes. Results The most prevalent polymorphisms identified were pfdhfr 108N (100%), 51I (93%), 59R (57%) and pfdhps 437G (93%). Resistance-mediating polymorphisms in pfdhps less commonly observed in West Africa were also identified (540E in 10%, 581G in 7% of samples). Conclusion This study documents an important prevalence of 4 P. falciparum polymorphisms that predicts an antifolate resistance in Luanda. Further, some samples presented additional mutations associated to high-level resistance. These results suggest that the use of SP for IPT may no longer be warranted in Angola