Point mutations in thepfcrtandpfmdr-1genes ofPlasmodium falciparumand clinical response to chloroquine, among malaria patients from Nigeria

Abstract

Chloroquine (CQ) resistance in Plasmodium falciparum has been associated with specific point mutations in the pfcrt and pfmdr-1 genes. In the present study, 30 children aged 1-12 years, who were all suffering from acute, uncomplicated, P. falciparum malaria in Ibadan, Nigeria, were evaluated to assess the association between these mutations and clinical outcome following treatment with CQ. The parasites, in blood samples collected pre-treatment and, in those who failed treatment, on the day symptoms re-occurred post-treatment, were genotyped using the polymorphic MSP1, MSP2 and GLURP loci and PCR-RFLP. The results showed that, pre-treatment, all 30 patients had polyclonal infections, the mean numbers of P. falciparum clones detected per infection being 2.6 with MSP1, 4.2 with MSP2 and 2.8 with GLURP. The T76 allele of pfcrt and the Y86 allele of pfmdr-1 were found in 53% and 40%, respectively, of the pre-treatment samples from the 15 patients who failed CQ treatment, but the Y1246 mutation in pfmdr-1 was never detected. Although the parasites from the two patients with high-grade (RIII) resistance to CQ had both of these point mutations, the presence of the T76 allele of pfcrt or the Y86 allele of pfmdr-1 (considered individually) could not be used to predict treatment outcome. However, a high frequency of clonal multiplicity may confound attempts to associate the point mutations in pfcrt or pfmdr-1 with clinical response to CQ. It remains unclear whether the present results represent the characteristics of the predominant parasite populations in the study area. Further studies are needed before the strength of the association between the point mutations identified as markers of drug resistance and clinical outcome can be accurately evaluated, in this and other regions of intense transmission.

Chloroquine Resistant Plasmodium falciparum in Nigeria: Relationship between pfcrt and pfmdr1 Polymorphisms, In-Vitro Resistance and Treatment Outcome

“…Some isolates of P. falciparum harboring the mutant pfcrtT76 and pfmdr1 Y86 alleles were sensitive to CQ in-vitro. These finding are similar to earlier reports from Senegal [41], the Philippines [42] and South East Asia [24,43 ].…”

“…It has been difficult to establish an association between the Plasmodium falciparum mutations and patients' treatment outcomes in Ibadan, Nigeria [24] and in many other malaria endemic countries of Africa and Madagascar [37]. The high prevalence (60%) of the mutant pfcrtT76 allele in pre-treatment isolates of all patients treated with CQ in this study makes it difficult for this allele to be predictive of treatment failures.…”

“…In-vitro and in-vivo CQ resistances were 54% and 38% respectively. The current level of in-vivo resistance (38%) is apparently lower compared to 51% [24][25][26] reported previously from the same study site. This sharp reduction in the level of in vivo CQ resistance may be explained by the 2005 antimalarial treatment policy change from CQ to artemether-lumefantrine or artesunate-amodiaquine as first lines treatments for acute uncomplicated malaria in Nigeria, although, chloroquine has not been completely withdrawn, despite the change in drug policy.…”

“…The lysine (K) to threonine (T) mutation at codon 76 of the pfcrt gene was detected by nested PCR followed by RFLP as previously described by Happi et al [24]. DNA from two laboratory adapted P. falciparum clones, 3D7 (Wild type) and Dd2 (mutant) were used as negative and positve controls respectively.…”

Plasmodium falciparum gametocyte carriage, sex ratios and asexual parasite rates in Nigerian children before and after a treatment protocol policy change instituting the use of artemisinin-based combination therapies

“…The population sex ratio in this endemic area is similar to that reported in neighbouring Cameroon [0.217 (Robert et al 1996)], but it is lower than the 0.346 reported in Senegal (Robert et al 2003). In this endemic area clone multiplicity in P. falciparum infections is approximately three-four (Happi et al 2003(Happi et al , 2004(Happi et al , 2006) and this appears to have changed little over the years (Happi et al 2003(Happi et al , 2004(Happi et al , 2006.…”