The occurence, distribution and frequency of membrane transporter resistance alleles in Plasmodium falciparum and their association with response and resistance to Arteminisin based combination therapy (ART) in Northern Nigeria

Abstract

Malaria infection is caused by, Plasmodium falciparum (P. falciparum) parasite. It is the most significant cause of high morbidity and mortality rate in humans. This has created an enormous social and economic burden in many endemic regions in the world. Disturbingly, P. falciparum genome has shown to have recently developed resistance to the most successful related group of drug treatment, known as Artemisinin combination therapies (ACTs), primarily in parts of South East Asia, but possibly also in other parts of the world e.g. East Africa.
The purpose of this research was to; analyse the occurrence and distribution frequency of membrane transporter resistance alleles, in two different P. falciparum proteins, that possibly confer resistance to Artemisinin, and statistically analyse whether any of these resistance alleles; show a significant association with the response, and resistance of ACT’s, present in Northern Nigeria. The two membrane transporter proteins, studied in this project were, firstly, the P. falciparum chloroquine resistance transporter (Pfcrt), which belongs to the drug metabolite transporters; that acts by directly facilitating the efflux of chloroquine, from the digestive vacuole. The second protein associated with the multi-drug resistance, in P. falciparum, is the Pfmdr1 gene, which belongs to the ATP binding cassette (ABC) superfamily of transporters. The common polymorphism in the Pfcrt protein, is an A or C allele at position 228 in the coding sequence; which causes a Lysine residue to be changed to a Threonine residue (c.228A>C p. K76T). The Pfmdr1 gene, has two common resistance alleles, associated with drug resistance, namely c.258A>C (p. N86Y) and c.452A>C (p.N184Y). These changes in amino acids, in both of the proteins confer resistance to specific drug treatment.
Six-hundred individuals, suffering from uncomplicated malaria symptoms, who were also receiving the ACT ‘Artemether-Lumefantrine (Coartem) treatment, were chosen for this research. The statistical result showed that, 209 samples had the malaria infection, which includes 169 with the resistance alleles. The polymorphic alleles included; 75 samples with the Pfcrt resistance alleles, 71 samples had the Pfmdr1-184Y variant and 66 samples had the Pfmdr1-86Y variant. Randomly, selected malaria infected sample results showed that, 19 did not respond to treatment whereas 45 responded. There were 12 unresponsive and 21  responsive samples, with the Pfcrt resistance alleles. The combined Pfmdr1 resistance alleles results showed that, among the unresponsive samples, 5 samples had both the Pfmdr1 variant alleles, 8 samples had either one of the variants and 2 samples had neither. The responsive group showed that, six samples had both the Pfmdr1 variants, 29 samples had either one of the Pfmdr1 variant and 10 samples had neither. The combined resistance alleles showed that, within the unresponsive groups, 5 samples had the combined resistance alleles and 14 samples had either the Pfmdr1 or the Pfcrt resistance alleles. The responsive groups showed that, only one sample had both resistance genes, 38 samples had either Pfmdr1 or Pfcrt and 6 samples had neither resistance allele. These results significantly showed that, an individual with malaria infection would have either one or more of the malaria resistance alleles, used in this study. Significantly, the results of this study also showed that one of the analysed polymorphism is probably not enough to provide resistance to ACTs, but it is enough for chloroquine resistance. These significant results could perhaps be used as a baseline, for future larger West  African population study, which should positively confirm the findings in this research.

Date of Award	Jan 2017
Original language	English
Awarding Institution	Abertay University
Supervisor	Graeme Walker (Supervisor) & Yusuf Y. Deeni (Supervisor)