Host candidate gene polymorphisms and associated clearance of P. falciparum amodiaquine and fansidar resistance mutants in children less than 5 years in Cameroon

Abstract

Background: In this post-hoc analysis, we determined the influence of single nucleotide polymorphisms in host candidate immune genes on the outcome of drug resistant malaria in Cameroon.

Methods: Human DNA from 760 patients from a previous clinical trial was subjected to mass spectrometry-based single nucleotide polymorphism (SNP) genotyping. Allele frequencies of candidate immune genes were calculated for 62 SNPs on 17 human chromosomes for their possible involvement in clearance of drug-resistant parasites with the triple mutations of pfcrt76T, pfmdr86Y, and pfmdr1246Y (TY) and pfdhfr51I, pfdhfr59R, pfdhfr108N, and pfdhps437G (IRNG) which were determined by dotblot or PCR-restriction analysis. Differences in SNP frequencies and association analysis were carried out by comparing Chi-square odds ratios (ORs) and stratified by Mantel-Haenzel statistics. An adjusted P value (OR) <0·0008 was considered significant.

Results: Post-treatment drug failure rates were amodiaquine (36·4%); sulpadoxine/pyrimethamine-amodiaquine combination (15·4%); and sulphadoxine/pyrimethamine (18·1%). SNPs in IL22, IL-4R1, and CD36 appeared to have been associated with clearance of resistant parasites [p = 0·017, OR (C allele):1·44, 95% CI (OR): 1·06-1·95]; [P = 0·014, OR = 1·31, 95% CI (OR): 1·07-1·83]; [P = 5·78×10(-5), OR = 0·27, 95%CI (OR): 0·13-0·54], respectively, with high fever (>39°C for 48 hours) [IL-22, P = 0·01, OR = 1·5, 95% CI (OR): 1·8-2·1] and also in high frequency among the Fulani participants [P = 0·006, OR = 1·83, 95% CI (OR): 1·11-3·08)]. The CD36-1264 null allele was completely absent in the northern population.

Conclusion: Independent association of SNPs in IL22 and IL-4 with clearance of amodiaquine- and sulphadoxine/pyrimethamine-resistant parasites did not reach statistical significance, but may suggest that not all drug-resistant mutants are adversely affected by the same immune-mediated mechanisms of clearance.

Keywords: Amodiaquine,; Drug resistance markers,; Fever clearance,; Immune response; Interleukin-22,; Parasite clearance,; Sulphadoxine/pyrimethamine,.

Figure 1

Proportion of amodiaquine resistance conferring alleles in the three study sites. This figure indicates that except for Garoua in the north of Cameroon, the prevalence of 654 AQ resistance conferring alleles was high and comparable in Mutengene and Yaounde.

Figure 2

Prevalence of sulphadoxine/pyrimethamine alleles in the three study distes. This figure indicates that compared to Garoua, SP resistance conferring alleles were higher in Mutengene and Yaounde. The K540E mutation was found in one parasite isolate in Mutengene.

Figure 3

Proportion of patients with SP and AQ resistance conferring mutations in the study population. This figure show that for all study participants, a majority (≧65%) of pre-treatment parasites carried resistant conferring alleles for both trial medications.