Identification of human immune response factors and molecular correlations with fever and parasite clearance during infection with Plasmodium falciparum among children in Cameroon

Abstract

Background This study undertook to characterise drug resistance mutants of Plasmodium falciparum in-fections in five key geo-ecological locations in Cameroon and investigated parasite and molecu-lar immune factors associated with clinical response and clearance of drug resistant Plasmodium falciparum among infected children less than 14 years. Methodology We conducted clinical efficacy trials of antimalarials in five locations in Cameroon. Total parasite nucleic acid from 750 P. falciparum infected samples was used to amplify target se-quences by polymerase chain reaction (PCR) and restriction fragment length polymorphism and/or enhanced chemluminescence for point mutations in Pfcrt, pfmdr-1, Pfpfdhfr and pfpfdhps genes. Single nucleotide polymorphisms (SNP) in candidate immune genes identified through bioinformatics were detected by matrix-assisted laser desorption mass Spectrometry (MALDI-TOF). The distribution of SNPs was analysed by drug response, by pre-therapy hyperpyrexia, by ethnic/ecological group and also by clearance of drug resistant parasite forms. Results. Mutations in the pfdhfr (51I, 59R, and 108N), pfdhps 437Gly as well as Pfcrt 76T and pfmdr-1 86Y, 184F and 1246Y were detected invariably in all regions. The fansidar resistant SGK haplotype appeared to be associated with the drug response in Mutengene but not in Ya-oundé or Garoua; and correlated inversely with adequate clinical and parasitological response. SNPs in IL-22, 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) of 1.06-1.95]; [P= 0.014, OR = 1.31, 95%CI (OR):1.07-1.83]; [P= 5.78 x10-5 OR=0.27, 95%CI(OR):0.13-0.54] respectively; with high fever (> 39°C, 48 hrs) [IL-22, P= 0.01, OR=1.5, (95%CI(OR): 1.8-2.1)] and also in high frequen-cy 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 No independent associations were found between parasite factors and drug response. Mo-lecular immune signatures in IL-22, IL-4, IL-4IL-4R, and CD36 could potentially influence drug resistant parasite clearance in Cameroon. Differences in CD36-T1264G mutants may reflect eth-nic lipid metabolic differences or an unknown evolutionary genetic phenomenon in West Africa.