Background: In malaria, the toll-like receptors (TLRs) have recently emerged as major player of innate immunity. However, implication of TLR variants on clinical manifestations of malaria is conflicting. The present study aims to provide relevant information of growing interest in understanding the role of TLR4D299G, TLR9T-1237C and TLR9T-1486C polymorphisms on clinical outcomes of malaria.
Methods: We genotyped TLR4D299G, TLR9T-1237C and TLR9T-1486C polymorphisms by PCR-RFLP methods and subsequently analyzed in 200 uncomplicated patients and 200 severe patients. Further, the severe malaria categorized into sub-clinical groups such as cerebral malaria (CM), non-cerebral severe malaria (NCSM), single organ dysfunction (SOD) and multi-organ dysfunctions (MODS) are analyzed.
Result: The TLR9-1237CC genotype was observed at significantly low frequency in MODS (p=0.0008), while in heterozygous state (TC) it was proportionately more frequent in SOD (p=0.087) as compared to mild malaria. The TLR9T-1486C heterozygote was more common in all categories of severe malaria. However, pair wise LD analysis revealed significant linkage between T-1237C and T-1486C, whereas haplotype analysis showed significantly low frequency of C-T haplotype in CM (p=0.005, pc=0.02) and high frequency of T-C haplotype in NCSM as compared to mild malaria.
Conclusion: Although TLR9-1237C could be a risk factor for severe malaria in heterozygous state, negative association of CC genotype with MODS warrants caution of segregating severe malaria into its sub-clinical groups while interpreting data. Further, clinical outcome in malaria was observed to be apparently modulated by LD between TLR9 promoter variants.
Keywords: Cerebral malaria; Organ dysfunctions; Plasmodium falciparum; Polymorphisms; TLR.
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