Mutations in Plasmodium knowlesi Kelch protein 13 and the dihydropteroate synthase gene in clinical samples

Objective: To determine the genetic diversity, natural selection and mutations in Plasmodium (P.) knowlesi drug resistant molecular markers Kelch 13 and dhps gene in clinical samples of Malaysia. Methods: P. knowlesi full-length gene sequences Kelch 13 gene (PkK13) from 40 samples and dhps gene from 30 samples originating from Malaysian Borneo were retrieved from public databases. Genetic diversity, natural selection, and phylogenetic analysis of gene sequences were analysed using DNAsp v5.10 and MEGA v5.2. Results: Seventy-two single nucleotide polymorphic sites (SNPs) across the full-length PkK13 gene (63 synonymous substitutions and 9 non-synonymous substitutions) with nucleotide diversity of π~0.005 was observed. Analysis of the full-length Pkdhps gene revealed 73 SNPs and π~0.006 (44 synonymous substitutions and 29 non-synonymous substitutions). A high number of haplotypes (PkK13; H=37 and Pkdhps; H=29) with haplotype diversity of Hd ~0.99 were found in both genes, indicating population expansion. Nine mutant alleles were identified in PkK13 amino acid alignment of which, 7 (Asp3Glu, Lys50Gln, Lys53Glu, Ser123Thr, Ser127Pro, Ser149Thr and Ala169Thr) were within the Plasmodium specific domain, 2 (VaI372Ile and Lys424Asn) were in the BTB/POZ domain and no mutation was observed within the kelch propeller domain. The 29 non-synonymous mutations in the Pkdhps gene were novel and only presented in exon 1 and 2. Conclusions: Monitoring the mutations from clinical samples collected from all states of Malaysia along with clinical efficacy studies will be necessary to determine the drug resistance in P. knowlesi.