RESUMO
BACKGROUND: Plasmodium malariae is a widely spread but neglected human malaria parasite, which causes chronic infections. Studies on genetic polymorphisms of anti-malarial drug target genes in P. malariae are limited. Previous reports have shown polymorphisms in the P. malariae dihydrofolate reductase gene associated with pyrimethamine resistance and linked to pyrimethamine drug pressure. This study investigated polymorphisms of the P. malariae homologous genes, chloroquine resistant transporter and multidrug resistant 1, associated with chloroquine and mefloquine resistance in Plasmodium falciparum. METHODS: The orthologous P. malariae crt and mdr1 genes were studied in 95 patients with P. malariae infection between 2002 and 2016 from Thailand (N = 51) and Myanmar (N = 44). Gene sequences were analysed using BioEdit, MEGA7, and DnaSP programs. Mutations and gene amplifications were compared with P. falciparum and Plasmodium vivax orthologous genes. Protein topology models derived from the observed pmcrt and pmmdr1 haplotypes were constructed and analysed using Phyre2, SWISS MODEL and Discovery Studio Visualization V 17.2. RESULTS: Two non-synonymous mutations were observed in exon 2 (H53P, 40%) and exon 8 (E278D, 44%) of pmcrt. The topology model indicated that H53P and E278D were located outside of the transmembrane domain and were unlikely to affect protein function. Pmmdr1 was more diverse than pmcrt, with 10 non-synonymous and 3 synonymous mutations observed. Non-synonymous mutations were located in the parasite cytoplasmic site, transmembrane 11 and nucleotide binding domains 1 and 2. Polymorphisms conferring amino acid changes in the transmembrane and nucleotide binding domains were predicted to have some effect on PmMDR1 conformation, but were unlikely to affect protein function. All P. malariae parasites in this study contained a single copy of the mdr1 gene. CONCLUSIONS: The observed polymorphisms in pmcrt and pmmdr1 genes are unlikely to affect protein function and unlikely related to chloroquine drug pressure. Similarly, the absence of pmmdr1 copy number variation suggests limited mefloquine drug pressure on the P. malariae parasite population, despite its long time use in Thailand for the treatment of falciparum malaria.
Assuntos
Resistência a Medicamentos/genética , Inseticidas/farmacologia , Proteínas de Membrana Transportadoras/genética , Proteínas Associadas à Resistência a Múltiplos Medicamentos/genética , Plasmodium malariae/genética , Polimorfismo Genético , Proteínas de Protozoários/genética , Cloroquina/farmacologia , Mefloquina/farmacologia , Proteínas de Membrana Transportadoras/metabolismo , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Mianmar , Plasmodium malariae/efeitos dos fármacos , Proteínas de Protozoários/metabolismo , TailândiaRESUMO
Plasmodium vivax is the most prevalent malaria infection in Thailand. P. vivax uses Duffy Antigen Receptor for Chemokines (DARC) or Duffy antigen (Fy) as a receptor for entry into reticulocytes. Polymorphism of DARC exon 2 gene (FYA/FYB) in 40 P. vivax-infected subjects were investigated using nested PCR of blood samples spotted on filter paper collected during August 2013 to November 2013 from various malaria clinics in Thailand. Distribution of DARC genotypes was FYA 62.5%, FYB 20% and FYAB 17.5%, consistent with that of Hardy-Weinberg equation. Mutation G17A was found in both FYA and FYB alleles, resulting in Gyl48 and Asp48 of Fya and Fyb antigen, respectively. Mean parasitemia among the three groups is not statistically different. To the best of our knowledge, this is the first such study in Thailand.