Polymorphisms of pfcrt, pfmdr1, and K13-propeller genes in imported falciparum malaria isolates from Africa in Guizhou province, China

Designing hybrid CRISPR-Cas12 and LAMP detection systems for treatment-resistant Plasmodium falciparum with in silico method

Genes associated with drug resistance of first line drugs for Plasmodium falciparum have been identified and characterized of which three genes most commonly associated with drug resistance are P. falciparum chloroquine resistance transporter gene (PfCRT), P. falciparum multidrug drug resistance gene 1 (PfMDR1), and P. falciparum Kelch protein K13 gene (PfKelch13). Polymorphism in these genes could be used as molecular markers for identifying drug resistant strains. Nucleic acid amplification test (NAAT) along with DNA sequencing is a powerful diagnostic tool that could identify these polymorphisms. However, current NAAT and DNA sequencing technologies require specific instruments which might limit its application in rural areas. More recently, a combination of isothermal amplification and CRISPR detection system showed promising results in detecting mutations at a nucleic acid level. Moreover, the Loop-mediated isothermal amplification (LAMP)-CRISPR systems offer robust and straightforward detection, enabling it to be deployed in rural and remote areas. The aim of this study was to develop a novel diagnostic method, based on LAMP of targeted genes, that would enable the identification of drug-resistant P. falciparum strains. The methods were centered on sequence analysis of P. falciparum genome, LAMP primers design, and CRISPR target prediction. Our designed primers are satisfactory for identifying polymorphism associated with drug resistant in PfCRT, PfMDR1, and PfKelch13. Overall, the developed system is promising to be used as a detection method for P. falciparum treatment-resistant strains. However, optimization and further validation the developed CRISPR-LAMP assay are needed to ensure its accuracy, reliability, and feasibility.

A review of malaria molecular markers for drug resistance in Plasmodium falciparum and Plasmodium vivax in China

China has now achieved the elimination of malaria, but it still faces severe challenges in the post-elimination stage. China continues to be plagued by imported malaria cases, and preventing re-transmission of imported malaria is critical. The effectiveness of antimalarial drugs for malaria control largely depends on the study of drug resistance markers in vitro. Monitoring molecular markers of parasite-associated drug resistance can help predict and manage drug resistance. There is currently a lack of systematic reviews of molecular markers for indigenous and imported malaria in China. Therefore, this review summarizes the published articles related to molecular marker polymorphism of indigenous and imported malaria cases in China in the past two decades, to study the mutation frequency and distribution of crt, mdr1, dhps, dhfr and K13 gene resistance-related loci. This can provide a whole picture of molecular markers and the resistance mutations of imported cases in China, which has certain significance for drug resistance surveillance planning, safe and effective treatment, and preventing the recurrence of local transmission by imported malaria in China in the future.

Assessment of Plasmodium falciparum anti-malarial drug resistance markers in pfcrt and pfmdr1 genes in isolates from Honduras and Nicaragua, 2018-2021

Background

Central America and the island of Hispaniola have set out to eliminate malaria by 2030. However, since 2014 a notable upturn in the number of cases has been reported in the Mosquitia region shared by Nicaragua and Honduras. In addition, the proportion of Plasmodium falciparum malaria cases has increased significantly relative to vivax malaria. Chloroquine continues to be the first-line drug to treat uncomplicated malaria in the region. The objective of this study was to evaluate the emergence of chloroquine resistant strains of P. falciparum using a genetic approach. Plasmodium vivax populations are not analysed in this study.

Methods

205 blood samples from patients infected with P. falciparum between 2018 and 2021 were analysed. The pfcrt gene fragment encompassing codons 72–76 was analysed. Likewise, three fragments of the pfmdr1 gene were analysed in 51 samples by nested PCR and sequencing.

Results

All samples revealed the CVMNK wild phenotype for the pfcrt gene and the N86, Y184F, S1034C, N1042D, D1246 phenotype for the pfmdr1 gene.

Conclusions

The increase in falciparum malaria cases in Nicaragua and Honduras cannot be attributed to the emergence of chloroquine-resistant mutants. Other possibilities should be investigated further. This is the first study to report the genotype of pfmdr1 for five loci of interest in Central America.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03977-8.

First Detection in West Africa of a Mutation That May Contribute to Artemisinin Resistance Plasmodium falciparum

Background: The spread of drug resistance has seriously impacted the effective treatment of infection with the malaria parasite, Plasmodium falciparum. Continuous monitoring of molecular marker polymorphisms associated with drug resistance in parasites is essential for malaria control and elimination efforts. Our study describes mutations observed in the resistance genes Pfkelch13, Pfcrt, and Pfmdr1 in imported malaria and identifies additional potential drug resistance-associated molecular markers.

Methods: Chinese patients infected in Africa with P. falciparum were treated with intravenous (IV) injections of artesunate 240–360 mg for 3–5 days while hospitalized and treated with oral dihydroartemisinin-piperaquine (DHP) for 3 days after hospital discharge. Blood samples were collected and PCR sequencing performed on genes Pfkelch13, Pfcrt, and Pfmdr1 from all isolates.

Results: We analyzed a total of 225 patients from Guangxi, China with P. falciparum malaria acquired in Africa between 2016 and 2018. All patients were cured completely after treatment. The F446I mutation of the Pfkelch13 gene was detected for the first time from samples of West African P. falciparum, with a frequency of 1.0%. Five haplotypes of Pfcrt that encode residues 72–76 were found, with the wild-type CVMNK sequence predominating (80.8% of samples), suggesting that the parasites might be chloroquine sensitive. For Pfmdr1, N86Y (13.1%) and Y184F (58.8%) were the most prevalent, suggesting that artemether-lumefantrine may not, in general, be a suitable treatment for the group.

Conclusions: For the first time, this study detected the F446I mutation of the Pfkelch13 gene from Africa parasites that lacked clinical evidence of resistance. This study provides the latest data for molecular marker surveillance related to antimalarial drug resistance genes Pfkelch13, Pfcrt, and Pfmdr1 imported from Africa, in Guangxi, China from Chinese migrate workers.

Clinical Trial Registration: ChiCTROPC17013106.