Abstract:

Objective To investigate the polymorphism of Plasmodium falciparum K13 gene kelch domain region and provide basis for understanding the artemisinin resistance of falciparum malaria in Yunnan Province. Methods The filter blood samples and relative information of falciparum malaria cases were collected in 16 prefectures of Yunnan Province from January 2013 to December 2015. The source of infection was determined by epidemiological investigation and the place of case discovery was confirmed according to the China Information System for Disease Control and Prevention Epidemic Registration. The K13 gene kelch domain region was amplified by nested PCR, sequenced, and blasted against the reference strain 3D7（PF3D7_1343700）. The K13 gene kelch domain region polymorphism was analyzed with Mega 5.04. The variable sites and genetic distance between sequences were analyzed. The constituent ratio of amino acid mutation sites was calculated and analyzed with χ2 test. Results A total of 202 blood samples were collected from 2013 to 2015, comprising 190 from imported cases, 12 from local cases in Yunnan Province. The constitutent ratio of infection cases were 30.7% （62/202）, 34.2% （69/202） and 35.1% （71/202） respectively, increased year by year. The K13 gene kelch domain was successfully amplified from 192 samples and 190 were successfully sequenced, detecting missense mutation of K13 gene in 66 samples, the mutation rate was 34.7% （66/190）. The detection rate of K13 gene mutation was 40.9% （27/66）, 37.9% （25/66） and 21.2% （14/66） respectively, decreased year by year. In this study, ten types of mutations were detected, which were F446I, A578S, N458Y, P574L, A676D, G449A, C469Y, V494I, E556D and S16L. The highest mutation rate occurred in F446I which was 72.7% （48/66）. The proportion of F446I mutation type was 58.3% （28/48） in an age-range of 18-56 years, 70.8% （34/48） in farmers, and 91.7% （44/48） in patients with infection source in Southeast Asia, all significantly higher than that of other groups with the same characteristics （41.7%, 20/48; 29.2%, 14/48; and 8.3%, 4/48, respectively）（χ2=4.633, 5.556 and 5.152, both P＜0.05）. There was a 248 bp homologous sequence in the 190 sequences, composed of 235 conservative sites （94.8%）, 13 variable sites （5.2%）, 5 parsim-info sites （2.0%）, and 8 singleton sites （3.2%）. The genetic distance among the 190 sequences ranged 0.000-0.036, with an average of 0.001±0.001. Conclusion There are 10 types of mutations in the K13 kelch domain in Yunnan Province, the predominant mutation type was F446I.

Key words: Plasmodium falciparum；Artemisinin；Drug resistance；Gene；Polymorphism；Analysis； , Yunnan Province