喀麦隆无并发症疟疾儿童中恶性疟原虫的遗传多样性和遗传特征。
Genetic diversity of Plasmodium falciparum and genetic profile in children affected by uncomplicated malaria in Cameroon.
机构信息
Department of Biochemistry, Faculty of Science, The University of Bamenda, P. O. Box 39 Bambili, Bamenda, Cameroon.
National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Shanghai, 200025, People's Republic of China.
出版信息
Malar J. 2020 Mar 18;19(1):115. doi: 10.1186/s12936-020-03161-4.
BACKGROUND
Malaria is a major public health problem in Cameroon. The study of the genetic diversity within parasite population is essential for understanding the mechanism underlying malaria pathology and to determine parasite clones profile in an infection, for proper malaria control strategies. The objective of this study was to perform a molecular characterization of highly polymorphic genetic markers of Plasmodium falciparum, and to determine allelic distribution with their influencing factors valuable to investigate malaria transmission dynamics in Cameroon.
METHODS
A total of 350 P. falciparum clinical isolates were characterized by genotyping block 2 of msp-1, block 3 of msp-2, and region II of glurp gene using nested PCR and DNA sequencing between 2012 and 2013.
RESULTS
A total of 5 different genotypes with fragment sizes ranging from 597 to 817 bp were recorded for GLURP. Overall, 16 MSP-1 genotypes, including K1, MAD20 and RO33 were identified, ranging from 153 to 335 bp. A peculiarity about this study is the RO33 monomorphic pattern revealed among the Pfmsp-1 allelic type. Again, this study identified 27 different Pfmsp-2 genotypes, ranging from 140 to 568 bp in size, including 15 belonging to the 3D7-type and 12 to the FC27 allelic families. The analysis of the MSP-1 and MSP-2 peptides indicates that the region of the alignment corresponding K1 polymorphism had the highest similarity in the MSP1and MSP2 clade followed by MAD20 with 93% to 100% homology. Therefore, population structure of P. falciparum isolates is identical to that of other areas in Africa, suggesting that vaccine developed with K1 and MAD20 of Pfmsp1 allelic variant could be protective for Africa children but these findings requires further genetic and immunological investigations. The multiplicity of infection (MOI) was significantly higher (P < 0.05) for Pfmsp-2 loci (3.82), as compare with Pfmsp-1 (2.51) and heterozygotes ranged from 0.55 for Pfmsp-1 to 0.96 for Pfmsp-2.
CONCLUSION
High genetic diversity and allelic frequencies in P. falciparum isolates indicate a persisting high level of transmission. This study advocate for an intensification of the malaria control strategies in Cameroon. Trial registration This study was approved by Cameroon National Ethics Committee. It is a randomized controlled trial retrospectively registered in NIH U.S. National Library of Medicine, ClinicalTrials.gov on the 28/11/2016 at https://clinicaltrials.gov/ct2/show/NCT02974348 with the registration number NCT02974348.
背景
疟疾是喀麦隆的一个主要公共卫生问题。研究寄生虫种群内的遗传多样性对于理解疟疾病理学的机制以及确定感染中的寄生虫克隆谱至关重要，从而制定适当的疟疾控制策略。本研究的目的是对恶性疟原虫高度多态性的遗传标记进行分子特征分析，并确定等位基因分布及其影响因素，以调查喀麦隆的疟疾传播动态。
方法
2012 年至 2013 年间，使用巢式 PCR 和 DNA 测序对 350 株恶性疟原虫临床分离株进行了 msp-1 第 2 块、msp-2 第 3 块和 glurp 基因第 2 区的高度多态性遗传标记的基因分型。
结果
共记录到 GLURP 大小为 597-817 bp 的 5 种不同基因型。总体而言，鉴定出 16 种 MSP-1 基因型，包括 K1、MAD20 和 RO33，大小为 153-335 bp。本研究的一个特点是 Pfmsp-1 等位基因类型中 RO33 单态性模式的揭示。此外，本研究还鉴定出 27 种不同的 Pfmsp-2 基因型，大小为 140-568 bp，包括 15 种属于 3D7 型和 12 种属于 FC27 等位基因家族。MSP-1 和 MSP-2 肽的分析表明，与 MAD20 相比，与 K1 多态性相对应的对齐区域具有最高的相似性，在 MSP1 和 MSP2 进化枝中同源性为 93%-100%。因此，恶性疟原虫分离株的种群结构与非洲其他地区相同，这表明使用 Pfmsp1 等位基因变体的 K1 和 MAD20 开发的疫苗可能对非洲儿童具有保护作用，但这些发现需要进一步的遗传和免疫研究。PfMsp-2 基因座的感染多重性（MOI）显著更高（P<0.05）（3.82），而 PfMsp-1 基因座的感染多重性（MOI）为 2.51，杂合子的范围为 0.55-PfMsp-1 至 0.96-PfMsp-2。
结论
恶性疟原虫分离株的高遗传多样性和等位基因频率表明持续存在高水平的传播。本研究主张在喀麦隆加强疟疾控制策略。
试验注册
本研究得到喀麦隆国家伦理委员会的批准。它是美国国立卫生研究院美国国家医学图书馆 NIH 临床试验.gov 于 2016 年 11 月 28 日在 https://clinicaltrials.gov/ct2/show/NCT02974348 上进行的一项随机对照试验，注册号为 NCT02974348。
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