Inducible nitric oxide synthase 2 promoter polymorphism and malaria disease severity in children in Southern Ghana

Objective
We assessed the association of mutant allele frequencies of nitric oxide synthase 2 (NOS2) gene at two SNPs (-954 and -1173) with malaria disease severity in children from a malaria endemic area in Southern Ghana.
Method
Using children recruited at the hospital, assigned into clinical subgroups of uncomplicated and severe malaria and matching with their “healthy control” counterparts, we designed a case control study. Genomic DNA was extracted and genotyping using Restriction Fragment Polymorphism was done.
Result
A total of 123 malaria cases (91 uncomplicated, 32 severe) and 100 controls were sampled. Their corresponding mean Hbs were 9.6, 9.3 and 11.2g/dl and geometric mean parasite densities of 32097, 193252 and 0 parasites/ml respectively. Variant allele frequencies varied from 0.09 through 0.03 to 0.12 for G-954C and 0.06 through 0.03 to 0.07 for C-1173T in the uncomplicated, severe and healthy control groups respectively. There was a strong linkage disequilibrium between the two alleles (p<0.001). For the -954 position, the odds of developing severe malaria was found to be 2.5 times lower with the carriage of a C allele compared to those without severe malaria (χ2; p< 0.05) though this isn’t the case with -1173.
Conclusion
The carriage of a mutant allele in the -954 NOS2 gene may have a protective effect on malaria among Southern Ghanaian children.

## 研究目标
我们旨在评估加纳南部疟疾流行区儿童的一氧化氮合酶2（nitric oxide synthase 2, NOS2）基因的两个单核苷酸多态性位点（-954与-1173）的突变等位基因频率与疟疾疾病严重程度的关联。

## 研究方法
本研究为病例对照研究，纳入医院收治的儿童受试者，将其划分为单纯性疟疾与重症疟疾两个临床亚组，并匹配健康对照人群。提取基因组DNA后，采用限制性片段多态性（Restriction Fragment Polymorphism）技术完成基因分型。

## 研究结果
本研究共纳入123例疟疾病例（91例单纯性疟疾、32例重症疟疾）与100例健康对照。三组受试者的平均血红蛋白水平分别为9.6、9.3与11.2g/dl，几何平均寄生虫密度分别为32097、193252与0寄生虫/ml。在单纯性疟疾、重症疟疾与健康对照组中，G-954C位点的变异等位基因频率分别为0.09、0.03与0.12，C-1173T位点的变异等位基因频率分别为0.06、0.03与0.07。两个位点间存在显著的连锁不平衡（Linkage Disequilibrium）（p<0.001）。在-954位点，携带C等位基因的受试者发生重症疟疾的比值较未携带者低2.5倍（χ²检验；p<0.05），但该关联未在-1173位点观察到。

## 研究结论
加纳南部儿童携带NOS2基因-954位点的突变等位基因，可能对疟疾感染具有保护作用。