The Prevalence of Human T-Lymphotropic Virus Infection among Blood Donors in Southeast China, 2004-2013

BackgroundThe human T-lymphotropic virus type 1 (HTLV-1) which is associated with the diseases of adult T-cell leukemia/lymphoma, HTLV-1 associated myelopathy / tropical spastic paraparesis (HAM/TSP) and HTLV-associated uveitis, can cause transfusion-transmitted infections. Although HTLV screening of blood donors was already routinely performed in developed countries, little is know about the HTLV prevalence among blood donors in developing countries which do not perform HTLV screening, such as China.Objectives &AimsTo systematically characterize the prevalence of HTLV infection among bloods in southeast China.MethodsA 10-year survey for HTLV prevalence in blood donors was performed in Xiamen, southeast China, during 2004-2013. The HTLV-1/2 of blood donations were screened by enzyme-linked immunosorbent assay, following with confirmation by western blot assay and 9nucleic acid testing. The HTLV-1 prevalences in donors from different cities were calculated. Viral sequences derived from identified HTLV-positive cases were sequenced and analyzed.ResultsAmong 253,855 blood donors, 43 were confirmed to be seropositive for HTLV-1 (16.9 per 100,000 95% CI: 12.3-22.8) and none HTLV-2 infection was found. The HTLV-1 prevalence varied significantly in donors from different cities. Donors from cities in Fujian province (24.3 per 100,000, 95%CI: 17.4-33.1) had a significantly higher (p=0.001) HTLV-1 seroprevalence than those who were born in non-Fujian cities (3.4 per 100,000, 95%CI: 0.7-9.8). Among nine cities in Fujian province, the highest prevalence was found in blood donors from Ningde (171.3 per 100,000, 95%CI: 91.3-292.8) which is a coastal city in the northeast of Fujian. Molecular characterization of viral sequences from 27 HTLV-1 carriers revealed 25 were Transcontinental subtype of genotype A and 2 were Japanese subtype of genotype A. Interestingly, 12 of 25 Transcontinental subtype sequences harbored a characteristic L55P mutation in viral gp46 protein, which was only presented in the Transcontinental subtype sequences from Japan and Taiwan but not in that from other countries.ConclusionsAlthough China is considered to be a non-endemic region for HTLV, the HTLV-1 prevalence in blood donors is significantly higher in Fujian province, southeast China. A higher prevalence of HTLV-1 in the Fujian may be attributed to endemic foci in the city of Ningde.## 背景 人类嗜T淋巴细胞病毒1型（human T-lymphotropic virus type 1, HTLV-1）可引发成人T细胞白血病/淋巴瘤、HTLV相关脊髓病/热带痉挛性截瘫（HTLV-associated myelopathy / tropical spastic paraparesis, HAM/TSP）以及HTLV相关性葡萄膜炎相关疾病，还可导致输血传播感染。尽管发达国家已将献血者HTLV筛查纳入常规检测流程，但对于未开展HTLV筛查的发展中国家（如中国）的献血者HTLV流行现状，目前学界认知仍较为有限。 ## 研究目的 系统阐明中国东南部地区血液捐献者群体中HTLV感染的流行特征。 ## 研究方法 本研究于2004-2013年在中国东南部厦门市开展了一项为期10年的献血者HTLV流行率调查。采用酶联免疫吸附试验（enzyme-linked immunosorbent assay, ELISA）对献血者血液样本进行HTLV-1/2筛查，随后通过免疫印迹试验（western blot assay）与核酸检测进行确认。计算不同城市献血者的HTLV-1流行率，并对确诊HTLV阳性病例的病毒序列进行测序与分析。 ## 研究结果 本研究共纳入253855名献血者，其中43例经确认HTLV-1血清学阳性，流行率为16.9/10万（95%置信区间：12.3~22.8），未发现HTLV-2感染病例。不同城市献血者的HTLV-1流行率存在显著差异。福建省籍献血者的HTLV-1血清流行率为24.3/10万（95%CI：17.4~33.1），显著高于非福建省籍献血者的3.4/10万（95%CI：0.7~9.8，p=0.001）。在福建省下辖的9个城市中，宁德市献血者的HTLV-1流行率最高，达171.3/10万（95%CI：91.3~292.8），该市为福建省东北部的沿海城市。对27例HTLV-1携带者的病毒序列进行分子特征分析，结果显示25例为基因型A的跨大陆亚型（Transcontinental subtype），2例为基因型A的日本亚型（Japanese subtype）。值得注意的是，25例跨大陆亚型序列中有12例在病毒gp46蛋白（gp46 protein）中存在特征性L55P突变（L55P mutation），该突变仅见于日本及中国台湾地区的跨大陆亚型序列，未在其他国家的对应序列中被检测到。 ## 研究结论 尽管中国被认为是HTLV非流行区，但中国东南部福建省献血者的HTLV-1流行率显著升高。福建省较高的HTLV-1流行率可能与宁德市存在的地方性疫源地相关。