第二型登革病毒在G6PD缺乏病人單核球體外感染之研究

Abstract

登革病毒是屬於黃質病毒科的一種，並可區分為四種血清型（分別為DENV-1、DENV-2、DENV-3及DENV-4），其媒介是白線斑蚊及埃及斑蚊，在臨床上可造成一般的登革熱、嚴重的登革出血熱（dengue hemorrhagic fever，DHF）及登革休克症候群（dengue shock syndrome，DSS）。蠶豆症（favism）是由於Glucose-6- phosphate dehydrogenase (G6PD) 酵素缺乏所造成的疾病，有研究指出嚴重的G6PD酵素缺乏容易遭受細菌或病毒的感染，甚至造成慢性肉牙腫(chronic granulomatous disease, CGD) 的情況。台灣地區G6PD缺乏患者平均約有3 %的盛行率，且台灣地區同時為登革病毒流行的區域，因此為研究G6PD缺乏患者是否較容易被登革病毒感染及是否若感染後較容易造成嚴重的病症，於是收集12位蠶豆症患者及24位健康個體來進行研究，並從人類周邊血液中分離出單核球，在體外以每細胞中的病毒感染量（multiplicity of infection, MOI）為0.1時，去感染第二型登革病毒兩種病毒株（New Guinea C及16681），再培養三天後將單核球進行雙色染色，最後以流式細胞儀進行結果分析。 結果顯示New Guinea C在健康個體之單核球的感染率平均值為20.23±6.22 %（8.03 % ~ 30.40 %）；在G6PD缺乏者中的感染率平均值為33.36±3.48 %（27.20 % ~ 39.16 %）（p<0.01）。16681在健康個體之單核球的感染率平均值為27.41±7.11 % （12.29 % ~ 37.10 %）；也在G6PD缺乏者中的感染率平均值較高而為40.74±3.73 %（35.06 % ~ 48.87 %）（p<0.01）。由此可知G6PD缺乏者之單核球對第二型登革病毒的兩不同病毒株（New Guinea C或16681）的感染率均比健康個體單核球的感染率來得高，且具統計意義。此外16681無論在G6PD缺乏者或在健康個體之單核球的感染率也均高於New Guinea C（p<0.05），即來自登革出血熱病人的病毒與來自登革熱病人的病毒也有所不同。 從本研究中可得到初步之結論，即宿主因子可能在登革病毒感染中扮演重要之角色。此外本研究亦發現不同登革病毒株在同一宿主下，所引起之感染率不同，即引起重症（DHF/DSS）之登革病毒株16681比引起登革熱之病毒株New Guinea C具更高之感染力。此項研究有助於台灣未來登革流行加強對患有蠶豆症病人的衛生教育工作。

Dengue virus is a member of family Flaviviridae. There are four serotypes of dengue virus, DENV-1, DENV-2, DENV-3 and DENV-4. The vectors of dengue virus are Aedes albopictus and Aedes aegypti and dengue virus can cause mild dengue fever (DF), or severe dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). Favism is a disease resulting from deficiency of Glucose-6-phosphate dehydrogenase, G6PD. The G6PD deficiency patients are easier infected by bacteria or virus even develop chronic granulomatous disease (CGD). In average, the prevalence of G6PD deficiency is about 3% in Taiwan and Taiwan is also an epidemic area of dengue virus. To study whether G6PD deficiency patients are susceptible to dengue virus and the infection is easier to cause severe syndrome. We have collected twelve G6PD deficiency patients and twenty four normal people to investigate. Monocytes were isolated from peripheral blood mononuclear cell (PBMC) and these monocytes were in vitro infected by two different strain of dengue virus serotype 2 (New Guinea C and 16681) at multiplicity of infection (MOI)= 0.1. After culturing for three days, the monocytes were double stained and analyzed by flowcytometer. The result found that the average infection rate of New Guinea C to normal people monocytes was 20.23±6.22 % (8.03 % ~ 30.40 %) and to G6PD deficiency patients’ monocytes was 33.36±3.48 % (27.20 % ~ 39.16 %) (p<0.01). The average infection rate of 16681 to normal people monocytes was 27.41±7.11 % (12.29 % ~ 37.10 %) and to G6PD deficiency patients’ monocytes was 40.74±3.73 % (35.06 % ~ 48.87 %) (p<0.01). According to the results, G6PD deficiency patients’ monocytes had statistically significant higher infection rate than normal ones even in New Guinea C or 16681. In addition, 16681 has higher infection rate than New Guinea C both in G6PD deficiency patients’ monocytes and normal ones (p<0.05). In conclusion, this study demonstrates that the host factor plays an important role in the infection of dengue virus. In addition, the infection rate of different strains of dengue viruses in the same host was not the same. The strain of dengue virus 16681, isolated from DHF/DSS, possesses better ability to infect human monocytes than New Guinea C isolated from dengue fever. Therefore, we can apply theses above finding in educating patients with favism to avoid dengue virus infection and thus minimize their healthy threat.