Studies on dengue virus infection in Thailand

(1)在Nakorn Phanom省医院开展了登革热住院患者和不明原因发热门诊患者的研究。将患者血清接种于C6/36细胞，分离出31株登革热病毒，其中2型19株，4型8株，1型4株。在这项研究中，4型登革热病毒的流行是登革热流行的特征，仅次于2型登革热病毒。结果与直接在血清标本上进行的逆转录聚合酶链式反应(RT-PCR)病毒基因组检测和分型结果一致。在RT-PCR之前提取RNA并没有显著提高检测病毒基因组的效率。患者血清中的细胞因子水平(I 1-1β、I 1-6、肿瘤坏死因子-β)与疾病的临床严重程度无关，肿瘤坏死因子-1水平正常。酶联免疫吸附试验检测抗登革热免疫球蛋白和免疫球蛋白M可鉴别原发和继发登革热病例。在滤纸条上干燥的血液或血清标本的序贯ELISA法显示，抗登革热抗体在室温下保存4个月是稳定的，而IgM抗体不稳定，特别是在初发登革热病例的血清中。(2)昆虫学研究是在Mahidol大学热带医学院进行的。对3株埃及伊蚊的口腔感染，对不同临床严重程度的登革2型病毒株的感染率无显著差异。对埃及伊蚊的杀灭效果表明，昆虫生长调节剂扑灭灵对埃及伊蚊的LC_(50)为0.01~0.05 ppb。雌成虫接触该化合物后，将其带到幼虫栖息地，对幼虫有杀灭作用。

(1) Studies on hospitalized dengue patients and outpatients of fevers of unknown origin were carried out at Nakorn Phanom Provincial Hospital. Inoculation of patients'serum specimens into C6/36 cells isolated 31 dengue virus strains (19 type 2, 8 type 4, 4 type 1). Prevalence of type 4 dengue virus, next to type 2, was characteristic to the dengue epidemic in this study. The result genrally agreed with viral genome detection and typing by reverse transcriptase-polymerase chain reaction (RT-PCR), which was performed directly on serum specimens. RNA extraction prior to RT-PCR did not improve the efficiency to detect viral genome significantly. Cytokine levels (I 1-1beta, I 1-6, TNF-beta)in patient's sera did not correlate with clinical severity of the disease, with normal level of TNF-1. ELISA on anti-dengue IgG and IgM levels differentiated primary and secondary dengue cases. Sequential ELISA on blood or serum specimens dried on filter paper strips showed stability of anti-dengue IgG antibodies upto 4 months storage at room temperature, with instability of IgM-antibodies , particularly in sera from primary dengue cases.(2) Entomological studies were carried out in the Faculty of Tropical Medicine, Mahidol University. Oral infection to 3 Aedes aegypti strains did not reveal significant difference between the infection rates of dengue type 2 virus strains, which had been isolated from different clinical severity of the disease. Larvicidal effect on Aedes aegypti sgiwed that LC_<50> of an insect growth regulator, pryproxifen, was 0.01 ^- 0.05ppb. The female adults, exposed to the compound, carried it to the larval habitat, resulted in larvicidal effect.