Studies on dengue virus infection in Thailand

(1)在Nakorn Phanom省医院对住院登革热患者和门诊不明原因发热患者进行了研究。将患者血清标本接种于C6/36细胞，分离出31株登革热病毒（2型19株，4型8株，1型4株）。在本研究中，登革热流行的特征是4型登革热病毒，其次是2型登革热病毒。该结果与直接在血清标本上进行逆转录聚合酶链反应（RT-PCR）的病毒基因组检测和分型基本一致。在RT-PCR之前提取RNA并不能显著提高病毒基因组的检测效率。患者血清中细胞因子（I 1-1 β、I 1-6、tnf - β）水平与临床疾病严重程度无相关性，TNF-1水平正常。ELISA检测抗登革热IgG和IgM水平可区分原发性和继发性登革热病例。对在滤纸条上干燥的血液或血清标本进行序列ELISA检测，结果显示抗登革热IgG抗体在室温下保存4个月后具有稳定性，而igm抗体不稳定，尤其是在原发性登革热病例的血清中。(2)昆虫学研究在玛希隆大学热带医学院进行。3株埃及伊蚊口腔感染对不同临床严重程度登革热2型病毒株的感染率无显著差异。对埃及伊蚊的杀幼虫效果表明，昆虫生长调节剂吡虫胺的LC_<50>为0.01 ^- 0.05ppb。雌性成虫暴露于该化合物后，将其携带到幼虫栖息地，产生杀幼虫效果。

(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.