GENETIC VARIATION AMONG DENGUE VIRUSES

登革热病毒家族包含4种不同的血清型，它们是 以病毒中和区分的。在登革热人群中，2型 病毒最常与出血热有关，出血热是一种严重的 致命形式的登革热。它们之间存在着相当大的多态性 由寡核苷酸指纹变异所指示的2型病毒 这种变异在特定的模式中有地理分布 仅限于特定地区。目前正在努力研究 应用分子克隆和核苷酸技术研究登革病毒的遗传变异 测序。选择登革2型(PR159株)进行序列比较 我们实验室也在克隆和测序登革热4型病毒。 提纯登革2型病毒基因组RNA并转录成RNA-cDNA杂交物 按照已建立的程序在pBR322载体中直接克隆 登革热4.琼脂糖凝胶Pst I酶切质粒DNA分析 显示大多数重组质粒含有DNA插入 长度从500-4000个碱基对不等。最大的重组体 选择插入(2,000个碱基对或更多)来定位全长 基因组序列。为此，我们利用了基因 存在于2型和4型登革热病毒之间的同源性。放射性标记 登革4型病毒DNA片段在不同图谱上的克隆探针 位置被用于登革热2插入物的初始测绘和筛选。 到目前为止，超过一半的登革热2基因组序列已经 克隆，我们的最终目标是获得全长的DNA拷贝。完成 将进行序列分析，以努力获得更好的 对登革热流行中病毒多态模式的了解 不同病毒株对登革出血热的影响。

The dengue virus family contains 4 distinct serotypes that are distinguishable by virus neutralization. Among the dengue group the type 2 virus is most frequently involved in hemorrhagic fever, a severe and often fatal form of dengue disease. There is considerable polymorphism among type 2 viruses as indicated by variation in oligonucleotide fingerprints and this variation has a geographic distribution in that specific patterns are limited to specific localities. Efforts are now underway to study genetic variation of dengue viruses by molecular cloning and nucleotide sequencing. Dengue 2 (strain PR159) was chosen for sequence comparison with dengue 4 that is also being cloned and sequenced in our laboratory. Dengue 2 genomic RNA was purified and transcribed into RNA-cDNA hybrids for direct cloning in the pBR322 vector according to the procedure established for dengue 4. Analysis of plasmid DNA after Pst I digestion on agarose gel showed that a majority of recombinant plasmids contained DNA inserts ranging from 500-4,000 base pairs in length. Recombinants with the largest inserts (2,000 base-pairs or more) were chosen for mapping the full-length genomic sequence. For this purpose we took advantage of the genetic homology that exists between dengue virus type 2 and type 4. Radiolabeled probes prepared from cloned DNA segments of dengue 4 at various map positions were used for initial mapping and screening of dengue 2 inserts. Thus far, more than one-half of the dengue 2 genomic sequences have been cloned and our ultimate goal is to obtain a full-length DNA copy. Complete sequence analysis will be performed in an effort to gain a better understanding of the pattern of virus polymorphism in dengue epidemics and the involvement of different virus strains in dengue hemorrhagic fever.