COLD-ADAPATION OF HUMAN ROTAVIRUSES

急性非细菌性胃肠炎早已被公认为整个 世界上最常见和最重要的人类疾病之一。 在这一广泛的疾病复合体中，A组轮状病毒是唯一的 最重要的病原体严重，往往危及生命 全球婴幼儿腹泻。 已评价的三种候选口服轮状病毒活疫苗 在世界各地都是使用“詹纳” approach. 在该方法中，抗原相关的活病毒衍生自 来自非人类宿主的疫苗用作针对其 人类病毒对应物。 两种单价的保护功效 牛或猿轮状病毒疫苗已被证明是可变的。 在 此外，目标人群为2至5个月大的婴儿， 典型地只发展了同型免疫反应， 预防针 因此，修改后的“詹纳”方法被 用于四价疫苗的配方。 这涉及 将动物（恒河猴或牛）轮状病毒的VP 7基因替换为 主要临床表现的人轮状病毒的每一种的相应基因 重要性 A组轮状病毒具有两种外部衣壳蛋白，其功能是 独立的中和抗原，即VP 4（由基因组编码 片段4）和VP 7（由基因组片段7、8或9编码，取决于 应变）。 虽然最初VP 7被认为是占主导地位的 中和抗原，后来的研究表明，VP 4是有效的 与VP 7一样，在实验后诱导中和抗体 实验动物感染或疫苗诱导的感染 易受感染的婴儿或幼儿。 此外，VP 4或VP 7的抗体 独立地与特定菌仔猪对 用毒性轮状病毒进行实验性攻击。 然而，VP 7是 仅候选者中存在相关轮状病毒保护性抗原 目前正在评估的减毒活疫苗， 在人类中的保护效力;这些疫苗含有 动物轮状病毒，与以下任一种的VP 4抗原性无关： 流行病学上重要的人类轮状病毒。 为了最大化活轮状病毒疫苗的免疫原性， 掺入两种保护性抗原（即，VP 4和VP 7）临床上 重要的轮状病毒，我们寻求另一种疫苗方法， 冷适应（ca）和温度敏感（ts） 寻找人轮状病毒的突变体。 这一战略需要 在病毒适应生长过程中选择这种突变体 有效地在次最佳温度，已成功地采用 筛选出多种减毒候选人用病毒疫苗 脊髓灰质炎病毒、甲型流感病毒、副流感病毒型 3病毒和呼吸道合胞病毒。 该项目的目标是：（i）使选定的野生型 人轮状病毒，（ii）分析遗传学上的各种表型 这种冷适应病毒所表现出的特征包括温度 灵敏度，冷适应，和衰减，和（iii）评估这些 CA轮状病毒在活轮状病毒中的潜在用途 人类的疫苗

Acute nonbacterial gastroenteritis has long been recognized throughout the world as one of the most frequent and important human diseases. Within this broad disease complex, group A rotaviruses are the single most important etiologic agents of severe and often life-threatening diarrhea of infants and young children worldwide. Three candidate live oral rotavirus vaccines that have been evaluated in various parts of the world were developed using the "Jennerian" approach. In this approach, an antigenically-related live virus derived from a non-human host is used as a vaccine for immunization against its human virus counterpart. The protective efficacy of the two monovalent bovine or the simian rotavirus vaccines has proved to be variable. In addition, the target population of two-to-five-month-old infants characteristically developed only a homotypic immune response following vaccination. As a consequence, a modified "Jennerian" approach was developed for the formulation of a quadrivalent vaccine. This involved replacing the VP7 gene of the animal (rhesus or bovine) rotavirus by the corresponding gene of each of the human rotaviruses of major clinical importance. Group A rotaviruses possess two outer capsid proteins that function as independent neutralization antigens, namely VP4 (encoded by genome segment 4) and VP7 (encoded by genome segment 7, 8, or 9 depending on the strain). Although initially VP7 was thought to be the dominant neutralization antigen, later studies showed that VP4 is as effective as VP7 in inducing neutralizing antibodies following experimental infection of experimental animals or vaccine induced infection of susceptible infants or young children. Also, antibodies to VP4 or VP7 are independently associated with resistance of gnotobiotic piglets to experimental challenge with virulent rotavirus. However, VP7 is the only relevant rotavirus protective antigen that is present in candidate live attenuated vaccines that are currently under evaluation for protective efficacy in humans; these vaccines contain the VP4 of an animal rotavirus that is not related antigenically to the VP4 of any of the epidemiologically important human rotaviruses. In an attempt to maximize immunogenicity of live rotavirus vaccines by incorporating both protective antigens (i.e., VP4 and VP7) of clinically important rotaviruses, we pursued another approach to vaccine development in which cold-adapted (ca) and temperature-sensitive (ts) mutants of human rotaviruses were sought. This strategy, which entails the selection of such mutants during adaptation of virus to grow efficiently at suboptimal temperature, has been successfully employed by others to select various attenuated candidate human viral vaccine strains for the polioviruses, influenza A viruses, parainfluenza type 3 virus, and respiratory syncytial virus. The objectives of this project are: (i) to cold-adapt selected wild-type human rotaviruses, (ii) to analyze genetically various phenotypes exhibited by such cold-adapted viruses including temperature sensitivity, cold-adaption, and attenuation, and (iii) to evaluate these ca rotaviruses for their potential usefulness in a live rotavirus vaccine for humans.