Novel Strategy for Animal Model Testing of HCMV Vaccines

描述（由申请方提供）：预防人巨细胞病毒（HCMV）先天性感染的疫苗是一项紧迫的公共卫生优先事项。基于在中国仓鼠卵巢（CHO）细胞中表达的纯化重组糖蛋白B（gB）的亚单位疫苗目前正在临床试验中进行测试。该疫苗的基本原理是基于观察结果，即在人恢复期血清中发现的大多数病毒中和抗体对该蛋白具有特异性。在先天性CMV感染的豚鼠模型中，纯化的重组形式的豚鼠巨细胞病毒（GPCMV）gB对感染和疾病具有保护作用，这一观察结果证实了HCMV gB疫苗可能对先天性感染有效的假设。然而，迄今为止，不幸的是，不可能在动物模型（例如GPCMV模型）中测试HCMV gB疫苗的功效。这是因为各CMV的严格种属特异性使得不可能在豚鼠中进行HCMV病毒攻毒实验，即使人gB疫苗在这些动物中具有免疫原性。然而，近年来，基于CMV基因组作为细菌人工染色体（BAC）在大肠杆菌中的成功应用，病毒诱变策略的发展受到了极大的关注。大肠杆菌中表达的病毒在产生重组嵌合病毒方面取得了重大进展。现在，通过将异源HCMV基因靶向插入病毒基因组中来产生具有复制能力的GPCMV是可行的。1）在GPCMV基因组中表达HCMV gB蛋白的新的重组“交换”突变体将保留复制能力和在体内引起先天性感染和疾病的能力;和，2）纯化的重组HCMV gB，与MF 59佐剂一起给药，将保护怀孕的动物免受先天性感染和疾病的挑战与'人源化'病毒。这些研究将代表人CMV亚单位疫苗在先天性CMV感染小动物模型中的首次有效性试验。

DESCRIPTION (provided by applicant): A vaccine for prevention of congenital infection with human cytomegalovirus (HCMV) is an urgent public health priority. A subunit vaccine based on purified recombinant glycoprotein B (gB), expressed in Chinese hamster ovary (CHO) cells, is currently being tested in clinical trials. The rationale for this vaccine is based on observations that the majority of virus-neutralizing antibodies found in human convalescent sera are specific for this protein. The observation that purified, recombinant forms of guinea pig cytomegalovirus (GPCMV) gB are protective against infection and disease in the guinea pig model of congenital CMV infection lends credence to the hypothesis that HCMV gB vaccines might be efficacious against congenital infection. However, to date it has unfortunately been impossible to test the efficacy of the HCMV gB vaccine in an animal model, such as the GPCMV model. This is because the strict species-specificity of the respective CMVs makes it impossible to perform HCMV viral challenge experiments in guinea pigs, even though the human gB vaccine is immunogenic in these animals. Recently, however, the development of viral mutagenesis strategies based on the successful doing of CMV genomes as bacterial artificial chromosomes (BACs) in E. coli has represented a major advance in generating recombinant, chimeric viruses. It is now feasible to generate replication-competent GPCMVs with targeted insertions of heterologous HCMV genes into the viral genome. Against this backdrop, this proposal seeks to test the hypotheses that: 1) a novel, recombinant 'swap' mutant, expressing the HCMV gB protein in the context of the GPCMV genome, will retain replication competence and the ability to cause congenital infection and disease in vivo; and, 2) that purified, recombinant HCMV gB, administered with MF59 adjuvant, will protect against congenital infection and disease in pregnant animals challenged with the 'humanized' virus. These studies will represent the first efficacy test of a human CMV subunit vaccine in a small animal model of congenital CMV infection.