VACCINES FOR PREVENTION OF EXPERIMENTAL CONGENITAL CMV

人巨细胞病毒(HCMV)是一种重要的病原体，在包括新生儿在内的免疫功能低下的人群中引起严重的发病率。特别是，出生时患有先天性巨细胞病毒感染的婴儿神经发育不良的风险很高。由于先前存在的母体免疫系统可预防由人巨细胞病毒引起的严重疾病，因此人们对开发疫苗非常感兴趣，以预防与先天性感染相关的大量发病率。然而，由于巨细胞病毒的严格的物种特异性，CMV疫苗在临床前环境下很难进行评估。由于豚鼠巨细胞病毒(GPCMV)穿过胎盘，导致宫内感染，豚鼠提供了一个模型系统，在其中测试预防CMV疾病的疫苗。不幸的是，到目前为止，这个系统还没有得到充分的开发，这主要是因为人们对GPCMV的分子生物学知之甚少。然而，最近编码主要体液免疫靶标糖蛋白B(GB)和细胞介导性免疫靶标pp65(UL83)的GPCMV基因已被克隆、鉴定和表达。因此，亚单位疫苗研究现在在这个模型中是可行的。因此，这些研究提出了三个主要目标。首先，我们将在我们的先天性感染模型中评估重组形式的包膜糖蛋白GB的免疫原性和保护效果。我们将测试的假设是，重组GB将提供对先天性CMV的保护，但是以佐剂依赖的方式。我们将直接评估一种更有效的免疫调节剂--单磷脂A(MPL)是否比单独使用明胶佐剂提供更好的佐剂效果。这将是GPCMV模型中与人类临床使用相关的佐剂的第一次评估。在第二个特定目标中，我们将测试细胞毒性T淋巴细胞(CTL)靶标UL83作为载体疫苗在牛痘病毒中表达的作用。我们推测，针对这个CTL靶点的疫苗将提供对先天性CMV疾病的保护。这将是第一次对在先天性感染模型中仅引起细胞中介反应的疫苗进行评估。最后，在第三个具体目标中，我们将进行第一次研究，以测试DNA疫苗对先天性CMV感染的保护效果。我们假设，在我们的模型中，同时针对GB和UL83的DNA疫苗将提供对抗疾病的疗效。从这些研究中获得的信息将与正在进行的巨细胞病毒疫苗研究相关，并将有助于确定在预防先天性巨细胞病毒感染的进一步临床试验中应优先采用哪些疫苗策略。

Human cytomegalovirus (HCMV) is an important pathogen which causes severe morbidity in immunocompromised individuals, including newborn infants. In particular, infants born with congenital CMV infection are at high risk for poor neurodevelopmental outcome. Since pre-existing maternal immunity protects against severe disease caused by HCMV, there is considerable interest in developing vaccines designed to prevent the substantial morbidity associated with congenital infection. Vaccines for CMV have been difficult to evaluate in the preclinical setting, however, because of the strict species specificity of cytomegaloviruses. Since the guinea pig cytomegalovirus (GPCMV) crosses the placenta, causing infection in utero, the guinea pig provides a model system in which to test vaccines for the prevention of CMV disease. Unfortunately, this system has not to date been exploited to its fullest potential, largely because so little is known about the molecular biology of GPCMV. However, recently the GPCMV genes encoding the major humoral immune target glycoprotein B (gB) and the cell-mediated immune target pp65 (UL83) have been cloned, characterized and expressed. Subunit vaccine studies are thus now feasible in this model. Therefore, these studies propose three major aims. First, the immunogenicity and protective efficacy of a recombinant form of envelope glycoprotein gB will be evaluated in our congenital infection model. The hypothesis we will test is that recombinant gB will provide protection against congenital CMV, but in an adjuvant-dependent fashion. We will directly evaluate whether a more potent immunomodulatory agent, monophosphoryl lipid A (MPL), provides a better adjuvant effect than alum-based adjuvants alone. These will be the first assessments of adjuvants relevant to human clinical use in the GPCMV model. In the second specific aim, we will test the role of a cytotoxic-T-lymphocyte (CTL) target, UL83, as a vectored vaccine expressed in vaccinia. We hypothesize that vaccination against this CTL target will provide protection against congenital CMV disease. This will be the first assessment of a vaccine which elicits only cell-mediated responses in a model of congenital infection. Finally, in the third specific aim we will conduct the first studies to test the protective efficacy of DNA vaccines for protection against congenital CMV infection. We hypothesize that DNA vaccines which target both gB and UL83 will provide efficacy against disease in our model. Information obtained from these studies will be relevant to ongoing studies of HCMV vaccines, and will help to prioritize which vaccine strategies should be pursued in further clinical trials for the prevention of congenital cytomegalovirus infection.